Wierd Prom Issue - HELP

[corvairnut]

I almost dont know where to start, so I will from the beginning.

I bought 6 ea 16196395 ECMs. I remove each prom, cut out the existing chip and solder in a terminal to later install allow a removable 27C512 chip.. I use the OD$ mask and all is well with 4 of the 6. Each terminal and pinout was checked and passed. The Prom work in all ECMs and all ECMs were checked with other proms/chips and later with a romulator that I use. I have also tried the prom in a 16197427 ECM, but with the same results.

THE PROBLEM: The 2 proms will run my engine, but not well, both give have strange/low readings in turnerpro and dont run well....almost like I have the wrong mask. Timing is low and skips at lower RPMs. I have verified chips and plugs my romulator into the prom and still the same problem. It appears there is something up with these proms. Both proms have knock chips with 119**** numbers printed, but I dont know if that means anything.

Any ideas will be appreaciated as I dont know where to start.

Thanks,

Ted

[EagleMark]

4 out of 6 ain't bad? Were they all V8 and are they all going in V8? I think there's cylinder select issue with mis matched memcals... not in chip, in memcal...

[corvairnut]

Unknown, but the 16196395 is a V8 only ECM if all I read is correct. I change the Cly to 6 in a custom chip for the Chev Corvair and all runs fine. Correct me if im wrong, but the mem cal will only come into play in "limp home" mode.... correct? I have always discounted the "limp home" mode anyway since I run DIS and had to set the initial timing to a 60 degree offset to make the DIS work and will not work in limp home ever since I made the change.

I bought a 7427 today and will pay attention and document as I never thought this would be an issue. this issue first came up about a year ago with another prom, and I thought it was just a bad prom..... so there ya go.

Ted

[Six_Shooter]

Spark advance during LHM will not be affected by any changes that are made to the BIN. The ignitions system will run in a base timing mode, which for most GM DIS systems seems to be 10* BTDC.

I'm not sure how the hardware side of the CYL select issue is handled with TBI calibrations. If what I suspect to be true, actually is, then in TBI modes it is in a none issue and only affects MPFI applications.

[corvairnut]

EagleMark... you may have hit something. These are V8 TBI that I changing the Chip and making a 6 Cyl Corvair Engine Chip and A couple of the ECMs may have had unknown origin. I was looking at a writeup by Bill Hamilton on Bender and he was talking about netres (network of resistors) and the V6 has a 7.5k and the V8 had 15k between pins 12&13 on end memcal chip. I have found that the ones that work have the 15K between the pins (v8) and the 7.5k (v6) are the ones Im having trouble with. If nothing else, I have found a difference that makes one work and the other dont.... and sometimes thats half the battle

Ted

[EagleMark]

He's just wonderful at claiming everything that was figured out elsewhere...
http://www.thirdgen.org/techboard/diy-prom/306416-bpw-cyl-select-starting.html

And the instructions for how to do it...
http://www.thirdgen.org/techboard/diy-prom/345727-cylinder-select-netres-values.html

[1project2many]

This relates to infor in a couple of threads. The latest is here:
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?592-You-lost-your-Memcal...

The 2nd and 3rd digits on the knock board will tell you what engine the memcal came from. 19 is from a 4.3 V6 engine so there's no need to make a change in terms of the number of cylinders. But there are two versions of the 4.3 V6. One is TBI and one is CPFI. While the cyl select / memcal connections for a TBI are likely known, I have never seen the same info for the CPI version. The starting point imo would be to properly identify which engine the memcal is from. If you have the original chips you can us BCCFind to identify the application and fuel system. If not then you may want to do some looking around through the 7427 related threads and on other boards about the fuel mode select.

[EagleMark]

That's a sweet system you build for the Corvair! :happy:
www.Corvair-efi.com (http://www.corvair-efi.com/)

How do you wire the DIS? We've been talking about one from NorthStar V8 but always seems to come down to a crank sensor... looks like your using a crank sensor... very cook system! Now we know where all the one barrel TBIs are going.

[1project2many]

I've always loved those kits.
http://www.corvairnut.com/GMDis.htm

[corvairnut]

Thanks. The 6395 ECM did not use DIS, but a dizzy as you all know. The trick was setting the initial timing to 60 degrees and setting max timing at about 75. You loose you LHM, but you loose the dissy too (which is worth it....right). The wiring and signaling for the DIS and the dizzy is the about the same. I have the wiring documented if you need it. I know using the saw blade as a crank signal generator at the same time using my dizzy (which was a GM 4.3 mated to a Corvair base), was a little crude, but that was the only way I could work it out in my head. My crank wheel is provided by drilling holes in the HB and setting and the first holes are at 10 and 20 degrees and every 60 there after.

My stuff is mostly on www.corvair-efi.com. Corvairnut.com was my start and keep for mostly personal stuff.

Yes... I am always shopping for TBI-700s w/ left Pull (long metal bell crank) and buy about 10 a month for the conversions. I modify and rebuild them for that setup. See the site. I will say though, corvairnut.com does have the hovercraft on it.

Ted

[Six_Shooter]

Spark Advance is not affected by LHM.

If LHM is not working it is due to fueling, not spark.

I'm very familiar with the GM DIS systems. ;)

[corvairnut]

SS-Im sure your an expert, but when it goes in LHM (Tan disconnected), timing light shows from +25 to -10 (approx of course) and bearly runs... so you tell me. I figured the offset I had to install the make DIS work with a dizzy ECM caused all that.

Please enlighten me... I come here to learn

Ted

[Six_Shooter]

That's not "LHM," LHM would be running off the redundant fuel chips on the MEMCAL, you can force this by removing the EPROM from the MEMCAL, or G1 (style) adapter. In LHM, the ECM does not send the ESC/Bypass 5V trigger to take over timing, which is where the base timing of the ignition system itself comes into play.

That being said, the base timing of the DIS system, should be 10* BTDC, with the ESC/Bypass (tan/black) disconnected. So by the sounds of it, your base timing is not correct.

[corvairnut]

OK.. Im cool with all that. Bill Hamilton worked with me on that and that is why base is set at 60 degrees. It will not run on 10...Ive tried...hard. If you have a better idea... Im all ears. My bin is attached if you would look at it.

[Six_Shooter]

What do you mean by "it will not run on 10"?

Do you mean that when you set the base timing to 10* in the bin it will not run?

Wait a tick, is that what you're doing setting the base timing to 60* in the bin? If that's the case, then I think what you're doing is actually firing the wrong cylinder. The base timing setting will remove that much timing from overall calculation.

What you need to do is add 60* of total timing to the EST output.

The method I use, is to change a few of the offsets, I'm using $59 to do this so far, I haven't looked at $0D to see what will be needed to do that, even though it is planned, since I have a truck running on $0D currently that I would like to add DIS to.

1project2many has a different method that I couldn't get to work, that involves negative numbers.

I'll have a look at your bin.

[Six_Shooter]

Yeah, that is exactly what you're doing you're removing 60* from the timing signal, causing the coil to fire the wrong cylinder, which is why you have to set it at 10* ATDC, and why it won't run well with the bypass disconnected. I can't see it being too easy to start wither, since the base advance while cranking is on the module alone and only switches to ECM control once the engine is above 400 RPM or so.

I know this is a different code, but this is what I followed to get my $59 bin to work with DIS.

Reference Thread: http://www.code59.org/index.php?option=com_fireboard&Itemid=38&func=view&id=5960&catid=12

My success thread, it might have some useful info in it: http://www.code59.org/index.php?option=com_fireboard&Itemid=69&func=view&id=6321&catid=12

[corvairnut]

Can we look at what values we would change to get it where you think it would run with the Tan disconnected? Can you post your bin?

Thanks

Ted

[Six_Shooter]

To run with the disconnected, there doesn't need to be any settings in the bin for ignition. With the Tan disconnected, the ignition is running off base, what could be called "mechanical" timing only, based on where the crank position sensor is.

From what you've posted in this thread it sounds like you need to move the sensor 20* advanced, or turn the trigger wheel so that it's 20* advanced, you might find LHM mode works just fine then. ;)

I'll have to look through the $0D XDF to see how I would go about changing it for DIS.

I'm interested in seeing what 1project2many suggests for changes as well, maybe this will be one that using the negative numbers method will work for me.

[1project2many]

Wait a tick, is that what you're doing setting the base timing to 60* in the bin? If that's the case, then I think what you're doing is actually firing the wrong cylinder. The base timing setting will remove that much timing from overall calculation.

!!! There's some interesting stuff that happens in the spark hardware outside the processor. If timing values exceed a certain amount the processor seems to do extra delays and make instant, huge changes in the output signal. I found this back when I was trying to work out the GM values for DIS. As I exceeded 90 degrees in a 4 cylinder cal, the timing signal would change a bunch, maybe an additional 90 degrees? I never spent time working it out, I only said "Woah! This is bad so we never want to exceed 90 deg advance!" Once I understood how the limits worked I realized timing never does exceed 90 degrees. I wonder if this might happen at 60 degrees when the memcal is set for a V6??? Which would mean settings from 10 to 75 degrees are crossing this line. Thinking about it, if this happens the DIS module will simply fail to fire the next cylinder in line if the EST pulse changes that much and without a scope or a very sensitive ear it might not even get noticed. It'd be a good learning experience to spend time observing the REF, EST, and ALDL data.

When LHM is active there is no timing output from the ecm. All timing is performed within the DIS module just like when the 5V / bypass / tan wire is disconnected. Spark advance is typically fixed and unchanging until somewhere around 2000-2500 rpm, then there is a very fast increase in advance of about 10-20 degrees where timing will remain for the rest of the engine's rpm range. There is no setting in the computer calibration that will affect this function of the module. The crank position sensor has to be located correctly in order for the engine to run with the bypass disconnected. The factory locates the sensor at 60 degrees BTDC. I have diagrams from GM showing the factory crank sensor timing. LMK and I'll post a link.


Now here's where things get funny. The crank signal to the module is always advanced. And the REF signal from module to ecm is always advanced. But inside the module, if the tan wire isn't connected, the module changes that 60 degree advanced signal from the crank to something closer to 0 deg so the engine can start and run. I'm very familiar with the 4 cylinder versions of these modules and they will change the 60 deg advance to 0 degrees advance. I *believe* the V6 module will provide 10 degrees of advance with the engine at low speed and the tan wire disconnected. (I'll defer to Six or anyone else who's measured this on the V6 module). If we guess the total module advance is 20 degrees additional then you need to have your sensor anywhere from 62 deg BTDC to 50 deg BTDC for the engine to run on module timing. If the module provides less total advance then the sensor can be mounted a little more advanced, but with an air cooled engine I wouldn't push the limits of spark advance when on bypass because there is no temperature adjustment available to timing.

Where is your sensor mounted now?

[corvairnut]

I guess back to the orignal problem... the V8 Proms run great in my engines, the V6 ones do not which also my contribute to the LHM. The LHM does not matter to me as much as I just want a good running system (which I have). I modified the Chip with a resistor and a jumper wire and it ran great at idle and 50% or more throttle, but low to mid throttle it was almost skipping.

Im not sure what the answer is other than making sure I dont get anymore 6 cyl proms to run a 6 cyl (wierd as I stated).

[corvairnut]

Sensor in mounted in the 10 degree before TDC. The wheel (harmonic balancer with holes) first 2 holes is at 10~ and 20~. Changing the wheel orientation is a monster as you can guess.... I have to drill a new HB. Trigger wheels would be nice for testing, I just have to use a modified oil filter on the Corvair. Who makes trigger wheels for 6&1 and I see plenty for the 36&1 and others? If you look at the website, keep in mind the Corvair turns counter clockwise facing the HB.

[1project2many]

I turned a trigger wheel on my lathe and cut notches using die grinder.
completely understand issues with redesign system and / or potential requests for retrofit.

Believe injection strategy may be at fault for poor running... CPI 4.3 V6 has one injector! 2nd injector may not be firing, or may be firing 1/2 as often after modification.

Since reference pulse comes 60 deg before cylinder, current sensor placement puts sensor at 70 deg BTDC for the next cylinder in line. That's reasonable and workable. Later 4 cylinder designs moved crank sensor notches to same angle for improved starting. For system with 10 deg BTDC sensor, set reference angle to 70 deg, set max advance angle to -30 deg, set max retard (or min advance) to -70 deg. This will allow a 40 deg range in timing. Might want to make sure max advance with tan wire disconnected isn't excessive.

LMK if you can't set the desired values in your tuning software and I'll adjust .bin that's posted here.

[EagleMark]

Just throwing some ideas at the issue, I have no experience with DIS conversion an only experience fixing it on factory equipped vehicles. But the number 10 keeps being brought up and mention of counter clockwise revolution, is that reverse of factory system?

Doing distributor conversions I am experienced with and distributor rotation is an issue with both duraspark module to external EST or just GM distributor conversion. Timing on reverse rotation distributor can be set with tan wire disconnected, but when connected on reverse rotation will be reverse advance. Change wires from pick up coil to EST or wires from duraspark module to external EST fixes this. But base timing, tan wire disconnected is 10 degrees off! How does this play with ICM (which would be EST in distributor) in DIS pack?

[1project2many]

That's a great question. I know exactly what you're talking about with the distributor but the DIS sensor doesn't care which way the crank rotates. Furthermore the sensor can be rotated 360 degrees in it's mounting without changing the signal. GM did nice with that one.

[corvairnut]

I guess this sums it up. My TBI V8 memcal/prom modified to 6 cyl, etc runs my Flat 6 Corvair engine great.
The LMH prob would not work well even if I had a 6 cyl chip due to the amount of offset, but the 8 sure does not help
The wierd stuff im getting with that prom is because it is a 6 cyl CPI memcal (I took the knock sensor off and looked up the 16 pin chip number)
What Im using will work and is there really any reason to change the setup/values I have?
Reverse has no effect on the DIS system...just drilled the hole pattern backwards from the MS chart. I love it over the Dizzy and easy to setup for others.

If nothing else guys, you got my head using logic again instead of scrambling around for a quick answer.

Im throwing this 2 CPI chips in the trash to make sure I never pick them up again.

Ted

[1project2many]

What Im using will work and is there really any reason to change the setup/values I have?

Isn't that a two part question? Question 1: Is it worth it to change the sensor setup and physical configuration? The RPM based settings to enable fuel and spark are pretty low. The only potential problem I see with the current setup is with a low battery or very weak starter it's possible for the cylinder to get some fuel air charge then the module delivers spark at 70 deg BTDC. I like safety nets so I would probably lower the spark enable limit to around 50 rpm for spark. I'm not sure which tuner software you use but it's the constant at $4134.

The settings in the Eprom are a little different and I'd definitely make a few changes there. The max advance value should be brought inline with the DIS system values. Change it from 90 degrees positive to a much lower value such as 0 degrees. This prevents any errors in the spark table from accidentally delivering spark up to 90 degrees BTDC. Some trial and error may be necessary but the final result could be anywhere from minus 10 degrees to plus 10 degrees. I like to set initial advance (AKA Reference Angle) to match the sensor placement just as GM does but if the delivered timing at the engine matches what a scantool or laptop says then you've already found a way to account for the mismatch somewhere else in the calibration. There are a couple of other limits which could potentially cause bugs and they are Max Retard in DFCO and Max Retard for Torque Management. These values should be in the rang of the Max Advance and Max Retard to prevent 30 to 90 degrees of unintential advance being delivered to the engine. Set both of them to -75. Finally there's the spark latency table. Maybe someone with a table from a 3.1 / 3.4 V6 can help but the table from the 4 cylinder is completely different than the V8 you're using now.
Location Time RPM
L4541 FCB 13 ; 198 0
L4542 FCB 12 ; 185 400
L4543 FCB 10 ; 154 800
L4544 FCB 10 ; 154 1200
L4545 FCB 8 ; 123 1600
L4546 FCB 8 ; 123 2000
L4547 FCB 7 ; 107 2400
L4548 FCB 7 ; 107 2800
L4549 FCB 6 ; 92 3200
L454A FCB 6 ; 92 3600
L454B FCB 6 ; 92 4000
L454C FCB 6 ; 92 4400
L454D FCB 5 ; 77 4800


HTH

[corvairnut]

Hey Guys.. Thanks. Im here for an education and getting one.....appreciate ya'll feeding me with small spoons. As you can see from the bin, I am home grown, home taught tuner and as soon as you say the word "Corvair"... the other site pretend you have computer aids.
Really appreciate the way ya'll have jumped in. More to come.

Ted

[EagleMark]

I guess this sums it up. My TBI V8 memcal/prom modified to 6 cyl, etc runs my Flat 6 Corvair engine great.
The LMH prob would not work well even if I had a 6 cyl chip due to the amount of offset, but the 8 sure does not help
The wierd stuff im getting with that prom is because it is a 6 cyl CPI memcal (I took the knock sensor off and looked up the 16 pin chip number)
What Im using will work and is there really any reason to change the setup/values I have?
Reverse has no effect on the DIS system...just drilled the hole pattern backwards from the MS chart. I love it over the Dizzy and easy to setup for others.

If nothing else guys, you got my head using logic again instead of scrambling around for a quick answer.

Im throwing this 2 CPI chips in the trash to make sure I never pick them up again.

TedI would have started with a 4.3L TBI memcal since it's TBI to TBI and 6 to 6 conversion but could have run into same issues with LHM because of your DIS conversion? What about a V6 DIS memcal as a starting point? They are plentiful but MPFI and different ECM. Since your burning new bin file anyway could these be the cure to your DIS and limp home not working? They would have all other possibilities of DIS spark already handled.

I just don't like all the possibilities that 1Project2Many has brought up to come into play with timing changing so far or to wrong cylinder. The one that really caught my eye was weak batterey or starter since this is a conversion to older car and I have run into so many that would not keep 12 volt at idle to begin with even with perfect batterey and altenator from that time period. They just did not charge at idle like newer altenators. There has to be a way to get all bases covered even if it were just for future systems came with differentant memcal and harmonic balancer drilled differantly.

[Six_Shooter]

Mark, the DIS is not controlled in LHM mode, it sply runs off base timing (and any built in advance of the ICM itself). The problem in this case is that corvairnut has his DIS setup at 10 degrees ATDC instead of 10 degrees BTDC, base timing. I bet that if the base timing was set to OEM specs, that LHM would be fine.

[EagleMark]

OK thanks, I'm trying to catch up and learn the DIS. I understood LHM was in ICM but couldn't figure why it wouldn't work? I'll have to go back and read why he started 10 degrees wrong way to begin with? Why'd he do that? He doesn't seem worried about LHM but I would! Specially if something failed and LHM was enabled and timing ended up somewhere BAD! So what if it didn't run but what if it went to somewhere that could damage something?

So if harmonic balencer was drilled properly then LHM would work, seems he can cover other areas of tune 1Project2Many described. Or is there a better V6 DIS memcal that would be a better starting point? I don't recal a 6 cylinder DIS TBI engine ever made so theres no real starting point. He has done it and developed it but seems bandaid and not complete/correct. My intrest is not only to help him in future development but I or someone else may want to TBI DIS a six banger...

[Six_Shooter]

The ignition type doesn't matter for LHM, so a TBI MEMCAL is the best to start with. The ignition runs in LHM, just like it would if you disconnected the bypass (tan/black) wire, the ECM has absolutely no control at that point. IIRC, LHM just runs fuel in LHM, based on MAP and TPS inputs only.

I don't know why the base ignition timing would have been set up that way either, for me, it would have made it more difficult to get it running.

[corvairnut]

Correct me if I am wrong, but I have my setup (crank sensor) setup at 10 degrees BTDC not AFTER. I reverse rotate, so the Pic would show after if going clockwise, but I dont. Was you talking about something in my programming?

Please look at the bin and tell me if you see other problems. I run a romulator, so pretty easy to change.

Ted

[1project2many]

the ECM has absolutely no control at that point. IIRC, LHM just runs fuel in LHM, based on MAP and TPS inputs only.
Yep, except that LHM fuel is MAP or TPS.

A lot of guys tried different settings to make DIS swaps work in the early days. I remember a guy that set the crank sensor at 10 deg BTDC and built a small circuit to apply 5V to the bypass any time the key was on so the ecm would always be in control of timing.

Gotta say, for some reason I thought OP said he put sensor at 10 deg BTDC. Dunno how I looked at all the clues and missed the obvious, but I'm definitely going to turn down that rattlesnake hunter job I was offered. REF should stay at 54 deg but max advance and retard values that I listed will work. Downside is engine will never run right on limp or on module timing if sensor is at -10 deg. Proper settings from 0 to +10 will fix it.

[corvairnut]

Yep, except that LHM fuel is MAP or TPS.
. Downside is engine will never run right on limp or on module timing if sensor is at -10 deg. Proper settings from 0 to +10 will fix it.

I have the Sensor located at 10 BTDC. Wanted to make sure you caught that... My engine turns counter clockwise.

Ted

[1project2many]

That's what I thought you said but the .bin is set to 54 deg ref angle which is the same as 10 deg ATDC. Have you ever checked to see if the timing at the crank matches the timing displayed on the scantool?

[Six_Shooter]

If you're not reading 10 degrees before TDC, with the bypass disconnected using a timing light, then you have one of two things happening, your pointer is off, or you don't have it set to 10* BTDC.

According to the Megamanual, which was at least one source I used when setting up my second DIS system, the notches should align with TDC events, and the home notch should be 10* ATDC of #1.

If you look close at this picture, you'll see that the middle of the sensor is at the leading edge of the #1 notch, I think I need to set it to the trailing edge. The engine is at TDC #1 in this picture.
http://domestic.3400z24.com/sixshooter/My vehicles/Datsun/Under hood/DIS conversion/DIS01.jpg

[1project2many]

Ted, maybe a few basic questions will put everyone on the same page. Will the car crank over with the tan wire disconnected? Will it start and run? Have you checked the timing when the engine runs using a timing light?

Six, the sensor needs to be in the center of the notch. The module triggers when sensor voltage crosses zero volts. I don't know if this picture will help but it's GM's own timing diagram for the V660 DIS. You "read" it from left to right. Notice how the center of the pulse at the top corresponds with the changes to the REF pulse? That's the point where the sides of the notch are equally distant from the crank sensor tip.

http://i589.photobucket.com/albums/ss333/misc_photos_01/DISinj_timing2.gif

[corvairnut]

The Timing indication and the light are within a couple of degrees so that part works. I have not tried the Tan wire disconnect since the last set of harness I built, I just left the disconnect out. I want to get a known good V6 TBI Memcal/Prom that works with the OD$ mask and see what happens from there. I want to isolate, but you guys are really helping. As I learn more and look back a lot of my success with getting the Corvair engine running was pure luck, but as they say "I would rather be lucky than good".... and I am lucky.

Thanks Again,
Ted

[EagleMark]

Plenty of $OD bin files here:
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?303-16197427-PCM-Information-OD