What If? $8D (1227727 ECM) for 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.
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!

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.

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...