All s5 and up rotor housings are the same. The only difference with the s5 and the FD is that the FD rotor housings have a different coating on them from the factory and the area around the spark plugs offer better cooling supposedly. If you look at the Trailing plug hole on the outside of a s5 motor you will notice that there is a threaded hole above it. It is for a knock sensor and even the N/A s5 motors have these. S4 rotor housings don't have this and the knock sensor goes to the center intermediate housing. I've even used s5 N/A rotorhousings on turbo motors all I did was change out the exhaust isert sleeve. Timing is the same and you can find N/A rotorhousings more readily than Turbo housings. Hope this helps you out.

 

Thanks, I'm trying to source some s5 n/a housings out right now. The housings I have definately dont have this threaded hole. I dont think they are compatible with anything...