Ok, I have a complete S4 T2 coupe that I'm using as a donor to turbo a S5 'vert and I have a couple questions. My other FC is using a haltech so I've never really messed with the stock wiring. Upon searching I am mostly just seeing s5 t2 engines into s4 cars, not vice versa. Sorry for the newb-ish questions. I plan on making a write up for this once it's all said and done.

Should I use the S4 T2 battery/alt harness or the s5?
Does it connect right in or will i have to rewire some things?
What will i need to rewire?

I'm assuming I should be fine with leaving the s5 dash harness?
Is there anything I'll need to modify to make it work?

What about the tranny wiring?

I know I'm going to have to re-pin the front harness to work with the ecu but I'll tackle that obstacle when I get to that step.

Any comments/suggestions are welcome

 

nobody has ever done this?

 

Hey, I did/had done a S4 to S5 JSPEC full swap....major pain in the ***...ended up costing me a lot of money on wiring alone.

I assume your doing a full swap not just the block. If so, the ECU pin out is easy, in fact, I have it, you could use it in reverse, but that might confuse things. The engine stuff is tough, with the relays etc… because some stuff that plugs into the ECU in one car plugs into the junction wires and in the dash harness in the other. The junction wires are the killer. It took 4 months.

Let me be honest here, for me the results are awesome, but I went from 140 hp to over 225 hp. It was not worth the cost, months of trouble shooting, pouring over wiring diagrams for BOTH cars, cannibalizing the old harness and plugs.

One option, change everything, all dash components, dash harness, chassis harness, computer, your top won’t work but you can overcome it. EVERYTHING

For the time, money, and frustration your way better off getting a S5 USA TII engine, or a S5 JSPEC and a US TII engine harness, but with that still wiring due to emission differences.

Plug and play, **** all the bullshit.

 

BTW, you could do the block swap keeping all your accessories, there is a write up on rotaryresurrection.com. Good Luck!

 

thats what i was thinking...time to get another haltech. thanks