How much hp can i expect from an underdrive pulley? i have a cat back exhaust and a jwt pop charger, and also how hard are they to install?? help is greatly appriciated.

 

I am not certain that a pulley makes any horsepower. After all it does no increase air or fuel. And if it does increase air or fuel then someone explain how. Thanks.

Considering your mods, I recommend a intake or plenum spacer.

 

The after-market underdrive crank pulley (KJR or UR) will lighten your rotational mass for the pulley. So that put less stress on the alternator and the engine. Which then improves your throttle response and free up a little HP and TQ. The lighten pulley will help your engine rev up a little faster than the stock pulley.

Average HP increases from 5-8. TQ increases anywhere from 3-6 lbs.

 

It also underdrives the AC, so you loose less HP on the AC. Guess you culd also just shut it off ?

Don't get one if you plan on going Supercharged...

Danny

 

the KJR isnt an underdrive pulley. same diameter at stock.

 

I reccommend just the crank pulley. It doesn't really provide much, if any, power. But it does help smooth the power band out. Also provide a lower idle rpm. I say go for it. Installion is pretty easy but will need a friend to help hold the brake peddle.

 

There is a reason the factory puts a balancer on the front of the motor and it's not a good idea to take it off. If you want to loose some rotational weight and get the car to rev quicker get a lighter flywheel.

You can read a little about them here http://www.dinancars.com/whitepapersFile.asp?ID=5

Chris

 

This might be true for a BMW, but since the shown pulley doesn't look anywhere near the ones on the 350Z, I doubt it's true for our cars.

EDIT: I just looked at the pic again and actually that's a pic of a PULLEY + a HARMONIC BALANCER. Our cars don't have an harmonic balancer, just the pulley.

Another objection I have to the article is how it speaks about a perfectly balanced harmonic balancer, yet leaves out to discuss the effect the belt has on the pulley. Belts can be less or more tight (and stretch over time), which would really affect the pulleys behaviour (it's "weight").

Danny

 

if going supercharged dont get the UR get the KJR as stated above

ive never installed one but i hear its fairly simple (i did read the instructions for it and it seems pretty easy)

 

I stand corrected, your right, the VQ isn't running a damper.

Chris

 

Does every pully has different size?

 

Underdrive pulleys are (lighter and) smaller so they turn alternator and AC slower, hence less HP loss there.

Since a Supercharger relies on stock size crank pulley to turn it the correct rpm and make the correct amount of boost, they also make lightweight pullies in stock size.

Danny

 

Please noe that you can just get the underdrive crank pulley and leave the stock A/C & alternator pulley alone.

 

underdrive pulley also underdrives the power steering pump, the steering wheel therefore feels heavier...more like a real sports car.

 

can u pm me thoes instructions or send it to my email christopherdugas_25@hotmail.com