Topic: Lightweight Crank Pulley

[Bailey]

MRZ performance is offering a Lightweight Crank Pulley...I have been very pleased with other product from them, but I was wondering...is there any concerns with replacing this OEM part, i.e. balancing, etc?

[snaponbob]

MRZ performance is offering a Lightweight Crank Pulley...I have been very pleased with other product from them, but I was wondering...is there any concerns with replacing this OEM part, i.e. balancing, etc?

You have asked THE correct question. That pulley will be replacing a harmonic balancer. For competition purposes it will be a benefit. For "normal" use, the vibrations that will NOT be damped will be a) uncomfortable and irritating, and b) potentially eventually damaging to the engine.

There is no free lunch.

[KWhale]

There is no free lunch.

I don't know about that SOBob, perhaps you missed this post?  http://kappaperformance.com/forum/index.php?topic=3163.0;topicseen

 

[1LILNDN]

I though the Crank Pully is Balanced to conform to any offset in weight. You would think MRZ Performance allows for that also.

[Sol Asylum]

It's not a matter of the pulley being out of balance.  The stock pulley is a harmonic balancer meaning that it has the ability to cancel out vibrations that come from other parts of the engine.  This happens because the pulley is somewhat flexible and allows the pulley to move in a manner that counteracts the original vibration, think equal but opposite.  The lightened pulley does not have this feature so any vibrations generated elsewhere in the engine will not be dampened out.

[snaponbob]

It's not a matter of the pulley being out of balance.  The stock pulley is a harmonic balancer meaning that it has the ability to cancel out vibrations that come from other parts of the engine.  This happens because the pulley is somewhat flexible and allows the pulley to move in a manner that counteracts the original vibration, think equal but opposite.  The lightened pulley does not have this feature so any vibrations generated elsewhere in the engine will not be dampened out.

Well said. I spoke with a vendor (can't remember whom) about this, and he stated that when he installed one on a Kappa that there was an increase in harmonic vibrations, but certainly was tolerable to the drive, but over time would NOT be a good thing for a daily driver. I do recall him mentioning an increased likelihood of front seal leakage.

[DRGNSLR]

FWIW:

I ran across a thread on another forum some months ago discussing problems associated with the use of the lightweight pulley on a Kappa platform including throwing engine codes and a dealer that was voiding an engine warranty because that part was installed.  I wish I could remember which thread/which forum but the thread is out there. 

[Tom0000]

http://www.grapeaperacing.com/tech/dampers.pdf

I think this explains it pretty well now that I have reread the thread.


- Tom

[Critterman]

Very good find Tom, one would guess you could use lighter pulleys on the accessories, but leave the crank pulley alone.

[Tom0000]

another option is on my camaro I have underdriven pulleys.  They would help prevent losing as much power from the pulley system.  I don't have any information on how our cars would respond to them though.