I need to know What exactly is the Underdrive Pulley and what does it do or help?

 

It adds some TQ.... but toherwise not a 2 die for Mod... it's fun to do if your bored and you just want to see how it works out on your car... doesn't hurt.

 

It's a pulley or pulley set that is a bit smaller or larger (depending on which pulley it is) to make the drag (parasitic loss) from the engine mounted accessories less. On most cars, this means the water pump, the alternator, the power steering, the air conditioning, and in some cases the smog pump will spin fewer times per crankshaft revolution. On LT1's, the water pump is camshaft driven, and the "smog" pump is electric, so you don't see quite as much gains. Some cars report that underdrive pullies will make them over heat from not enough coolant flow, or the air conditioning not work correctly, or the electrical system won't function properly at idle. I haven't heard any of these complaints from any LT1 owners, but once again it doesn't effect quite as much. I believe www.ws6.com has some before/after dyno tests and gained like 1.7 hp to the wheels... not much.

Jonota

 

well i have some complaints about them lol i couldnt keep my battery charged for nothing when i had them. when it rained and i had to run the def., wipers, and lights i would catch pure hell. even on dry days when sitting in traffic or a drive thru or something i would have to put it in neutral and rev it up a few times. some people have luck with them but i sure didnt. i even bought an optima battery and it didnt help. i took the pulley off and havent had any problems since

 

It was only like 1.7 hp but it was more like 5torque and showed a nice increase over the intire powerband, if i had the money i would get one right now. But I have also heard that the only good ones were the underdrive/crank pulley all in one as apposed to a piggy-back style.

 

I think they work a bit better in m6 cars or cars with programmed higher idle. I isntalled some used asp underdrive balancer in my 96 auto z. I didn't like the way the volts went so low at idle at lights and then installed an overdrive alt pulley which helped quite a bit .I will raise idle a bit when get my cam installed with tunercat likely and that should help some more. Now not sure if this is related but yesterday it was very hot and my air conditioning is only putting out warm air. I might simply be low on refridgerant and will be checking it out as I have asp underdrive balancer on my ls1 and have no charging problems but also think have overdrive alt on that one.I have ok air on my 99.
So it might be messing up my air on the 96 but a bit premature to tell.