Turbo to N/A conversion
 

Hello, I’ve been searching for information on what I’m doing but so far I’ve come up with absolutely nothing. I want to know if it’s possible to run a S5 turbo 2 ECU and engine harness on a S4 N/A engine.

I bought a S5 T2 roller to transfer all my good bits to but all my wiring from my S4 N/A car is a complete mess from the previous owner cutting and rerouting new wires, but I have all the S5 T2 wiring and ECU so if I can get that to work on my N/A engine I’d be saving a lot of money buying new harnesses. Any information will be greatly appreciated, thanks

The ECU will run lean and overall very poorly, if at all. It'll also stay in limp mode since you don't have an oil metering pump.
Other S4 parts won't physically plug into the S5 harness and/or work significantly different: Alternator, Airflow meter, boost sensor, fuel injectors, idle control valve, oil metering pump.
Use the NA harness or find a replacement one.

So if I go with a stand-alone aftermarket ecu and change out a couple of connectors could I get everything to work?

welcome to board. :)

the simple answer is yes.

it's also worth mentioning though that you can get the major sensor connectors to aid in making the harness "plug" into the engine. i found that out after the fact, so i thought i'd share.