flywheel balance question

[Rick Houck]

Bernie,

Your logic makes sense on balancing individual parts, but I saw the flywheel
being checked for balance, and accepted their premise and the imbalance.
Either they were correct, or the imbalance I witnessed in their test makes
no apparent difference in operation. I can not detect any abnormal vibration
at all, even though I run it up to redline regularly on the track.

As to lightening the flywheel, the original 7A design is a heavy compromise
I was not willing to live with on a dedicated track car. Of the three engine
configurations I have (7A, MC, & 3B), the 7A flywheel is by far the
heaviest. Cutting this one will serve to bring it down close to the original
factory weight for a 3B.

This may be academic, since I may be able to use the 3B flywheel afterall.
The two flywheels have different hub and pilot bearing designs, to work with
their stock transmission shafts. The 3B has a needle bearing installed in
the crank, while the 7A has a ball bearing mounted in the flywheel hub. Now,
I may have found a way to use the 3B flywheel with the smaller coupe
transmission shaft.

Rick

 ----- Original Message ----- 
From: "Bernie Benz" <b.benz at charter.net>
To: "Rick Houck" <rhouck at neo.rr.com>
Cc: "audi-20v" <audi20v at rennlist.org>; "200q20V mailing list"
<200q20v at audifans.com>
Sent: Thursday, February 26, 2004 11:12 PM
Subject: Re: flywheel balance question


> Rick,
>
> IMO, components must be balanced at the component level, otherwise
> subassemblies must be balanced together as if a single component and tied
> together in the documentation.  Such is not the case, so your vendor took
> the easy way out and lucked out, meaning no unhappy customer.
>
> An as side point, if there were no need for flywheel inertia, why would a
> mfgr. add the additional material to a flywheel beyond that required for a
> suitable clutch plate surface?  IMO, your gain in acceleration is trivial,
> considering the vehicle momentum as transposed back to the engine.
>
> Bernie
>
> > From: "Rick Houck" <rhouck at neo.rr.com>
> > Date: Thu, 26 Feb 2004 20:10:41 -0500
> > To: <audi20v at rennlist.org>
> > Cc: 200q20v at audifans.com
> > Subject: flywheel balance question
> >
> > I need advice from someone who has lighteded an I5 flywheel. Should the
> > flywheel actually be balanced perfectly when removed from the crank?
> >
> > Background: A few years ago, I took my coupe flywheel to a local speed
shop
> > for cutting. They did the job, but when I picked it up, they told me it
was
> > out of balance before cutting, so they left it that way after cutting.
Not
> > knowing Audi 5 cylinder engines, they were not sure if this was done on
> > purpose to counter some effects from the rotating mass of the crank and
> > reciprocating parts. After 5-6 years of track duty behind my 7A and MC
> > engines, I can say that it is very smooth all the way to redline. I
think
> > they were probably right.
> >
> > Fast forward: I am now getting ready to do a 3B conversion on another
car,
> > and again will be using a lightened coupe flywheel. My experience tells
me
> > it is OK to just remove metal evenly, but I have never heard this
discussed.
> > Anyone else go through this?
> >
> > Thanks in advance,
> > Rick
> >
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