What If? $8D (1227727 ECM) for TBI

[dave w]

I'm thinking about trying to use the Under Hood 1227727 ECM for a TBI. I'm thinking of using definition $8D with a resistor network to trick the ECM to thinking the Low Impedance TBI are High Impedance TPI injectors.

I found the information (Formulas) below from a MegaSquirt website.

Injector Resistors
This method has been used by many OEMs as a simple approach to driving low-z injectors. The installer has the option of installing a 5 to 8 ohm resistor (with a 20 to 25 watt rating) in series with each injector (in effect converting them to hi-z.)
1980s Volvos were fitted with a resistor pack that conveniently combines a number of resistors.
To limit the current to under 2 amps, you need:
resistor ohms = (alternator voltage / 2.0 amps) - injector resistance
For example:
resistor ohms = (14.0 volts / 2.0 amps) - 1.2 ohms
=> resistor ohms = 7.0 - 1.2 = 5.8 ohms

The application I am thinking of converting to $8D TBI is a Marine SBC application. Using an under dash ECM is not an OPTION!:mad1:

Couple things I'm thinking about:
TPI and TBI are different DRP's.
The OEM '7727 TBI definition is not hacked as nicely as the $8D / Super $8D!
Injector flow settings; seems like injector flow of about 15 Lb / Hr would equal one TBI injector of 60 Lb / Hr?

Any thoughts Pro's / Con's are welcome.

dave w

[Six_Shooter]

I believe there was a TBI '7730/'7749/'7727 application. If it was in one of those three ECMs, it can be used ijn the others. I want to say it was a late '80s vehicle, but I don't recall exactly which one.

[EagleMark]

Well since 1227727 is underhood model of 1227730 and 1227730 was already used for TBI, and chips will run the same in both, and we have TBI wiring diagrams for it :
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?330-1227730-ECM-information

I think it may be easier than you think? But I am not sure what mask the 7739 TBI uses?

Also a 1227727 system either underdash or underhood would be not only great for marine but also great for Off Roaders who just want TBI!

EDIT: Ha! was posting same time as Six Shooter...

[dave w]

Thanks for the input. I've done some research, and have only been able to find 4 cylinder TBI '7727 / '7730 applications. I think the challenge is getting the '7727 TPI Distributor Reference Pulse (DRP) to work with the TBI DRP's?

From my research, I've seen information saying the TBI DRP is once every spark plug firing.

From my research, I've seen information saying the TPI DRP is once every other spark plug firing.

Any thoughts?

dave w

[Six_Shooter]

Yeah, once you set the "cyl count" to "TBI" (I don't recall the HEX value for that, off hand), the injector firing should take care of itself.

[dave w]

Does anyone have a $89.xdf? I've looked around, but can't seem to find one.

Thanks,
dave w

[EagleMark]

So that's what 1227727 TBI mask is? I went through everything I had and Robert from TP gave me and nothing for that or any bins?

I do have a 7749 2.8 TBI $3F xdf...

Since your probably dealing with a V8? Wouldn't it be better to start with readily available V8 xdf for 1227727? Change to TBI? If the $OD and $OE can do it I'd bet $6D, $8D could but really not sure how... there's also $A1, $88 and I think $55 were V6 PFI with 1227727

[dave w]

Based on the research I've done, $89 was for a 2.5 liter '7727 TBI. TunerCats shows $89 on it's website. I think to best path forward is to leverage the $3F.xdf, based on Six_Shooter's information that 7727 / 7730 / 7749 are interchangeable. I think a bench test is a good place to start. I'll need to do more research on the '7727 TBI pin out.

Howell EFI is advertising a Dual TBI system using the '7730, so I'm thinking a '7727 single TBI pin out is possible.

Any help on a $3F.xdf / $3F.adx is greatly appreciated!:rockon:

dave w

[EagleMark]

$3F coming right up!

no signs of $3F adx so I will look to see if there is an ads or ALDL/ds for it.

[dave w]

I've done more research on the '7727 Injector Drivers. Here is what I think can be done to get the '7727 to operate TWO peak and hold injectors. The scree shot below is from http://www.exatorq.com/ludis_obd1/quadplugecm.html When D1 and D5 are shorted, D14 will operate a peak and hold injector. When D4 and D8 are shorted, D9 will operate a peak and hold injector. From the schematics I've been able to find; the 1990 ~ 1992 VIN R 2.5 TBI has D4 and D8 shorted, so I'm thinking it would be logical to short D1 and D5 and use D14 for the second peak and hold injector.

dave w

[EagleMark]

Looks like you figured it out...

I did find the ALDL is A97, attached is this in adx format.

[dave w]

Hi Mark,
Thanks for the $3F.adx!

I had noticed the '7730 2.5 Liter TBI Jumper D5 / D7 Injector Driver Low. I was thinking there would be a '7727 configuration that would be set for low Z injectors.

Is there a starter $3F.bin file available?

dave w

[EagleMark]

Have searched all I have collected over the years and the huge files Robert Saar gave me. No signs of any $3F bins? It is not the type of car many would get involved in tuning... 2.5L TBI?

OK I searched CalData and I did find some 2.5L bin numbers for LR8 A96.ads (not A97.ads) which come back as 1227727!
AUAJ, ASLX, AUSS, ASLW, APTW

Did find one, may be more here in bins:
http://gearhead-efi.com/gearhead-efi/

Or at Moates library?

[dave w]

So that's what 1227727 TBI mask is? I went through everything I had and Robert from TP gave me and nothing for that or any bins?

I do have a 7749 2.8 TBI $3F xdf...


Mark,
I'm not sure $3F is a '7749 .xdf? I've bumped into information (maybe conflicting information) that is showing $3F is for the 1227429 / 2.8 Liter TBI using a 2732 chip? I'm thinking a 27C128 or maybe even a 27C256 would be used in the '7727 TBI.


dave w

[EagleMark]

Not sure Dave? I just happened to have what you asked for and I thought it was 7727?... That APTW (above) is listed as 1227727 ECM and A96.ads so if it shows info wrong in $3F then we need to look at hex for proper mask. I really don't know how to do that...

It's a rare oddball 2.5L TBI engine using a MPFI ECM... not much out there on it. But we do have the above bin which is 1227727 and 2.5L TBI!

[EagleMark]

CalData shows nothing for 2.5L in 1227429. All are 2.8L.

So if gregs78cam sees this maybe he can open that APTW bin and tell us what mask to even look for?

[dave w]

I agree, very odd to see a TBI application using the '7727. I've looked closely at the TunerCat $89 definition, and it appears that the '7727 uses BPW for fuel in TBI mode, similar to the '7747 BPW for fuel. It appears using BPW for the '7727 eliminates injector flow and number of cylinders.

dave w

[1project2many]

Wow.

I have a 4 cyl 7727 .bin and matching definition file. Remember when I was asking about a handy converter to make a TP def file? That's the first one I was going to do. Wouldn'tcha know.

Ok, TPI to TBI, big difference is in injector firing. PFI intakes are dry, TBI intakes are wet. TBI manifolds have to be kept wet. And they have to be kept wetter when it's cold and they have to be kept wetter during acceleration. To that end the TBI cals fire injectors more often than PFI cals. Lots of discussion about this on thirdgen with the 7427 ecm. Once upon a time Edelbrock offered a PFI intake and conversion chip for the 7747 TBI engines. I have a copy of the cal but the conversion wasn't all that great. Wrong firing strategy for one thing. Lots of strange bugs in driveability. Selecting software which supports TBI firing inherently is the best starting point.

Next, injector drivers. As realized, PnH mode is activated when the PnH jumper is installed. Current is held high for peak mode then reduced after the injectors are fully opened. The hold current is determined by the impedance of the injector and the value of the sense resistor. In OE form, one injector driver will operate one PnH TBI injector or 2 PnH port injectors. Decreasing injector impedance by adding injectors or switching injector styles will increase current through the driver and let out the magic smoke. Bill Shaw documented an injector driver upgrade along with selecting the proper sense resistor when he used the 7749 in his Porsche although I cannot say the parts are available today. Based on my experience using four tbi injectors in a PFI engine with a 7749 you could get two tbi injectors on one driver in a V8. The 7749 has two drivers while the 7727 and 7730 only have one driver. The second driver location may be present and may not take much to populate in both of those ecm's.

TBI 2.5 and 2.8 were common options on S10 trucks in the early '80s. I've only seen one 2.5 TBI Lumina (90 or 91 vintage) but I've worked on a bunch of 2.5 TBI Cutlass Calais over the years.

[dave w]

I've been looking at the cylinder select for the '7727 Memcal. What I've been able to find out, is the cylinder select voltage is about 5 volts for TBI any number of cylinders. Similar to how the '7727 cylinder select is set to ZERO volts to convert a '7727 V6 memcal to V8 memcal.

I've also researched wiring schematics for the Quad 4 using ECM 1228708 which uses 4 port PnH mode injectors. I suppose the 1228708 would be an optional ECM to use for under hood V8 TBI?

I think I'll need to do some bench testing to figure things out.:yikes:
dave w

[EagleMark]

Wow.

I have a 4 cyl 7727 .bin and matching definition file. Remember when I was asking about a handy converter to make a TP def file? That's the first one I was going to do. Wouldn'tcha know.
Can't wait to here about this? Your talking the bin def, right? I could probably help with the adx side...



TBI 2.5 and 2.8 were common options on S10 trucks in the early '80s. I've only seen one 2.5 TBI Lumina (90 or 91 vintage) but I've worked on a bunch of 2.5 TBI Cutlass Calais over the years.I did find a lot of them in 1227748, but didn't think that would help since he want's something convertible to weatherproof ECM and TBI so stuck with looking for TBI bin from 7727/7730.

I am interested in outcome because every spring I get to fix/replace/reprogram WET 7747 ECMs in Off roaders rigs! Replacing it with a weatherproof ECM would be a much needed update in these rigs.

[dave w]

I am interested in outcome because every spring I get to fix/replace/reprogram WET 7747 ECMs in Off roaders rigs! Replacing it with a weatherproof ECM would be a much needed update in these rigs.

Mark,
I think using a 1228708 (2.3 liter Quad 4) with $A8 or $8B as an under hood TBI ECM is the most realistic path forward? Any change you would consider pooling our resources to make this venture a reality? I'm thinking I could do hardware (complete test bench setup), and you do software (.xdf / .bin / .adx)?

dave w

[jim_in_dorris]

I opened the APTW bin EagleMark posted earlier in my hex editor. It appears that that is an $89 bin. Open a bin file in your hex editor, it is the 9th byte from the start of the bin.

[EagleMark]

I think there are many more available 1227727 ECMs then Quad 4 ECMs in JunkYards... once you have figured what's needed for injector driver then I guess either would work... some of what you and 1project2many are speaking of I do not fully comprehend nor do I have time right now..., so maybe that's why you are looking at Quad 4 ECM. I actually have a Quad 4 Cutlass Calisis across the street a friend wants me to replace timing chain in, when I have it I could gather more info on bin and mask etc...

I can surely help find xdf and make an adx work. Most of what I have is in that link above but I still may have something in my computer?

[EagleMark]

I opened the APTW bin EagleMark posted earlier in my hex editor. It appears that that is an $89 bin. Open a bin file in your hex editor, it is the 9th byte from the start of the bin.Thanks Jim! :thumbsup:

But no signs of a $89 xdf anywhere in my computer...

Seems like Jim and I know Greg and some others on here could give us new guys a hex lesson.....

[jim_in_dorris]

I wonder if an $8D xdf would work, probably not. $8F looks like a bin for boosted applications. Also, the $8D doesn't appear at a quick glance to be convertable to TBI from TPI like $0D or $0E.

[1project2many]

The 8707 / 8708 ecm's have slightly different hardware inside Unknown what all differences are but $58 at least chokes in the 8707. There is one calibration which will run in both ecm's. Is it AKAL?? I'll have to check the home PC because I can't remember for sure. But I have worked on disassembling it more than once, and in fact there's both an 8707 and a 7749 on my test bench from about 5 years ago when I last played with this.

[dave w]

I've been doing more research on the 1228708 Memcal, basically it appears some of the Quad 4 Memcals are still available from GM PartsDirect. I have a copy of the Moates.net BCC Lookup.xls spreadsheet. The spreadsheet shows eprom part numbers? When I put in what should be 1228708 Quad 4 eprom part numbers into GM PartsDirect, I'm given a price of about $50 along with a description ~ EPROM PKG. I find this information encouraging, as it might be possible to get a moderate price for a rebuilt 1228708 and possibly a new Memcal? I'm encouraged that TunerCats shows $A8 and $8B definitions and the Moates.net BBC Lookup shows which Memcal is associated with which definition. The only key piece I see missing in this venture is data logging software. I really can't confirm a functioning 1228708 TBI on a test bench without data logging.:mad1:

dave w

[dave w]

I wonder if an $8D xdf would work, probably not. $8F looks like a bin for boosted applications. Also, the $8D doesn't appear at a quick glance to be convertable to TBI from TPI like $0D or $0E.

My original idea was to use $8D with resistors in series with the TBI PnH injectors. I've since learned that $8D would trigger the injectors every other Distributor Reference Pulse (DRP), when normally the TBI injectors would trigger on every DRP.

dave w

[EagleMark]

If you can give me year motor and body style we can find the ALDL for it. Or just go to bottom of this page and get the Index Doc. It will open in word or notepad. You can find the ALDL.ds for the year motor and body style. Kindof like the BCC lookup for the ADX side...
http://gearhead-efi.com/gearhead-efi/def/aldl/

[EagleMark]

$A8 1228707 or 1228708 91 Grand Am, Cutlass, Calais, Beretta LD2/LG0 (Quad 4)
That A144 or A145 and we have both those.

$8B 1228707 or 1228708 90 Grand Am, Cutlass, Calais, Beretta LD2/LG0 (Quad 4)
That is A092 or A093 and we have both those.

So making the ADX work is just some testing?

EDIT: Found some...

[dave w]

EDIT: Found some...

Awesome!:rockon:

I'll do some homework and get back to you in a day or so. I need a break from this research.

dave w

[1project2many]

Back home now.

I didn't think of it earlier today but the best way to get TBI and weather tight P4 together is probably $58. It will support TBI mode and a gent from the UK named Robin Handley has done a bunch of work setting it up to run 1 BAR NA with 4 cyl race cars. Combine this with the Bill Shaw injector driver change and you've got 2 TBI injectors running on a V8. Plus it's upgradeable to PFI, or to pressurized tbi if desired.

Dual ecm cals are $6B mask. Cals include ARHM6030, ARPZ6720, and ANZF9577. Some quad 4 wiring had dual crank signals sent to the ecm from the ignition module, while others did not. The 8707 / 08 may have hardware designed to work with the additional signal. The code may check for the presence of this hardware then set a mode flag if found.

The 4 cyl TBI 7727 cal I have is FML7554. It is $3E mask. I just looked and knumcyl (number of cylinders) is selectable in this cal, unlike many of the 4 cylinder calibrations. So in theory it could be adapted to an 8 cylinder engine.

Why are you looking to get a quad 4 memcal? It's very inappropriate for an 8 cyl. If it's for testing / measuring, I have several here in various state of disassembly. I'm willing to check / measure these memcals. As far as running q4 code, it will run just fine in other 4 cyl memcals and IIRC it ran on a 7730 V6 memcal with no complaints.

The problem I'm facing with making TP defs is the time involved. I'd be happy to contribute $6B, $3E, and $89 defs if I didn't have to sit here and pull all the values from one software and manually enter them in another. It looks like that's the only option at this point. Anyone have any suggestions?

[dave w]

Back home now.

I didn't think of it earlier today but the best way to get TBI and weather tight P4 together is probably $58. It will support TBI mode and a gent from the UK named Robin Handley has done a bunch of work setting it up to run 1 BAR NA with 4 cyl race cars. Combine this with the Bill Shaw injector driver change and you've got 2 TBI injectors running on a V8. Plus it's upgradeable to PFI, or to pressurized tbi if desired.

Dual ecm cals are $6B mask. Cals include ARHM6030, ARPZ6720, and ANZF9577. Some quad 4 wiring had dual crank signals sent to the ecm from the ignition module, while others did not. The 8707 / 08 may have hardware designed to work with the additional signal. The code may check for the presence of this hardware then set a mode flag if found.

The 4 cyl TBI 7727 cal I have is FML7554. It is $3E mask. I just looked and knumcyl (number of cylinders) is selectable in this cal, unlike many of the 4 cylinder calibrations. So in theory it could be adapted to an 8 cylinder engine.

Why are you looking to get a quad 4 memcal? It's very inappropriate for an 8 cyl. If it's for testing / measuring, I have several here in various state of disassembly. I'm willing to check / measure these memcals. As far as running q4 code, it will run just fine in other 4 cyl memcals and IIRC it ran on a 7730 V6 memcal with no complaints.

The problem I'm facing with making TP defs is the time involved. I'd be happy to contribute $6B, $3E, and $89 defs if I didn't have to sit here and pull all the values from one software and manually enter them in another. It looks like that's the only option at this point. Anyone have any suggestions?

I've spent many hours of research, trying to figure out if there is a practical under hood ECM for TBI service. With any venture from a stock OEM computer set up, there are trade offs. Some of the trade offs include cost ~ availability ~ time. At the moment, the 1228708 seems to be a practical option for an under hood TBI ECM. Having the $A8 / $8B .xdf ~ .ads ~ .adx ~ .bin / files for the Quad 4 available is a huge time saver!:thumbsup:

Going forward with a 1228708 TBI project would not require any more time or information than you have already invested in this tread. Going forward with a 1228708 TBI project, for me, requires getting some parts together and scheduling time to get things assembled.

I think we are good for now.:thumbsup:

dave w

[1project2many]

Going forward with a 1228708 TBI project would not require any more time or information than you have already invested in this tread.

I think we are good for now.

This thread seemed to have a lot of energy but some of the ground it was covering looked familiar to me. The 8707 / 8708 have been called out as possible replacements for the 7749 and 7730 several times throughout the years but I am not aware of anyone successfully using code written for a different ecm in these boxes. I have more than a passing interest in solving this riddle.

If you are choosing to use TBI over PFI you are choosing a fuel system with more required compromise. From my perspective, with years of working on stock and modified vehicles, it doesn't seem like a huge challenge to find an ecm or code that will get the job done. The only requirements I've seen stated here are minimal: The ecm needs to be weatherproof. If you have others which are not stated then I may unknowingly suggest solutions which are not appropriate. As a practical suggestion, the 7727 is more common that the 7808. The 7727 was installed in W body cars with 60 deg V6 from 88 to 93. The 7808 was installed in W bodys with 2.3 in 90 and 91. The V6 sales far outnumbered the Q4 sales.

I have not complained about the time I've invested here nor am I complaining about the lack of time for the projects I'd like to do. I am simply stating facts. Since forums don't convey context clues well, and since I don't know you well enough to interpret your post accurately, I will ask up front if this is an invitation to become uninvolved in this project. No harm no foul either way.

[EagleMark]

I know Dave and when he asks? Your input is welcome! :thumbsup:

The reason of TBI over MPFI is a simple EFI conversion to a boat or off roader with a readily available weatherproof ECM. I think that is the bottom line?There's no question MPFI would be better. But complicates matters and raises cost beyond what most people would consider.

Because of the pure numbers or 1227727 ECMs out there, and the work done on them far out numbers anything done with Quad 4 ECM I would have to agree it would be a better starting point.

I am interested in learning to write XDFs so if files are available with information to write information on a new xdf from I may take that on when a decision is made to which ECM and mask. It may make my next learning challenge of understanding hex easier as well. It was a lot of hours to learn adx but I seemed to succeed there with working files that no one else ever accomplished!

[dave w]

I have not complained about the time I've invested here nor am I complaining about the lack of time for the projects I'd like to do. I am simply stating facts. Since forums don't convey context clues well, and since I don't know you well enough to interpret your post accurately, I will ask up front if this is an invitation to become uninvolved in this project. No harm no foul either way.

I invite your input! I feel collecting information and sharing information is a benefit to all.

Let me try to do a chronological order of my research in an attempt to think thru the options of building an underhood TBI ECM EFI System.
1. Use $8D with resistors in series for PnH injectors. My research revealed the DRP's are not the same TBI / MPFI.
2. $89 seems like a good path forward. The research revealed the '7727 has only one injector driver for PnH? $89 would require development of both a .xdf & .adx.
2a. I have not researched $3E.
3. $A8 & $8B seems like a good path forward, both .xdf & .adx are developed. The 1228708 ECM has two PnH injector drivers.

Based on my research, the Memcal cylinder select voltage will configure the DRP rate of injector fire. The Quad 4 will fire the injectors once every DRP, which is the same DRP rate as a TBI EFI System.

Maybe the 4 cylinder Memcals for both 1227727 and 1228708 have the same Memcal cylinder select voltage?

Some design considerations I think are important to me in an EFI system. Very low cost is highly desirable! The service parts (sensors, ignition system, and computer) installed in an EFI system should be OEM and unmodified. I think from my EFI design considerations, saying the underhood TBI system is really just a Quad 4 EFI system, with a custom programmed PROM Chip appeals to me. Being able to set up a scan tool, like an AutoXray or something similar, for a Quad 4 EFI vehicle application also appeals to me.

From what I've looked at $A8 & 8B have very nice Timing and VE Tables compared to the $42 TBI Timing and VE Tables.

I hope this lets everyone know where I'm coming from.

dave w

[EagleMark]

I hope this lets everyone know where I'm coming from.

dave wYes! We are still in development!

I think the XDF and ADX can be done, so that is not an issue. Will the end result be something a scantool can be used for? Not if we develope the XDF and ADX exclusivly for the project! So my question is, does the 1227727 have capibility of running TBI with 2 injectors? Which mask?

[1project2many]

Thanks for the reply. Glad I'm not stepping on toes.

I worked for many years with unmodified or easily duplicated modifications as a basis for many projects. These days it's becoming harder to find stock replacement parts for older vehicles. For example, many ecm's are no longer available from the aftermarket or from the dealer. So at this point I guess I feel the old arguments for stock sensors and control parts are less valid. Regardless, I'll work within these confines as it always makes the excercise more challenging.

The Quad4 calibrations I've looked at are not reconfigurable for a different number of cylinders. They are designed specifically for the Q4. Quad 4 code displays many small differences over other P4 code such as the use of 6811 opcodes vs 6809 instructions and a lack of configurable options found in many GM calibrations. Lotus manufacturing was involved in the development of the engine and may have been heavily involved in the code / calibration as well. Lotus uses the 7807 / 7808 in their cars and there are a couple of neat versions of Lotus turbo code floating around.

If the Q4 code cannot be made useful for other engines, and if other versions of P4 code cannot be made to run in the 7808, then the 7727 will be the next logical choice. I realized today the 7727 and 7730 have an additional quad driver over the 7749. I don't remember the details but I'm thinking there was a link between the second injector driver and the additional quad driver. I'll have to dig that info out later.

Regarding injector firing and DRP's... I think your research may not have revealed all the information and in fact the only ones who have it may be GM. The relationship between DRP's and injector firing for pfi is referenced in GM service literature as "synchronous batch fire" and "quasi-synchronous batch fire" modes. Thes modes may be affected by memcal resistance, but I will say for certain that stock pfi engines with stock size injectors will use synchronous batch fire mode almost all times and will fire the injectors with every DRP. In a few cases where I've worked on engines with very large injectors, including the 2.2 engine in the Cavalier, I've had to modify calibration data to enable "quasi-synchronous batch fire" at idle and low rpm. The primary reason for this mode is to prevent the minimum injector pulse width from becoming smaller than the injector allows. If you double the calculated pulse width and open the injector 1/2 as many times you still deliver correct fuel without the injector dripping, dribbling, or completely failing to open. Some of the syty guys switched their chips to this mode years ago and ran them there all the time just to avoid the work of making the transitions between modes smooth. Maybe this trick migrated to other groups as well.

I have never delved fully into the relationships between memcal, software, pfi, and tbi modes but I probably should. I have a memcal from a 4 cyl 7727 tbi here for comparisons and a pile of good reading material. Maybe I can ring in the new year by revisiting some old GM books.

Another thought I had while organizing the barn today is that the best ecm for the job might actually be the OBDII "black box" ecm used in a gazillion S10's and 1/2 ton pickups. I realize it's a complete different direction for you guys but it's available cheap and there's supporting software available. There's a partial disassembly available at thirdgen as well. Now I know for a fact that this pcm uses a 4X crank signal which could be reproduced inside the distributor, and the software changes from sequential mode to batch fire mode when the cam signal isn't present so it can fire all injectors on every crank / DRP. There are a host of other desirable options ( E trans control, one bit open loop selectable, high octane spark tables, economy / power mode switch present, etc) so if things don't seem to be working out for the OBDI box this might be worth considering.

[JeepsAndGuns]

Ok, mabey I am just stupid like this, but if this is simply going into a boat, and waterproof is your main goal, and unless its a show quality boat, would it not be much easyer to put the ecm in a waterproof box?
Simply run down to the local surplus store and pick up a dirt cheap ammo can. They are waterproof, sturdy, easy to open, and easy to mod. Simply cut a hole for the wires, then seal them up good with some sealant. Instant cheap waterproof box for whatever ecm you want. They come in many diffrent sizes.

[EagleMark]

Ok, mabey I am just stupid like this, but if this is simply going into a boat, and waterproof is your main goal, and unless its a show quality boat, would it not be much easyer to put the ecm in a waterproof box?
Simply run down to the local surplus store and pick up a dirt cheap ammo can. They are waterproof, sturdy, easy to open, and easy to mod. Simply cut a hole for the wires, then seal them up good with some sealant. Instant cheap waterproof box for whatever ecm you want. They come in many diffrent sizes.Thats what AFI used to do...

[1project2many]

I've done a bunch of reading and some testing. From the hardware perspective, here's the cyl select data. Bear with me if it seems repetitive. I'm trying to get this all together in one place.

Pin 56 of the memcal is the cylinder select pin. On some web pages it's referred to as cal56, on others it's VRFD, and in another it's called "pin 11" because it's connected to pin 11 of another chip. The voltage on this pin determines the fuel mode selected. Voltage is controlled by resistors connected between pins 56 and 58 and between pins 56 and 53 of the memcal. 58 is +5V and 53 is gnd. There are 5 modes available:




MEM/CAL
Mode Selection




Application Mode

Input Voltage (R29/R30 ratio)

Frequency Of Injection



1. Alternating TBI

2/3 VRFD + 10%

ALT. Every REF pulse



2. Single Injector TBI

VRFD + 0% - 10%

Every REF pulse



3. 4 Cyl. PFI

2/3 VRFD +/- 10%

Every 2nd REF pulse



4. 6 Cyl. PFI

1/3 VRFD + 10%

Every 3rd REF pulse



5. 8 Cyl. PFI

GND -0% + 10%

Every 4th REF pulse






Using this information and the schematic referenced earlier in the thread I went ahead and measured some memcals I have here.




ECM

CAL

APPLICATION

RFD CHIP NO

RESISTANCE TO GND (PIN 53)

RESISTANCE TO VCC (PIN 58)

CALCULATED CYL SELECT VOLTAGE



1227165


89 VETTE TPI

16133420

7.5K

INFINITE

0


1227165


1987 VETTE TPI

16055376

7.5K

INFINITE

0


1227727


3.1 PFI ENGINE


7.5K

15K

1.7



1228706

AYZD

1992 3.3 V6


7.5K

15K

1.7



16197427


1994 4.3 CPI


7.5K

15K

1.7



1227730

ADPS

2.8 V6


7.5K

15K

1.7



1228253

AJRZ

3.8 SFI


7.5K

15K

1.7



16196396


94-95 TBI TRUCK MANUAL TRANS


15K

7.5K

3.3



1227749

AMDD

1988 QUAD 4


15K

7.5K

3.3



16197427

BJYA

1995 TBI TRUCK AUTO TRANS


15K

7.5K

3.3



1227128

ARZW

W BODY 3.1


15K

7.5K

3.3



1227730

BABM

92 BERETTA 3.1


15K

7.5K

3.3



1227749

AMDD(2)

1988 QUAD 4


15K

7.5K

3.3



16197427

BPKW

4.3 VIN W


15K

7.5K

3.3



1227165

ACKD

4 CYL TRUCK TBI


INFINITE

7.5K

5



1227807

ASDD

W BODY QUAD4


INFINITE

7.5K

5



1227165

ACWS

2.5 TBI


INFINITE

7.5K

5
















According to the info in the first table, 5V is single injector TBI, 3.3V enables 4 cyl PFI or alternating TBI, 1.7V sets 6 cyl PFI, and 0V is 8 cylinder PFI mode. Almost all the measurements make sense except the Q4 memcal set for "single point TBI" and the cpi equipped 4.3 engines set for "alternating bank TBI or 4 cylinder PFI." I still need to understand the relationship between software controlled firing and the cyl select pins. I realized last night I don't even remember my logic gate diagrams anymore. :rolleye:

[dave w]

I've done a bunch of reading and some testing. From the hardware perspective, here's the cyl select data. Bear with me if it seems repetitive. I'm trying to get this all together in one place.

Pin 56 of the memcal is the cylinder select pin. On some web pages it's referred to as cal56, on others it's VRFD, and in another it's called "pin 11" because it's connected to pin 11 of another chip. The voltage on this pin determines the fuel mode selected. Voltage is controlled by resistors connected between pins 56 and 58 and between pins 56 and 53 of the memcal. 58 is +5V and 53 is gnd. There are 5 modes available:




MEM/CAL
Mode Selection



Application Mode
Input Voltage (R29/R30 ratio)
Frequency Of Injection


1. Alternating TBI
2/3 VRFD + 10%
ALT. Every REF pulse


2. Single Injector TBI
VRFD + 0% - 10%
Every REF pulse


3. 4 Cyl. PFI
2/3 VRFD +/- 10%
Every 4th REF pulse


4. 6 Cyl. PFI
1/3 VRFD + 10%
Every 3rd REF pulse


5. 8 Cyl. PFI
GND -0% + 10%
Every 4th rd REF pulse









Using this information and the schematic referenced earlier in the thread I went ahead and measured some memcals I have here.




ECM
CAL
APPLICATION
RFD CHIP NO
RESISTANCE TO GND (PIN 53)
RESISTANCE TO VCC (PIN 58)
CALCULATED CYL SELECT VOLTAGE


1227165

89 VETTE TPI
16133420
7.5K
INFINITE



1227165

1987 VETTE TPI
16055376
7.5K
INFINITE



1227727

3.1 PFI ENGINE

7.5K
15K
1.7


1228706
AYZD
1992 3.3 V6

7.5K
15K
1.7


16197427

1994 4.3 CPI

7.5K
15K
1.7


1227730
ADPS
2.8 V6

7.5K
15K
1.7


1228253
AJRZ
3.8 SFI

7.5K
15K
1.7


16196396

94-95 TBI TRUCK MANUAL TRANS

15K
7.5K
3.3


1227749
AMDD
1988 QUAD 4

15K
7.5K
3.3


16197427
BJYA
1995 TBI TRUCK AUTO TRANS

15K
7.5K
3.3


1227128
ARZW
W BODY 3.1

15K
7.5K
3.3


1227730
BABM
92 BERETTA 3.1

15K
7.5K
3.3


1227749
AMDD(2)
1988 QUAD 4

15K
7.5K
3.3


16197427
BPKW
4.3 VIN W

15K
7.5K
3.3


1227165
ACKD
4 CYL TRUCK TBI

INFINITE
7.5K
5


1227807
ASDD
W BODY QUAD4

INFINITE
7.5K
5


1227165
ACWS
2.5 TBI

INFINITE
7.5K
5



















According to the info in the first table, 5V is single injector TBI, 3.3V enables 4 cyl PFI or alternating TBI, 1.7V sets 6 cyl PFI, and 0V is 8 cylinder PFI mode. Almost all the measurements make sense except the Q4 memcal set for "single point TBI" and the cpi equipped 4.3 engines set for "alternating bank TBI or 4 cylinder PFI." I still need to understand the relationship between software controlled firing and the cyl select pins. I realized last night I don't even remember my logic gate diagrams anymore. :rolleye:

Thank you very much for the tables and information!:thumbsup:

I seem to have found some good information with my research, but nothing near as complete or as comprehensive as the post above!

Here is what I'm thinking.
I'm thinking maybe I could use an ohm meter on the '7727 injector driver pins and see if the '7727 has two PnH drivers? Maybe I need to short the PnH pins also to establish if the '7727 has two PnH drivers.

I'm thinking maybe I could use a '427 PCM TBI Memcal installed in a '7727 ECM and read voltages for the cylinder select pin? I'm thinking maybe the '427 PCM Memcal and '7727 Memcal share the same Limp Home and Knock Sensor circuitry?

The pic below is circuit board I purchased from a TGO member (who is not currently active) for a '7730 454 MPFI project I did a few years ago. I have the skill set to make a circuit board like the one pictured, but I would need a schematic. I use PCB design software at work! The circuit board pictured does not have the knock sensor circuit, but has the limp home mode. I think it it would be cool board to make, provided the cylinder select voltages could be adjusted to provide the 5 modes listed above.

dave w

[1project2many]

I found pictures of that memcal board assy on thirdgen. I've read so many threads I'm not sure who designed it... jwscab? ryan hampl? Anyway, there are a few schematics on thirdgen as well as one archived from "iroczone.com". I also know someone who has offered to reverse engineer some V8 resistor networks and reproduce them for sale. He already produces custom resistor networks designed to work with a specific 4 cylinder engine he sells. I think a jumper based configuration would work great for cyl select. The last hurdle, the old problem of unobtanium knock filter circuiry, has been worked around with options to use the old style external knock filter or the later plug in knock filter from an OBDII pcm. But the real cool trick would be getting the document that describes the entire resistor network so you could offer memcals with the correct backup fuel for a specific configuration.

By all means try the TBI 7427 memcal in the 7727. The RFD (backup fuel chips) and the knock filter are likely to work. In the P4, one injector driver will work in either saturated or peak and hold mode. The 7727 and the 7730 do not have a second injector driver but there's no reason why "4 cylinder TBI mode" can't be used with two injectors. If you do this, use the resistor trick to limit current and do not connect the "injector jumper" that loops injector current to the sense resistor.

I'm still working on the software side of the issue and how it all plays together. It really puts a crimp in things not having the diy / gmecm archives available. I *know* there are some posts that are relavant but they just don't show up in any searches.

[Six_Shooter]

I have two of those same MEMCAL boards pictured above. IIRC it was jwscab that I bought them from.

[EagleMark]

Back home now.

I didn't think of it earlier today but the best way to get TBI and weather tight P4 together is probably $58. It will support TBI mode and a gent from the UK named Robin Handley has done a bunch of work setting it up to run 1 BAR NA with 4 cyl race cars. Combine this with the Bill Shaw injector driver change and you've got 2 TBI injectors running on a V8. Plus it's upgradeable to PFI, or to pressurized tbi if desired.

Dual ecm cals are $6B mask. Cals include ARHM6030, ARPZ6720, and ANZF9577. Some quad 4 wiring had dual crank signals sent to the ecm from the ignition module, while others did not. The 8707 / 08 may have hardware designed to work with the additional signal. The code may check for the presence of this hardware then set a mode flag if found.

The 4 cyl TBI 7727 cal I have is FML7554. It is $3E mask. I just looked and knumcyl (number of cylinders) is selectable in this cal, unlike many of the 4 cylinder calibrations. So in theory it could be adapted to an 8 cylinder engine.

Why are you looking to get a quad 4 memcal? It's very inappropriate for an 8 cyl. If it's for testing / measuring, I have several here in various state of disassembly. I'm willing to check / measure these memcals. As far as running q4 code, it will run just fine in other 4 cyl memcals and IIRC it ran on a 7730 V6 memcal with no complaints.

The problem I'm facing with making TP defs is the time involved. I'd be happy to contribute $6B, $3E, and $89 defs if I didn't have to sit here and pull all the values from one software and manually enter them in another. It looks like that's the only option at this point. Anyone have any suggestions?Well if this goes back to $3E I have a disassembled bin...

[dave w]

Here are some Schematics 1228708 Quad 4 and 1227727 4 Cylinder TBI. The scan quality is not the best; first I copied from a manual at my public library the scanned in as a .pdf.

dave w

[EagleMark]

Found this in Euorpe...

"For the first few years that I used a GMECM, to control my engine's ignition, I adapted and ran the $8Dsoftware - as it has probably the most commented, freely available hack (and it runs PFI - which is what I want#. Thehack includes the calibration data from the hacker's application #a V8 Chevrolet Corvette of the early 90's#, and isconsequently referred to by the Corvette chip name 'ANHT'. #Note: $8D was used for all GM 1990-1992 5.7 litre V8engines.# Despite the fact that the software was originally used for a V8, GM provided the ability for it to beconfigured to work for a 4 cylinder engine. A binary file, containing the whole of the original ANHT EPROM can bedownloaded by clicking here, and a disassembled 'hack', created by 'ECMGuy', can be found as a.PDF file here."

Unfortunatly the here links are now gone, but I do have the Corvette bin and diassembly set for 4 clyinder by ECMGuy...

ADDT.txt is a dissambled 2.0L 1227730

Seemed to have lost the other $3E for now?

[1project2many]

Ummm...
"ANHT for 4 cyl" is a stock turbo Sunbird cal.
0x0008 KKPGMID Program ID 0x58
0x0000 PROMID Prom ID Code 0x0D53 <-- Scan ID 3411

***Found!!!
BCC year is 1988
BCC= AUWR3607 Scan id= 3411 Part number= 16153405
Release date= 05/01/90 Engine size= 2.0 Trans Type= Manual trans
ECM/PCM: ECM #01227749
Used in cars: Pontiac
Possibly used in:
SUNBIRD SUNBIRD SE SUNBIRD GT
GRAND AM GRAND AM LE GRAND AM SE

Options:
With LT3 2.0L GAS 4 CYL MFI OHC TURBO
With MG1 MAN 5 SPD MUNCIE 76MM 3.50 1ST

[EagleMark]

See you can't believe everything you find on the internet... :homer:

[dave w]

I have not given up on this project. I am wondering, just wanting to make sure that a Quad 4 Memcal from a 1228707 can be used in the 1228708 ECM? I've interchanged Memcals from '7730 and 7727 so I've been thinking the memcals are interchangeable with the 1228707 / 1228708? The memcal BCC is ASDD

Thanks,
dave w

[1project2many]

Dave, the only correlating data I have is anecdotal posts stating the two ecm's are functionally interchangeable. There are a few posts on a Lotus forum where the guys successfully replaced one with the other because they are apparently hard to get in the UK. Another post by Ludis IIRC reports one is an underhood version of the other. All GM made memcals I've looked at have the same 28 pin Eprom, 14 pin and 16 pin backup fuel device configuration. All with a knock sensor appear to use the same connection points as well. But other than this "feel good" data, the only hard evidence we will have is when you are successful.

[dave w]

I think the course is going to change for this project. I think the option of a 4 barrel TBI similar to the one offered by Howell is something more to the liking of the original 8D / TBI idea.

dave w

[EagleMark]

Wow that looks expensive...

[1project2many]

FWIW that 4bbl TBI unit looks veeeery similar to one sold years ago by FIRST / AirSensors EFI. A small company in AZ named AutoNomics (http://www.auto-nomics.com/ashistory.html) had all the old AirSensors TBI stuff for a while. Right now it looks like the TPI parts are being sold by First Fuel Injection (http://www.firstfuelinjection.com/index.html). They may also sell the TBI parts. It's worth it to contact them. I bought a TB from AutoNomics for about $300. There are no injectors or rails and the IAC and TPS from a GM vehicle need to be added. IIRC when the company later started selling the TBs with these modifications the total price was around $500 which wasn't too bad. If the Howell price seems high this may be an option.

[dave w]

FWIW that 4bbl TBI unit looks veeeery similar to one sold years ago by FIRST / AirSensors EFI. A small company in AZ named AutoNomics (http://www.auto-nomics.com/ashistory.html) had all the old AirSensors TBI stuff for a while. Right now it looks like the TPI parts are being sold by First Fuel Injection (http://www.firstfuelinjection.com/index.html). They may also sell the TBI parts. It's worth it to contact them. I bought a TB from AutoNomics for about $300. There are no injectors or rails and the IAC and TPS from a GM vehicle need to be added. IIRC when the company later started selling the TBs with these modifications the total price was around $500 which wasn't too bad. If the Howell price seems high this may be an option.

I'll look into the information posted.

Thanks,
dave w

[dave w]

The final decision for this marine project is to use an underhood '7727 ECM with a used Edelbrock MPFI system, similar to the one pictured below.

I want to thank everyone for the information that has been posted in this tread!:wtg:

dave w

[EagleMark]

I don't beleive the distributor or fuel pump is USCG approved for marine use. Remember gas fumes will lay in bottom of boat and you must turn blower on to vent engine compartment before startup. Any experianced boater will open engine hatch and look/smell for gas then turn on blower to vent hull.

Things like altenater and starter on boats do not have any exposed spark like a car. Cars fumes leak onto ground. Just be careful you don't install something non USCG approved for marine use... blow up boat... get someone hurt... liability... just a thought...

[1project2many]

^^^^ What he said!

Distributor can be modified by adding positive ventilation ala LT1 Opti. Use small ported fitting connected to TB and second larger fitting connected to air cleaner. Suggest to customer to spend saved money on proper marine EFI fuel pump.

Someday we can swap stories and I'll tell you about the distributor I accidentally launched out of a 5.9 Chrysler. :)

[dave w]

Agreed, Safety First!:thumbsup:

Basically, I had been thinking many of the newer (mid 90's) Mercuisers were TBI V6 / V8? I figured maybe a marine 4.3 TBI distributor would need to be converted to V8, if a marine V8 TBI distributor did not exist. Looking online showed some promising marine V8 TBI distributor options.

dave w

[dave w]

I'm bringing this tread back from the past because I'm re-visiting the idea of a '7727 TBI again. This time, it's an Automotive application not a Marine application.

My question is:How do I get the Distributor Reference Pulse (DRP) to show up on an oscilloscope?

I have an old o'scope with dual channel. I have a complete test bench set up with a '7727 and TPI wiring harness. I am thinking I will set the Memcal to the correct cylinder select voltage for TBI, and use the O'scope to look at the DRP vs. Injector Pulse Width. The idea I have is to compare the TPI cylinder select DRP vs. Pulse Width against the TBI DRP vs. Pulse Width. I am thinking of using Noid Lights to load the injector drivers for the inital testing. Ultimately, I will install resistors with TBI injectors loading the injector drivers. Basically, I'd like to use $8D with TBI injectors (with resistors) firing at the correct TBI DRP. I expect an RPM limit of about 4200 RPM with TBI injectors and resitors?

All feedback / input ishttp://www.gearhead-efi.com/Fuel-Injection/images/smilies/welcome.gif

dave w

[1project2many]

The DRP (Distributor Reference Pulse) signal is the same between the TPI and TBI systems. DRP can be tapped by placing the scope input on the REF line from the distributor and ground on the engine block. What you'll want to view is the injector signal generated when cyl select is at TPI and TBI and that signal is likely to vary between firing all injectors with every DRP or firing alternating injectors with every DRP. There were a few tidbits on thirdgen and some of Ludis' schematics show the signals involved. I can try and narrow it down tonight if I have time.

[EagleMark]

Also if the correct osiliscope signal needed is not available I can look up the sample signal in my Osiliscope. Need year make model of TBI car with 1227727 your looking for and can get sample for it and TPI to compare and make sure you got it right.

[dave w]

The DRP (Distributor Reference Pulse) signal is the same between the TPI and TBI systems. DRP can be tapped by placing the scope input on the REF line from the distributor and ground on the engine block. What you'll want to view is the injector signal generated when cyl select is at TPI and TBI and that signal is likely to vary between firing all injectors with every DRP or firing alternating injectors with every DRP. There were a few tidbits on thirdgen and some of Ludis' schematics show the signals involved. I can try and narrow it down tonight if I have time.

I found a '7727 schematic online. If I'm understanding correctly, I need to connect one of the o'scope channels to distributor reference pulse (REF HI / pin B of the 4 pin distibutor connector / pin R on the module / purple wire with white stripe). The other o'scope channel to one of the injector wires (either Black with Light Green Stripe or Black with Pink Stripe). I'm thinking for the injector pulses, the positive lead of the o'scope probe will go to the injector 12VDC and the negative lead of the o'scope lead will go to either the BLK-LT Grn / BLK-PNK wire. I'm thinking that when an injector is pulsed by the ECM, the o-scope will show a positive looking square wave. My o'scope is old so I can't capture / save any signals.:mad1:

dave w

[EagleMark]

If you have or find complete schematics send them to me for our inventory.

If you know what signal looks like your fine, but if there's a doubt I can get a picture of the sample stored in my scope for you!

[1project2many]

Dave, yes to connections. Scope connection across injector or from injector - (blk/lt grn, blk/pnk) to ground will show positive pulses when injector is commanded "on." Scope connection from injector + to ground will show positive pulse when injector is "off." Might be nice to use switch or other device to Tee into both bank injector negative wires for easy switching between banks to view alternating or simultaneous firing.

Plenty of old scopes out there. Camera phone still works. :)

[dyeager535]

All feedback / input is:welcome:


My expert feedback is, please keep going with this! I'm in the process of picking up another 1227727 or two, and may end up needing/wanting to use one in a TBI app, so I'll reap the benefits of whatever you can make work. About the only support I can offer is if you have a need for a 1227727 as a loan for testing. :(

[EagleMark]

I think the coolest thing about this ECM is there are a bizillion out there in JY V6 cars and it's underhood which would make an excellent conversion ECM for off road vehicles. Now to make the V6 Memcal work a V8 TBI...

[dyeager535]

Only thing I don't like about underhood is that the Autoprom cable isn't long enough to reach for driving and tuning. I'm sure an extension can be made.

I assume it's not as simple as doubling up the 4 cylinder MEMCAL or someone would have done it already. :)

[dave w]

Now to make the V6 Memcal work a V8 TBI...

Maybe all that is needed is a '427 PCM V8 Memcal? :innocent2:

Think about it ... Why would GM re-invent the 8192 Baud Knock Filter / Limp Home Resistor Network for the TBI PCM. Makes sense to me, GM would reuse what ever they could to keep production costs down.:homer: The TBI injectors will need resitors!

The test bench is set up with both MPFI and TBI stuffs ... :thumbsup:

dave w

[EagleMark]

That would simplify things!

That also looks like the Osiliscope I used in high school... late 70's... :laugh:

I like the MPFI intake with TBI for test bench! I've got some plans started to use aluminum plate for intake, mount TBI, drill and mount MPFI injectors, hole front and rear for distributors, on legs so I can have 2 distributors cut short, mounted and run a fan belt between the 2 on electric varible speed motor! Then I can do a harness front distributor or rear distributor, TBI or MPFI all on one set up!

[1project2many]

Maybe all that is needed is a '427 PCM V8 Memcal?

I got screwed up last night. There's only one injector driver so there's no way "alternating bank" is possible. The only thing to watch is firing on every DRP or every other DRP. You should be firing every DRP with the TBI system. Have you checked both memcals for this?

TBI on PFI... talk about extra fuel for the turbocharged apps.

[dave w]

I got screwed up last night. There's only one injector driver so there's no way "alternating bank" is possible. The only thing to watch is firing on every DRP or every other DRP. You should be firing every DRP with the TBI system. Have you checked both memcals for this?

TBI on PFI... talk about extra fuel for the turbocharged apps.

The '427 PCM Memcal outputs 3.3 VDC for Cylinder Select, or I think it will. I will measure the '427 Memcal for the Cylinder Select voltage very soon. My hope is, I'll be able to "see" if every DRP is possible from a '427 Memcal.

dave w

[RobertISaar]

man, if i had internet access when this thread was first started, i could have cut 90% of the work out for everybody....

[1project2many]

So it's at the point where there's only 10% left? ;)

[RobertISaar]

not necessarily, but it does seem to be very close to a reasonable set of compromises decided on.

what i meant by the 90% was that i had 90% of everything that was already done/discussed(in this thread) either memorized or stored somewhere on my laptop from other people's work or stuff that i've discovered on my own.

10% left probably isn't that far off honestly.

[1project2many]

I'm still concerned that the code will have shortcomings. I remember how poorly the Edelbrock PFI conversions ran using TBI strategy. But the first step is determining how the memcal will cause the driver to fire.

[RobertISaar]

personally.... my opinion/route would be to grab a MEMCAL or mod one to use single-injector peak/hold TBI mode and use a mask that is intended for single-injector TBI on a 7727/similar. then just skew a few values in the calibration and you have a more or less fully functional unit. BPW at idle could be pretty low even with factory sized injectors.

or internally mod the 7727 to use the second driver. requires some delicate solder work. then you just need to use a mask that supports the second driver natively(or mod the code to use it). would allow twin injector TBI scheme.

or on the really oddball end of things... run a pair or more of low impendance injectors wired in series... kind of defeats the purpose of low-z injectors, but it would work, just need some serious tweaking of the BPW offset tables.

factory applications, the 7727 was used on the 90-91 corvette L98 with high-impedance injectors, so 8 amps per driver is safe enough for GM to release on the road in their highest echelon of car.

[dave w]

No progress made today on the bench testing, maybe I'll get time in the next few days. I have a few Old School EFi business appointments that I need to complete in the next few days. My plan is to verify I have a fully functioning TPI / MPFI configured '7727, then use the o'scope to get a "baseline" DRP / alternating injector firing. This is not my first "from scratch" EFI harness I've built, but I need to verify everything is functioning first, then experiment with a '427 Memcal. This entire system is already sold, so I need to be cautious with my experiments.:thumbsup:

dave w

[dave w]

Some progress this morning before going to work (day job). I connected the O'Scope to the injector, O'Scope ground to Battery Negative and O'Scope positive to the Ignition On connection to the injector. I have the injector harness unplugged from the injectors and a noid light on one of the injector connectors, thinking some sort of load is needed? The electric drill motor I'm using is at max speed about 2600 RPM shown in the .adx dash screen shot. I'm going to keep the speed at about 2600, hoping the dual trace measurements will be consistent.

dave

[1project2many]

The drivers will supply a current path without a load but since they're on the ground side you'd have to measure between B+ and the injector- to see what's happening. The P+H drivers will stay in P mode without any current.

[RobertISaar]

and IIRC, you'll need to give it at least 4 amps of load to get it to switch into hold mode, yes?

[dave w]

I plan to test / O'Scope with the injectors connected to the ECM wiring. I'm wanting to make sure I still have a good system to deliver to the customer, so I'm going at a slow pace.

dave w

[EagleMark]

Just to let you know I ran a set of TBI injectors dry on the test bench probably 10 minutes each time at least 100 times and they were serviced at Mr Injector as fine and have been running in kids truck tuned fine for over a month now. So I don't beleive short periods of dry testing hurts them...

[dave w]

I have a few very quick video's of the stock TPI, showing dual trace. The upper line is the injector, the lower line is DRP. I'm having trouble getting a good sync. BTW, after blowing two main battery fuses, I figured out one of the probes I was using was bad.:yikes:

dave w

http://i239.photobucket.com/albums/ff290/buildabot2002/TPI%20System/th_DSCN3703.jpg (http://s239.photobucket.com/albums/ff290/buildabot2002/TPI%20System/?action=view&current=DSCN3703.mp4)

http://i239.photobucket.com/albums/ff290/buildabot2002/TPI%20System/th_DSCN3702.jpg (http://s239.photobucket.com/albums/ff290/buildabot2002/TPI%20System/?action=view&current=DSCN3702.mp4)

http://i239.photobucket.com/albums/ff290/buildabot2002/TPI%20System/th_DSCN3701.jpg (http://s239.photobucket.com/albums/ff290/buildabot2002/TPI%20System/?action=view&current=DSCN3701.mp4)

[dave w]

I have attached a zip folder with the data capture, O'Scope Video's and a couple .xdl files. The only change I made between the O'Scope video's and .xdl files was the TBI memal. The O'Scope settings were not changed. The same PROM chip was reused. I've varied the distributor speed (ENGINE RPM) for the O'Scope videos hoping to get a good sync. I can't tell for sure, but I'm not seeing a change in the DRP's vs Injector Trigger? Maybe what I'm seeing is the TBI video is showing 2 DRP's and 2 Injector Triggers compared to the TPI video showing one 1 DRP and 1 Injector Trigger in the same time interval? The video's are Quick Time, so hopefully a frame by frame review of the video will capture the data? I'm on a very strict timeline, the Harness / ECM has to be delivered Monday!:yikes:

If anyone has a suggestions on how I can better capture the data, "NOW" is the time to speak up! I'm not likely to have another opportunity to reproduce this test setup in the near future! I will make a very focused effort to accomplish a logical suggestion!:thumbsup:

Feel free to link this post to other forums, hopefully to cast a larger "net" of ideas.

dave w

[dave w]

More Pics of the O'Scope settings.
Channel 1 is the injector pulse.
Channel 2 is the DRP.
dave w

[EagleMark]

Dave, I'm swamped with work and have not been able to keep up here and probably won't this week. If you are referring to needing some help from me give me a call and I'll get the scope out with shots of whatever your looking for so you can verify your findings.

[dave w]

Dave, I'm swamped with work and have not been able to keep up here and probably won't this week. If you are referring to needing some help from me give me a call and I'll get the scope out with shots of whatever your looking for so you can verify your findings.

Mark, I'm looking for alternative ideas for data collecting while I have the test bench set up. The video's / .xdl's should serve as a library to reference at a later date. If you happen to have time in the future to review the data, that would be welcomed and greatly appreciated!:jfj:

dave w

[1project2many]

Dave,

Capture both injector outputs with TBI memcal installed. Forget DRP as we know synchronous pulses are tied to it. Do same with 7727/7730 memcal.

[dave w]

Dave,

Capture both injector outputs with TBI memcal installed. Forget DRP as we know synchronous pulses are tied to it. Do same with 7727/7730 memcal.

Excellent idea, that is exactly the kind of suggestion I'm looking for!:wtg:

dave w

[dave w]

Dave,

Capture both injector outputs with TBI memcal installed. Forget DRP as we know synchronous pulses are tied to it. Do same with 7727/7730 memcal.

As requested. I will do more video later today, to include the TPI chip.

dave w

[1project2many]

Clearly alternating output pulses. After $8D and TPI chip try $8D in TBI memcal.

[RobertISaar]

Clearly alternating output pulses. After $8D and TPI chip try $8D in TBI memcal.

and if i had to guess, i'd say this will be the winner.

[dave w]

Clearly alternating output pulses. After $8D and TPI chip try $8D in TBI memcal.

The "TBI_Chip Injectors-DSCN3746.zip" video file is $8D in the TBI Memcal.

dave w

[1project2many]

and if i had to guess, i'd say this will be the winner.

The "TBI_Chip Injectors-DSCN3746.zip" video file is $8D in the TBI Memcal.

dave w

Yep. You have a winner. No cyl select errors? If not I'd start putting a cal together and planning a test run. Prolly scope the TPI memcal + $8D just to see what happens but the tbi memcal is the path I'd follow first.

[dave w]

Yep. You have a winner. No cyl select errors?

Not a winner with the TBI Memcal! I have an error code 41 (Cylinder Select).:mad1: I'm sure the $8D definition file is the reason for the code 41. I'm sure there a path forward, definition file, to get the '7727 / ' 7730 to run TBI with a '16197427 TBI Memcal. I also had code 33 (MAP) on both TBI and TPI Memcals.

For the library, see files below:

dave w

[Six_Shooter]

Did you try setting the cyl select in the bin to "TBI" with the TBI MEMCAL?

[dave w]

I had $8D in the chip with the TBI memcal. I am wondering, is there a TBI cylinder select with 8D?

dave w

[dave w]

Did you try setting the cyl select in the bin to "TBI" with the TBI MEMCAL?

Maybe if I set the number of cylinders to V6 "192", I'll be OK?

dave w

[Six_Shooter]

From what I understand, the same cyl select values are used for all (P4) OBD1 ECMs, so you could look at other code to find the hex value for TBI to use it. That was my plan when I thought about using $59 for TBI, I just haven't got around to testing it, and up until recently didn't have an O-scope to verify results with.

[RobertISaar]

^ correct. i think $18 is correct for dual injector TBI? been a while since i've looked at something like that though.

[dave w]

^ correct. i think $18 is correct for dual injector TBI? been a while since i've looked at something like that though.

I'm not quite understanding $18, is that a definition file? I have to deliver this system later today, so I can only get one more test done before it's gone from my test bench! If anyone has a specific test, or maybe a .xdf, .bin, .adx they would like data for I'm very willing to give the test a try.:welcome:

I'd like to thank everyone for the input I've received on this test!:thumbsup:
dave w

[RobertISaar]

i have this in the DTC portion of my A1 XDF. and the comments i entered into the notes box.

$18=TBI
$10=4 CYL PFI
$08=6 CYL PFI
$00=8 CYL PFI

setting that to match your MEMCAL should remove the DTC41 from being set. i have the item listed as "Fuel Delivery Mode (KK41MODE)"

[1project2many]

Cylinder select is also known as "number of cylinders." Robert's suggestion to try changing that to TBI value of $18 is next step.

[RobertISaar]

not 100% certain of how 8D works, but in A1 and it's successors and predecessors, there is the "fueling mode select" and "cylinder count" as seperate items.

cylinder count is simply a multiplier for RPM/airflow/etc calculations, it's the fueling mode select that's used for the DTC41 info.

[dave w]

not 100% certain of how 8D works, but in A1 and it's successors and predecessors, there is the "fueling mode select" and "cylinder count" as seperate items.

cylinder count is simply a multiplier for RPM/airflow/etc calculations, it's the fueling mode select that's used for the DTC41 info.

Ok, I have loaded $A1 .xdf/.bin/.adx into TunerPro RT. I'm not going to have much time to modify the ARUT.bin I have loaded. I'm on a learning curve with $A1! My thinking is, I should be able to flash the ARUT.bin with the $18 change and capture a couple more O'scope videos and .xdl file. Any other changes I should do to the ARUT.bin before I flash a chip and do one last bench test?

I also wonder, is there a make / model / year I can program into my AutoXray 7000 to scan $A1 with after making the $18 change?

Thanks,
dave w

[RobertISaar]

if you have the "KK41MODE" value (found at 04F1, assuming it's not in the XDF) set to $18, then no, not really? it should be enough to test anyways.

what's with the sudden change to A1? the same value should work in 8D.

and ARUT is a 91 J-body (cavalier) with a 3.1, should be easy enough to find an application for.

[1project2many]

cylinder count is simply a multiplier for RPM/airflow/etc calculations, it's the fueling mode select that's used for the DTC41 info.
Nothing in the old hacs is listed as a fueling mode select or anything similar. However, when looking at the code for "cyl select" error in $8D same values are listed in comments as what you've listed for the fuel mode values. Years of confusion over a simple misnaming? It's not like it hasn't happened before.

Dave, check the value at $8293 in $8D. I suspect it's currently $00. Change it to $18 and try in the TBI memcal.

[dave w]

if you have the "KK41MODE" value (found at 04F1, assuming it's not in the XDF) set to $18, then no, not really? it should be enough to test anyways.

what's with the sudden change to A1? the same value should work in 8D.

and ARUT is a 91 J-body (cavalier) with a 3.1, should be easy enough to find an application for.

The switch to A1 is for two reason, one is to capture data that could be useful in the future, and I have not been able to figure out how to change $18 in 8D. I'll look at Hex address 04F1 and post back what I find.

Thanks for the help,
dave w

[dave w]

oneproject2many, I can't find hex address 8293 in $8D.
I can try setting the $8D Cylinder Number to 18 and see what happens?



RobertISarr, I think I have correctly found hex 04F1 in $8D which I think is set to value 0C?
I can try setting, what I think is 04F1 from 0C to 18 and see what happens?

dave w

[RobertISaar]

you're referencing 04F0(line starts with 0), 04F1 is next to it and is currently $18 already.

[dave w]

you're referencing 04F0(line starts with 0), 04F1 is next to it and is currently $18 already.

Thank you for clarifying the Hex reference!

dave w

[EagleMark]

Humans start counting at 1. Computers start counting at 0. So who's the human who made computers count wrong? :laugh:

[dave w]

Humans start counting at 1. Computers start counting at 0. So who's the human who made computers count wrong? :laugh:

That reminds me of a sign I saw once ... there are 10 kinds of people ... those who understand binary and those who don't. :laugh:

dave w

[1project2many]

Sorry, Dave. Too many years working with this stuff and too little time to make complete posts caused confusion. The addresses in the $8D hac are the addresses at which the calibration and program reside in the ecm. They begin at $8000 but the hex editor addressing (unless you change it) begins at $0000. So in order to view or change $8293 from the hac you need to look at $0293 in the hex editor.


I grabbed a sample cal (AWFU) from the $8D reference thread. The value there is $00. I can change it with hex editor and attach but you'll probably want to try it with the cal you've been using.


That reminds me of a sign I saw once ... there are 10 kinds of people ... those who understand binary and those who don't.

I love that joke. I think it was six_shooter's sig in a forum I was on.

[dave w]

Sorry, Dave. Too many years working with this stuff and too little time to make complete posts caused confusion. The addresses in the $8D hac are the addresses at which the calibration and program reside in the ecm. They begin at $8000 but the hex editor addressing (unless you change it) begins at $0000. So in order to view or change $8293 from the hac you need to look at $0293 in the hex editor.


I grabbed a sample cal (AWFU) from the $8D reference thread. The value there is $00. I can change it with hex editor and attach but you'll probably want to try it with the cal you've been using.



I love that joke. I think it was six_shooter's sig in a forum I was on.

I'll try changing $0293 and post back what I find.

dave w

[dave w]

I'll try changing $0293 and post back what I find.

dave w

Here is the screen shot of what I've done to $0293.

dave w

[EagleMark]

That would be correct.

[Six_Shooter]

I love that joke. I think it was six_shooter's sig in a forum I was on.

Yeah, I think I used that on V6Z24.com for a while.

[dave w]

I've completed the bench testing, the wire harness and ECM have been delivered.

I have a some interesting video's using $A1 with a TBI Memcal and $A1 with a V6 Memcal.

The testing I was able to complete late this afternoon.
Test 1: TBI Memcal $8D Hex address 0293 = 18 resulted with Error Code 41.:mad1:

Test 2: TBI Memcal $8D Hex address 0293 = 00 with Number of Cylinder = 18 resulted with Error Code 41.:mad1:

Test 3: TBI Memcal $A1 Cylinder Number = 18 (TBI) resulted with Error Code 41.:mad1:

Test 4: V6 Memcal (BCC ASHH) $A1 Cylinder Number = 18 (TBI) Did Not have ERROR Codes.:jfj:

Note: $A1 .adx file did not show a data stream, most likely because of the wiring differences between a V8 TPI and V6 PFI?

At this moment, I'm not sure what a good path forward could / should be. I like a combination that does not set error code 41.

Thanks again for everyone's assistance!
dave w

[1project2many]

Reading the code, the value at $0293 is compared to bits 3 and 4 of a value obtained from $0032, which is a value based on a memcal read. With only bits 3 and 4 compared, this confirms the only values possible in $0293 are those previously listed; $00, $08, $10, and $18. There is a bit of additional code after this comparison but really, the only reason code 41 should set is because $0293 doesn't match those two bits in $0032. $0032 is transmitted on the ALDL stream as FMD Word 2 so you can probably view it in the ALDL and get a look at what the relevant bits are set to.

Dave, dumb question but is there any chance the code was left over from a previous test?

[dave w]

Reading the code, the value at $0293 is compared to bits 3 and 4 of a value obtained from $0032, which is a value based on a memcal read. With only bits 3 and 4 compared, this confirms the only values possible in $0293 are those previously listed; $00, $08, $10, and $18. There is a bit of additional code after this comparison but really, the only reason code 41 should set is because $0293 doesn't match those two bits in $0032. $0032 is transmitted on the ALDL stream as FMD Word 2 so you can probably view it in the ALDL and get a look at what the relevant bits are set to.

Dave, dumb question but is there any chance the code was left over from a previous test?

I used a 27SF512 chip for the testing, which was erased and flashed for each test. I used the same TBI Memcal with a Moates.net memory adapter board. I removed power from the ECM after each test for the chip swap. I verified no codes before each test.

Maybe in the near future we can regroup (build another harness) and test again?

dave w

[1project2many]

Love to do more testing. If I had time and space I'd set up my ecm bench and drive a few injectors here.

Any chance you recorded any $8D ALDL data? Maybe we could extract $0032 to see what was reported?

[dave w]

Love to do more testing. If I had time and space I'd set up my ecm bench and drive a few injectors here.

Any chance you recorded any $8D ALDL data? Maybe we could extract $0032 to see what was reported?

I think these files will have the information you are requesting?

dave w

[JeepsAndGuns]

I don't have a '7727 / '7730 harness for testing. I'll take you up on your offer to do some testing, it's greatly appreciated!

I ran out of time to do any further testing for a TBI '7727.

I used a memory adapter board with the '427 PCM TBI Memcal using a 27SF512 chip with the $8D .bin file. Resistors are not needed for testing when using Noid Lights or 4 TPI injectors on each bank. It should be Ok to not have injectors plugged in. The first test I'd like to have help with would be to set the $8D definition .bin file for cylinder hex value to the $18 Mark posted and see if the cylinder select error occurs? With my test, I got a cylinder select error with 0x293 set to hex $18.

Thanks,
dave w

Ok, to keep the thread from getting too mixed up, I will put this into this thread.

I hooked up a 7727, took a AUJP bin, and changed the 0x293 value to 18 for tbi. I then installed a stock un touched 7427 V8 tbi memcal and gave it a go. (using a moates G1 adapter) I too got the cylinder select error. I then tried my mpfi modded tbi memcal just for the hell of it, and got the cylinder select error too.
So it appears a one of a few things might be happeneing.
1. The 7427 tbi memcal is not giving the bin what it wants to see when its set to tbi (0x293 set to 18)
2. $8D can not run tbi, but someone added in the comments that it could if 18 was entered into 0x293
3. $8D can run tbi, but 18 is not the correct value
I'm thinking maybe the memcal is not giving the ecm what it wants to see.
Does anyone have one of those 7727 tbi memcals? Maybe measure what its has for resistance on the specific (unknown to me) pins and see if we could change a 7427 tbi memcal to the same resistance?

Or if you have any other things yould would like me to try, either make a bin and post it up/send to me, or tell me what to change and try.

[dave w]

I've done a bunch of reading and some testing. From the hardware perspective, here's the cyl select data. Bear with me if it seems repetitive. I'm trying to get this all together in one place.

Pin 56 of the memcal is the cylinder select pin. On some web pages it's referred to as cal56, on others it's VRFD, and in another it's called "pin 11" because it's connected to pin 11 of another chip. The voltage on this pin determines the fuel mode selected. Voltage is controlled by resistors connected between pins 56 and 58 and between pins 56 and 53 of the memcal. 58 is +5V and 53 is gnd. There are 5 modes available:




MEM/CAL
Mode Selection



Application Mode
Input Voltage (R29/R30 ratio)
Frequency Of Injection


1. Alternating TBI
2/3 VRFD + 10%
ALT. Every REF pulse


2. Single Injector TBI
VRFD + 0% - 10%
Every REF pulse


3. 4 Cyl. PFI
2/3 VRFD +/- 10%
Every 2nd REF pulse


4. 6 Cyl. PFI
1/3 VRFD + 10%
Every 3rd REF pulse


5. 8 Cyl. PFI
GND -0% + 10%
Every 4th REF pulse






Using this information and the schematic referenced earlier in the thread I went ahead and measured some memcals I have here.




ECM
CAL
APPLICATION
RFD CHIP NO
RESISTANCE TO GND (PIN 53)
RESISTANCE TO VCC (PIN 58)
CALCULATED CYL SELECT VOLTAGE


1227165

89 VETTE TPI
16133420
7.5K
INFINITE
0


1227165

1987 VETTE TPI
16055376
7.5K
INFINITE
0


1227727

3.1 PFI ENGINE

7.5K
15K
1.7


1228706
AYZD
1992 3.3 V6

7.5K
15K
1.7


16197427

1994 4.3 CPI

7.5K
15K
1.7


1227730
ADPS
2.8 V6

7.5K
15K
1.7


1228253
AJRZ
3.8 SFI

7.5K
15K
1.7


16196396

94-95 TBI TRUCK MANUAL TRANS

15K
7.5K
3.3


1227749
AMDD
1988 QUAD 4

15K
7.5K
3.3


16197427
BJYA
1995 TBI TRUCK AUTO TRANS

15K
7.5K
3.3


1227128
ARZW
W BODY 3.1

15K
7.5K
3.3


1227730
BABM
92 BERETTA 3.1

15K
7.5K
3.3


1227749
AMDD(2)
1988 QUAD 4

15K
7.5K
3.3


16197427
BPKW
4.3 VIN W

15K
7.5K
3.3


1227165
ACKD
4 CYL TRUCK TBI

INFINITE
7.5K
5


1227807
ASDD
W BODY QUAD4

INFINITE
7.5K
5


1227165
ACWS
2.5 TBI

INFINITE
7.5K
5
















According to the info in the first table, 5V is single injector TBI, 3.3V enables 4 cyl PFI or alternating TBI, 1.7V sets 6 cyl PFI, and 0V is 8 cylinder PFI mode. Almost all the measurements make sense except the Q4 memcal set for "single point TBI" and the cpi equipped 4.3 engines set for "alternating bank TBI or 4 cylinder PFI." I still need to understand the relationship between software controlled firing and the cyl select pins. I realized last night I don't even remember my logic gate diagrams anymore. :rolleye:

JeepsAndGuns,
Thanks for testing the '7727 with a '427 Memcal.

I'm thinking the TBI '7727 cylinder select is looking for 5 volts.

I'm thinking the '427 Memcal will need to be modified so the resistance to ground on pin 53 is infinite, not 15K. I'm thinking the infinite resistance on pin 53 of a '427 Memcal will send the 5 volts the '7727 is looking for when 0x293 is set to $18.

I have a spare, '427 Memcal, but I think the Limp Home is faulty. When this Memcal was in service, the TBI injectors were dumping lots of fuel for no apparent reason. I could snail mail you the spare Memcal, once I figure out how to modify pin 53 for infinite resistance.

dave w

[JeepsAndGuns]

I have a few spare V8 7427 tbi memcals that are all workig. It would be quicker and cheaper just to tell/show me exactly what pins to connect and I will add a jumper wire to one and give it another test. I dont think a faulty memcal would be good to test this with.
Just snap me a picture and draw arrows pointing to the exact pins that need connected together and I will do it.

[dave w]

I have a few spare V8 7427 tbi memcals that are all workig. It would be quicker and cheaper just to tell/show me exactly what pins to connect and I will add a jumper wire to one and give it another test. I dont think a faulty memcal would be good to test this with.
Just snap me a picture and draw arrows pointing to the exact pins that need connected together and I will do it.

I'm working on figuring out how to get pin 53 to 5.0 VDC. The pics below are from some of my research over at Thridgen.org. I think the challenging part is 2/3 VRFD (3.3 VDC) for alternating TBI, and have 3.3 VDC to the cylinder select without an error.:mad1:

Post #39 at ThridGen.org http://www.thirdgen.org/techboard/diy-prom/643208-question-jwscab-netres-resistor.html

dave w

[dave w]

I have a few spare V8 7427 tbi memcals that are all workig. It would be quicker and cheaper just to tell/show me exactly what pins to connect and I will add a jumper wire to one and give it another test. I dont think a faulty memcal would be good to test this with.
Just snap me a picture and draw arrows pointing to the exact pins that need connected together and I will do it.

The pic below is another pic from my research over at Thridgen.org.

dave w

[JeepsAndGuns]

All that my friend, is over my head....lol
When your figure out what pins need connected, let me know and we will give it a go. :thumbsup:

[yelruhde]

I managed to run a tbi set up on a 7727 as a v6 mpfi using 8D and a vette tune by changing the values at both 0293 and 04F1 to 0C. It runs well enough to get driven everyday and does not throw error 41. Maybe changing both values to 18 with a tbi memcal will work.

[1project2many]

Dave,

Pin 53 is ground. That pin should remain at 0V. The voltage needs to be 5V on pin 56. Pin 56 of the memcal is directly connected to 8 of the RFID. Break this connection and you are free to solder resistors equal to GM's values between the remaining two pins. If you remove the leg at pin 8 then connect a 7.5K resistor between 8 and 10 you will provide 5V to the ecm at pin 56 which should enable "4 cylinder TBI mode." But now you may get a cylinder select code due to calibration set for 8 cyl and fuel mode set for 4 cyls. The easy answer to that would be to disable the error code. A more complicated answer would be to alter the code to allow this mismatch.

The 2/3 Vref +10% and -10% requirement is a fairly close tolerance value. Most resistors are 10% tolerance so you'll need 1% or 2% resistors, preferably temperature stable versions so the engine doesn't switch fueling modes in cold or hot weather. But with infinite resistance between GND and pin 56 you don't need to worry so much about the resistance to pin 58.

yelruhde, what was the memcal originally from? Was this on a six cylinder engine? Are you sure you changed 04F1 also? Why did you choose $0C?

Thanks.

[dave w]

Dave,

Pin 53 is ground. That pin should remain at 0V. The voltage needs to be 5V on pin 56. Pin 56 of the memcal is directly connected to 8 of the RFID. Break this connection and you are free to solder resistors equal to GM's values between the remaining two pins. If you remove the leg at pin 8 then connect a 7.5K resistor between 8 and 10 you will provide 5V to the ecm at pin 56 which should enable "4 cylinder TBI mode." But now you may get a cylinder select code due to calibration set for 8 cyl and fuel mode set for 4 cyls. The easy answer to that would be to disable the error code. A more complicated answer would be to alter the code to allow this mismatch.

The 2/3 Vref +10% and -10% requirement is a fairly close tolerance value. Most resistors are 10% tolerance so you'll need 1% or 2% resistors, preferably temperature stable versions so the engine doesn't switch fueling modes in cold or hot weather. But with infinite resistance between GND and pin 56 you don't need to worry so much about the resistance to pin 58.

1project2many,
I've been thinking about just disabling the cylinder select error code. I've been thinking, even with the cylinder select error code active the O'Scope showed alternating injector firing. What I have not been able to understand, what does the ECM do to fueling or spark when cylinder select error code is active. I've been thinking the cylinder select error was set up to detect / prevent a mismatch of Memcals on the assembly line? I've also been wondering, what error indication is given to the SES from the ECM when "Limp Home" is active. I'm thinking there is no indication "Limp Home" is active in the data stream? The only time I've ever encountered a cylinder select error was on my test bench, which if cylinder select causes "Limp Home" I did not see it. I'm thinking the cylinder select error is an "inert" error message and does not cause changes to the fuel or spark functions of the ECM? I'm thinking a cylinder select error does not set "Limp Home"?

dave w

[JeepsAndGuns]

Ya know, I too have wondered exactly what causes "limp home" Vs just a trouble code? I know you can get trouble codes and not go into limp home mode. So you make a good point, is there any way to know, (when using a test bench) if the ecm is in limp home mode?
When its running a engine you could probably tell. I know in my tuning adventures, there has been a couple times I have either didnt get the chip installed correctly, or forgot to install it completely :innocent2::homer: and when I started the engine the iac pegged wide open and I could not get aldl connection. Not to mention the spas attack check engine light.
When running the 7727 on my test bench, I have noticed, when I changed it to tbi and got the cylinder select error, all the data appeaered to be the same as it was without the error. Iac counts, injector bpw, etc..

[RobertISaar]

from what i've seen on my bench(no scope), even with no MEMCAL attached(just a PROM) and setting a LOT of error codes, it still seemed to fire based on the setting in the BIN. i'm pretty certain it's only used in limp-home mode for fueling, since limp-home spark is done via the EST module without bypass voltage applied.

EDIT: easiest way to determine limp-home: ALDL will not function, since the PROM is entirely bypassed.

[JeepsAndGuns]

from what i've seen on my bench(no scope), even with no MEMCAL attached(just a PROM) and setting a LOT of error codes, it still seemed to fire based on the setting in the BIN. i'm pretty certain it's only used in limp-home mode for fueling, since limp-home spark is done via the EST module without bypass voltage applied.

EDIT: easiest way to determine limp-home: ALDL will not function, since the PROM is entirely bypassed.

Interesting, I did not know it would function at all without a memcal (prom only)

I also assume that the check engine light could possiably be a way to tell you if its in limp home mode? Only time I have seen it do the super fast flicker spas attack is when it was in limp home mode. I would assume if it does its normal slow once flash, its a reasonable bet its working and not in limp home mode?

[RobertISaar]

well, if it does the expected blink at key-on, that means the PROM is being read and that the light is being commanded on off on by the program, so it's a safe bet that if the light acts normally, at the very least, the ECM started in a normal mode.

for those of us with factory electronic fans, usually fan 1 will be stuck on at all times during limp-home mode. and if you have a speedometer that is ECM driven, that will fail to work as well.

[1project2many]

Limp mode is just that, a way to limp the vehicle to a safe place. The check engine light illuminates and stays on because the code to turn it off isn't running. The injectors fire once per reference pulse as the REF in signal is routed to the injector driver(s). Ignition timing is limited to whatever advance is built into the module. Electric cooling fan (if equipped) is energized but usually no other outputs work.

The super fast flicker happens when the code or chip itself is messed up. Yes, the ecm is in limp mode but the flicker is due to the code looping through the shutoff steps over and over, quickly. When I built my ecm bench I used LED's to show me when the REF and EST lines were active. With those in place it's easy to tell if REF is working and EST is not, which is a good indication the ecm may be in limp mode.

The real name for the limp chips is "Redundant Fuel Device" which means that what it does is already done by something else, namely the code in the eprom. It's redundant. I have custom memcals here which have no limp chips or resistors. The ecm will function just fine but if the code or the eprom fails there's no backup and the engine will die.

Funny story... talked to a friend / tech at a Ford dealership who had a TPI F car from the '90s in his bay. He was stumped over a strange problem. Car would not crank. He could jumper the starter relay and make it crank but no start / due to no fuel. He thought it might be the chip and grabbed another memcal that he had in his toolbox. The car would start and run but really badly. So he'd start the car on the bad chip then pull it really quickly while the car was running and replace it with the original which wouldn't crank and wouldn't start. As long as the car kept running during the swap he was fine, could run all day. But first time he shut off the engine the problem reappeared. I told him to fix the wire to the VATS ignition cylinder and put the original chip in. I also told him that he'd found the simplest method I'd heard of to bypass VATS. He was starting the car on a memcal from a 165 car, so it was starting on the limp module. Then he'd change it really quick before the engine could stall, putting the correct memcal back in. Apparently GM's code was written so that once the car was running, a failure to recieve a good VATS signal didn't kill the engine.

[RobertISaar]

wow..... i actually never thought of even attempting that.

and yes, the PCM only looks for the VATS signal for a short amount of time after it powers up due to the ignition switch. usually, there is a timeout constant to play with in the DTCs section for the VATS diagnostic.

[1project2many]

Limp mode is just that, a way to limp the vehicle to a safe place. The check engine light illuminates and stays on because the code to turn it off isn't running. The injectors fire once per reference pulse as the REF in signal is routed to the injector driver(s). Ignition timing is limited to whatever advance is built into the module. Electric cooling fan (if equipped) is energized but usually no other outputs work.

The super fast flicker happens when the code is messed up. Yes, the ecm is in limp mode but the flicker is due to the code looping through the shutoff steps over and over, quickly. When I built my ecm bench I used LED's to show me when the REF and EST lines were active. With those in place it's easy to tell if REF is working and EST is not, which is a good indication the ecm may be in limp mode.

The real name for the limp chips is "Redundant Fuel Device" which means that what it does is already done by something else, namely the code in the eprom. It's redundant. I have custom memcals here which have no limp chips or resistors. The ecm will function just fine but if the code or the eprom fails there's no backup and the engine will die.

It appears that code 41 is just a code. There doesn't appear to be any change in code operation. In the days of the C3 the RFD was a separate, replaceable chip which had to be moved to a new ecm and I'll bet that one was forgotten more than once.

Why do I keep thinking you'll see alternating injector pulses from a single driver ecm??

[dave w]

All that my friend, is over my head....lol
When your figure out what pins need connected, let me know and we will give it a go. :thumbsup:

JeepsAndGuns,
Now that the topic of Redundant Fuel Device (aka limp home) has been discussed, I think disabling the code 41 cylinder select error is a good option to try. If you have noid lights to install into the injector connectors, you can possibly see the alternating injector pulses?

Another idea I have, based on information I found at ChevyThunder: http://www.chevythunder.com/code_41.htm

Code 41, Cylinder select error
Due to the same ecm being used for different engines, it is important that the proper prom is installed for the particular engine, a incorrect prom, not installed properly, or faulty. Another cause is the pins of the harness are not properly connected to the appropriate pins on the ecm, and/or the grounds could be open. For V8 applications, ecm pin D3 is grounded.


B12 Use 4 cylinder input
D3 Use 6 cylinder input


4 cylinder Ground
4 cylinder Open


6 cylinder Open
6 cylinder Open


8 cylinder Open
8 cylinder Ground



The chart above shows the appropriate pins on the ecm that need to be grounded for proper engine family.

So I'm wondering if the '7727 needs a different ground for TBI mode $0293 set to $18 to fix the code 41? I don't know what ECM the above chart is for, maybe the '7730? I'm wondering if a different ground is used for the '7727 TBI mode, will the '427 Memcal still provide alternating injector pulses? Wish I had a '7727 on the test bench.

dave w

[RobertISaar]

what ECM uses external grounds for cylinder select??? the 7727 and 7730 certainly do not.

you won't get alternating injector pulses out of a 7727 anyways, there is only one injector driver(and the code isn't setup for it), unless you opened it up and added in the pieces necessary to do so.

[dave w]

what ECM uses external grounds for cylinder select??? the 7727 and 7730 certainly do not.

you won't get alternating injector pulses out of a 7727 anyways, there is only one injector driver(and the code isn't setup for it), unless you opened it up and added in the pieces necessary to do so.

I was thinking, because of the information on ChevyThunder, the 7727 uses a different ground pin for the 4 cylinder TBI operation vs. the 8 cylinder TPI operation?

I agree, only one injector driver in the '7727. I was thinking one injector driver being switched between the left and right banks on every other DRP?

dave w

[RobertISaar]

the 7727 has no such operation. the only thing that might be different externally in terms of injector related stuff would be if running saturated vs peak/hold mode. you can view the electrical difference there by looking at the one 7727 TBI application from the factory and comparing it to any 6 or 8 cylinder PFI application. i think the only difference is that a wire comes out of the ECM from one pin, and back into another pin, which goes through a current sensing resistor, then out to the injector, rather than just through the injector.

to switch between injectors on every other reference pulse, external hardware would be needed.... and with that setup, going beyond a 50% injector duty cycle would be impossible, since half of the time would need to be spent on each injector.

[dave w]

the 7727 has no such operation. the only thing that might be different externally in terms of injector related stuff would be if running saturated vs peak/hold mode. you can view the electrical difference there by looking at the one 7727 TBI application from the factory and comparing it to any 6 or 8 cylinder PFI application. i think the only difference is that a wire comes out of the ECM from one pin, and back into another pin, which goes through a current sensing resistor, then out to the injector, rather than just through the injector.

to switch between injectors on every other reference pulse, external hardware would be needed.... and with that setup, going beyond a 50% injector duty cycle would be impossible, since half of the time would need to be spent on each injector.

Thanks for answering my questions.

I mentioned the 1228708 earlier in this tread, because the 1228708 has two injector drivers. The Quad 4 is wired similar to the TBI 1227727, except has two sense resistor paths (one for each injector driver).

dave w

[RobertISaar]

the 8708 IS heavily based on the 7727(and to a smaller extent, the 7749), to the point of where almost every pin is actually used identically.

i made this spreadsheet a few months ago.... comparing the 90-92 2.5TBI and the 90-91 2.3Q4 stuff may be interesting....

the Q4 fired the injectors in pairs (1/4 and 2/3), essentially identically to the TBI system. the Q4 ICM creates a 2X signal for the ECM, which it uses for the typical engine speed and position calculations. it also has a 1X(or possibly 1/2X) signal, that it uses to determine which cylinder pair to fire, essentially semi-SFI. or at least that's how the factory documentation describes it, if it's real, i have no idea.

anyways, based on GM information(which may or may not be accurate), the idea is that a pulse will happen, time until the next pulse happens is recorded, now the ECM knows engine speed and position. so 2 pulses have happened, now the injectors can start firing.

pulse #
0 waiting for pulse
1 start timer
2 end timer, prep for injection/spark, start new timer
3 end timer, inject(either 1/4 or 2/3 depending on 1X signal), start timer
4 end timer, start timer
5 end timer, inject(other cylinder pair), start timer
6 end timer, start timer
7 end timer, inject(cylinder pair injected at pulse 3), start timer



and it keeps on going.... it actually seems to operate similar or identically to dual-injector TBI, does it not? or does dual-injector TBI switch between which injector is fired with every ref pulse?

[dave w]

it actually seems to operate similar or identically to dual-injector TBI, does it not? or does dual-injector TBI switch between which injector is fired with every ref pulse?

I have not put a dual TBI on a two channel O'Scope to watch the injector firing. I'm thinking '8708 is operating like dual TBI with alternating pulses.

dave w

[JeepsAndGuns]

So why is it so important for the injectors to pulse alternately? Can a tbi not operate with just both of them pulseing at the same time?

[RobertISaar]

i imagine it could be done, but i think the main reason for it is due to injector location.... in essence, the engine rotates 2 times(one full 4 stroke cycle), 8 intake events happen(with a V8), 4 on each side, so each injector is fired 4 times, alternately, so that there aren't overly fuel-laden and overly air-laden situations?

IDK, i'm a port FI guy, not single-point, so i could be wrong.

[1project2many]

the Q4 ICM creates a 2X signal for the ECM, which it uses for the typical engine speed and position calculations. it also has a 1X(or possibly 1/2X) signal, that it uses to determine which cylinder pair to fire, essentially semi-SFI. or at least that's how the factory documentation describes it, if it's real, i have no idea.

8708 is to 7727 as 8707 is to 7730. Details of Q4 firing strategy are incomplete but clues are accumulating. 1st year of Q4 had mystery "dual ecm" calibration which has escaped some GM documentation. This cal was used in 8707 and 7749. When 7749 was installed in Q4 car, extra "2X" signal was not present. Measurements previously reported indicated memcal from 7749 equipped car operated in "four cylinder tbi mode." There is some code in this memcal which was believed to be able to detect additional 2X hardware. But maybe GM engineers hacked the memcal so it would fire all injectors at once. Wouldn't be the first time they used a simpler than guessed solution to a problem. Trick might be to see if code 41 is enabled or even present in this cal.

Wiring and grounds referenced on Chevy Thunder are related to physically driving the injectors. Peak and hold injectors such as most TBI require the driver sense current flow to switch from "peak" to "hold" mode. GM uses external loopback wiring to accomplish this. When different grounds are called out it's not uncommon for them to turn out to be connected internally. "Cylinder select" is not related to this.

I've seen people set up tbi with both injectors driven simultaneously and it will work. So it's a good question, "why should they alternate?" With both injectors firing on every injector pulse you've got to cut the injector PW in half to deliver the same amount of fuel. At low rpm and idle this can lead to injector instability if the commanded minimum PW is smaller than the injector is capable of opening. Large displacement or higher hp engines requiring larger injectors are more likely to encounter this. I had to deal with it when I put four TBI injectors into a PFI manifold. I had to use "semi-synchronous batch fire" mode which could be software enabled to fire the injectors 1/2 as often but with double the commanded PW.

I think there's some real investigation to be done into the relationship between hardware and software injector mode selection. I was using a Q4 "dual calibration" memcal in the Cavalier 2.2 yet $58 is set for "four cylinder pfi" firing and is able to switch to the special firing mode I mentioned above. I sent another Q4 memcal set up for DIS to a guy using a 7749 on a turbo Geo with $58. $58 has "tbi mode" selection bits and constants and I believe there was someone running the 7749 in tbi mode successfully with a PFI Sunbird memcal. I realize the main goal is to make the underhood TBI ecm but this really highlights an area where there isn't much understanding in these ecm's.

[RobertISaar]

this, along with some of the limp-home stuff, i think are the last real mysteries to some of the popular ECMs.

i need a scope. :D i mean, i can watch the 3X pulses and the resulting EST and injector outputs at low RPM on my bench via LEDs, but it would be nice to see it at speeds faster than my eyes can deal with.

[1project2many]

Well, old lab scopes can be had for short money on Ebay but there's inexpensive software that will allow you to use the sound card as a scope as well. You might be able to locate a trial or demo copy and use equipoment you already have to get started. Come to think of it, you can "record" a signal obtained through a mike or line input then analyze it with wave editing software.

[RobertISaar]

i've actually considered doing that before, i just need to make sure i have all of my level-matching stuff in order, i really don't want to kill the audio output on my laptop. from a guess, i'd say i have a stereo mic input, which would allow me to watch the 3X and either injector or EST pulses at the same time, then open the resulting file in audacity, since it allows for some really fine magnification of whatever part of an audio track to see the waveform.

48KHz should be far beyond the range i'll need too.

[Six_Shooter]

I have one of these, it works decently, powered by USB and is portable.

http://www.vellemanusa.com/products/view/?id=522377

[1project2many]

48KHz should be far beyond the range i'll need too.

lol... unless you're trying to watch a 48x crank signal at speed above 60k rev/minute you should be ok.

[RobertISaar]

I have one of these, it works decently, powered by USB and is portable.

http://www.vellemanusa.com/products/view/?id=522377

as much as i like the idea, i don't want to spend $300+ on something that i wouldn't use anywhere near enough to make it worth that.


lol... unless you're trying to watch a 48x crank signal at speed above 60k rev/minute you should be ok.

yeah, i'm pretty sure ~9000 RPM with a 4X signal would be all i would get up to for automotive stuff..... unless i start playing with high frequency MAFs, in which case ~12KHz would be the ceiling there.

[EagleMark]

If your ready to do some testing I will lend you my Osiliscope.

[RobertISaar]

i'm not the one that needs it.

that and i'm not sure what target ECM we're trying to mess with ATM, the 7727 or the 7808?

actually, this last page has me all turned around, what exactly is the current issue we're trying to solve?

[JeepsAndGuns]

Ok, so I'm thinking. If we need 2 injector drivers to "properly" run a tbi, and the 7727 only has 1 driver, then why are we still trying? Unless we can run a tbi with only 1 driver and pulse both injectors at the same time. I guess one thing we need to find out, is it putting out the correct pulse for the tbi injectors whenit has the bits changed to tbi?

Also, if this 8708 has two drivers and is also weatherproof, why are we not trying to use it? Could it be used with a tbi 4727 (or simillar) memcal?

[RobertISaar]

the 8708 was only ever used in Q4 W-bodies.... which were made in 90 and 91 and extremely rare at that.

if i had to guess..... i'd say that due to it's similarity to the 7727(it's actually a little closer to the 16149396 due to the 8708 having the extra RAM that the 9396 had), it MIGHT run 8D natively. and due to it's 7727 roots, if the 7427 style MEMCAL worked in a 7727, i'd bet it works in a 8708.

you COULD add in the second driver to a 7727 to fire it alternately, but you would still have to deal with modifying the code to utilize it. that may or may not be simple. this would actually need to be done with the 8708 as well, assuming still using 8D as a base.

i could change the bit pattern to either TBI mode on my nAst1 bench BIN(and set it up for V8 operation) and watch the results from that on LEDs. i just need to know what pattern you want to see.

[dave w]

I think the '7727 could be used for TBI, even with one injector driver:
If the '427 memcal can trigger TBI injectors on every other DRP?
When the cylinder select error is disabled (when using the '427 memcal), will "limp home" become active?
Install resistors in series with the TBI injectors to "electrically look like" 4 port injectors.

I'm thinking with the cylinder select error disabled, the '427 memcal will still trigger the injectors every other DRP without causing "limp home".

I'm thinking the $8D injector flow setting will be very odd when firing the TBI injectors every other DRP, compared to a normal $8D injector flow setting firing the injectors every 4th DRP?

I'm thinking it would be better if the TBI injectors would alternate, but my O'scope video leads me to think both TBI injectors will trigger at the same time on every other DRP, but not alternate?

dave w

[RobertISaar]

disabling the cylinder select DTC will only prevent it from causing the SES to come on. when in non limp-mode, the injectors SHOULD fire based off of the BIN setting, when in limp mode, it SHOULD fire based off of the MEMCAL setting.

flowrate in the BIN WILL be odd... but that shouldn't be too difficult to figure out. yes, with a normal 8D BIN, you would see 1 injector pulse for every 4 reference pulses.

i don't think it would be too difficult to use some of my dupont cables and use some resistors in place of the MEMCAL to test what happens in and out of limp-mode in terms of what the MEMCAL based cylinder select does.

[yelruhde]

I think the '7727 could be used for TBI, even with one injector driver:
If the '427 memcal can trigger TBI injectors on every other DRP?
When the cylinder select error is disabled (when using the '427 memcal), will "limp home" become active?
Install resistors in series with the TBI injectors to "electrically look like" 4 port injectors.

I'm thinking with the cylinder select error disabled, the '427 memcal will still trigger the injectors every other DRP without causing "limp home".

I'm thinking the $8D injector flow setting will be very odd when firing the TBI injectors every other DRP, compared to a normal $8D injector flow setting firing the injectors every 4th DRP?

I'm thinking it would be better if the TBI injectors would alternate, but my O'scope video leads me to think both TBI injectors will trigger at the same time on every other DRP, but not alternate?

dave w

Dave -

Try this bin on your bench. It's 8D with 0293 set to 10 for 4 cyl pfi. If a 4cyl pfi and dual injector tbi memcal are throwing the same voltage off of the memcal then the computer should be looking for the same bit.

It is not throwing a code with a TBI memcal on the 7727 in my truck. But that doesn't mean its is firing the injectors the way it should.

[JeepsAndGuns]

I still have my test bench set up and can give it a try.
What memcal should I use with this bin? A 7427 tbi memcal?

[yelruhde]

I still have my test bench set up and can give it a try.
What memcal should I use with this bin? A 7427 tbi memcal?

I'm using a 95 obd 1.5 mini-memcal. Chances are the 7427 will have the same/similar netres set up.

[yelruhde]

I still have my test bench set up and can give it a try.
What memcal should I use with this bin? A 7427 tbi memcal?

Did the bin file work?
I still do not have a light on my truck.

[JeepsAndGuns]

Sorry about that, I've been real busy lately and havent had a chance to try it out. I did however look at it in tunerpro and compare it to a stock aujp bin.
What bin is yours? Was it made from aujp? I found a lot of really strange differences. Some random parameters are like stupid crazy high numbers, the spark tables do not look like they should, and fuel tables are a little odd. Are you sure this is a $8D bin? I have seen odd stuff like this when I have looked at bins with the wrong xdf.

[yelruhde]

Yes, it is 8D. At least that is the title of the xdf file.

What makes the numbers crazy high?

[yelruhde]

The bin does not throw a code for me and definitely did something. The truck had much more off idle and low end torque, and would break up around 4,500. When it is set to v6 mpfi mode it runs straight past 5000 without a problem. Then ecm fried this weekend at the end of a 200 mile trip. Here's to keeping spares in the vehicle when doing something stupid.

It may be a setting in the bin file, it may just be the hardware can't do it alone. I have another spare on order and don't mind trying it again...but I'm new at this and don't know where to look for improvement in the files. All of the injector pulse times were cut at first by a third, then down to a quarter of the original value. This didn't seem to make any difference.

I don't mind being a guinea pig, but need some guidance.

[JeepsAndGuns]

So are you running a V6 with a 7730/7727 and tbi?

Difference tool found 598 differences between this and a stock aujp bin.
Not sure if it makes a difference, but code mask is set to AA to disable checksum.
One odd one, is speed sensor is 4006.96 on stock aujp, on yours is 102400.00.
Timing table looks significantly different, and timing doesnt drop down at higher map readings and is kinda level across the board. Never seen a timing table like it.
Also lots of other random parameters are different, not by much, but just enough to make you wonder why.

Is this a bin you have modded from a stock bin, or is it one you got from someone else?

I hope to have time tomorrow to run a test on my test bench with 0x293 set to 10 for 4cyl.

[dave w]

Did you install the resistors? http://www.vishay.com/resistors-linear/list/product-30201/

dave w

[yelruhde]

There are not any resistors installed.

There is a 40 ppr speed sensor coming out of the transfer case. The ridiculous number makes up for it.

Most of the spark timing is lower. The numbers that are higher came with from enginne analyzer. So far there haven't been any knock problems.

[RobertISaar]

the lack of resistors probably killed the injector drivers.... just saying.

[yelruhde]

the lack of resistors probably killed the injector drivers.... just saying.

I don't think it is this simple. The truck has been running without a hitch as a v6 MPFI for months now. I told it to fire every crank pulse using the Crank pulse multiplier vs Ref Pulse 1 - 24, divided all of the pulse width tables by 3 and ran it with a v6 mpfi memcal. It ran nearly the same as it did before, but I have no way of telling how often the injectors were actually firing doing this.

Then when it gets changed to TBI mode the entire behaviour of the engine was different. The obnoxious off idle stumble was gone, but the engine would break up past 4,000. And the fuel mileage was cut in half. 10 mpg with a 4.3 liter is pathetic. The only parameter changed was 0293 to 10 and a tbi memcal was installed.

It felt like the pulse width was over lapping. Almost as if the single driver was being switched from one injector to the next while under load. It doesn't make sense that this would happen. The amount of fuel and tables used to calculate the amount were the same. I feel like there is a base pulse width parameter or value plugged in somewhere which needs to be changed and I can't find it.

Is this wrong?

[JeepsAndGuns]

I fired up my test bench and ran a aujp bin with 0x293 changed to 10. I used a 100% stock un modded 7427 V8 memcal. I did not get the cylinder select error. But, is it firing the injectors correctly for tbi? That I have no way of knowing.

[dave w]

In an eailer post I wrote "I had noticed the '7730 2.5 Liter TBI Jumper D5 / D7 Injector Driver Low. I was thinking there would be a '7727 configuration that would be set for low Z injectors." I think the injector driver is not functioning correctly, if the engine looses power (fuel) at 4000? The thinking I have is; the TBI Injectors (low Z) will work in MPFI mode if resitors are used. The thinking I have is; the factory '7727 V6 memcal is Ok to use for a TBI 4.3 V6 (with resistors). The thinking I have is; the 7727 will only operate one low z injector, if there is a TBI jumper similar to the '7730 jumper setting. The thinking I have is; the voltage telling the '7727 to operate MPFI or TBI needs to be verified on the memcal (I'll need to look back on my notes to figure out which memcal to measure voltage on).

dave w

[dave w]

I fired up my test bench and ran a aujp bin with 0x293 changed to 10. I used a 100% stock un modded 7427 V8 memcal. I did not get the cylinder select error. But, is it firing the injectors correctly for tbi? That I have no way of knowing.

I'm wondering what voltage pin 56 has with a 100% stock '7427 memcal? Look back at page 3 post 41 of this tread from 1project2many.

dave w

[yelruhde]

In an eailer post I wrote "I had noticed the '7730 2.5 Liter TBI Jumper D5 / D7 Injector Driver Low. I was thinking there would be a '7727 configuration that would be set for low Z injectors." I think the injector driver is not functioning correctly, if the engine looses power (fuel) at 4000? The thinking I have is; the TBI Injectors (low Z) will work in MPFI mode if resitors are used. The thinking I have is; the factory '7727 V6 memcal is Ok to use for a TBI 4.3 V6 (with resistors). The thinking I have is; the 7727 will only operate one low z injector, if there is a TBI jumper similar to the '7730 jumper setting. The thinking I have is; the voltage telling the '7727 to operate MPFI or TBI needs to be verified on the memcal (I'll need to look back on my notes to figure out which memcal to measure voltage on).

dave w

It wasn't losing power in the loss of fuel sort of a way. It was pumping black smoke out of the tail pipe. Somehow changing 0293 to 10 made a tremendous difference in the way it calculated the amount of fuel...or it came to the same value and shot that in 6 times per cycle instead of twice. Perhaps the best thing to try is if I change the injector value to the flow of the tbi injector and not the per cylinder value which is currently in the bin file.

I would rather wire in a solid state relay then the resistor. The relay would take the load off of the driver instead of dropping it by a factor. It ran like that with the old tbi vcm. Crydom makes a 10 amp SSR with a 1ms on time max. The engine shouldn't notice this.

[RobertISaar]

instead of a SSR, you could use a FET instead... probably a lot cheaper, a better response time, and higher amperage capability.

[EagleMark]

It wasn't losing power in the loss of fuel sort of a way. It was pumping black smoke out of the tail pipe. Somehow changing 0293 to 10 made a tremendous difference in the way it calculated the amount of fuel...or it came to the same value and shot that in 6 times per cycle instead of twice. Perhaps the best thing to try is if I change the injector value to the flow of the tbi injector and not the per cylinder value which is currently in the bin file.

I would rather wire in a solid state relay then the resistor. The relay would take the load off of the driver instead of dropping it by a factor. It ran like that with the old tbi vcm. Crydom makes a 10 amp SSR with a 1ms on time max. The engine shouldn't notice this.Sounds like Syn/Async fueling? Is there a way to see in ADX data?

1 ms is going to be way short...

[yelruhde]

Sounds like Syn/Async fueling? Is there a way to see in ADX data?

1 ms is going to be way short...

1ms is the time it takes to turn on. The signal from the ecm will keep it on as long as necessary...hopefully. I'll do some research on FET's and see if one will fit.

If I can get the timing belt in the daughter's mom's volvo and through the junkyard, then I'll take some screenshots while driving. It may not happen for a week or so though.

[yelruhde]

Here is one way to fix the injector driver problem. Response has improved, but running with the tbi mamcal is going to require some massive tuning. Feel free to flame the file.

[dave w]

Here is one way to fix the injector driver problem. Response has improved, but running with the tbi mamcal is going to require some massive tuning. Feel free to flame the file.

I'm not going to "Flame the File", instead I'm going to say "Thank You" for your hard work!:thumbsup: Tuning is managable using data logs and Microsoft Excel spreadsheets. I'm thinking the tuning is the easy part. Figuring / doing the "Electronics", you did very good!


dave w

[RobertISaar]

that method will work perfectly fine.... fairly certain the injector drivers are FETs though, not regulators.

another method would be to do that outside of the ECM case itself, just use the existing injector trigger signal to fire off another FET, which has it's other two legs connected to the injector circuit and ground. a little less likely to kill something inside the ECM by accident.



also, a 7727 CAN be modified to run two injector drivers.... just need to rob some parts from another ECM to do so, then change the code to fire them in an alternating fashion.

[EagleMark]

I'm not going to "Flame the File", instead I'm going to say "Thank You" for your hard work!:thumbsup: Tuning is managable using data logs and Microsoft Excel spreadsheets. I'm thinking the tuning is the easy part. Figuring / doing the "Electronics", you did very good!


dave w Yup did good! :thumbsup:

[JeepsAndGuns]

Ok, a little confused. Mainly because I do not know anything about the internal workings of the ecm's or the code running them. But what exactly has been done here? If this isnt another injector driver, to make tbi easyer, then what does it do? You state in the file that it will "add additional power capability to the driver already there" Whats the purpose/need for doing that?

[RobertISaar]

it is another driver... just that it's triggered at the exact same time as the original driver.

think of it like parallel wiring: if you have a single 10 guage wire feeding something, you can push something like 30 amps through it. now give it another 10 guage wire and you can support another 30 amps, for 60 total.

the existing driver can handle something like 8 amps safely(at least that's the largest it did in a factory application, the 90-91 corvette L98), now you're basically adding another 8 amp capability. most TBI injectors i've seen draw 6 amps before they hit "hold" mode, so with 2 of them, that's potentially 12 amps of draw.

[yelruhde]

Thanks, it went pretty easily once I was told how to trace a circuit board. Before that it was impossible.

The tbi piece that is soldered in carried the part number IR9508. Specs on the piece are scarce, it probably went out of production with the vcm 17 years ago. Best I could find came from the China market, which is what called it a voltage regulator. That info may not be correct. I never found a data sheet with current or frequency limits.

[1project2many]

Are you using the peak and hold jumper or running purely in saturated mode?
The proof that the capacitor isn't needed... because the engine starts and runs?

[daleulan]

I've not read through this whole thread, but to avoid a lot of blown-up electronics or injectors, I thought I'd write some of my TBI experience just in case it might save some frustration.... most TBI injectors (certainly the Delphi/Rochester ones) must be driven from a true peak-and-hold current source. The Rochester/Delphi TBI injectors are fast but they need 'correct' drive. Not so much of a requirement for the low-impedance multipoint injectors, but the TBI injectors are really a mechanical marvel. Well, diesel injectors are faster, but the TBI injectors are pretty good. The proper waveform ramps the injector to 4 amps then drops it down to 1 amp to hold it. If you try to drive it without the peak-and-hold jumpers in place properly then you can fry the FET, injector, or both. The 'usual' failure mode for a FET is a short-circuit (ie. full fuel flow). There is also enough inductive 'kick' out of those TBI injectors to seriously fry anything not designed to drive them. Those injectors don't have a good enough opening force-to-energy handling capability to just use a dropping resistor like some of the multipoint injectors can get away with.

The 1227727 base PC board and chipset has 'space' to support 'proper' TBI - two injectors worth of it. There's a calibration field that changes the pattern written to 3FFC (B93A or B91A) for the type of injection you are doing. What I would probably do is look to see if the second driver could be added easily and just solder in the parts. Most of the resistors, capacitors, and certainly a suitable FET and the zener diodes, etc. could be added. The calibration bit flip and a two-injector TBI MEMCAL (or a MEMCAL suitably modified) oughtta do the trick after the parts are added. If anybody is really interested in this I could take a run down to the junkyard, mod one up, and give specific instructions on how to do it. Then I'd test it on my bench (not a vehicle - my GM wagon has the 6.5L electronic turbo diesel). I don't really 'feel like doing it' but what the heck, if it helps everyone out on the forum get some of their EFI stuff running properly, it's worth it.

Also, the ECM generally has an injector flow constant. This generation of controllers don't always divide the number by two when you enable the second injector. So you need to adjust some constant (either fuel flow of the injector or something like that) when you switch modes like that. The software I write (not for GM) automatically does this calculation for you. Most of our customers are switching to multipoint but we have a lot of customers still running TBI on natural gas (which is actually a very sane thing to do even after TBI hasn't been able to meet gasoline emissions for almost two decades), and many of them are perplexed by injector sequencing on something like a two-injector straight-six application.....:mad1:

[dave w]

I've not read through this whole thread, but to avoid a lot of blown-up electronics or injectors, I thought I'd write some of my TBI experience just in case it might save some frustration.... most TBI injectors (certainly the Delphi/Rochester ones) must be driven from a true peak-and-hold current source. The Rochester/Delphi TBI injectors are fast but they need 'correct' drive. Not so much of a requirement for the low-impedance multipoint injectors, but the TBI injectors are really a mechanical marvel. Well, diesel injectors are faster, but the TBI injectors are pretty good. The proper waveform ramps the injector to 4 amps then drops it down to 1 amp to hold it. If you try to drive it without the peak-and-hold jumpers in place properly then you can fry the FET, injector, or both. The 'usual' failure mode for a FET is a short-circuit (ie. full fuel flow). There is also enough inductive 'kick' out of those TBI injectors to seriously fry anything not designed to drive them. Those injectors don't have a good enough opening force-to-energy handling capability to just use a dropping resistor like some of the multipoint injectors can get away with.

The 1227727 base PC board and chipset has 'space' to support 'proper' TBI - two injectors worth of it. There's a calibration field that changes the pattern written to 3FFC (B93A or B91A) for the type of injection you are doing. What I would probably do is look to see if the second driver could be added easily and just solder in the parts. Most of the resistors, capacitors, and certainly a suitable FET and the zener diodes, etc. could be added. The calibration bit flip and a two-injector TBI MEMCAL (or a MEMCAL suitably modified) oughtta do the trick after the parts are added. If anybody is really interested in this I could take a run down to the junkyard, mod one up, and give specific instructions on how to do it. Then I'd test it on my bench (not a vehicle - my GM wagon has the 6.5L electronic turbo diesel). I don't really 'feel like doing it' but what the heck, if it helps everyone out on the forum get some of their EFI stuff running properly, it's worth it.

Also, the ECM generally has an injector flow constant. This generation of controllers don't always divide the number by two when you enable the second injector. So you need to adjust some constant (either fuel flow of the injector or something like that) when you switch modes like that. The software I write (not for GM) automatically does this calculation for you. Most of our customers are switching to multipoint but we have a lot of customers still running TBI on natural gas (which is actually a very sane thing to do even after TBI hasn't been able to meet gasoline emissions for almost two decades), and many of them are perplexed by injector sequencing on something like a two-injector straight-six application.....:mad1:

I am interested in a "How To modify a '7727 for TBI". I've have good soldering skills. I could use some help with the TBI code.

dave w

[JeepsAndGuns]

I have a 7727 that's bad. I tried a few times to get it to work, it never would. If anyone thinks they can salvage it for parts, they are welcome to it. I opened it up and looked for burnt/melted parts, and nothing appeared damaged. I even have a 7747 I can donate to the cause, its unknown condition, as I no longer have a way to test them.

[yelruhde]

Are you using the peak and hold jumper or running purely in saturated mode?
The proof that the capacitor isn't needed... because the engine starts and runs?

I am not using a peak and hold jumper, mostly because I can't find any consistent info on which pins to jump. Please share what you have. Also, peak and hold appears to be more of a current limiting method than something done to control a flow profile. Maybe it does both.

The capacitors are not wired in because I can't get a good reading from them. I am calling them capacitors because they are not resistors or the diodes and there aren't any other choices. I'll post a picture after work.

This is my first ecm project and its on my daily driver....so i won't do anything to it until the information behind the action makes sense. Hopefully that will make it easier to figure out what happened when things go wrong.

[yelruhde]

I don't have proof of what this is. 0 ohms across in both directions and the capacitance readings can be 10 nF or the same as shorting the leads.

I don't mind doing the work to add them to the circuit but need to know what it is first.

[1project2many]

Dale's post describes the importance of using peak and hold mode. Driving TBI injectors in saturated mode is very likely to kill them. The 4A ramp / 1A hold is a method of getting the injector to full flow quickly then holding it open without burning it out.

The picture above appears to be the injector current sense resistor, .103 Ohm, located at the RH corner of the board next to two green capacitors. The board is silkscreened R76 at that point indicating the component installed is a resistor. Next to R76 is a location for R93, the sense resistor used with the second injector driver. My camera batteries are dead now but you can see a set of modified sense resistors installed in those locations at Bill Shaw's injector driver upgrade page: http://home.comcast.net/~p-928/749mods.html
http://home.comcast.net/~p-928/749/749inj.jpg

The injector jumper enables the current sensing peak and hold driver circuitry. To locate the pins where the driver should be connected you could use the wiring diagram for the turbo Sunbird as a starting point (Note: diagrams on this site are for Syty). Jumpers in the 'Bird are connected between C13 and C15, then between D5 and D6. Then you could use the 7730/7749 to 7727 pin map at http://www.exatorq.com/ludis_obd1/triplugecm.html to locate the corresponding points which are as follows:
7730 = 7727
D5=D8
D6=D4 or D10
C13= D1
C15 = D5

You need to install the sense resistor and complete the circuit before applying the jumper.

I don't understand what you're saying by "control a flow profile." The time between injector closed and injector open, while the pintle is in transition, is a time of variable flow and should be reduced to a minimum. P&H does this and should be utilized.

I'm sure there's more I want to say but my kids are up now and the three year old is starting to play with these disassembled ecm's so I've got to go.

[daleulan]

The peak-and-hold circuit doesn't control much in terms of the flow profile. I worked with a mechanical engineer on developing the AFS/Impco GS60 natural gas fuel injector - in particular the current drive profile and how it relates to the magnetic and mechanical aspects of the injector. In a fuel injector there is a 'resistance' and an 'inductance' on the electrical side. On the mechanical side it takes a certain amount of current to open the injector, and a certain amount of current (always lower) to keep it open.

To apply enough force on a 'large' injector such as a TBI injector - remember they flow around four times the flow of a multipoint injector and that means you need roughly four times the opening force - it takes a lot of 'amp-turns'. Now, the designer can increase the turns by just winding more wire when making the injector. But increasing the number of turns increases the amount of inductance - and that inductance delays the current rise time and thus, slows the injector down - to get enough amp-turns for a TBI injector the designer would need to use maybe a 8 ohm coil but it would end up with something like 50 millihenries of inductance or thereabouts which makes for a very slow injector. It probably would not open in less than 3 or 4 milliseconds and that time would be very sloppy. But the end user of such an injector could put 12V across the coil and everything would be happy electrically. But mechanically it would pretty much suck.

The other alternative that the designer has to get enough injector opening force is to reduce the number of turns but increase the current. This reduces inductance and speeds up the injector. However if he/she reduces the number of turns so that the inductance is where it needs to be (for speed) and magnetism is where it needs to be (for force), then we end up with around a 1.2 ohm coil and maybe around a 3 or 4 millihenry inductance. If the user plops 12V across that coil then the injector get ten amps of current, and the injector driver will not like it very much. The injector won't much care for it, either - that is about 120 watts of heat in the injector!!! But the injector will open really quick - maybe it will open in 0.5 or 1 millisecond - exactly where we need to be on a TBI injector application. So once we have the valve that will meet the specification (which we now do), the second part is to make a power limiter that will reduce the power dissipation in the coil so that it does not burn up. A secondary function of this is to reduce the current to what is only needed to hold the injector open so that when the ECM turns off the output the injector closes as quickly as possible. These functions are performed by the peak-and-hold circuit within the ECM. The injector opens at a current level of about 2.5 to 3.2 amps, depending on various conditions - temperature, fuel pressure being the most critical. Any power after that is just wasted. The injector only needs maybe 1/2 amp to stay open. So the peak-and-hold circuit in the ECM is designed to deliver this profile. The average power dissipated in the injector will be about two or three watts, and the ECM will have to dissipate around ten or so watts (per injector).

Does anyone have a good close-up photo of the injector driver circuit area of the 7727 ECM? I was going to go down to the junkyard today but I pulled something in my back - probably lifting my bass amp - and I can't really do that right now as I'm kinda stuck in bed for a couple days. If most of the 'flyspeck' parts are on the board already it may not be a hard mod to put two drivers in the 7727. If you have to do all of the SMT parts it's not so bad but you have to clean up the conformal coating off the board before attaching the SMD parts. If you have a 'decent' temperature-controlled soldering iron and use good Kester solder with a good active flux (#44 or something like that) then SMT is not nearly as frightening as people make it out to be - at least not on the 0805 and 1206 parts used on this generation of controllers. What you can do is compare the population of a 7727, 7730, and 7749. Basically you need to have all of the parts that a 7749 has.

[EagleMark]

this may be what your looking for?
http://www.exatorq.com/ludis_obd1/schematics.html

[daleulan]

I have the schematic of the 7727/7730/7749 already, but I'm not sure which of the parts were 'no populates' on the production version of the 7727 - that's where the photo comes in. If my back is up to it I might try making a junkyard trip later this coming week.

[1project2many]

I have both a 7749 and a 7727 here and open. The boards are extremely similar in regards to missing quad drivers (7749) or injector control circuitry (7730/7727). I also managed to pick up some new batteries today. After I get done moving the wood I've split, and covering the splitter, and putting away other tools, and putting the kids to bed, and maybe a few other chores I'll see about snapping some close up pictures of both boards.

Take care of that back. Living with a long term injury, even after it's been "fixed," is no fun.

[EagleMark]

Take care of that back. Living with a long term injury, even after it's been "fixed," is no fun.Amen! Don't push it, get healed, then get strong. Or you fight it for 25 years and three surgeries and still hurt every day...

[daleulan]

I injured it about 10 years ago and if I'm not careful it comes back. It's a herniated L3-L4 disk. No surgery. After having been through this a couple times, I just wait for it to get better, see my massage therapist a few times, and get out on the ski trails to help strengthen the muscles around there. The first time it took about 6 months to heal up. Every other time I tweak it, it's more like 1-2 weeks.

[1project2many]

Well, this is the first time I've heard of skiing as a therapy for a back. I suppose it's all good if you can get insurance to cover the lift pass. :)

I've taken the pictures and hopefully I'll get them posted tonight.

[daleulan]

Thanks for getting the photos. I'll see what I can figure out when I see them; if I need to do a junkyard run I probably can do it later this week or maybe next weekend. I will also need to get myself a TBI memcal to get the resistor strapping right, so I sense having to get two computers. Well, actually doesn't the Quad4 or other 7749 use alternating double-fire? If it does, then any two-injector TBI should have the same setting as a 4-cylinder alternating double fire... or am I smoking something I shouldn't?

After getting through the therapy part (a couple weeks) I find that cross-country helps keep my back flexible and strong. I don't do downhill any more, and I used to cycle a lot but that I found to be getting hard on my wrists. Getting on a pair of skis, though, seems to suit me well. Even if my back is a bit sore once I get on the trails I find that my lower back really loosens up and I feel much better once it gets all warmed up.

[1project2many]

I've uploaded the pictures. I've tried to capture the areas where the additional driver and support components need to be located. Where the boards are physically the same I've pointed out missing components with arrows. Where the board differs physically it would be wise to actually check traces before assuming components are missing. And for some reason I can't locate my meter right now so I'll just post what I've got. Tomorrow I'll try and identify some of the components in relation the the schematic Ludis made up.

If the only part of the resistor network that matters is the "cylinder select" I posted a chart with some measurements in this thread, http://www.gearhead-efi.com/Fuel-Injection/showthread.php?454-What-If-8D-(1227727-ECM)-for-TBI&p=3374&viewfull=1#post3374. Some of the Q4 memcals I've measured use alternating double fire but it's not consistent even within the same BCC. I have a hunch as time progressed GM moved to firing all four injectors simultaneously, maybe using up memcals that were already manufactured.

My passion for skiing ended abruptly at the back wall of our house when I was eight or nine years old. Some lessons are learned well if learned young.

[RobertISaar]

If the only part of the resistor network that matters is the "cylinder select" I posted a chart with some measurements in this thread, maybe two or three pages back. Some of the Q4 memcals I've measured use alternating double fire but it's not consistent even within the same BCC. I have a hunch as time progressed GM moved to firing all four injectors simultaneously, maybe using up memcals that were already manufactured.

this does sound like GM.... however, if the cylinder select stuff changed for a given BCC, wouldn't that cause an issue in the calibration in that it would constantly be setting a DTC41?

[1project2many]

You'd think so but without checking we don't know if that DTC is enabled.

[daleulan]

Looking at the schematic, it *could* be done but it looks like the 44 pin PLCC that has the injector driver logic is missing. So if you felt like soldering down U15 (and the other parts) you could make it work. But that U15 kinda throws a wrench in the works because you can't get that one at Digikey or Mouser or something like that, I was afraid of that one being missing off the board. You probably could make something using a LM1949, a shift register (maybe an HC589 to fake the input signal for the SPI bus).... or if you have the PLCC desoldering tools you could swap that chip from a donor ECM. For any injector driver MOSFET, though, I recommend the STP80NF55L-06 for 5V logic inputs. It's one tough puppy. There's almost certainly a standard-level version which is what the GM controllers would use. You can actually skip the zener diode clamp (the back-to-back diode and zener in the schematic) as those MOSFETs can actually take the avalanche energy without active clamping.

[1project2many]

I seem to remember getting a 7730 from Scot Sealander years ago that had been raided for U15 and associated parts. Looked like a bunch of work to me. But Scot, well, he did some amazing stuff with OE ecms so who was I to question it.

I don't know if it's even worthwhile to buy a P4 or later ecm then spend the time to parts if the goal is simply to drive two TBI injectors from a single underhood ecm. It seems to me there's a practical solution to be found in using single point four cylinder TBI mode and running two injectors simultaneously. You'd have to adjust the BPW to reflect twice as many pulses and make a reasonable effort at redefining the voltage corrections but it could go. On the hardware side replace the driver with a more robust part, replace the sense resistor, connect the P&H jumper and you're done.

Another option is to move to the 7807 / 7808 platform. Like the 7730 / 7727 these ecm's share hardware but one is in an underhood case and this ecm has both drivers. There are a few anecdotal stories about people trying to make $58 work with a 7807 with limited to no success but we may have more success now. The memcal's fuel (cyl) select strategy is better understood than previously which may be a cause for failure. And no one has tried using this ecm with TBI AFAIK which may turn out to be no trouble whatsoever.

[daleulan]

If the manifold would accept and mix fuel with a 1/2 speed firing mode (set the MEMCAL to alternating TBI mode but only hook on one injector) then you could make it work but the timing of the injection is pretty critical. But if you need to fire every TDC for good fuel distribution then you would run out of time for injection. It's really a dynamic range issue of the injector (ratio of minimum flow rate to maximum flow rate) and response times, not just the flow rate - if GM could have gotten away with one bigger injector instead of two smaller ones for their V6 engines they certainly would have. One 7.4L TBI injector would have almost fed a 4.3L engine and a little screw adjustment at the top would have made it flow enough, but they used two injectors anyways. Just hooking two injectors together is basically equivalent to installing a single massive injector.

-Dale

[dave w]

I am going to try using a 1228708 underhood Quad 4 ECM / Memcal for TBI. See thread http://www.gearhead-efi.com/Fuel-Injection/showthread.php?1377-1228708-ECM-8B-for-TBI&p=17087#post17087 for more information.

dave w

[diver14_98]

bringing this one back from the dead did anyone ever make any headway on this

[dave w]

bringing this one back from the dead did anyone ever make any headway on this

The original idea was to have an underhood TBI ECM. I just recently learned the factory has an underhood TBI ECM, 16184738. At this point in time, there is no support (flash, .xdf, or .adx) for the 16184738 ECM.

dave w

[sailorbob]

anyways, based on GM information(which may or may not be accurate), the idea is that a pulse will happen, time until the next pulse happens is recorded, now the ECM knows engine speed and position. so 2 pulses have happened, now the injectors can start firing. pulse # 0 waiting for pulse 1 start timer 2 end timer, prep for injection/spark, start new timer 3 end timer, inject(either 1/4 or 2/3 depending on 1X signal), start timer 4 end timer, start timer 5 end timer, inject(other cylinder pair), start timer 6 end timer, start timer 7 end timer, inject(cylinder pair injected at pulse 3), start timerIs this GM information available anywhere? Thanks.

[RobertISaar]

I don't remember where exactly that info came from.

[sailorbob]

Shame, I was hoping it might have helped me get a grasp on the coding they used for the 1x signal and the injectors. The 1x pulse is used in a counter that has values of 0, 1 and 2 and I was trying to figure how that related to the firing of the 4 injectors (fired in pairs) on a 4 cylinder engine.

[1project2many]

I believe I posted the small amount of info we had earlier in this thread. The info was from the Ecmguy webpage, same guy that released the original partial disassemblies of popular gm code many years ago.

[sailorbob]

Now that Geocities has gone I'm not sure how much of the original Ecmguy information has survived. His example hacks have helped quite a bit but the injection code seems to be more like what I see described for Quad4 than those and I haven't found any Quad4 disassemblies.

The workshop manual describes the following injector operation:

Each port injector circuit pulses its two injectors simultaneously once every crankshaft revolution, with half of the fuel necessary for each cylinders combustion delivered by each injector pulse. For minimum fuel supply conditions however, such as idle, a single pulse every two engine revolutions is supplied. The ECM receives an engine speed and crankshaft position signal twice per engine revolution from the ignition module, and uses these to trigger the 'alternate pairs' injector timing sequence. Each injection pulse occurs only when both inlet valves for that pair of cylinders, are closed.

There are two injector circuits on this 01228708 ecu with the injectors paired as 1 & 4 and 2 & 3.

[1project2many]

I'm sure I posted the injector firing strategy. There's a circuit in the memcal that selects the injection mode based on voltage. If you can't find any info in this thread then look for a thread entitled "so you lost your memcal" or something like that. The injector pairing is due to the cylinder firing order. It could be thought of as injector 1 and injector 2 for simplification.

The ECMGuy page got migrated to (I believe) oocities but I believe you'll want good antivirus software before visiting. The info was there at last visit.

[sailorbob]

Thanks. You did post some of the injector firing strategy in this thread but said the details are incomplete. I've looked at your "You lost your Memcal ID???" thread and unfortunately it doesn't help me with figuring out the coding. I'm not sure how complete the oocities webpages are as I couldn't see any info on this subject.

[1project2many]

The code isn't there. What's there is the injector pairing and what should be expected as each reference pulse occurs in terms of injector driver application. Knowing there are several different expected output patterns can help identify switches and code paths as you work through the instructions. Time between reference pulses is a primary variable and is obtained as soon as the engine begins cranking. You'll find it used in several calculations including RPM. There are GM documents and some hacks as well here for several ECM's including $58 used in the 7749. Although $5D uses a newer instruction set, many of the functions found in $58 can be translated to $5D.

[sailorbob]

I think the $8B code may be closest so I'll see if that reveals any clues to me. I can see myself ending up having to put a 'scope on the ignition module to try to see how the injector firing relates to its input and output signals.

[ralmo94]

Bringing this back from the dead again,

I planned on doing a single TBi 4cyl swap with a

16199396

Can anyone confirm if the 9396 actually has the peak and hold components?
https://pcmhacking.net/ludis/p4xref.html#16149396 shows it is the same as 727 with extra ram.
I remember reading that the 727 could be used with TBi with the jumper, and I remember reading it reported that the 9396 will run $8d.

My plan was to run super $8d in TBi as the docs say, and use the 7730 4cyl pinout converted to 727 pin locations.

If my plan is successful I plan to writeup how I did it and what it took.

I have 4 ECU's I purchased off of eBay and a TBi from a 1990 4cyl cavalier.

If it does NOT have the required hardware for Peak & Hold, I might look at finding a 7730 or 727.

The pcm hacking site also shows a 727 being used in a factory 4cyl TBi, BCC, APTW in the W body cars, looking on part store websites and salvage yard searches, I can't find parts for a 4cyl W body, so I don't know how accurate that information is.

Any insight experience or criticism is welcome, and I believe it pertains to the original quest of this thread, an underhood TBi ECU, even though I'm looking for 4cyl single injector.

[dave w]

The 1985 - 86 4-cylinder TBI engines used the 1226864 ECM: http://www.gearhead-efi.com/Fuel-Injection/showthread.php?362-1226864-ECM-Information-1C

[ralmo94]

The 1985 - 86 4-cylinder TBI engines used the 1226864 ECM: http://www.gearhead-efi.com/Fuel-Injection/showthread.php?362-1226864-ECM-Information-1C

The fiero ECU, but it has card type harness connectors and is not water tight.

Can the 9396 run that mask?

$1c

[dave w]

The 1990 Chevy Lumina 2.5 Liter is listed as 1227727 TBI with DIS. The injectors appear to be similar to the injectors used by the Holley TBI.

My research shows the 1990 Lumina 4 cylinder is chip AUAJ, but I don't know the mask.

Not sure if Dynamic EFI is in the budget but it is a good option. Single TBI unit on a 4-cylinder engine. http://dynamicefi.com/EBL_P4_Flash.php

Injector driving information: http://dynamicefi.com/InjectorDriving.php

[ralmo94]

The 1990 Chevy Lumina 2.5 Liter is listed as 1227727 TBI with DIS. The injectors appear to be similar to the injectors used by the Holley TBI.

My research shows the 1990 Lumina 4 cylinder is chip AUAJ, but I don't know the mask.
Im quite certain the s_$8d code will run in the ECU I have purchased, and was about 99% sure of the TBi path with it, until reading this thread all the way through where it is reported that the 7727 might be missing the sense resistor to use peak and hold as was stated here, unless I'm misunderstanding

Looking at the schematic, it *could* be done but it looks like the 44 pin PLCC that has the injector driver logic is missing. So if you felt like soldering down U15 (and the other parts) you could make it work. But that U15 kinda throws a wrench in the works




Not sure if Dynamic EFI is in the budget but it is a good option. Single TBI unit on a 4-cylinder engine. http://dynamicefi.com/EBL_P4_Flash.php]
With that budget I would probably fashion a crank trigger and attempt 0411 4cyl. I don't mind swapping chips.


The link for injector driver info is good, but it doesn't clarify what ECU's have the hardware to support TBi mode.

[ralmo94]

The 1990 Chevy Lumina 2.5 Liter is listed as 1227727 TBI with DIS. The injectors appear to be similar to the injectors used by the Holley TBI.

My research shows the 1990 Lumina 4 cylinder is chip AUAJ, but I don't know the mask.

A quick look at rockauto confirms this, ECU is 727, and a TBi injector. Says plug and play for ECU with original prom. This is looking more promising, just hoping the 9396 also has the injector sence circuit needed? I might need to wait until I get home to open the case and confirm, but not sure what I would be looking at.

[ralmo94]

Looking more at the pcm hacking site
https://pcmhacking.net/ludis/1227749schematic.html
Seems to show u15,
That was the item in question to make the jumper functional, correct?
18562

[ralmo94]

Looking closer at the schematic I posted a screenshot of, it looks like it has 2 inj sense circuits,
U13 & u15, would this be a viable alternating 2 injector TBi ECU? If I'm understanding everything in this thread and schematics from 20+ years ago is correct I think so.

[dave w]

The attached documents might be interesting / helpful?

[ralmo94]

The attached documents might be interesting / helpful?

Valuable information for sure. Any reason the pinout diagram is not on the 727 information page?
Also on the 9396 information page it seems that just like the 727 9396 only has 1 injector driver. Capable of being peak and hold.
Seems like ike it wouldn't be cheap enough to add another driver on the board from that pdf. The 9396 seems to be a lot cheaper to get ahold of than the 727.

[dave w]

Valuable information for sure. Any reason the pinout diagram is not on the 727 information page?
Also on the 9396 information page it seems that just like the 727 9396 only has 1 injector driver. Capable of being peak and hold.
Seems like ike it wouldn't be cheap enough to add another driver on the board from that pdf. The 9396 seems to be a lot cheaper to get ahold of than the 727.

It appears definition $89 is for the 1227727 TBI system, which is not available on gearhead-efi.

Perhaps $89 will work with the 8 pin ignition module vs. DIS (crank trigger) with an updated initial spark advance programmed in the chip? I've seen 60 degrees initial spark advance for DIS systems.

It appears datastream A097 is for the 1227727 TBI system, but will it work with the 8 pin ignition module?

Memcal Cylinder Select might be a possible challenge, 8 pin ignition module vs. DIS?

[ralmo94]

I bought a memcal off eBay for a 87 Corsica or Beretta BCC ADDX.
Once I get home look forward to getting the bin off of it. I have no idea if that is $89 or something else.
Might be a couple months.

Most things I looked at before reading this thread show the 8pin HEI and dis module producing the same reference signal to ecu.

I plan on using s_aujp, with my i4 memcal.
S_aujp has documentation for using i4 TBi, but says no one has tried it yet.

[Reiembor]

I bought a memcal off eBay for a 87 Corsica or Beretta BCC ADDX.
Once I get home look forward to getting the bin off of it. I have no idea if that is $89 or something else.


Did you ever figure out the .xdf for the ADDX? I also have one and am trying to find a way to read it.

[ralmo94]

Did you ever figure out the .xdf for the ADDX? I also have one and am trying to find a way to read it.

I still have not got back to pull the bin yet.

But looking at the bcc lookup spreadsheet
http://www.gearhead-efi.com/gearhead-efi/doc/BCC%20lookup.xls

It shows the mask as 3E.
There does not seem to be a 3E xdf on here. There is however a 4E . Weather or not it would be close enough to develop one, is above my pay grade.

If you have a bin, could you post it?

[Reiembor]

I still have not got back to pull the bin yet.


If you have a bin, could you post it?


Here you go!

[dave w]

ADDX information screen captures below. It appears to me ADDX is definition $3F (Hex address 0008)

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[dave w]

ADDX information screen captures below. It appears to me ADDX is definition $3F (Hex address 0008)

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Hmm,
Came across a different ADXX.bin showing definition $3E

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$3E is available at TunerCats http://tunercat.com/tnr_desc/ecm_sup.html

TunerCats Software $69.95 (includes $42 definition) http://tunercat.com/tnr_desc/sw_dwnload.html
Add $19.95 for definition file $3E


TunerCats is NOT compatiable with TunerPro

TunerCats is Pay-Per-View only . . . and worth every $$.$$ your spend:thumbsup:

[Reiembor]

Dave, Everything I had read online referenced the 3e xdf, which I could not find except on Tuner Cat. I also had noticed the same 3f reference when I read the hex file so it made me doubt the 3e information I had seen... But when I load the $3f xdf I found this is what displayed for VE and spark, certainly not right.

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Also I come up with a totally different prom ID that you show. What tool are you using to get the PROM info that you screen captured?

I am not opposed to using TunerCat as long as the 3E will really work. Since this bin reads 3F, I am not sure? At some point I will probably take this to S_AUJP, but figured this was the quicker way to get it rolling.

I wonder if the $3F adx I have is a good one? Do you now if there are multiple versions I could check out?

Sorry for all the random comments and questions, a lot of pondering going on here this morning!

[dave w]

Dave, Everything I had read online referenced the 3e xdf, which I could not find except on Tuner Cat. I also had noticed the same 3f reference when I read the hex file so it made me doubt the 3e information I had seen... But when I load the $3f xdf I found this is what displayed for VE and spark, certainly not right.

18891

Also I come up with a totally different prom ID that you show. What tool are you using to get the PROM info that you screen captured?

I am not opposed to using TunerCat as long as the 3E will really work. Since this bin reads 3F, I am not sure? At some point I will probably take this to S_AUJP, but figured this was the quicker way to get it rolling.

I wonder if the $3F adx I have is a good one? Do you now if there are multiple versions I could check out?

Sorry for all the random comments and questions, a lot of pondering going on here this morning!

I used the hex editor from my chip programmer ( https://www.batronix.com/shop/programmer/BX32/eprom-programmer.html ) to open the 1227730_addx.bin file.

I'm not sure why there is a hex difference $3E vs. $3F, very odd!

I do not have experience with $3E or $3F, not very common.

My only experience with S-AUJP was a V6 MPFI application, which worked good. At a later date in time the V6 MPFI application was converted to Dynamic EFI which worked better than S-AUJP. In all fairness to both S-AUJP and Dynamic EFI; remote tuning has challenges! The Dynamic EFI system was the better "remote tuning" option.

[ralmo94]

Dave, Everything I had read online referenced the 3e xdf, which I could not find except on Tuner Cat. I also had noticed the same 3f reference when I read the hex file so it made me doubt the 3e information I had seen... But when I load the $3f xdf I found this is what displayed for VE and spark, certainly not right.

18891

Also I come up with a totally different prom ID that you show. What tool are you using to get the PROM info that you screen captured?

I am not opposed to using TunerCat as long as the 3E will really work. Since this bin reads 3F, I am not sure? At some point I will probably take this to S_AUJP, but figured this was the quicker way to get it rolling.

I wonder if the $3F adx I have is a good one? Do you now if there are multiple versions I could check out?

Sorry for all the random comments and questions, a lot of pondering going on here this morning!

Looked at some other parameters, and yeah it seems like $3F is definitely not correct.

Maybe Robert can Help you out?
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?993-3e

[ralmo94]

Also, for what it's worth, this thread also refers to ADDX being $3E

https://pcmhacking.net/forums/viewtopic.php?f=8&t=7805

[ralmo94]

I downloaded Tuner CATS and tried to open the bin 1227739_ADDX and it said the $3F Definition File should be used.
Maybe Tuner CATS has a different Definition for it than the XDF?
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[dave w]

I downloaded Tuner CATS and tried to open the bin 1227739_ADDX and it said the $3F Definition File should be used.
Maybe Tuner CATS has a different Definition for it than the XDF?
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The screenshot in the previous post shows the ECM is 1227747 / $42

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Screenshot of the TunerCats definitions I have.

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[In-Tech]

Shoot Dave,
I've lost a few over the years but I am surprised I have more than you :thumbsup: