does it just reduce weight? or does it actually give some HP too? if so, how much? (weight reduction and/or hp?)

 

Don't have one, but I'll tell you what I know about it. It basically increases HP because it replaces a heavier OEM pulley. It doesn't add any power on its own, per say, but it makes the car quicker (I would imagine VERY slightly) by making the car a LITTLE lighter.

 

Not quite right. It does not 'increase' HP...it simply frees up some of what the engine is producing but losing to accessories. The weight difference is to allow for more efficient transfer of the crank "turning energy" than for any overall vehicle weight savings.

 

That's what I meant. That's why I said "per say" I guess you used the better expression "frees up ALREADY existing HP".

 

gotcha

 

how much does it "free up"?

 

not sure...search on 'UDP and INCREASE' or something like that...should be some stuff out there

 

From what I've read on here, I think it only frees up a couple or so, not much though.

 

By 'freeing' up I think they mean it is a smaller pulley than stock. That being the case, it is easier for the engine to turn a smaller pulley because of leverage. This makes your accessories (alternator) run a little slower than normal. People that replace all the pulleys usually do it for looks to get them all to match. I think.

 

It is the same effect as lighter wheels or a lightened flywheel. Anything the rotatates takes energy to accelerate and a lighter object takes less energy. Supposedly a UDP frees up about 5 WHP.

A UDP also frees up some power by underdriving the accesories, so less power is use to turn the power steering/alternator and AC but most of the gains come from less weight. Theres a pretty good explanation on the custommaxima site -- http://www.custommaxima.com/UnorthodoxPulley.php

 

Rotational mass is reduced, making it much more efficient. It's kinda the same theory as putting lighter wheels on your car. Less weight to turn= more efficiency......but not necessarily pure hp.