'95 S10 '7727 conversion, need guidance.

[yelruhde]

I'm a newb at programming, but have 95 S10, 4.3 tbi, with the 16183748 VCM-x.

Largely due to some mods, I've been trying to run it with the 7727, autoprom and tunerpro. I tried wiring the 7727 in and could not get the thing to even fire, I thought it was a VATS issue, but can't get a datastream out of the thing to verify. If anyone has the time to help with software/different wiring schemes, jumpers, whatever. I can try it out and troubleshoot on the weekends, it is my daily driver.

[Six_Shooter]

Not getting data through the ALDL is usually indicative of either a corrupt or missing bin/EPROM. This is especially true if a quickly flashing CEL accompanies the lack of data connection.

In a conversion, the cause could be many things. Wrong pin connected to the ALDL line, mispin somewhere in the conversion, etc.

What is the CEL doing when you turn the key on?

Did you upload the bin to the emulator?

Have you tried using a stock MEMCAL from a similar application to verify hardware?

What code are you using?

[yelruhde]

I used the 7727 files from diy-ecm. 8D, AUJP and the 1227730 datastream file. I tried setting the cylinder select to 192 for v6, not to 18 for tbi as shown in the other thread. The combination may be wrong, but you guys seem to be able to mix and match them pretty easily.

The check engine light was on and steady.

The bin was on the emulator, it gave the confirmation beep. Also, the fuel pump and iac would fire when the ignition lead was put to 12 v. The ecm is an ebay special and may not be any good. The prom i have is a v6 mpfi.

Is there a matched set of files to try? The vcm has a knock sensor/memcal board which i can also try.

I apologize if my first post hijacked the other thread. I'm willing to try any suggesstions and post the results if it will help.

[PJG1173]

any reason you didn't go with the 7427? I have also found just because you get a confirmation beep dosen't mean it took. I always upload the bin to the emulator then verify. sometimes it will say sucessful when I upload but fail on the verify, so I have to upload again.

[EagleMark]

any reason you didn't go with the 7427? I have also found just because you get a confirmation beep dosen't mean it took. I always upload the bin to the emulator then verify. sometimes it will say sucessful when I upload but fail on the verify, so I have to upload again.

Yup x2...

[yelruhde]

Motive and opportunity.

I have the 7727 w/wiring and my truck has a weatherpack, underhood vcm. It would be nice to combine what is already in the garage into something useful. The ideal situation would be to reflash the vcm to get the truck running properly, but there is no information on these. It appears a Moates G4 adapter will plug into it, but noone has a definition file or a "how to" on pulling the files out without erasing or destroying it in the process. And I'm a newb at this.

I was searching for information on how to pull and reflash when a thread popped up about running 2 barrel tbi with the 7727 and appeared to have a fair amount of interest.

I have the ecm and a similar application. If there is interest on this topic I can run some trial and error, while solving some driveability problems for myself in the process.

On paper it seems like an easy swap. TPI ran two banks, TBI ran two injectors. The 7727 ran both style systems, only a single barrel TBI. From some research the tbi injector was driven out of the same pin as one of the tpi banks. Hooking another injector to the free tpi injector bank pin and doing some lying to the ecm seems like it would get the job done. Is this an over simplification?

[PJG1173]

On paper it seems like an easy swap. TPI ran two banks, TBI ran two injectors. The 7727 ran both style systems, only a single barrel TBI. From some research the tbi injector was driven out of the same pin as one of the tpi banks. Hooking another injector to the free tpi injector bank pin and doing some lying to the ecm seems like it would get the job done. Is this an over simplification?

the question is do you have to modify the injector driver for the different impedance injectors. one of the people on here with the 50lb brains can weigh in on this. from the research I have done helping someone on another forum the ODB1.5 is not tunable and everyone I found went to the 7427 to be able to tune their rigs. Not saying what you are trying to do is impossible just above my skill level.

[EagleMark]

That's what that entire other thread was about was using the 7727 for 2 barrel TBI. I think Dave W had it worked out. 7727 came in a car with one barrel TBI. I was very busy at the time and did not get in on that one. Maybe post there to see what Dave ended up with?

[Six_Shooter]

I only split this post from the other thread because I thought this deserved it's own thread.

I can understand wanting to use the weather resistant ECM for this application.

The injector firing needs to be addressed first and foremost.

You will need to set the cyl select to TBI, and I'm pretty sure there is a MEMCAL modification needed as well.

There will likely be an injector driver modification needed as well. TBI uses "Peak and Hold" scheme, where as the MPFI uses Saturated. Peak and Hold, will open the injectors with a high current, then drop off after a few milliseconds to a lower current to hold in the injector(s) open. Saturated, just uses a single current setting to open and hold the injector(s) open.

I can tell you how to modify the wiring on a '7749 to do this, which may apply to the '7730, but I don't know how to do this on a '7727, due to the different connector type. Keep in mind that the '7749 has two injector drivers, one for each bank, or pair of injectors as they were originally used in 4 cylinder applications, 6 cyl apps used saturated with the '7749. The '7730 and '7727 both have a single injector driver, the separate injector outputs are bridged internally in the ECM, this may or may not cause an issue when trying to drive 2 TBI injectors. Mathematically, the injectors drivers should be able to run the two TBI injectors.

I would compare the schematics between the '7727 single TBI application, the Turbo Sunbird ('7749), and even compare ECM schematics (internally) between the '7730/'7749 and the '7727, to see if there is a need and how to change the injector driver wiring.

[yelruhde]

Continuing the work Dave W had started was the intent of my orignal post. It seemed like he was about 80% of the way there, then had to stop.

Correct this if it is wrong, old tpi used 8 ohm injectors and tbi uses 2 ohm injectors. Four 8 ohm resistors wired in parallel makes the resistance across the system 2 ohms using 1/r for parallel circuits. So the driver would see the same thing regardless of which system it was driving. If the problem is just a lack of current, then an inline amp could solve it.

I'll google the board schematics tonight.

Maybe the thing to do is set it back up this weekend with a light to see if the injector driver is doing anything. The paper stuffed under them last time stayed dry. If the peak current wasn't enough to activate the solenoid, then it would answer a few questions. It would run with gas dumped down its throat, so i did something rigght.

It looks like the 3800 guys have hacked their obd 1.5's. I haven't seen anything saying how though.

[PJG1173]

Continuing the work Dave W had started was the intent of my orignal post. It seemed like he was about 80% of the way there, then had to stop.

Correct this if it is wrong, old tpi used 8 ohm injectors and tbi uses 2 ohm injectors. Four 8 ohm resistors wired in parallel makes the resistance across the system 2 ohms using 1/r for parallel circuits. So the driver would see the same thing regardless of which system it was driving. If the problem is just a lack of current, then an inline amp could solve it.

your math is correct all things being the same it would work. from six_shooter's post it appears all things are not the same.

"There will likely be an injector driver modification needed as well. TBI uses "Peak and Hold" scheme, where as the MPFI uses Saturated. Peak and Hold, will open the injectors with a high current, then drop off after a few milliseconds to a lower current to hold in the injector(s) open. Saturated, just uses a single current setting to open and hold the injector(s) open."

[yelruhde]

your math is correct all things being the same it would work. from six_shooter's post it appears all things are not the same.

"There will likely be an injector driver modification needed as well. TBI uses "Peak and Hold" scheme, where as the MPFI uses Saturated. Peak and Hold, will open the injectors with a high current, then drop off after a few milliseconds to a lower current to hold in the injector(s) open. Saturated, just uses a single current setting to open and hold the injector(s) open."

That is the part I am trying to understand. Given a 2 ohm resistance and a 14.5 volt supply, from the alternator when running, the injector driver needs to be capable of a little more then 7 amps to work. Which is fine. I just wired a 2 amp light to the battery and fired the injector without blowing it up. This changes the circuit so, I need to get some spare fuses to see what the power requirement really is to drive the injectors.

[Six_Shooter]

It's not so much what the driver needs to see or do, but what the injectors want to be driven with.

Also, high Z injectors are 12 ohms average, but you need to devide by 8, since the '7730 and '7727 both use a single injector driver.

Couple all of this with the fact that TBI needs to fire twice as often as MPFI, and you will be driving the injector driver pretty hard, trying to drive a TBI system.

[RobertISaar]

post the 7730/7749 low-z procedure and i'll make it 7727 friendly. :D if i had to guess, i could look at the TBI application that was run on the 7727 and make sense of it from that or use it to double check the pin interchange.

the hardest driving saturated setup on the 7727 was as noted the 8 cylinder TPI stuff. 8 parallel 12 ohm loads will appear to the driver as a single 1.5 ohm load. at 14.4 volts, that's 9.6 amps.

IIRC, when in peak/hold mode, the driver switches over to hold mode once the load passes 4 amps? and when in hold, roughly 1 amp is fed to the injector? i'm not 100% on those though, it's been a while since i've looked into driving low-z injectors.

[yelruhde]

It's not so much what the driver needs to see or do, but what the injectors want to be driven with.

Also, high Z injectors are 12 ohms average, but you need to devide by 8, since the '7730 and '7727 both use a single injector driver.

Couple all of this with the fact that TBI needs to fire twice as often as MPFI, and you will be driving the injector driver pretty hard, trying to drive a TBI system.

Is the firing scheme the same for v6 mpfi and v8 tpi? The reason for the question is with a v8 the firing scheme is even. Each bank sees two squirts per cam revolution. But for a v6 it would alternate, 1, 2, 1, 2 and so on. GM has a long standing history of only doing what is cheap and easy unless Uncle Sam twists their arm, but, this sounds like a driveability nightmare.

Another question, do these bins have the ability to alter the injection timing. Not the pwm, but when the fuel is released relative to crank position? Although it seems redudant with batch fire, I worked with a Motec system with this feature and it would impact the engine's response.

I'm asking a lot of questions, but there is an EE at my work who is willing to help me modify the system. I need to learn more about it and get a datastream out of tunerpro for it to happen.