what is a pulley and is it a significant mod?

A pulley is where the belts area attached too..Now if your asking what a lightened pulley does for the supercharger,the pulley is lighter than the stock one(sometimes smaller)but when you lighten it,it makes the engine have a bit less strain on it causing it to turn a bit faster and easier freeing up some horsepower...In a round about way..

I hadn;t heard of lighter pulleys, just smaller ones. Do you have any more information?

Smaller pulleys spin the supercharger faster and generate more boost. If you get small enough you can have serious problems and doing this voids your warranty.

Well most pulley's are made of regular metal(whatever that might be)but most aftermarket pullies are with metals like aluminum which make them lighter than the traditional....
For example if you look at a Unorthodox racing pulley(which I use on both of my SE-Rs)they use aluminum.I can't remember exactly what the weight comparison was but it was twice as light as the OEM pullies...
www.unorthodoxracing.com

will a lighter pulley do well with an X w/o a supercharger? If so, where can I order it.

Nothing, if you don't have a SC it doesn't apply to you.

Unfortunetly there's no applications for a non-SC'd X....

But I know the company I stated above makes the lightened pullies just not for an Xterra..Like I said I use them on my Sentra SE-R and I replaced the alternator,power steering,crank and water pump pullies...

When you first posted on lighter pullerys I thought you were talking about the supercharger pulley. Now it makes sense.

If you just replace the pulley for the SC with a lighter one of the same size you will gain very very little and would never notice it. If you replace it with a smaller one that is the same steel you will gain boost and thus HP. IF you replace the pulley with a smaller one that weighs twice as much as the orig. you will still have the HP increase without any real difference in "feel"

The U.R racing pulleys replace Main and accessory pulleys with lighter ones and the main pulley is smaller than stock to underdrive the accesories saving HP and a little in rotational mass.

These pullies are big $ and the gain is not that great no matter what they claim. Bigger gains ar to be found in the exhaust and intake.

I have a modded 93 RX-7 and I do have the pullies but only after doing everything else.

If you do not have the SC you can still do underdrive pulleys if you wish to spend your $.

From what I understand, replacing the ASP pulley does not help because a decrease in rotational mass, but an increase in mechanical advantage. The only time that rotational mass would come into play would be during starting. Even then it is insignificant in comparison to the other forces at play. As for doing that mod last, I'm going to do it ASAP because it is supposed to help the low-end torque.

Somebody's ad:
"ASP Pulleys:
Improve the performance of your vehicle in three ways. Underdrive pulleys are an inexpensive solution to more horsepower. By reducing the size of your crankshaft pulley, your power robbing accessories turn slower, resulting in less drag on your engine. That means more horsepower to your rear wheels. You also get better fuel economy and longer lasting accessories. By careful design and sizing, no adverse effect occurs to cooling or charging systems. All pulleys are top quality, machined steel with multiple finishes."

I have, however, been unable to find one for the X. The only pulley that seems to be currently available is for the supercharger.

Anybody know of a pulley replacement for the non-supercharged X?

I haven't seen one yet...I've checked with a few companies too...

I can maybe add some insight here - I work in the automotive industry and mostly on Miatas. We supercharge quite a bit of these cars and we also work with Mini Coopers as well. Today we just finished installing a smaller pulley on a Cooper S - all for under $400. When we deal with increasing HP and boost, one of the most popular choices is to go with a smaller pulley - having a lighter pully makes no difference in real world HP gains.

Having a pully that is smaller with in turn spin the blower faster and increase boost and then HP. There are some great gains for doing this. For a Miata lets say, if you started at 6psi of boost with a basic SC, a 15% pulley (reduced in size by 15%) may yield a 20% increase in HP. That is about 15-20HP.

On a Cooper S - about the same thing - again, this is based on what engine size you have and the standard output of HP - so my numbers are a bit generalized.

But reducing a pully does make a great difference in HP gains. The bad news is that you increase heat and therefore detonation (especially for you RX7 guys) which is not a good thing. You also run the risk of voiding that warranty asap as well.

I would love to see is anyone has done a smaller pulley yet for the Xterra. I do not know how the ECU would handle the difference and the belt size would change a bit - but honestly, this is an area that needs to be investigated - based on my experience with the Miata and Mini crowd - it is a cheap wway to get added boost and HP.

Here is a great example of a dyno run (PDF file) with a Miata with base engine, then supercharged at 6psi and the finally with the smaller supercharger pulley:
CLICK ME

I know the SC Xterra is not a street rocket, but I'd love to have some additional HP - Anyone know what boost a 2002-2004 SC Xterra makes?

-Peter/Atlanta

I havent had mine on a dyno but the boost gauge read 6~7 psi stock. After the pulley, 10~11 psi. Now, I also have an FIPK and Flowmaster installed, dont know if that can affect numbers.

I get the same boost numbers with stock intake and exhaust...2.3" pulley

Chang, what pulley do you have, and how is the pinging?

Installing aluminum underdrive pullies (3) on a stock 5.0 mustang gained 15rwhp & 18tq on a dyno (not the manufactures test).

These are not hocus pocus bolt ons.

Here is the ASP pulley for the S/C Xterra/Frontier
Click

Pacopico, I have ASP pulley, no ping even with your boost mod from a year and a half ago. I run super every tank with no problem, even when it gets hot. I have the FIPK and Flowmaster 40 series, and dont laugh, the famous Ebay mod, resistor. That thing has be on for about the same time all the other mods were done. I want headers but I dont think I will have this vehicle too much longer, I need something bigger, QX56 perhaps.

Thanks for the input...maybe the intake resistor mod does something after all.

Have you seen a QX in real life yet?

It is MASSIVE - the grille is about as high as my shoulder sitting in the X - and I'm 6'2".

No prob. Yeah the QX is large, but I think this Japanese Escalade is better than its competitors.