underdrive (crank) pully

[tanklugz]

just wondering if the crank pulley really adds 5 horsepower or if this is just a gimmick... thanks

[oneday]

It adds WHP by reducing rotating mass. BHP is still the same, the reduced mass allows more HP to be transfered to the wheels. Every 1 lb of rotating mass is equal to loosing 10 lbs in the car. Now, 5 hp is optimistic, and I am not a big fan of the lightened crank pulley especially if it's underdriving the accessories.

[navylife59]

Most lightened crank pullies are just that; lightened by changing to aluminum with less mass and no dampner. It does as stated in the previous post. Now, if you were to run a different size pulley to underdrive your accessories, then you would actually be recovering lost power by reducing the load on the engine.

Just to reiterate what oneday stated, it does not make power but makes more efficient use of the power the engine already has.

[tanklugz]

ok, thanks for clearing that up, i was confused. how much should i expect to pay, are there any brands out there?

[navylife59]

ZPI makes and excellent one and so does NST. I think Perrin and AEM make one to but not sure. Be sure to get it anodized because aluminum will corrode faster w/o it. My ZPI one works just fine and easy install. Be sure to use thread locker and a good torque wrench to install.