Supercharger Pulley Ratios
 

Hi friends, a you know i have a m44 supercharger at 7-9psi, the great new is that i have a "free" ($200.00 and a set of use bmw seats)M44 engine remove from a running 318i, i want to convert those engine in a serious animal with the help of my brotjer and some mechanic that are my friends, 3 months ago i buy on ebay othe Nissan Frontier Eaton m62 supercharger, we are planing go close to 12-15 psi of boost the question is how i know the perfect size of the pulley i know that i current use a 3.4" pulley on my setup to run 7-9psi at max rev.. so how i calculate the numbers, thanks for read:smile:


Fernando Raul

I have the 3.6" pulley and run ~9-10 psi. A 3.2" pully should be good for you.

yeah Dustent but remember that my blower nose is diferent that yours, actually i run a 3.4" pulley and boost 7-9psi in the MA page said 10.5psi with 3.1"pulley, i like to run over 12, also i read in the exterra forum that the oem pulley that i have on the ebay blower is 2.64 i think is too litle for me, those guys reach the oem numbers from 6psi with 2.64"pulley to 12!!!!psi with 2.3 pulley and without other modification , only change the pulley but the have some issues with the bearings by the high temps on the blower for the high rpms, first i repair the m44 but this work is from milton ( my best friend) my work is the blower manifold and the boost items, so i think that the first step is goin to the machin shop with the blower and order 3 diferent size of pulleys maybe 3.00, 2.90 and 2.80 and remanufacturate the use blower

http://www.eatonm3.com/318_supercharger.htm

check the numbers of the pulleys ...

You can buy a little gadget thats really for working on small engine like on mowers, its called a contact tachometer, you press it to the center of the blower input shaft and it will show you the blower RPM. Compare that to engine RPM and do a spread sheet using the pulley diameter, and RPM and just do the math upward. You should be able to calc exactly the size pulley you need. You can get the blower sheets off eatons web page which will show you the CFM of the blower at a given RPM.

Good Luck
Dave