Does and s5 turbo bolt up straight to an s4?

What are the differences between the s5 turbo and the s4?

 

Wastegate is the primary difference. Mazda did something write and added dual wastegate flappers instead of one small 15mm like in the S4. The hot and cold side, I've been told, are identical.

Will they bolt up? I have no idea, I have only seen the S4 turbo flange.

 

Yes you can interchange them, so long as you retain all the oil lines/coolant lines, and have the manifold with it.

 

So just to clarify.. to bolt up an s5 turbo to s4 you need

s5 oil and coolant lines and s5 exhaust manifold... is that it?

 

If you use an s5 turbo on your s4, you must use the s5 manifold. The manifolds are different and the turbos will not interchange. You will also need to reuse the oil and coolant lines as mentioned above.