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Thread: Destroying the dogma: lightweight crankpulleys

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    Advanced Tech? verified Feedback Score 0 i3igpete's Avatar
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    Destroying the dogma: lightweight crankpulleys

    http://www.scribd.com/doc/17767722/Vibration-dec-0508

    a short and concise presentation.

    -a torsional damper (OEM crankpulley) is not the same as a isolator (rubber engine mount)
    -engine balance (centrifugal/reciprocating loads that add up to engine vibration) is not the same as a crank twist
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    Recently torn down a engine that had the lightweight under drive pulley...After inspecting the main caps and crank it was determined that the crankshaft had been walking, everything was balanced on the bottom.. The engine was a VG30DET.. We rebuilt the engine and installed a ATI racing damper.. a little heavier but gives the engine a longer life...

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    Forum User Not Verified Feedback Score 0 Ultimate's Avatar
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    Good post, I liked it on 3stech too.

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    Does anybody know where i can find one to replace my old lightweight pulley? The thing worries me....

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    Runs on alcohol. The car does too. Not Verified Feedback Score 2 (100%) Intropy's Avatar
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    Now if only we had some good products available.

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    Im trying to find my stocker, im in the middle of putting my third engine together and i dont want to use this same pulley again, i have a old IPO one and it looks and feels really cheapo.

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    1PNCHMN Not Verified Feedback Score 3 (100%) Unknownvr4's Avatar
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    So, would having a lightweight flywheel on the other side yet again (in theory since you now have less weight on one side) unbalance the crank?
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    Forum User Not Verified Feedback Score 0 marshallh's Avatar
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    Quote Originally Posted by Unknownvr4 View Post
    So, would having a lightweight flywheel on the other side yet again (in theory since you now have less weight on one side) unbalance the crank?


    From what I understand the torsional damper (rubber ring) in the OEM pulley is to prevent vibrations shown in the picture from building up.

    Imagine you are playing guitar, and then someone lays a towel over the strings. You hear very little sound because the strings then hardly vibrate beyond the initial wave, because the towel is a damper.

    It doesn't take very much material to prevent resonation from building up. That is what the rubber ring does.

    Again, this kind of buildup occurs mostly at constant engine speeds (cruising, etc), but still happens to an extent under all conditions.

    Pete if any of this needs fixing let me know, this is how I currently understand it.
    Last edited by marshallh; 09-12-2010 at 12:07 AM.

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    Quote Originally Posted by i3igpete View Post
    http://www.scribd.com/doc/17767722/Vibration-dec-0508

    a short and concise presentation.

    -a torsional damper (OEM crankpulley) is not the same as a isolator (rubber engine mount)
    -engine balance (centrifugal/reciprocating loads that add up to engine vibration) is not the same as a crank twist

    OMG... the first "underdrive vs. OEM" crank pulley post! The new forum is now official!!

    Thanks, Pete. But IDK that this will end the debate any time soon.

    Oh, and for the record... I've always been on the side of OEM harmonic dampers.

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    Shit I just installed my 3sx lightweight crankpulley to replace the OEM one(which was by the way in perfect condition) now I come here and see this FUCXK

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