ive got acsess to an 86 computer to put in my 85 305 TPI. Ive heard that this computer runs faster, therefore better preformance, right?

Any Help? Curtis

 

85TA,

The old ECM from '85 is a lot slower than the '86-up version. Unfortunately, the MAF is also completely different. The '85 used a digital AC/Delco MAF sensor that output a frequency modulated 5VDC signal. The MAF burnoff was controlled by a module that was piggybacked to the ECM. The '86 ECM (P/N 1227165) has provisions for MAF burnoff built in the ECM, and used an analog MAF signal (0-5VDC). If you decide to perform the conversion, you'll need most of the wiring harness from an '86 or later MAF car, the MAF, and the MAF power and burnoff relays. The MAF electrical connectors are also different.

There is a fairly good article on the change at http://www.ece.udel.edu/~davis/z28/

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

I recently changed from my 85 ECM to a 86-89 ECM. The change was reletively simple. It could be done in a couple hours but it is best to take a few hours and check, re-check, and then check again to make sure everything is OK. The only thing you need to buy (beside basic soldering equip.) are two relays and two plugs for the relays. I can't say the computer swap increased my mileage or doubled my horsepower but for chip burning purposes it allows me greater flexibility. I can use the latest MAF files and take advantage of the faster computers' monitoring for better behaviour. If you just want to do it to have it, it probably isn't work it unless your computer or burn-off module is broken.


James

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1985 Z-28 305 TPI
165 ECM,STB,SFC,GW "wonderbar"

 

From my experience you will not need any of the 86-89 wiring harness or change MAF sensors. You will just need:

Parts:
* two relays
* 2 relay plugs ( plugs into relays and has 12" of wire)
* 1 ECM terminal pin

tools:
* soldering iron and some solder
* shrink tube & electrical tape
* 4 screws for mounting relays
* hacksaw to trim burnoff module bracket to clear memcal opening and hold relays
* correct memcal for application


In 85 each bank of injector wires had two wires, they must be soldered into one for 86(splice). You have to change the pin locations of 10 wires including the 2 main injector wires. And then build the burn-off relay and MAF power relay circuits using the pigtails on the relay plugs and splicing them into existing wires and in one case by using the ECM terminal pin to go to the ECM.

Perhaps the MAF sensor vader speaks of is on the earlier 85 TPI but it wasn't the case with mine. In previous posts I believe he mentioned a difference in the number of wires plugging into the MAF sensor being used to differentiate between the two style but mine had five and the 86 has five. So who knows.

James

 

Same here... Using the same MAF sensor with my 165 setup as I was with the 870 setup.



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Kevin Irving
85 Trans Am WS-6, 305 TPI, custom burned '86 PROM with '87 "165"ECM, Accel Supercoil & 8.8 Wires, Rapidfire #2 @ .055", MSD 6AL, 1.6:1 Roller tipped rockers, Homemade AFPR, K&N cone, no airbox, Aluminum Driveshaft, Wonderbar, TB Coolant Bypass, Ported Plenum, Descreened MAF, Syclone Fuel Pump, JET Airfoil, Mobil 1 synth in all but transmission.

http://www.geocities.com/transam85tpi/

 

I believe this was done because on the '870 ecm a single output driver couldn't handle the current alone. The two wires for each bank coming out of the ecm are spliced in the engine compartment, and I really don't feel that they need to be spliced again at the ecm end. You should just be able to use one of the existing wires and tie the other back (insulating it first, of course). It won't hurt anything if you do splice them again, however.

BTW, I'd give anything (almost) to see one of these mysterious AC/Delco MAFs that supposedly came on '85s. I've got a Bosch. Owners of these cars must have also gotten the "secret edition" Helms manual, 'cuz mine sure don't reference no FM MAF for the V-8.

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-Greg

'85 Trans Am - WS6,TPI:
Original owner, original paint/engine/interior, plus the usual bolt-ons

 

"I really don't feel that they need to be spliced again at the ecm end"

That's probably true from looking at the diagrams but I had six hours to get it right and get going. I didn't have time to experiment.

James

 

what about the benifits?

Curtis

 

the only benifit I can see is the ability to use more refined PROM code and faster data logging for chip burning. If it is working OK and nothing is broke you won't gain much, if anything. If the burn-off module is broken you will save yourself several hundred dollars.


James

 

Yup.