http://i50.photobucket.com/albums/f3...35/Pulleys.jpg



Going on the car Thursday

 

nice and shiny! how much did u pay for those?

 

with all those mods and nos your 1/4 time is only 13.76???

 

1/4 time is from last year, and a few mods ago

It's still winter up here, first track opens late Feb


Pulleys and belts shipped from Stillen for about $350. I thought about getting the anodized red but wasn't sure about color match with the car.
Polished matches any color

 

Man. They look good. Are they underdrive pulleys or are they just lightweight?

 

Light and 15% underdrive. I have the 3 pc. set in black. Nice precision stuff. And yes, you can feel the difference.

 

what kind of difference?
I've been also told that lightweight pullies benefits MT system more than AT system? Is that true? How much does lightweight pulley set benefit an AT car?

Thanks

 

Nothing like 2 whp and some increased bearing stresses to get your car really movin'. Just playin'!

 

Pulleys are on the car now, looking pretty nice.

I weighed the crank pulleys on a postal quality scale, Stock pulley is 6 lbs 4 oz. and UR crank is 1 lb 6 oz. That is quite a difference.

As advertised by the retailer your supposed to get 2.7 hp per pound lost from the crank pulley......I will take this with a grain of salt and say 2 hp per pound and maybe 3 more for the underdrive gain. So I should see 13 hp at the crank from this mod.......hmmm.

Well, going to dyno tomorrow

 

i just drove a friends AT sedan like 15 mins ago with the crank pulley and his car feels way more responsive! i guess this is one of thoes things that might not show up in the dyno.

 

it's like lightening the flywheel - won't show up on the dyno.

 

well, Pulleys are just like flywheel, their gains are never shown on Dyno since they are supposd to let the car rev faster.

+ his mods are good enough for his time, since he has a 5AT like me.. and it is not ricer math., it is a combination of tuning, mods and how well do they act with each other

 

And a select few on this site told me I was full of crap when I said the VQ35 crank pulley probably weighs close to the VQ30 crank pulley (6.0 lbs) in my old Maxima.

If you remove a lot rotational weight, the results will show up on a dyno. It's simple physics. Replace the 50lb tire/wheel combo with a 30lb tire/wheel combo and you'll see increased power on the dyno because less power is required to the spin the lighter wheels. As for pulleys making a gain? In my opinion, no. I saw absolutely no gains on the dyno or after a lot of track runs on mutliple track outings in my VQ30. The stock pulley weighed 6 lbs and the UR UDP weighed about 1.5lbs. The VQ30 revved quicker, but that's it. Since the rotational weight is terribly small in diameter and mounted directly to the crank, the gains simply aren't there.

 

FYI, that old wive's rule of thumb is complete BS. The power gained is directly related to the rate of acceleration of your engine. The faster the engine accelerates, the more torque it takes to accelerate your pulley. A blanket statement like "2.7 hp per pound" is ridiculous.

In case you're interested, I've detailed the math behind lightened pullies or a lightened flywheel here: http://www.stanford.edu/~mpg/lighten...omponents.html

Skip to the bottom if you don't care about the derivations. The final numbers work out to be about 2 whp in 1st, 1 whp in 2nd, and under 1 whp in higher gears from just the lightening of your crank pulley. The underdrive portion is basically where you're getting any gains in this case.

For a car to "rev faster" in gear it has to put out more power to the ground. And therefore lightened components will show up on a dyno if it is an inertial based dyno (that is, that it measures the rate of acceleration of the drum, loaded or not, to determine output power at the wheels). If you measure torque on a steady-state load based dyno that keeps the engine at constant RPM to measure steady-state torque output, there will be no changes from lightened components, but the underdrive gains will still show up here.

This is simply how it is, choose to believe it if you want.

 

[QUOTE]with all those mods and nos your 1/4 time is only 13.76???[/

His MPH is near 105. That's about 7 MPH over the mag time standard of about 98 in the quarter. For a 5AT, he's smoking down the lane. At 105 you can run a with many 80k cars.