what is underdrive pulley for?
I am newbie

 

It's a replacement pulley for things like your alternator, water pump, A/C compressor, etc, so that the engine doesn't have as much load to drive. The premise being that this will free up some HP. The consequence is that the accessory that has that pulley performs at a fraction of it's previous efficiency. You make a little sacrifice here or there to gain a few extra horses.

 

anyone have any real hp #'s associated with underdrive pullys?

I am removing my A/C compressor anyway and won't mind the power steering being just a tad less boosted anyway.....

thanks if you can post some hp #'s.

and how long it takes to install, and which pullys you installed....

 

What does power steering have to do with underdrive pullies? It's electrical.

 

And you can't adjust the power steering boost anyway.

 

ahaha.. shows how much I know about S2000's..... i thought normally the underdrive pullys were for the a/c, alternator and the steering....

apparently the only one I could use on my car would be the alternator.... maybe i will pass....

 

What kind of hp are we looking at for these pullies...

 

I think you can get 2-4whp for the alternator, PS and tension pulley. No one really has the crank pulley so don't really know. PM AJ PwR, I saw he has one on his desk. It weighs about 50% lighter and I think another 2-3whp is possible.

It is not just about HP gains, it also eliminate stress to the engine so response will be improved as well.

 

Keep in mind that the crank pulley is not just a pulley. It's also a damper for the oscillations of the crank shaft. Remove it and you remove the dampening. That will result in far more stress than a lighter pulley eliminates.

 

I wouldn't want to risk the loss of the harmonic damper for 2hp.

Crankshafts aren't cheap.