I am looking at a '91 GTUs tomorrow as a potential track car but I would be transplanting an S4 modified engine/ECU into it. I know there will be differences in the engine bay wiring harnesses between the S4 and S5 versions but is it anything that would make it a problem to swap over. I am fine with having wires that I don't need, just making sure I'm not getting myself into something that will create more work than it is worth. Thanks for any input.
It would be best to use a complete S4 wiring harness from the ECU to the engine, too. Lots of the connectors are different. I think some of the connectors on the body harness are different, too, but that shouldn't be as much of a problem.
I'm sure you've already implemented a work around, but the auxiliary port actuation is different between the s4 and s5's (exhaust vs air pump).
Why go back to the s4? The s5 was a better motor?
An s5 motor with a mechanical OMP setup is the best, but he probably has a good s4 engine to use.
The S4 is a known good engine that I will remove from my previous car, it is set up for the track and has the 5th and 6th port kit. At this point I'm trying to decide if the engine harness is similar enough to do the engine swap or just pass on the car. I already bought a car that I know will be plug and play, but I am still waiting for it to arrive (bought from MD) and it will need other work. It is a base model S4 with 4 lug hubs and an open diff, I will need to move over alot of parts from the previous car to get the parts I need onto the new car. The S5 has lots of desirable parts and would need less things moved but if the harness is a pain it may not be worth it. Anyone know which parts may not play nicely with each other?
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