"Since the supercharger w/15% pulley really gives a lot of oomph at the lower ranges as well. It would seem to me to be more beneficial to put a 20% pulley reduction or more on and limit the redline of the engine. This would start giving you more useful horsepower/torque at an area of the engine powerband that would be more useful. The benefits would be not only preserving the life of the supercharger, but also the engine, since the engine would, at a maximum spin much lower anyway. I would be willing to give up some of my rpm (i.e. maybe only redline up to 5750) but gain quite a bit of extra torque over the 15% reduction pulley."

My thinking exactly.



I know of two cars that have fitted a creatively machined, custom P&D 20% pulley after trying the 15% and can report worthwhile torque/hp gains; both have several thousand miles and track time.
There has been no evidence of cavitation or blower overheating.
My main worry is belt wear, but that has not been a problem either.

 

I think a 20% can work. And I may end up trying it. All of the individuals who expressed negatives, obviously didn't read my post. I agree with the water pump and limits on rpm for the supercharger. That is why I stated lowering the redline slightly to make sure that the belt and supercharger didn't spin past the limits of either. Instead of screaming the engine to 7500rpm (which by the way also adds wear and tear to the engine) and having the capability of going 140+ mph (which I will rarely ever get to), I would rather have the mid-range torque. I would much rather have the acceleration from 30mph to 70 or 80mph which I would use every day.

jlm,

Do you know how much extra horsepower/torque these individuals saw with the 20%?

 

To be quite honest, it sounds like a good idea to me too. I don't need power over 100 mph....so what's wrong with a 5500 or so redline?

 

Sorry if I didn't read everything completely before commenting. I'm so impatient that way.

Another question for the 20% gang, is there any noticable problems at low rpm or idle due to added parasitic losses?

Thanks,
Jim