Which size pulley

[brown_fv]

So the underdrive pulley wont run my alternator, AC properly??

The underdriven crank pulley underdrives the other ones by maybe 15-20%. if you live in a hot climate and use your A/C a lot that may be a problem or if you have a big sound system. if thats the case you might want to stick to the stock sized pulley.

this is all only speculation from things i have read and i might be completely wrong.

 

[Psiclne]

The underdriven crank pulley underdrives the other ones by maybe 15-20%. if you live in a hot climate and use your A/C a lot that may be a problem or if you have a big sound system. if thats the case you might want to stick to the stock sized pulley.

this is all only speculation from things i have read and i might be completely wrong.

+1 with Brown.... same as what I have read.

 

[jc'sfx]

maybe WRP can chime in?

 

[Deecarp]

I'd like the underdrive unless there is an issue with the electrical system while running the smaller pully.

 

[wperdigon]

guys - about the electrical system, it's really hard to determine which one to use. I know that on the z and g35, there are zero issues as far as underdriving the component. -

what i can do is offer someone who is on the forum, and a lot of people respect on here one of my underdriven ones for a full evaluation. i would like to have a before and after dyno done as well in exchange for the component. who would be up for it?

 

[wperdigon]

So the underdrive pulley wont run my alternator, AC properly??

thats a misconception - a lot of g drivers have the underdriven ones with no problems at all -

 

[Deecarp]

thats a misconception - a lot of g drivers have the underdriven ones with no problems at all -

any belt issues with the smaller pully?

 

[wperdigon]

you need smaller belts -

also, i would like someone in my area or someone to come to my shop so that we can install the pulley to make sure it's installed properly

 

[Deecarp]

wish I was in Philly, I realize that the pully would require a smaller belt. I guess I just wanted to know if they wear any faster due to higher revolutions at the pully if that makes sense or since, lol...

 

[wperdigon]

oh no, no faster wear or tear on the belts at all-

 

[jc'sfx]

you need smaller belts -

also, i would like someone in my area or someone to come to my shop so that we can install the pulley to make sure it's installed properly

Im about an hour from Philly .. Give me a time and date or we can figure something out.

 

[wperdigon]

send me a phone number

back to topic - the component i think will work best is the underdriven one, what do you guys think you would prefer?

 

[jc'sfx]

PM sent

 

[Deecarp]

underdriven...for me

 

[wperdigon]

ya underdriven for me as well

 

[muchilus]

with the underdrive version you have to change for a small belt, you get a smooth , quicker aceleration and around 9 hp to the wheels.


i'm installed and i felt


believe me worth the investment.

Any particular reason why people would choose the stock size over the underdrive pulley when there's no gain in hp just faster revs?

 

[rookie]

This is a very interesting read. http://my350z.com/forum/showthread.php?t=348671&highlight=wperdigon

 

[turbocad6]

yeah, pretty interesting I'd say

 

[jc'sfx]

Wow .. talk about drama.

 

[jumbosrule]

Stock vs Underdrive pulley

Just wanted to throw the results of my research out there. I have been looking into a pulley set for a few weeks now and think I can summarize it here. PLEASE if I have something wrong, somebody tell me.

Swapping out the crank pulley for a new, lighter, stock size pulley impacts HP by 2.7 HP per pound of weight removed from the crank. So if you can reduce the weight of the crank shaft & pulley, it takes less energy to spin it to the same RPM. The sole purpose of the crank pulley is to drive the other system pulleys.

Underdriven crank pulleys are smaller than stock - let's assume 20% smaller for this. So at the same RPM as a stock pulley, the underdriven pulley has only driven the other system pulleys at 80% of the stock speed. This reduces the demand on the engine crank pulley.

The disadvantage is that most systems are designed to run ideally close to 2000 rpm. When you underdrive the crank at idle, the system pulleys are spinning at something like 80% of the stock design. Driving the car around, the RPMs pick up and the system pulleys spin closer to the stock design speeds, but never quite get there. The concern is that some systems might suffer, depending on driving habbits and demands.

On the upside, it's less long term wear on all of those pulley driven systems. My initial concern was reading about harmonic balancing. I read on this thread that the VQ engine is internally balanced. In other cars this is not the case and putting a non-balaced underdrive pulley on an engine could cause vibrations in the shaft that would eventually weaken the seal to where you get an oil leak - and a host of other issues. But since the VQ is internally balanced, proper installation of an underdrive pulley should not cause this problem.

The only things I have not been able to find are testimonials from FX drivers - anybody have aftermarket pulleys and care to talk about them? Also, I have read that we need a pulley set SPECIFIC to the FX. G35 and 350 systems are different than ours, even though they are driven by the same engine.