under drive pulley systems for jeeps

What exactly are they?

They usually have a smaller crank pulley smaller alternator pulley and a larger water pump pulley. It reduces the drag put on the motor in turn enhancing horsepower. However it usually only works well if the motor puts out a decent amount of horsepower.

The pulleys are made by a couple of companies.
First one that comes to mind is MARCH.
Not sure if they have a site, check out http://summitracing.com/
I know they make them for Jeeps though not to many carry them.
They will work on high mileage vehicles,just not as affective.

I'd personally pass on underdriving my accessories in one of my Jeeps...and this comes from someone that _has_ underdrive pulleys on his car. Depending on the step down most have a _significant_ effect on the output of the accessories. For a vehicle that spends the majority of the time at low revs on the trail I personally would rather retain the coolant flow and charging of the stock setup at the expense of the marginal increase in power. Just my 2c...YMMV...

--Ian

That true however most companies offer kits available
in single double or tripple pulley set up
I think it would be worth checking w/ the manufactuer first before purchase.

Quote from "jeeprubicon"

That true however most companies offer kits available
in single double or tripple pulley set up
I think it would be worth checking w/ the manufactuer first before purchase.

???...I'm not following. Yes most mfrs. offer multiple pulley setups that replace the pulleys on each accessory instead of the crank pulley but it still has the same effect. Are you saying to pick and choose and only put one or two on? Even then I'd still stay with my first statement...on trail rides where 95% of the time you're at idle/low rpms IMHO it's imperative to retain good cooling, charging, and power steering (esp if you've got full lockers).

--Ian

Quote from "jeeprubicon"

That true however most companies offer kits available
in single double or tripple pulley set up
I think it would be worth checking w/ the manufactuer first before purchase.

Are you saying that the are offered in non-serpentine belt set ups? If so they you could pick and choose what accessory you wanted under driven as long as you could find a belt the correct the length.

Quote from "JasonY"

The ideal setup would be like the pullies i have on my VR4, same size but way less weight. my main pully was like 7lbs now i think its 1.11ounces. doesnt slow down any accessories but makes one heck of a difference. I had a noticable increase in power...

Anyone make em

Jason

That sounds, in theory, like a good idea. But my question would be what material are they making the pulleys out of to reduce that much weight, and would the lighter material hold up under heavy torque situations???

Also, why would you want to produce that much more power under the hood of a 4.0L Jeep? You are then more likely to break more stuff (i.e. drivetrain)

-Chris

The pulleys are generally made a aluminium. I had a set on my 70 and I did pick up 3 tenths in the quarter mile afte the install. The problem with them though was as Ian stated. The larger pulley on the alternator just barely charged the battery and the large pulley on the water pump slowed down the cooling. It worded on the car cause i had an electric fan but i wouldnt do it on a jeep.

Quote from "JeepSahara"

my question would be what material are they making the pulleys out of to reduce that much weight, and would the lighter material hold up under heavy torque situations???

-Chris

Some lightweight alloys may be as strong as the stock stamped pulleys. They would of course be more pricey though. I'd have to wonder if the power gains would be worth the money since your not looking at a racing application. If it improved the gas milage a few mpg it might be worth it though with the price of gas up near $2 per gallon.