Has anyone done this? I know an underdrive pulley on the crank would slow down the supercharger but it would be nice to have the added performance of both. A smaller pulley for the supercharger would help but how would we calculate what size the new supercharger pulley would need to be to speed it back up for full psi?

 

that stuff is prety easy to calculate but we would need to know a few things like stock crank pully size, existing blower pully size and new crank pully size. with that i could tell you your new blower pully size to keep the same boost.

in my case i have a 2.875" blower pully, 6.25" crank pully. if i switched to a 5.5" crank then the formula would be.
5.5x2.875/6.25=2.53

so a 2.53" blower pully

<small>[ February 17, 2003, 06:47 PM: Message edited by: parish8 ]</small>

 

I use a handheld digital meter than measure belt speed in ft/sec. at work. This would be the ideal device to figure out your blower pulley diameter. All you would need to do is use it to compare the stock belt speed to the underdriven speed to figure how much of a change you need to make on the blower pulley diameter. The blower manufacturers assume that you have the factory diameter pulley on your crank when you buy a blower, but they sell pulleys of different diameters to increase or decrease boost.