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harmonic balancer


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19 replies to this topic

#1 hatchsub

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Posted 15 November 2006 - 06:46 PM

Hey guys,
My mechanic heard that i was converting from auto to manual and he suggested to my mother that i get a harmonic balancer. Do i need one for this engine? Ive never heard of a harmonic balancer on an old suby.

#2 GeneralDisorder

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Posted 15 November 2006 - 07:08 PM

No. Your mechanic is an idiot. The boxer engine doesn't need one as it's already balanced. Besides that, they were never equipped on EA81's in any form so it would have to be custom made. Non-turbo EA82's didn't have them either. The turbo's had one (or something very similar) but I can't recall at the moment exactly why.

GD

#3 DerFahrer

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Posted 15 November 2006 - 07:12 PM

On OHC EA engines (so just EA82s), the flywheel is the harmonic balancer, not the crank pulley.

#4 grossgary

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Posted 15 November 2006 - 07:19 PM

GD is right.

No. Your mechanic is an idiot.

tell us how you really feel GD!!!! WOO HOO!

#5 GeneralDisorder

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Posted 15 November 2006 - 07:25 PM

On OHC EA engines (so just EA82s), the flywheel is the harmonic balancer, not the crank pulley.


Huh? Explain yourself. I've used EA81 flywheels on EA82's without issue, and the other way around as well. Harmonic blancers are rubber mounted crank pulley things.... flyhweels are cast iron.... EA82 Turbo's have harmonic balanced pulley's, but the EA82 NA does not.

GD

#6 GeneralDisorder

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Posted 15 November 2006 - 07:27 PM

GD is right. tell us how you really feel GD!!!! WOO HOO!


:grin:

#7 DasWaff

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Posted 15 November 2006 - 08:30 PM

As I understand it, harmonic balancer is a shock mounted crankshaft pulley that compensates for the stresses caused by the (unequal) angle(s) at which power strokes exert force on the crankshaft. One angle in an inline or slant, two in a 'V' configuration. Since the flat four power strokes are inherently 180 degrees apart the crankshaft sees equal opposing forces which eliminates the need for the harmonic balancer. A smooth running boxer looks motionless at idle because of the great balance, probably could pass the old Duesenberg nickel standing on edge trick.

#8 Syonyk

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Posted 15 November 2006 - 09:47 PM

A smooth running boxer looks motionless at idle because of the great balance, probably could pass the old Duesenberg nickel standing on edge trick.


Hm. I think mine needs some work, then. :-/

-=Russ=-

#9 Prospeeder

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Posted 15 November 2006 - 10:03 PM

Hm. I think mine needs some work, then. :-/

-=Russ=-


yea same here, lol

#10 DasWaff

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Posted 15 November 2006 - 10:08 PM

A smooth running boxer looks motionless at idle because of the great balance, probably could pass the old Duesenberg nickel standing on edge trick.


Notice I did not say "my boxer"...:brow:

DW

#11 GeneralDisorder

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Posted 15 November 2006 - 10:13 PM

Notice I did not say "my boxer"...:brow:

DW


I've had/have some Webered EA's that run nearly that smooth. I'm getting there with my SPFI, but it's real finicky about small crankcase vac leaks - such as the o-ring around the oil dipstick tube :mad:

GD

#12 hatchsub

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Posted 15 November 2006 - 11:05 PM

ok thanks everyone..thats what i thought. Just making sure cause if i needed one i was going to be pissed.

#13 Ross

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Posted 16 November 2006 - 04:02 PM

A harmonic balancer is a seperate shaft driven off the crank to balance dynamic loading caused by the motion of the crank/rod/piston assembly. It can also be incorporated in the cam shaft on OHV engines.
Many enignes have more than one harmonic balancing shaft, suck as the buik (sp?) 3.8l V6 used in our Holdens....

They have the same effect as the balancing weights on your crank shaft, which balance the first mode reaction forces, which oscillate at crank speed. The Harmonic balancers rotate at multiples of crank speed to balance other reaction modes.

#14 GeneralDisorder

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Posted 16 November 2006 - 04:12 PM

A harmonic balancer is a seperate shaft driven off the crank to balance dynamic loading caused by the motion of the crank/rod/piston assembly.


That's called a counter-balance shaft, and is needed for smooth running in inherenty unbalanced engines (3 cylinders, 5 cylinders, most inline engines, etc). It is DIFFERENT from a harmonic balancer which is designed to counteract resonance between the cylinder fireing vibrations, and the engine RPM:

http://en.wikipedia....rmonic_balancer

The harmonic isn't needed with the EA81 because of the opposed nature of the cylinders - when one side fires, the forces are transfered directly across to the opposing cylinder.

GD

#15 NorthWet

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Posted 16 November 2006 - 05:45 PM

A harmonic balancer is a seperate shaft driven off the crank...

In the USA, an "harmonic balancer" means something different, typically a special front pulley. On our V8s, it is typically used where the crankshaft does not provide proper internal balancing (does not have crankthrow counterweights, or they are insufficient).

#16 Ross

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Posted 16 November 2006 - 06:00 PM

In the USA, an "harmonic balancer" means something different, typically a special front pulley. On our V8s, it is typically used where the crankshaft does not provide proper internal balancing (does not have crankthrow counterweights, or they are insufficient).



Ha, you guys have to do everything different don't you!! :lol:

#17 NorthWet

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Posted 16 November 2006 - 06:07 PM

Ha, you guys have to do everything different don't you!! :lol:

As was said regarding us and Great Britain..."Two countries separated by a common language." :lol:

I try to be sensitive to the USA not REALLY being the center of the known universe, and that words and physicality ("driver's side") are not the same to all. But then, my first car was a Triumph, and its manuals were all British. My second car was a Datsun (Nissan), and its manual was a British translation from the Japanese. :rolleyes:

#18 dixracing

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Posted 16 November 2006 - 08:59 PM

hmmmmmm mine too..............lol

#19 mikeshoup

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Posted 16 November 2006 - 10:22 PM

Careful on saying the flat fours are balanced. They have an excellent primary balance (the momentum of the pistons is balanced), but they don't have a very decent kinetic energy balance because one side of the engine has two power strokes, then the other side. The large heavy flywheels on these help to make up for that and absorb the extra vibrations.

#20 Prospeeder

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Posted 16 November 2006 - 11:50 PM

a harmonic balencer can also be a seprate shaft, i know the 3300 GM V6's used a harmonic balencer that balenced it all out it was a shaft driving off the cam i think, but somehow it went like backwards or somthing and had wieghts on it to counter act the off balence situation on the 90* V6




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