I have an 87 TPI setup complete the only problem is its a MAF setup can i convert this to run speeddensity without having to buy a new computer? maybe just changing the chip and some other things?

 

The MAF computer and the Speed Density computer are completely different. To change, you need the computer, the PROM, the wire harness (or re-pin yours), the knock sensor, the MAP sensor, and various other little things.

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I too am planning to convert to speed density. It is looking like its not that hard to do. I was scanning the archives here and i found that you can get a 730 computer from a 90-91 lumina, beretta, grand am, and a couple of other cars. If you can pick one of those up out of the salvage yard it shouldnt cost that much. You just have to get a memcal with eprom from the 90-92 camaro. I dont know if the wiring harness from any of those cars will work though, im trying to find out. I really hope one will work because those harnesses are hideously expensive new. Anybody know if a harness off of a lumina or something will fit?

 

I have a Lumina. As far as I know, the MAF is different, and there are 6 injectors instead of 8. Other than that I think most of the GM harnesses were the same, but dont quote me on that. All I know is when I look under the hood of my Lumina, all I see are wires everywhere, and I Dont even have ABS.

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The comptuers are the same in the lumina-body cars and the 5.7 TPI. The injectors on these setups batch-fire (each side fires all 4 injectors at the same time) so the 6 cyl 8 cyl makes no difference. The only difference is in the prom. If look, you will find a 4 pin connector from the ecm harness to the injector harness, that is 2 pins for each side.

I would think that the harness would have the connectors at different places, or would have different lengths, but they may be close enough that you can just modifiy the harness from the ecm donor vehicle.

As far as the maf being different, i dont know about that. Mave the v6 uses a maf with a lower cfm range.




[This message has been edited by cfabe (edited March 30, 2001).]

 

GM Tech over on sethirdgen.org told me the same, the ECM's listed above are the same as the 90-92 TPI, and much cheaper out of the yard then if you pulled a "camaro performance" part.

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so let me see if i take a computer from a 90-91 lumina and plug it up to my harness it will work for speed denstiy as long as i change the eprom. or do i have to buy a harness from a speed density car?

 

There is no way a harness from one of those cars will work. Everything would be in the wrong position, and would not bolt into the car.

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What if we did grab the correct computer, what else is needed to convert. Do we need to completely rewire the system, or can we just modify our existing one. Anyone have an indepth article on this?

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Rob
'86 TA 305 TPI
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Rob, I did give a list of "donor" cars, but the Lumina wan't on that list. The Lumina is a "W" body car, along w/ the Cutlass, Regal, and Grand Prix and the computer WILL NOT work. The computers on these cars are mounted under the hood, behind the passenger side fender. Because of this, GM had to re-design the ECM to be waterproof, so the ECM has the 4 square connectors like the Vette.

You also cannot use the wiring harness from any of the V6 donor cars. You can, however, re-pin the existing wiring harness, providing you ****** the connectors along with the 1227730 ECM from the donor car.

I plucked mine from a Corsica. It MUST say 1227730 in the ECM. There is one similar looking to it, but I don't know if its the same. Then you will just need to get a PROM for the vehicle the ECM is going into. I used a '91 T/A chip as a starting point, and custom burned it to fill my needs.

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You can use the australian 808 code in your existing ecm, but it's not that great od system, going to the 730 is the best answer. Pep boys will have some extra terminals for adding a few wires. No big deal just takes some time. Get some wiring diagrams, from the DIY_EFI.ORG incoming area and you'll see how easy it is. Might even just do some reading at the Prom burning area and see how others have already done it

 

that's why they invented soldering irons and heat shrink tubing.
Couple guys have made adapters so most of it at the ecm end is just a PnP for the ecm.