Title is kinda hard to understand but ill explain


I have a 90 GXL with an S4 engine, only thing being it has all S5 externals. UIM,LIM the works, it running on the S5 ECU. If your still unclear on what it is, if you popped my hood and looked at the engine, you would think it is an S5 engine. So should my engine be able to safely be able to rev 8k while still making power ?

 

yes, the only reason mazda raised the redline on the S5s is becasue they have lighter rotors. you can still rev the S4 ones up that high, it just won't be as smooth and you motor will be working harder to get it there.

 

I rev my engine up to 9k rpm. It likes it. It repays me in large clouds of smoke.