I want to get some under drive pulleys from my car. Do they affect charging o fthe alternator etc.? I want to get a March U.P. but I'm not sure if those are good. What else will I need for installation with them? Is there a certain configuartion I just could with them as well?? I can't find it in a search. How much are U.P. sets, and what is better steel or aluminum? If you could help me out as much as possible that would be great! Are U.P.'s worth it? What is harmonic balancing and should I get a pulley that has this? How hard are they to install?

Also what is an alternator overdrive pulley, would I need that at all? I don't want to lose charge at all. How are the pulleys from tbyrne? Is the underdrive alternator pulley different? I'm really confused on the types of pulleys to get. I see a lot of crank and alternator pulleys sold seperately. And I see a different combo of underdrive and overdrive for both. What would most likely fit my needs? How much are the belts and how many will I need if I get alternator and crank underdrive pulleys? What is an overdrive pulley.

 

I can't answer all your questions and you have a lot, but I can answer some. I recently bought a BBK underdrive crank pulley. This is an aluminum piece was about 75$ I think from jegs. I think most that are 100$ or less aren't like replacement parts for the factory piece which is a combined pulley/balancer. You take the stock pulley/balancer off, put the new pulley on, and then put the stock pulley/balancer (now just a balancer), on the new pulley, then just route the belt on the new pulley.

An alternator overdrive pulley, didn't come with the BBK kit but basically, it's to compensate for the crank pulley being smaller so that charging doesn't change. With just a crank pulley right now, there is a difference in charging, but it's only a concern sitting in idle traffic for a long long time. I'd say if you have any stereo equipment you'd want a setup for that (I think march has a kit for this).

It's all just one belt, cost me 23$.

 

They effected both my buddys 93 and 94 a4's...they ended up having to take them off..never got them myself, didnt think the few extra hp was worth the possible problems

 

MBA also makes a set for LT1s. I did feel the difference up top when i floored it.

I have the MBA crank pully on my car only and i have the alt. pully sitting in the garage. The charge will drop to about where the red starts at idle or at a light. But it does go back to normal once i hit the gas.

I've been wondering, the point of the underdrive is to lessen the weight and have a smaller ratio then the stock, so technically isn't putting a underdrive on a LT1 and still having to use the stock pully for a balancer a bit of a weight addition?

 

I got the March "power & Amp two piece set, i really havent had any problems. I got my stock radio--I hear if your radio has a big amp etc, you may have a problem of sorts. When i have all my lights, fog etc and the air on my alt gauge does go into the red area but i have had no problems----But after i got my set i read here they weren't worth a whole lot in hp--i always read this stuff after i spend a $100--You might want to spend your money elsewhere even though i still have mine installed. Dwayne

 

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

 

I have had an aeromotive underdrive crank pulley on my 94 A4 for years.
It currently has 155k on the motor and has the STOCK alternator. I have a decent stereo setup in it as well and it has never given me problems.
My headlights will dim a bit at idle in gear but come right back up as soon as the revs do, this has never had any adverse effects.
The aeromotive came as a kit with an overdrive alt pulley but I could never find the right length belt with my AC delete pulley.

 

I've used many different brands of pulleys on my cars from the March power and amp series to the latest asp replacement balancer combo. Every time I put them on an auto car I wound have issues with charging. The M6 cars rarely had issues. But from now on I won't wast anymore money on the piggy back style. I can feel the diffence with the asp and don't have any issues. Also it shaves a few pound off the crank, rather than adding weight.

 

$75 for <1 hp? I dont know about that one. You get more from a free mod (TB bypass=~2hp).