TKR Performance

iTrader: (1)

Ok guys... here's my dilemma. My 1985 Trans Am has a 406 c.i. chevy, w/ a compression ratio of 11:1. World Sportsman II heads (72 cc chambers), Holley Stealth Ram (twin 58mm bore throttle body), and the stock computer. I've searched, and read the tuning guide (by ecm). The computer part no. reads as 7-6870. Unfortunately, its not listed. My question is: is there a way to reliably tune this? Is the math the same for figuring everything out? (Is there a section on math calculations? Or a guru out there who could draw it in crayon for me?) I've got a stock ECM out of a later model T/A (1989 I think), would I be better off investing in the parts for the conversion? Anyone out there with some knowledge please help a helpless newb make his T/A run like it should. Thanks for your time!!

RFmaster

TKR

You probably have one of the remanufactured ECM’s. My guess it has a bluish looking label. I have seen these before and the last four digits correspond to GM part numbers. In your case I believe it corresponds to 1226870 which was used in 1985 TPI engines as well as 1985-86 2.8 V6 MPFI “S” LB8; 1985-86 2.8 V6 MPFI “W” LB6; 1985 5.7 V8 TPI “8” L98. You can find engine harness schematic here:

http://www.chevythunder.com/1226870_ecm.htm

It uses program id: 31 ($1F)

For a new ECM you need to provide ECM part number and at least its original usage.


//RF

TKR Performance

iTrader: (1)

You're exactly right... it has a blue and gray label on the front. I didn't know it was reman'ed. The ECM itself works... but data logging is super slow, and I can't get TunerPro RT to work live with it. WinALDL works ok (except it somehow reads 6500 RPM at all times), and I can burn chips using the Moates software. The car runs ok, idles well. I've got an old Hypertech Chip that was burned for it years ago, but it seems like they've cut the O2 sensor out, cuz WinALDL shows it has a constant voltage of 0.442 v (even after the car warms up). Ever since I went up in cam size the Hypertech chip works like crap, the poor car puffs more smoke than a Cheech and Chong movie. If you sniff the exhaust your eyes will water cuz its so rich (ask me how I know). The cam is as follows: .477 Intake, .480 Exhaust, 269 Intake, 280 Exhaust, with 1.5 roller rockers. It's not like I can just put the stock computer chip in, cuz it won't run the 406. Oy... very confused.

RednGold86Z

iTrader: (1)

You'd probably be better off converting to an 86-89 wire harness, and '165 ecu. It might cost you about $200-$300, though, unless you get really lucky. I honestly don't know if you must change the harness though. The big problem is the MAF burn-off module on the 85.
Also, you don't have to keep it MAF, if you can find a good deal on a 90-92 '730 harness and computer. The 730 is speed density, and eliminates the MAF, and can be easier to tune for some applications.

TKR Performance

iTrader: (1)

Thank you for the advice, I think I'm gonna try that. Somewhere out there is a step by step conversion process using a breadboard... some extra components, and the existing harness. What is the MAF burn off?? I've seen that in the TunerPro, but never messed with it. I'd like to make the switch, there is a post on here where someone took a computer out of an 86 and put it in an 85 and it worked. Until I make the swap, is there any helpful advice or math equations that could be useful to me on my journey? I'm in this with both feet and somehow gotta get the car running "right". Right now it's way too rich, but I don't want to back down Fuel Pressure (42 psi) and blow something up. Unless ya'll think that's too high.

RBob

iTrader: (1)

The MAF burn off is: when the ignition is turned off a voltage is sent through the MAF wire to burn off any dirt. It actually lights up orange from the heat. The '85 ECM and the '86-'89 ECM handle the burn off differently. I believe they also use a different MAF.

Mr Davis has a great site on doing the '85 to newer '7165 ECM. And then from the '7165 to a '7730 ECM:

http://www.eecis.udel.edu/~davis/z28/ecm_swap/

The downside of your current ECM is that there isn't a lot of information out there on tuning it. Although at the moment some work on the MAF airflow tables would probably make a world of difference.

RBob.

TKR Performance

iTrader: (1)

Hmm... that doesn't look too hard. I'm an Electronics Technician in the Navy... so I'd hope I would be able to do that. According the the site RBob directed me to, the MAF Burn Off is a module attached to the top of the ECM. My ECM doesn't have that, but there is a funny looking unidentified box up behind the actual "glove flap" further up the dash. I will start on this once my car enters its "winter hibernation". Until then... RBob said I should try adjusting my MAF tables... any ideas or words of advice on what I should be looking for? I've been slowly tweaking my Injector PW (with what seems to be no result). I'm not sure what I did exactly, but the car runs very very smooth now... has decent punch... but still smokes like a blunt. I can't express how thankful I am that I am part of such a knowledgable network of fellow thirdgenners. I hope one day I can repay the favor!

Mangus

You car uses the $1F mask. There's a TunerPro definition for it here:

http://www.moates.net/fileman/index.php?dir=3)%20Binary%20Editor%20Definitions/1)%20TunerPro%20XDF%20Files/1%29%20General%20Motors

u: moatesuser
p: moatespassword

I do agree, however, that it might be worth going w/ the 86-89 harness and omputer.