Quote:
Originally Posted by Excelerate
That is what you might want to call an elastomer. It is there to reduce NVH (Noise, Vibration, Harshness). Instead of re-writing this entire argument I will just post UR's response:
4) "Is my crank pulley a harmonic/torsional/vibration damper or a harmonic balancer?"
People are getting their crank pulleys confused with the harmonic dampers found on some V6 / V8 engines. "Harmonic Balancer" is a term used loosely in the automotive industry. Technically, this type of device does not exist. The "balancer" part comes from engines that are externally balanced and have a counterweight cast into the damper, hence the merging of the two terms. None of the applications we offer use a counterweight as part of the pulley, as these engines are all internally balanced.
The pulleys on most of the new import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley that makes them look similar to a harmonic damper. The elastomer in the OEM pulley serves as an isolator, which is there to suppress natural vibration and noise from the engine itself, the A/C compressor, P/S pump, and alternator. This is what the manufacturers call NVH (Noise Vibration & Harshness) when referring to noticeable noise and vibration in the passenger compartment. It is important to note in these applications, the elastomer is inadequate in size and durability to act as an effective torsional damper. If you look at the pulleys on some imports there is no rubber to be found at all. We have samples of these, mostly from Acura/Honda, the Nissan Altima, 1.8L Eclipse, 2.3L Fords, Chrysler 2.2L's, and 1.8L VW's, to mention a few. This is not to say with our pulleys you will hear a ton of noise or feel more vibration from your engine compartment. Most owners who have installed our pulleys notice the engine actually feels smoother. This is result of replacing the heavy crank pulley with our crank pulley. NVH is variable and unique to every car. NVH will increase with the installation of an aftermarket intake and/or exhaust, for example. Think of OEM intake systems in newer cars, they use baffles and resonators in the intake to quiet all the intake noise. Aftermarket intakes eliminate these resonators and create dramatic increases in engine noise from the throttle opening and closing. So to most tuners, certain types of NVH can make the driving experience more enjoyable.
The purpose of a traditional harmonic damper is to protect against crank failure from torsional movement. This is not necessary in most modern engines because of the many advances in engine design and materials. Factors such as stroke length, displacement, inline, V configurations, piston dwell time, piston pin off-set, power output, etc., do determine when and how these harmonics and torsional movements occur.
Again, there is a lot of internet hearsay about crank pulleys. When engine problems occur, too often people are quick to blame the pulley first, rather than taking the time to look logically into why there was a problem. We hope that after reading this you will understand the crank pulleys better.