My main question is what is the better intake system the s4 intake or the s5 intake? I am putting a rebuilt s5 motor in my s4 rx7. I have the intake system, wiring harness and ECU from the s5 but it obviousely doesn't match up to the s4 wiring harness in the dash. The big question is should I buy the s4 intake system and wiring harness and save the hassle of rewiring the hole car?

 

You will need to rewire the whole car to use a S5 engine in a S4. The intake doesn't change anything.

 

You don't have to rewire your harness and put in a diff ECU if you are only swapping the block and intake manifolds. Use all the s4 sensors and injectors if you still have them. For emmisions, im not sure if you can use S4 stuff on S5 manifolds.

The S5 Intake is designed better, you will loose power installing a s4 intake on the s5 motor and same goes for S4 motors. I installed the s5 intake manifold assy on my S4 engine and it increased my top end a good amount.

I heard, and this is just from what I have heard, that the S4 intake is better for ported motors. This may be a myth though and hopfully someone can jump in here.

 

Do you realise it's responsible for most of the S5's extra 16hp, and its broader torque curve...