Explain how/why aluminum 2-piece pulley set can add 15-22 ponies??
 

.....As advertised on E-Bay where they're being sold by different sellers. How can this add so much more H/P by just changing them out. Does anyone have data/documentation to support the statement?.

I've e-mailed the seller(s) but no response yet! Thanks.

I didn't notice much of a difference if any when I installed my greddy pullies and pettit power pulley

Did Greddy make any claims that installing their set would add/gain more H-P??

very little is gained from the actual underdriving.

Most is done with the rotational weight reduction.

i think long ago i heard on a piston for every 1lbs off a crank you roughly gain 2hp.

15 ponnies i don't know.

there are more compelling reason for me to buy a pulley kit than hp. It's just an added side effect.

I've actually heard something like 2 hp about the greddy kit.

I just took a look at it...looks real good for the price. Same thing as the greddy kit. I'd buy if I didn't already have the greddy

I don't think the aluminum pulleys will increase 15-20 HP. Light pulleys will reduced the mass and its rotational inertia which make the engine less effort to spin the pulleys. This result in increased response of the engine and gain some HP and Torque to the wheel.

The entire pulley set (like the RX-7 store sells) will give you 15-20 rwhp. Jason dynoed a set as did a couple others here on the forum. There is a thread about this.

um is it just me or does it seem like not so good of an idea to underdrive your water pump? i really wouldnt consider the waterpump an "accessory"

Actually its a good idea to, so at high rpm you dont get just water slushing around and actual movement.
Example: a blender on high just makes a hole in the middle compared to on low when it actually mixes.
Helps save your water pump.

the unorthodox is best..dyno proven

That's amazing. Will you gain 15-20 hp just with the aluminum pulleys? Does it need other modificaiton to achieve this gain?

BC

What are the side effects ? I heard some horror stories about them - with their lessened weight, they cause more vibration and can cause the main shaft failure. Is this true ? 15rwhp gain is incredible ! Especially at that price + the good looks. Yummy.

your talking about harmonic imbalance

the main pully is the big one.

It's hard to prove either way. I've heard that some engines were engineered to account for it but never seen facts.

i would replace any other pully except the main one. I had a very bad experience with a main pully and is the most integral.

Think of a light flywheel. You lighten it up alot of time u need a new counter weight.

you just doing it on a smaller scale

The gains might be a little decieving. If someone saw 15hp gains it sure wasn't on a stock car or anything close to stock. The honest way to list the gain is as a percentage not as a certain HP gain. The point is that a small percentage gain in a 600hp motor will yield some pretty big numbers but will give 300%less in a 200hp motor. You get the point I assume. In cases like this companies test components on very high hp motors to produce distorted gains. A good example would be garbage like those tornado air filter things. If they actually had a test showing a gain it was probably on an 800hp big block and it gained 5hp so they advertise a 5hp gain from using the product. Hype is what sells. Learn to be a cynic : )

Kevin T. Wyum

Oh really? And when does the typical owner most need good cooling? Stop-and-go traffic. How much time are you spending above 7k rpm in that situation?

Too many of you guys justify getting a product for some benefit you will never experience. I can tell you that less than 5% of the FD owners on this board road race their car, which is about the only time you are spending significant time at high rpm.

Ya but it still doesnt hurt the motor to do it. Im just trying to explain why you would.

[EDIT] And still helps the daily driver for less stress on the water pump for those burst of WOT.

Pullies aren't worth it IMO. You may see a couple hp gained on a dyno but don't expect much from the butt-dyno.

you could calc how much it's underdriven by finding the radius then the circ. of the pullies then finding the ratio to give a percentage underdriven correct?

your car shouldnt' have a problem with underdrives and cooling. To fast of a coolant flow will result in poor heat transfer. This goes way beyond my scope and lies in the realm of thermodynamics another area i'm not well versed in.

nothing is really easy or straight forward

hp is not the only reason to get them

replacing the alt/wp will improve your rev.

also wp slippage also concerned me.

WP slippage as in you removed your air pump and your belt cant get enough leverage on the water pump? this is the only reason why im hesitant about removing the air pump.... if more leverage can be gained by using a pully kit then ill be all over one of those kits!!! but the kits DECREASE your pully size so would you not get MORE slippage with a removed airpump and pullies?

***does anyone have a picture/diagram looking straight on at the pullies?*** id like to see exactly how much leverage i could get on that water pump with some new pullies.

thanks guys! -heath

I ditched my airpump, and no freakin 5 rib belt exists which will fit so I had to go down to a 4 rib.

Daddy, can I get a sum Greddy pullies now? :D

hmmm... i wonder if we can get oem fitting belts w/ the pullies

So is this set a direct bolt-on or will we have to modify or lose a stock component, ie: air pump..ect..??

In a sense pulleys act like a flywheel.
It will not give you any HP, but it will free a few ponies for earlier response/acceleration.
This is due to less mass/rotating inertia.
Think of it as 10 speed bike.
Your legs are the engine or driving force and the crank being the pulley.
On the smaller crank you can accelerate faster than on the bigger crank, yet the force applied is the same(you don't become any stronger, you still have the same pair of legs).
As stated before, on high power cars you can notice a difference, but not so much for others.
I had an extra $250, so why not get the pulleys.
They look good on.:D