auzoom

Can someone explain what/how gains are to be made by new pulley sets such as these:

http://www.srmotorsports.com/RX8_Power_Pulleys.html

I understand the "Slippage" statement, but not the "by underdriving the crank shaft pulley, alternator and the water pump to keep down the chance of cavatation"

TIA

Andrew

SharkDiver

You will not see any HP gains but you should see a diffrence in how fast you can get your RPMs up too red line.The underdrive pulleys should really only help your engine get up to speed faster.I jsut installed mine today but havent had any time yet to test it much.The install was easy in-case you are wondering.Someone will prob. explain this better then me so jsut hold on a bit.
shark

Dark8

Sort of. By under driving the alternator and water pump you are getting rid of some of the parasitic loss and giving back that lost HP to the drive train. Granted, it is not much. I have a hard time believing its 12 HP. And I wouldn't worry about water pump cavitations unless you do some track driving where you might be at 7K+ RPM for long periods of time.

Fanman

With lightened pullies you are reducing the weight that the engine has to push, similar to the lightened aluminum flywheel. You are taking away weight making it easier for the engine to move the components. You always hear how their is an "18% driveline loss," what that means a lot of times is that the energy it takes to push these mechanical parts takes away hp. With lightened components it just takes less energy to push/pull these parts, so instead of losing 18% at the wheel, you may only lose 17%. In essence, you haven't gained hp, but really just freed up hp from your engine that used to be used to push these components.

With underdriving you are not turning your engine components as fast. An example, all things being equal, is it takes less energy to turn something 4X than 5X around. Only problem is if you don't turn something enough you can run into negative effects, like less cold air from your AC, or your alternator not charging your battery enough, etc. Many pully manufacturers play around & try to find the optimum balance, where you are still getting the intended effects of the component, but also turning them slower & reducing losses from turning these parts.

That being said, I have them on my car & I would not recommend them. 1) they are too expensive for what they do. I got 1-2 hp, not 12 hp that they claim 2) Caused idling & CEL on my car. save you money & do the flywheel, or get the Canzoomer unit.