Before UD pulley the car did 414/383 and after the install it put down 423/386 on a Mustang dyno. Different days but I thought id share anyway. I was pretty pumped to pick up 9rwhp.

 

Nice results! Which UD pulley was it and what %? Notice dimmer lights or anything?

 

So the same dyno in similar weather conditions?

 

SLP 25%. I was very concerned of any side effects but so far there have been none. I feel like the car still has more power in it too. Might need a stronger clutch soon.

 

Same dyno was used. The weather the first time was much less humid and about 40 degrees. Today was high humidity and around 65 out.

 

Very nice gain then!

 

Only other thing I did was clean the air filter. I cant really tell but it looks like peak power is right at 6200.

 

Yeah with your setup that sounds about right

 

Those were about the same numbers I pulled on a Mustang dyno. I Put on FAST setup, 1 7/8" headers and it gained me another 40rwhp.

 

thats about what i expected. well worth it imo.

 

Hmmmm I may consider getting one after seeing this. How much did you pay?

 

$240. I did the install in my garage so it was free. Took about two hours.

 

Do you need a tune after doing a underdrive pulley?

 

nope.

 

Nice gains! I just bought an ATI 10% + belts and ARP bolt. What bolt did you go with, and did you buy an install tool or make your own with the all thread and nuts/washers?

 

We do have a gp sale on the powerbond pullies and install tool. Powerbond makes the slp pulley. 25% ud is great. 10% seems like a waste imo. We also have the od alt pullies for those worried about charging issues.

 

^^True but a 10% ati will yield just as much of a dyno gain as the powerbond due to the fact it is a real dampener and will dampen all chaotic engine harmonics freeing up power that way. just 2 approaches to get the same goal.

nice gains for the op either way though

 

What kind of effect on the A/C are you guys seeing w/ the ATI 10% under drive pulleys? Mine already doesn't blow very cold (need to take it to an A/C shop soon to get that fixed) and wondering how much an effect the ATI 10% will have on it.

 

For that price, that's money well spent. I'm going to do some research on different pulleys.

 

I am not so sure about the "true damper part" over the powerbond or the fact that it till gain just as much as a 25% powerbond and I have seen no factual evidence to support that claim. ATI does have a 25% UD, so again, getting the 10% seems like a waste.
Torsional shock and the harmonics produced by the engine are what is "dampened" or reduced/absorbed. The torsional load is put on by the firing of the cylinders. When each one reaches the combustion event, the piston speeds up and puts a torsion or twist on the crankshaft, speeding it up, then another cyl fires and twists the crankshaft again and speeds it up again, then it flexes back. Those are the torsional vibrations that are absorbed by the balancers and the resulting harmonics that occur. The only ones that do not do that are the ones that are one solid piece. The balancer absorbs the shock so the rest of the engine does not feel the effects.
Tell me how much more different the ati is than the powerbond to be considered a true damper, and the powerbond is not then. They both use elastomer bands/rings to absorb the bad juju. Harmonics are not "chaotic". If they were, they would not be called harmonics.
The ONLY balancers I have had issues with are the one piece, the all alum, or the ones with alum hubs. ATI does offer an alum shell for alot of their balancers which cuts down on weight, but then you have different values for harmonic dampening between the 2 dissimilar metals.
The ATI is more expensive yes, and is considered as a higher quality balancer by many, but I would have zero hesitation to use the powerbond balancer in any application, and have in fact used them in nearly EVERY LS application from all stock to 1k hp supercharged setups.
The other balancers to look at are the Innovators West. They use a reported wet clutch pack to absorb the load/shock created by the engine.
Hard to tell which one is exactly the winner, but I can tell you which one is purchased more and used on more DDs/weekend racers than the others.