Underdrive Pulley: Useless?
 

I was chatting with my father (a long time Porsche tech) about my next mod--which was UD Stillen pulley-- and he said it didn't free up any power. He said it was completely useless to underdrive the accessories because 1. when you're going in a straight line or dyno'ing you're not putting the power steering under a load, 2. when you're battery is fully charged there is very little load on the alternator, and 3. if you're A/C if off you don't have the AC clutch engaged and the pump is under little to no load.

These accessories are basically free spinning and drain very little power from the system so why waste money on an UD pulley?

Got me thinking...

... Holy crap...

It lowers rotational mass... And why spin the accessories when you don't need to?

Underdrive pulleys usually are a performance enhancing item that increases the torque and horsepower output of an engine by reducing drag caused by belt-driven accessories.

Horsepower gains from underdrive pulleys alone are usually around 4-7 hp.

^^^Although most of that is from the crank pulley...

Was debated here ................

http://www.the370z.com/engine-drivet...leys-help.html

IMHO opinion, the benefits are outweighed by the drawbacks, and since I am an old f4rt, I agree with your father

learn something new every day

I thought a Porsche Tech would know any better.
But it wont harm if you do listen to a fathers advise!

I would in certain circumstances :tup:

Honestly, when factoring the risk vs. reward, a couple HP isn't worth it to me to install pulleys.

I believe sombody on here tested it after the install and got like 5 hp.

My 2 cent on this. Why take a chance with the underdrive pulley. It's well known that our our oil pump isn't the greatest. And any new induced harmonics on the end of the crank will have some affect on it. For a DD, it may take awhile. But for a trackday car......tick..tick...tick...tick...tick....:eek: I've seen a couple of V8s with broken cranks. All had an underdrive pulleys. So from what I've seen. I don't what to take that risk for a couple hp.

I think the OP is talking about things like the oversized (to under drive) alternator pulleys and such -- I don't know about the difference they make, but a lighter crank pulley will definitely make a few extra ponies.

Of course, you are putting faith in the presumption that all automotive engineers are dampening the harmonics produced by their crank pulleys because they have nothing better to do...

I agree with this statement 100%. Which is why I will never install them.

^Agreed.

Dude your engine will come unraveled within a thousand miles lol

I went against my ole man's recommendation and bought UD Stillen from Elmo370z

http://www.the370z.com/parts-sale-pr...ml#post3064080

I hope my harmonics aren't affected :)