v4 ecu coding
 

i have a v4 sti, i want to replace the gems ecu on it with a std 8S (i think it should have an 8S?).

Will the new 8S ecu need coding to the car? its a rally car so does not even have a key.

cheers

If the car is a JDM STi v4, it would have had a 75 ecu as standard, not an 8S. The 75 has no immobiliser.

Be aware that if the car was a rally car, it may have been modified to the point the standard ecu will no longer run the car safely (or perhaps even at all); there might also have been some rewiring for the GEMS that you might have to put back to standard. This won't be a big job, but might be worth checking.

the car is a sti ra V4, the casing in the car says 8S on it, i dont think the loom has been modded, is the 8S coded? and did the ra v3 v4 come with the 8S? I dont realy need an 8S i just want the car to run on a std ecu, whcih ecu should i go for?

No, the 8S ecu was only ever fitted to 97/98 UK turbo 2000 cars. The UK turbo 2000 has different MAF sensor, different turbo, different injectors, different cams, different valve trains, different compression ratio (etc. etc.) to the STi RA v4. Unless you've had a complete engine, sensors and turbo transplant from a UK turbo 2000, you should not be running an 8S.

The v4 STi RA should have a 75 ecu.

Be aware that the wiring for the ecu is likely to have been changed; for example, depending on which GEMS you have, it may not have any knock sensing capability (and the knock sensor may have been removed), and the intake air temperature sensor is usually connected to that pin. If this is the case with your car, then the standard ECU will straight away throw a knock sensor code and run extremely poorly. Also, the GEMS ecu is speed-density rather than MAF so there may be other changes such as a MAF delete. You should check for all of these things first!

The sti engine blew up so i removed it and fitted a uk wagon engine. i fitted the yellow sti injectors to the wagon engine and dropped it in, it ran perfectly. It even ran with the standard wagon engine loom. I assumed that meant the loom pinouts at the ecu were standard as it ran with bog standard loom? i guess the only way is to plug a standard ecu in and try it! many thanks for you help

Ah, okay. This changes things quite a bit. When you swapped the engine, did you swap the turbo and MAF sensor, or did you keep the STi turbo and MAF sensor? These items are quite different and the 8S will not be calibrated for them - if you want to run the 8S in the STi, you'll need the uk MAF and turbo.

The sti injectors are only a little larger than the uk ones, and the lambda sensor will deal with it in the cruise no problem, you may end up running a bit rich on boost, but that will just cost you power, shouldn't be so bad to cause any problems.

Not sure what you mean here. The STi has a slightly different loom to the UK turbo 2000 (cam and crank pins swapped, fuel pump relay line different, no immobiliser connections). That doesn't include changes to run the GEMS though.

To answer your original question now I know what you are doing, yes the 8S will require the immobiliser wired in. You'd need the immobiliser control module, amplifier and antenna module, wiring, and the keys with the chips in them to make it work.

PM me if you need any of the bits I have a matching set of 8S ECU, key and transponder ring.