I was just wondering, if anyone that has installed lightweight pulleys, did you feel any big difference once the pulleys were installed?

 

Have em' & they are worthless. Save your money & get a nice air intake, or hi-flow cat.

 

I have them also. I think they dynoed out at 1 HP gain by somebody else on the board. On a regular piston car these work just fine because they have a heavy harmonic balancer. The RX-8 does not. Reducing weight on the crank shaft increases HP to the rear wheels...or reduces inefficiencies that rob HP from the Rear Wheels. A standard harmonic balance on my 300zx must have wieghted ~ 18lbs and I replaced that with an aluminum unit that weighed ~ 4-5lbs or so. That is where the performance gain is to be had. RX8's underdrive crank pulley must weight ~ 1.25lb stock.