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sam c. · 03-07-2013, 10:28 PM

I've been looking at UD pulleys for the 2.5l base and had a quick question for all you guys with more knowledge on the subject...

It seems all the UD pulleys currently on the market were cut to the 4" spec dictated by race rules which were put into place to protect overheating PS components.

The UD pulleys were not cut to a size that squeezes the most power out (or more accurately, minimizes the most parasitic drag) while leaving the stock functions intact (in particular the cooling and charging functions).

So my question is has anyone done the necessary testing to see how small a pulley can be cut without impacting those important functions for a strictly street car that has no concern for race rules? If 4" pulleys are fine, would a 3.5" or 3" pulley be ok?

I've talked to some CNC owning shops and can get some custom pulleys prototyped for approximately $250/each but was curious if anyone else has already been down this road and what were the results of their efforts? As it sits, I plan on installing a 4" off the shelf pulley until my 3.5" and 3" prototypes are cut and then begin testing.

03-07-2013, 10:28 PM	#1
sam c. Registered User Join Date: Mar 2013 Location: idaho falls Posts: 257	custom ud pulley I've been looking at UD pulleys for the 2.5l base and had a quick question for all you guys with more knowledge on the subject... It seems all the UD pulleys currently on the market were cut to the 4" spec dictated by race rules which were put into place to protect overheating PS components. The UD pulleys were not cut to a size that squeezes the most power out (or more accurately, minimizes the most parasitic drag) while leaving the stock functions intact (in particular the cooling and charging functions). So my question is has anyone done the necessary testing to see how small a pulley can be cut without impacting those important functions for a strictly street car that has no concern for race rules? If 4" pulleys are fine, would a 3.5" or 3" pulley be ok? I've talked to some CNC owning shops and can get some custom pulleys prototyped for approximately $250/each but was curious if anyone else has already been down this road and what were the results of their efforts? As it sits, I plan on installing a 4" off the shelf pulley until my 3.5" and 3" prototypes are cut and then begin testing.