does the under drive pulley make any difference hp

 

Yes, iv heard of 7~hp at redline. Some people mention that the altinator(sp) pulley will cause low charging, others say it works fine.

 

Yes it does help HP. I have the 25% underdrives on my car and it charges fine.

 

Dyno test:

http://www.ws6.com/mod-2.htm

0.7 peak HP, 4.4 avg HP.

You aren't going to save much power because the water pump is not belt driven. Whether is causes charging problems depends to some extent on which tranny you have. 25% U/D might be OK with the 800rpm idle of the M6, but the A4 at 550rpm may show the voltage gauge headed for the red.

 

I had that problem on my 94-A4. and so have a bunch of my friends. thats y i got an M6 after my 94 got totaled.