ckpitt55

iTrader: (4)

Looking to make a selection on what ATI damper to run, as there are lots available for the LS1. http://www.atiracing.com/products/da...ts/damserp.htm

From the standpoint of horsepower, the lightest and smallest one will provide for the least amount of parasitic losses. But is the 25% UD pulley less effective at damping than say a 10%? Similarly is a steel housing better than an aluminum housing in that respect? Or are differences there negligible? Trying to weigh all these parameters: material selection (weight), size, and their impact on parasitic losses and damping performance. The choice might not be ultra critical but I'd like to optimize my selection since I have the ability to do so.

I was considering PN# 917278, 10% UD made of aluminum that has a 10% UD ac pulley on the back of it. Anyone running this guy?

Thanks for any input,

Chuck

JakeFusion

iTrader: (7)

Do you have a Y-Body or F-Body Serpentine? I got the 917276, which is the same thing you're looking at but for F-Body.

ckpitt55

iTrader: (4)

F-body

JakeFusion

iTrader: (7)

Yeah. It's not an all-out race balancer. But it's a good street balancer. Most of the power comes from the weight reduction and actual harmonic dampening. The 10% UD is as much as I want to go with the accessories. I mean, it is a street car in my case, not a drag car.

ckpitt55

iTrader: (4)

agreed. as far as belt length, can you run the stock one or do you need to pick up a shorter one?

JakeFusion

iTrader: (7)

Goodyear 4060775 Gatorback Poly-V Belt
Goodyear 4040390 Gatorback Poly-V Belt

And right now I'm chasing down a squeal with my stock balancer and stock belt. I want to get that solved before putting the ATI on there.

ckpitt55

iTrader: (4)

Jake all over it, as usual. Thank you sir.

Do you think maybe your belt tensioner or pulley could be suspect? When I was tearing my motor down, I noticed that all of the bearings in my accessory pulleys were dry. It's possible to remove the bearing seal with a pick, flush them, and repack them with grease. Might be worth a shot if it ends up not being a belt.

JakeFusion

iTrader: (7)

I've replaced all those. I think it's my Power Bastards alternator. I'm going to have to drop the alternator out (PITA) and put the stock one back on and see if it fixes it. Maybe the pulley on there is bad and I can just reuse the stock one, because I'd love to keep a 220A alt on the beast...

spy2520

iTrader: (3)

I assume there isn't one that's full aluminum with AC? Does steel vs aluminum hub make that much difference?

Also, it appears 917276 doesn't have underdrive for the AC like the y-body one does.

Dracer35

iTrader: (7)

Im also looking for an ATI damper for my setup. Im using f-body accessories. My car will be for street/strip use. 2900 lb car with balanced rotating assembly and no forced induction. ATI recommended the 917242 pulley setup. I was also wonder on how big a difference people notice or see by going to the lighter pulley or the difference between the steel vs aluminum.

ckpitt55

iTrader: (4)

the weight of the pulley itself is more important than that of the hub when you're talking about things like parasitic losses and damping performance. a steel hub concentrates most of its mass close to the center of rotation, so it has very little resistance to spinning. it's going to do primarily what the crank tells it to do without much fuss. when using a steel pulley however, I imagine it would be more ideal for damping in lower engine speeds or responses to sharp throttle input (be it on or off gas). The crank accelerates and the outer pulley doesn't want to rotate with it due to its moment of inertia. This mismatch in acceleration rates between the hub and pulley puts the damping material in shear until the pulley can match the speed of the hub - "padding" the accel/decel so to speak. Aside from taking more hp to turn, I think a heavier pulley would also lose damping effectiveness at higher rpm, dampening materials being equal. ATI may compensate for this by modifying the durometer of the rubber though.

But for peak performance, the lighter weight damper with the aluminum pulley is the winner. Frees up engine hp, and is more responsive to changes in engine speed. Basically the same effect (though not as drastic) as a lightweight flywheel, but on the opposite side of the crank.

Forgive my ignorance, but is there a reason you couldn't use a y-body damper on an f-body? Are the belt spacings on the accessory drive different or something?

JakeFusion

iTrader: (7)

Bingo. It's that the whole acc drive is spaced differently from the block, so you'd have some horrid belt alignment issues.