I asked for an underdrive pulley for my birthday, and told my parents not to get the under drive alternator pulley. So the package came in from UPS today, and I got the underdrive pulley, and it came with the underdrive alternator pulley too. Should I just go ahead and put the underdrive alternator pulley on too? The pullesy are 23% underdrive asp pulley, and a 15% underdrive alternator pulley. I don't have any aftermarket stereo stuff or anything like that, and my idle is 800 RPM's (actual 800 RPM's from a scanmaster).

 

I had the ASP 23% crank/15% alternator U/D pullies and didn't like the way the volt meter dropped into the red on hot days in stop-and-go traffic with the lights or AC on. And that was when the car was still an M6 and stock 800rpm idle. The only extra electric load that I had was an inline fuel booster pump.

When I did the stroker, the ASP crank pulley got replaced with an ATI damper, but I kept the U/D alternator pulley because I figured it wouldn't hurt to slow down the alternator a bit with a 7,400rpm redline.

 

I had overdrive alt on my 97 with the 34 % underdrive pulley.Are you sure you got the 23% is it a balancer pulley if not then its likely 34%.

In my 96a4 went first with just the 23% but didn't like it that much it also seemed to go to low in traffic but a4 idle generally a few hundred rpm lower than m6 cars. I installed overdrive alt and its fine now.

In you m6 I guess maybe just try the different combos but you will have to by a couple different length belts. Also for my asp balancer and asp overdrive alt pulley the recommendation for belt a gates 605 think it was slipped bad. I went to a gatorback 600 and it works fine. I had terrible screeching with the gates. The recommended gatorback for when just ran the underdrive balancer on their site also worked fine. I have no aftermarket stereo in my vert.

 

Its the 23% pulley that replaces the harmonic ballancer. I decided to just put on the pulley alone without the alternator pulley. Then I drove around for 15 minutes last night in the city with the lights and A/C on, and I was watching the volts with my scanmaster. They never dropped below 13.5 volts, even sitting at a stop light. It kinda makes me wish I put on the alternator pulley too. I'm going to leave it though, I don't feel like spending another $30 on a belt though..

 

You like bragging about that don't you.

 

A friend of mine down here has an LS1 A4 camaro that gets dead batteries all of the time with an underdrive crank pulley. He gets pissy when I make fun of him. I don't know that the pulleys are worth the extra 3-5 peak hp, but they sure seem to be popular. At least get an underdrive crank pully and an overdrive alternator pulley to keep the battery happy.

 

I had the asp underdrive alternator pulley as well as the 23% underdriven crank pulley. I too didn't like how the voltage would go down under 13 when I was idling, so I took if off and put a stock sized pulley back on the alternator, but kept the crank pulley on, and now the voltage is fine and stays above 13 pretty much all the time. Only way I would suggest the alternator underdrive would be if you had a bigger alternator like a 180 or 200 amp.

 

What's your problem?

 

I need somemore Revs