Experience with Under drive pulleys

[-83MONTESS-]

I looked into installing under-drive pulleys on a 328i bmw. I always heard bad reviews of under-drive pulleys on a sbc / bbc so I would never even consider installing them on my cutlass tbh. bmw makes a great clutch but not such a great automatic. On the 328 in chicago traffic it would always shift into 3rd when I really needed it to stay in second gear. This would cause me to waste so much breaks b/c the car is always trying to shift into 3rd. I rode w/ a friend in his 328i with the under-drive and noticed when he was in 1st or second gear if he took his foot off the gas his bmw would just coast and remain in w/e gear he was in before he took his foot off the gas and it would continue coasting in that gear. This looked much more enjoyable / easy to drive in Chicago traffic and was therefore very appealing to me. I never got around to installing the under-drive pulleys on the car b/c my brother crashed in it. I can't imagine any situations outside of Chicago traffic where this would be very helpful. It looked like a huge improvement for driving on highway 94 to downtown chicago, IMO. Idk anything about horsepower gains and charging and all that, I'm a driver not a mechanic.

But under-drive pulleys have nothing to do with changing actual engine rpm. They just change the accessories rpm. The car wasnt shifting different because of the pulleys unless BMW has a totally different setup than anything I have worked on.

 

[pontiacgp]

underdrive pulleys are used in high revving engines so you don't burn up the alternator bearing and you don't overdrive the steering pump and boil the fluid. We use them on all our race engines which are SBC and they never cause a problem when set up properly. 83MONTESS is right, they have nothing to do with the operation of the engine

 

[pencero]

I never finished setting up the car I was talking about. I was going to just copy w/e my friend did to his bmw onto mine. I guess I just had a poor understanding of how it works. All I know is my friend had them and his bmw took much longer to drop rpm's than mine so it was a lot easier to drive in traffic since you could coast in 2nd and not have to worry about the car sliding into 3rd gear just at the moment you needed to break for traffic, yet if you let off the gas entirely it wouldn't just drop back down into 1st gear right away, there was a longer delay than on mine (same car). His car would not leave 2nd gear for a long time unless you tapped the breaks (in which case it would go back to 1st immediately) He put a turbo on it and it was still easy to drive in city traffic even w/ an automatic np this way... This all of course was on a bmw. I guess it is entirely irrelevant

I wonder why every guy I ever heard of installing underdrive pulleys battery dies b/c charging problem around here and they end up taking the pulleys off... Is it really that hard to get this part to work effectively on a gm car? I have never seen someone get it to work correctly except on bmw's and mustangs... why?

 

[pontiacgp]

you don't need an underdrive pulley unless your driving your car around 5 or 6,000 revs whenever you are driving. Like I posted the only purpose of underdrive pulleys is so you don't burn the bearings in the alternator and you don't boil the power steering fluid. On our race cars we are constantly over 6,000 rrpm so we need an underdrive set up and our set up costs up close to $800

 

[don4life]

I understand what they do just wondered how peoples experience with them on street cars was. I plan to run some, later on now, just thought about getting them now since i need a couple of the pulleys anyways.
Thanks for info
Don