Harmonic Balancer Pulley....problem or paranoia

[awdonald]

At Watkins Glen for the Boston Club "Intense" track days last week one of the Z3MCoupes had the lower pulley shear causing overheating and premature end to a great event.

The reason I mention it is that while being replaced I am informed the mechanic said it happened on occasion and the lower pulley should be checked for tightness and red Locktite was a good idea. Apparently check from below is easier than attempting to do so from above.

I've tracked my Coupe a fair bit, carefully check for the rear separation issue ( no problem so far 7 years on) but have never concerned myself with the harmonic balancer/lower pulley.

What is the wisdom of the Forum...an unfortunate incident or are we driving time bombs ? ( see paranoia above)

[BenFenner]

Harmonic dampers contain a rubber isolation layer, which gets stressed and heated with use and dry with age. They can and do fail, just like any other component. In my opinion it is something we will see more of as these cars reach the 15-20-year mark, but it isn't something to freak out about. Knowledge is power here.

[ticklemejoviemo]

Now whats the advantage of an ATI over OEM?

[BenFenner]

The main advantage (without getting into serious detail) is that the ATI units damp the crank harmonics better, over a wider RPM range, and are tuned to damp harmonics at RPM intervals more often seen by those doing performance driving with raised rev limiters. I think they are also lighter, and I think fluid-filled, and can have under-drive ratios built in, and a few other fun things. But the main benefit is best shown by a chart comparing OEM crank harmonics with no damper, with OEM damper, and with ATI damper (if one could find such a chart).

[ticklemejoviemo]

and as far as overall durability and/or longevity of them (in regards to the rubber, if different)?

not to threadjack, but I was intending on getting a new damper when I do my engine work, so I'm glad this came up

[cleanerPA]

I know this was covered before, but the ATI damper works better and does not come apart from sustained high rpm use, unlike the OEM damper.

[CMM3]

I did a fair amount of research on the damper subject.
For a street driven car not too much of a concern, with 100k+ mile cars good to keep a close eye on it.
For a track driven car that sees sustained elevated temps and rpms they are know to fail, due to heat weakening the rubber.
Most race cars will have additional duct work to cool the damper and if using OEM they will replace annually.
Even if the damper does not fail catastrophically the degradation in it's ability to dampen crank vibrations can cause accelerated wear to main bearings.
For a track driven car with 75k+ miles on it installing a new one or upgrading to an ATI is a good practice.
BTW - VAC has the exclusive rights on the ATI damper for the s54 apparently they helped to develop it and can now rape on the price.
ATI dampers have been around for years are race proven and worth the added cost in general.
I've used them on several cars and never had an issue and now have one installed on my s54.

[BenFenner]

Even if the damper does not fail catastrophically the degradation in it's ability to dampen crank vibrations can cause accelerated wear to main bearings.

Any theory on how/why main bearing wear would accelerate due to crank torsion harmonics? Do we know this happens for sure? With the forces involved, I don't see how it would possibly have any effect on main bearings. Rod bearings, maybe, but not main bearings?

[ticklemejoviemo]

Thanks for additional info CMM3!
Apparently VAC seems to have the same thing going on with the M54 damper, it's more expensive than the S54 one :O

[CMM3]

Any theory on how/why main bearing wear would accelerate due to crank torsion harmonics? Do we know this happens for sure? With the forces involved, I don't see how it would possibly have any effect on main bearings. Rod bearings, yes, but not main bearings?

Here is a good article on the subject

http://www.enginelabs.com/engine-tec...mper-dynamics/

[BenFenner]

Read the article. There is no substantiation of the claims there either. Main bearing wear? I don't think so Tim.