The difference in performance on the seat-o-pant meter is just perceptable.
Said another way, you can't feel less than 10 hp difference.
The down side is the alternator runs slower at idle and voltage is down depending on the load.
Water pump, power steering pump, A/C compressor all turn slower unless you pully up the ones whos speed are too slow and causing a problem.
Doing this begins to defeat the reason to do it.
Better to go a tuner/reprogram route and e-fan installation and not get into these possible issues.

 

sounds like what id be buying wouldnt be that great since i wont **** my pants when driving and it will make my lights and horns run bad at idle...

 

no problems with cooling or charging whatsoever with my asp pullies-faster revving with them-phil

 

exactly the same with my MAC pullies

 

Not exactly. Most pulley kits have at least 2 some 3 pulleys. My kit from Summit Racing (159.00) has 3. The crank pulley/dampner is smaller in diamter, thus spinning the belt less times around. The water pump and alt pulleys are larger than stock, further INCREASING the reduction. If the pulleys were the same size, the only reduction would be from the crank pulley. If the new pulleys were smaller than stock, then you would in fact reverse the effects of the reduced crank pulley. All the kits I looked at have the crank smaller and the accessory pulleys larger than OEM.

The summit racing and ASP pulleys provide for a 25% reduction (in what I'm not sure; hp needed for accessories; reduction in rpms?). In any event, they divert HP (and torque) to the drive train instead of sending to the accessories.

I initially noticed a slightly heavier steering response when standing still in the drive way (don't notice it at all now). Power supply to windows, lights etc. dropped a little at idle, but you would have to be looking for it to notice it.

I have an 03 Expy, 4.6, and have lots of power appliances - 4 windows, cd changer, lots of lights inside and out and two big heater/ac blower motors. And e-fans! No problems w/ stock alterntor.

Check out summit racing for their pulleys - can't beat the quality for the price. And - this is important - I got a bunch of stickers and a free hat too (which must be worn for a proper installation)

This is a mod that is well worth the results.

 

Although I am still waiting to receive and install the correct water pump pulley (I have the stock pulley on tempp.), I just checked my first fill up with the UD pulleys. 316 miles on 18 gals of gas = 17.5 mpg. About 85% highway w/ the rest as around town or stop and go highway. My best winter mileage has been about 15 for that kind of driving. This represents about a 2.5mpg increase from the pulleys and I am not complete yet!

Can't wait to check it with the summer blend. Best I was getting last summer was 17.5 with a high of almost 19.

Even my wife notices and likes the added gear range, torque and hp from the pulleys.

Do it and enjoy!

 

2.17

 

not a whole lot, all the power you gain will be from 4000rpm and up.

 

Yes, that is exactly what I was trying to say...somewhat. You made it a little clearer for me, thanks. You are correct...the accessory pulleys that come in multiple pulley kits are larger than stock. Although I did not mention this, the effects are exactly what I mentioned. After placing a smaller than stock pulley on the crank, placing a larger pulley than stock on an accessory returns the speed of that accessory to it's pre-underdrive pulley speed creating just what I said. The larger pulley on the accessory does not increase the reduction. It causes that item to turn faster than it would be turning had you left the stock pulley on there.

 

Picture it like the gears on a ten speed bike. The resistance of your accesories is what causes the horsepower loss. If they turn slower there is less rsistance. You dont need your accesories turning that fast when you are at WOT like built said above 4000 rpm. If you are out cruising main st. and parked in the drive thru all the time dont do it. Your charging system and everything else will be fine as long as you drive more than you sit and idle. I ran them on a 327 Camaro I built to race, and my 92 civic work car to increase the mileage. I never had a problem with either one on a charging or cooling aspect. Added bonus your pumps and alt will last longer as they make less revolutions. It is a very good investment, you might not feel 5 horseys but 5x5 is 25 5x10 is 50.

 

HI
To answer you.

Think of the pullies as transmisions, they make things that are attached
to the motor run faster (overdrive) or slower (underdrive).

MY understanding came from 1950 1960 racers. They decited, a gain
of useable horsepower was to use smaller than normal pullies for
charging the battery and cooling the motor (underdrive pullies).
Some of these would overheat if they had to sit throught two
red lights in a row.
They soon found out, Do not do it.
The motor runs too hot (takes out life).

Motor corps have spent millions of dollaes, tens of years,
to find out these pully sizes, they are set for average market usage.

Do a test drive 15 min max, with the belt,
with no belt (best case underdrive).

Math example :
Yes it will take 100 ft lb to turn the steering instead or 5.

If total aux is 50 hp, and you use a .8 (20 percent reduction) .2 x50=10hp
saved. so 10 hp saved out of 200 =5 percent. THIS IS HP ?????
You will not notice any differance in other things execp,cooling.

I have pulled 10,000 pounds with 6,000 load in Houston,
what more could you ask for driving a 1995 F150 at 300k miles?

In my time, taking the air filter off could save more than that.

Study

wrong100

 

Not quite there my friend. A larger accessory pulley goes around less times at the same rpm than a smaller pulley. The larger pulley is there to further reduce the load on the accessory. In effect the larger pulley does not turn the acc. shaft as many rpms as would a smaller pulley.

for example, lets say on my water pump pulley, OEM. It is about 5" in diameter. so it takes 15" of belt to turn it one time completely around. The UD water pump pulley is about 8" in diameter (give or take). It would take 24 " of belt to turn the same waterpump shaft all the way around once. At the same engine rpm, it would take longer for the larger pulley to spin the water pump once. That effect is enhanced or increased by the fact that the crank pulley now is only 6" in diameter and the old one was 8 or 9". So less belt is moved per rpm from the crank pulley and more belt is needed per rpm to turn the accessory around once. It is an overall reduction.

You really gotta stop and think about it for a minute. I know what your saying... but it is backwards. Think about a bike with multiple gears. If you want to go fast, the crank gear gets shifted to the largest one, and the wheel gear gets shifted to the lowest one. If you want to go slow (lower burden uphill), you shift the crank gear to the smallest one and the rear wheel gear to the largest sprocket. The rear wheel goes around less times per turn of the pedal and requires less effort.

At any rate, the kits they sell work well, whatever way it works!

I just check my mileage with the Summit UD pulleys (with the OEM water pump pulley still on; I am wating for a swap for the correct UD pump pulley). Even with the OEM (not getting full benefit of the underdriven pulleys) I got 17.5mpg in my 4.6 Ex 4x4. That is up just about 2.5mpgs from the 15 that I usually get in winter!!!

Very well worth 159.00

 

Yep!! You're exactly right. I know what I was thinking now! Had to put it in my own rationalization. Thanks.

 

Bicycle analogies work in almost every situation

but I know what you were getting at

 

I had to use my motorcycle analogy!! Changing to a smaller front (drive) sprocket or a larger rear (driven) sprocket accomplishes the exact same thing. Doing both at the same time, like you said, exaggerates the ratio!

Word up!!