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Thread: Balancer shaft removal

  
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    frostyD's Avatar
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    Balancer shaft removal

    I have been offered a courtenay balancer shaft removal kit.

    What will i gain by fitting this ? I know the Z20LEH's do not have the balancer shafts ?

    Whos in the know ?

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    trickyb's Avatar
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    The engine will rev a bit quicker and you will prob gain 4 or 5 bhp top end maybe a bit more with a map. You might get a slight vibration on idle, some do some dont it depends how well vaux balanced your particular engine.

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    DJ Sheridan's Avatar
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    Quote Originally Posted by frostyD View Post
    I have been offered a courtenay balancer shaft removal kit.

    What will i gain by fitting this ? I know the Z20LEH's do not have the balancer shafts ?

    Whos in the know ?
    Hi M8,
    Have a thread search on this as there are pro's and con's for removing the balance shaft.
    I feel if it's in the engine then it's there for a purpose...
    If she's not sticking her fingernails into the roof lining and digging her stilettos into the dash then you ain't going fast enough!!!

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    aussiegman's Avatar
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    I posted this on here a while ago on balance shafts...Here it is again..

    The balance shafts in the Z20LET and dual mass flywheel in the later Z20LEH are there to try and compensate for or dampen the secondary harmonic imbalances (or secondary vibrations –twice engine rpm) that are found in ALL in-line 4 cylinder engines due to the inherit asymmetry of the layout.

    Despite what anyone tells you, these cannot be eliminated with internal component balancing, no matter how well it is done or by whom. End of story, it is simple physics, its impossible.

    This is because the harmonics are not generated by a weight imbalance, but by a speed imbalance from the speed differential and actual movement (descending and ascending) of the rod/piston assemblies which are not always completely equal / opposite through their 360 degree rotation.

    The vibration is generated by the fact that the movement of the rods is not symmetrical throughout each crankshaft rotation. Descending rods are moving at differing speeds through their rotation in relation to ascending rods, causing a net vertical imbalance twice each crankshaft revolution. Increase the stroke and there is a greater difference in these speeds and accelerations because of increased distance traveled.

    Increase the bore and there “CAN BE” an increase in mass (of the piston and rod assembly) which increases inertial forces and hence increase the imbalance again.

    The big issue is that these forces increase 4 fold/4 times/quadratically as RPM increase, no matter how well balanced the bottom end is because its not a weight imbalance issue, it's a distance vs. speed issue. This is why balancing the bottom end components won't cure the problem.

    By removing the balance shafts you will reintroduce the secondary harmonics and vibrations into the engine, simple.

    The Z20LEH works around this with a heavier dual mass flywheel to isolate the vibrations from the gearbox and chassis.

    So why does GM use balance shafts and DMF's while Nissan and Toyota don't in the SR20DE/DET and 4AGE series engine?

    It is mainly done for 2 reasons:
    1. to reduce Noise/Vibration/Harmonics in production cars making them smoother and quieter, and
    2. to reduce component stress particularly on the gearbox/transaxle.

    So removing the Z20LET balance shaft will slightly increase HP, might increase the noise in the cabin of the car, could increase wear in the engine (slightly) and increase the risk of gearbox component failure due to increased introduced harmonics and vibrations.

    So remove or keep??

    My guess would be, if your going to do it keep the standard flywheel and pulley assembly then remove the balance shafts.

    If you really want the extra “urge” then go the whole way and lighten the flywheel and/or pulley too, but strehthen the rods and rod bolts too.

    I've removed mine and IMHO I can feel the extra urge of the engine, however it also feels "harsher".

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    chr15astra's Avatar
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    took mine out revs alot better and no other problems

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