s4/s5 swap
 

My buddy Jus picked up an s4 engine,harness and ecu. He wants to put it in his 90' because his had blown. How hard is the swap? Can we use s5 ecu with s4 motor?? Thanks

i believe this is the wrong section for the question, and might get moved there but ask the guys in the 2nd gen section. u'll get a quicker response there. i try not to give misinformation but if i remember right from reading bout others, u can't use an s5 ecu on an s4 engine. or maybe it's the other way around. there's probably differences in sensors maybe. but as for the swap, it's a straight bolt in. what i would do is use everything off the s5 engine on the s4 one. come to think of it, the injectors may be different as in one uses low impedance and the other uses high. so that's what i'd do, use all s5 on the s4 engine.

Answered in the thread you started in the 2nd gen section. Use the S4 short block with S5 front cover, and leave everything else alone. Keep all electronics and wiring S5 to save yourself from a wiring nightmare.