I have a turbo S4 with a bad motor. I found a running s5 turbo that got totalled. The rear end is pushed in to the seats.

can i swap the motor and ecu and wire harness to from the s5 to my s4?

 

I don't know much about these swaps so don't hit me with a bunch of questions for I won't have any, but the best thing to do is change over the sensors on the S5 engine to S4 and you will also need an S4 ECU. You will also have to figure out how you want to deal with the OMP for the S5 electrical version will not work on the S4 if installed as suggested. You could either add your own oil or change the front cover so a manually driven S4 OMP will work.

 

I agree, use just the S5 short block and turbo (if its good) and premix, or change the front cover to your mechanical OMP. You will save yourself a good bit of electrical headaches..

Swap everything else over from your S4 motor, all the intake and fuel stuff, A/C, PS, etc...

I would recommend you get an Rtek to tune to the difference in compression and turbo characteristics etc..

 

If you have the know how and good mechanical intuition I would personally swap the entire thing over including harness, ecu, etc. etc.. I am sure there a tons of write ups on the net to do that procedure.

Oh and to answer your question, yes, yes you can.