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Another underdrive/harmonic balancer pulley question

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Old Oct 20, 2013 | 04:19 PM
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Default Another underdrive/harmonic balancer pulley question

Ok, so sorry if this has been covered 100 times before, but I couldn't find a concrete answer. Which would be more beneficial and why? A 10% or 25% underdriven pulley? And which brand is acceptable? ATI? ASP? Fluidamper? And why? For what its worth, I have heads, cam, intake, full exhaust, stock cubes. What is the best bang for my buck?
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Old Oct 20, 2013 | 04:30 PM
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Depends how much extra little power you want. Almost anyone goes with a 25% UD now days. A SLP is a legit pulley for the price and quality, but ATI is top notch but its more $. Id rather go with a ATI regardless of the price if you are willing to pay for it. You dont wanna go too cheap on a pulley specially if you drive around alot.
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Old Oct 20, 2013 | 05:13 PM
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Nothing wrong with the slp pulley. Should be a good 5 hp gain.
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Old Oct 20, 2013 | 05:24 PM
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Ok, for what it is worth, it is not a daily driver. Do the claims about charging issues prove false or true?
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Old Oct 20, 2013 | 05:28 PM
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ATI 10% . Great design and rebuildable
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Old Oct 20, 2013 | 05:34 PM
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Originally Posted by UnVMySS
Ok, for what it is worth, it is not a daily driver. Do the claims about charging issues prove false or true?
False....stick with 10%. ATI, move on
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Old Oct 20, 2013 | 06:06 PM
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I have an SLP UDP. Gained 1/10" and a couple mph. I see no charging issues. My car is cammed and idles at 900rpms vs the stock 650 or so...that may be why.

ATI is almost twice the cost of the SLP/Powerbond.
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Old Oct 20, 2013 | 06:40 PM
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the ATI is the far superior pulley to the others.... its the reason why NHRA guys use it and they dont use anything else.
you probably wont see issues from a 10% underdrive....but if you do, just know there are alternator upgrades you can do to counteract it....the simplest thing is to buy a different alternator pulley..you can also buy a better alternator with an exciter made to come in sooner at lower alternator RPM.

one thing to remember....

Just switching to an ATI damper alone(the full size one) is good enough to gain you a little power thru superior Harmonic Dampening.
as you go up in power, you need all the dampening you can get...vibration will tear the hell out of your bottom end...
guys with an ATI typically can push the limits of the stock bottom end further because of better harmnonic control.

once you get upwards of 600 RWHP... its time to stick with the bigger one...not enough dampening power in the underdrive pulleys....
and if you use a cheaper SLP underdrive... dont expect much past 500 RWHP to be safe.

also, High RPM, means you need a full size damper and not a smaller underdrive one
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Old Oct 20, 2013 | 07:01 PM
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Originally Posted by soundengineer
the ATI is the far superior pulley to the others.... its the reason why NHRA guys use it and they dont use anything else.
you probably wont see issues from a 10% underdrive....but if you do, just know there are alternator upgrades you can do to counteract it....the simplest thing is to buy a different alternator pulley..you can also buy a better alternator with an exciter made to come in sooner at lower alternator RPM.

one thing to remember....

Just switching to an ATI damper alone(the full size one) is good enough to gain you a little power thru superior Harmonic Dampening.
as you go up in power, you need all the dampening you can get...vibration will tear the hell out of your bottom end...
guys with an ATI typically can push the limits of the stock bottom end further because of better harmnonic control.

once you get upwards of 600 RWHP... its time to stick with the bigger one...not enough dampening power in the underdrive pulleys....
and if you use a cheaper SLP underdrive... dont expect much past 500 RWHP to be safe.

also, High RPM, means you need a full size damper and not a smaller underdrive one
Couldn't have said it better myself, ATI is NHRA approved for a reason. And another example of the " You get what you pay for" saying.
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Old Oct 20, 2013 | 07:07 PM
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you can gain more power from Superior harmonic control than you can from underdriving a couple of accessories a little bit.
not to mention, no charging headaches.
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Old Oct 20, 2013 | 07:09 PM
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i have a powerbond and its been fine.

i had an ASP before that. i now have been told to avoid them.
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Old Oct 20, 2013 | 07:10 PM
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ATI seems to be the general concensus. Thanks fellas.
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Old Oct 20, 2013 | 07:11 PM
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So if anyone wouldn't mind, post a link to the exact one I should get. Preferably the least expensive.
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Old Oct 20, 2013 | 07:16 PM
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Also, it seems these are all for supercharged vehicles. i am not s/c, will it matter or benefit me still?
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Old Oct 20, 2013 | 07:41 PM
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Scoggin Dickey has a Powerbond 25% underdrive pulley, new bolt, and belts for $200-$225 I believe. I've had a Powerbond 25% underdrive on both my ws6 (a4) and now my c5 (m6). Never have I had any issues with lights dimming, steering getting harder, battery not charging, AC getting warmer, etc. I think very very few people even experience one of these issues above and just re-post what they've seen other people post. My throttle response was quicker, not sure how much power I gained from it but my car was tuned/dyno'ed with it installed with other parts. I have a few friends with the Powerbond 25% underdrive with heads/cam setup's on their f-bodies and c5z's.
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Old Oct 21, 2013 | 10:43 AM
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Originally Posted by UnVMySS
Also, it seems these are all for supercharged vehicles. i am not s/c, will it matter or benefit me still?
They are not all for supercharged vehicles... you are just looking at the wrong ones



Originally Posted by UnVMySS
So if anyone wouldn't mind, post a link to the exact one I should get. Preferably the least expensive.
its multiple part #'s... its not one solid piece....its a modular Pulley

Damper - 917242
4 Rib Rear for AC - 916734
Hub for Pulleys - 916031


and "Cheap" is not going to go in the description when you are talking about a Good Damper



http://www.atiracing.com/products/da...ts/damserp.htm
Attached Thumbnails Another underdrive/harmonic balancer pulley question-ati-dampers-f-body.jpg  
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Old Oct 21, 2013 | 11:13 AM
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Originally Posted by soundengineer
the ATI is the far superior pulley to the others.... its the reason why NHRA guys use it and they dont use anything else.
you probably wont see issues from a 10% underdrive....but if you do, just know there are alternator upgrades you can do to counteract it....the simplest thing is to buy a different alternator pulley..you can also buy a better alternator with an exciter made to come in sooner at lower alternator RPM.

one thing to remember....

Just switching to an ATI damper alone(the full size one) is good enough to gain you a little power thru superior Harmonic Dampening.
as you go up in power, you need all the dampening you can get...vibration will tear the hell out of your bottom end...
guys with an ATI typically can push the limits of the stock bottom end further because of better harmnonic control.

once you get upwards of 600 RWHP... its time to stick with the bigger one...not enough dampening power in the underdrive pulleys....
and if you use a cheaper SLP underdrive... dont expect much past 500 RWHP to be safe.

also, High RPM, means you need a full size damper and not a smaller underdrive one
Yes, yes, yes!! Full size non UD ATI super damper part # 917242
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Old Oct 21, 2013 | 12:43 PM
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Thanks for the part numbers fellas. So full size and not 10% underdriven?

Wait, I need to order those other 2 parts to get this to work? The hub and ac ?

Last edited by UnVMySS; Oct 21, 2013 at 01:36 PM.
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Old Oct 21, 2013 | 02:10 PM
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your engine will be happier with the full size...
and honestly, it will make more power into higher rpms with the full size than you will with the underdrive....
it takes Mass to absorb vibrations....and the underdrive pulley has less mass than the full size.
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Old Oct 21, 2013 | 02:36 PM
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Do I have to use that hub and ac thing? Sorry im a newb on this but trying to learn.
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