I have a 1991 RX-7 convertible with the S5 NA engine. My older brother is rebuilding his 04 RX-8 and we were wondering if we could improve my S5 with the renesis rotor assembly out of his old engine? (his housings expand after a bit of driving so he got a brand new renesis.) The renesis rotors have already been milled to 3mm and have ceramic apex seals. Can this be done? and if so is the power and/or efficiency gain worth the trouble? thanks in advance (:

 

It's been done many times but there really hasn't been an observed power increase past maybe a few HP. The lighter rotating assembly will allow a higher redline, but your ECU will still hit the rev limiter, the ports will be a limitation and the intake manifold will be a restriction.