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underdriven crank pulley

Old 03-14-2007, 06:21 AM
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Join Date: Mar 2007
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Default underdriven crank pulley

i've been looking around for a while and i've seen a lot of arguments about this. i'm pretty much a n00b when it comes to this kind of stuff. something about taking off the harmonic balancer or something that causes some engine failure. what i got out of it was that the harmonic balancer was actually built into the stock crank pulley. is this right? what would be the dangers of underdriving the crank pulley for a 94 ex?
Old 03-14-2007, 10:27 AM
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Default RE: underdriven crank pulley

The stock crank pulley is really made in different pieces. The outer pulley is separated from it's hub by a layer of relatively hard rubber. The rubber kinda looks like a groove in the face of the pulley. That's to handle some higher-order vibrations.

The danger isn't about underdriving the accessories. The danger is about not having that layer of compliant material. OTOH, people have done it without problems. AFAIK, nobody makes an underdrive pulley that incorporates the balancer.
Old 03-14-2007, 02:20 PM
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Default RE: underdriven crank pulley

Here's a little more information.... also, note that some honda's don't even have that little rubber ring....


People are getting their crank pulleys confused with the harmonic dampers found on some V6 / V8 engines. "Harmonic Balancer" is a term that is 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 that we offer utilize a counterweight as part of the pulley as these engines are internally balanced. The pulleys on most of the new import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley that looks 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 that in these applications, this elastomer is somewhat inadequate in size, as well as life span, to act as an effective torsional damper. If you look at the pulleys on some of the 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 that with our pulleys you will hear a ton of noise or feel more vibration from your engine compartment. Most who have installed and driven a vehicle with our pulleys will notice the engine actually feels smoother. This is a natural result of replacing the heavy steel crank pulley with a CNC-machined aluminum 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, displacement, inline, V configurations, power output, etc., do determine when and how these harmonics and torsional movements occur. Again, there is a lot of internet hearsay about the 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.
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