I was looking for an underdrive pulley to put on my car and found this one from RX7.com.
http://www.rx7.com/cgi-local/2catalog.cgi?cat=3&part=1
What I wanted to know, if someone could please help me out, is first if this is a good one, or does anybody have this one, or can suggest another one? If I do get this one should I get the alternator pulley as well; I do have the air pump on my car still. Thanks!

 

I don't know about everyone else, but I am not a big fan of the underdrive pulley... Sure, it makes more power, but it makes your water pump run slower too, as well as your alternator and a/c. That's just my $.02

 

for an all out race car yes! for a street car no...

 

The main underdrive pulley is not needed on a street car, and the dual alt pulley can only be used if the air pump belt is removed.

 

Thanks for responding but I have another question. I know a few people with underdrive pulleys on other kinds of cars that are street cars, is there a difference because it's a rotary that it's not good to have one?

 

Most of those underdrive the alternator and power steering - sort've standard and not really detrimental to those cars (ie - AEM stuff).

 

Whether piston or rotary, underdrive pulleys are pointless for a street car. They're for race cars that spent a lot of time at constant high rpm. This gains a few hp and stops cavitation of the water pump. This is not a concern on a street car, and the pulleys have been sized to make everything work effeciently at the lower rpms you use most on the street. Slowing everything down could hurt your cooling and will definitely make your sucky alternator even worse.

 

SOME of us run our water pump at a constant speed....
Sean Cathcart

 

Practical experience on a Trans Am, no problems.

Impractical experience on an RX7 race car.. No problems.

Up to you to do, just read carefully, mazdatrix' warning about removing the eccentric shaft bolt to prevent the bearing from coming loose..

Ppaul