Actually, the whitepaper on underdrive pullies on the UR website admits that the majority of the gain comes from the lighterweight, not the underdriving effect. That's why you seem similar gains (claimed) from either the UR or KJR.

 

what makes you think the KJR wont free up any power and the UR one will? the fact thats its underdriven? Even UR admits that being underdriven might only add 1 hp. The gains are from the weight loss, not the size. The KJR and the UR are almost the same weight....like 0.3lbs difference

 

the KJR does free up some power... not as much as the UR, but its not a huge difference between the two...

A Supercharged Car will see even more of a gain from the KJR pulley then an NA car will see from the UR...

 

im sorry sir but this is incorrect information. Jason posted a dyno showing that the increases at the top end are actually higher than lowend. if anything the pulley will only increase the lowend by little and the top end more.

this is due to the increased revolutions of the motor (which now has to turn less weight) being higher at the upper end. this decreased weight allows it to spin easier translating to less parasitic loss on the drivetrain.

i had the ur pulleys on my z and noticed a significant improvement not only in drivability but also in power.

 

From the weight reduction ( less rotating mass) the gain in performance will be linear accross the rpm range.. The lighter pulley means more of the engines tq is available to the wheels..The angular momentum of a pulle is H=I W where I = inertia (the mass component) and W = rpm..When you substitute the I difference between the 2 pulley sets the difference in H is the performance gain..The W is the same in both cases..

 

here is some good reading...

Moment of Inertia:

 

I dyno'd the KJR here are my results.
http://g35driver.com/forums/showthread.php?t=75567
I still can't figure out why I didn't see any gains.

 

AT's dont show as much gain from Pulley mods...

:-/

 

http://www.turbomagazine.com/tech/0403tur_350z/

Dyno from turbo magazine, their project Z.

And here is the nissan magazine articles.
http://www.nissanperformancemag.com/august03/350pulley

Most people do get gains, what are you trying to prove here?

 

Don't you think that if Crank Pulley's were worth it that Nismo would have already produced a crank pulley?

 

There are a lot of things that NISMO doesn't offer, that has nothing to do with their worth as a performance mod. NISMO offers a grounding kit - nuf' said.

 

NISSAN MOTOR SPORTS USA offers the Grounding Kit...

NISSAN MOTOR SPROTS USA is different then NISMO JAPAN...

like their 4 point adjustable shifter, is a NISSAN MOTOR SPORTS USA product...

These parts are not manufacturerd by NISMO...