Got my lightweight pulley !

[Vtim]

yar I know, but the power is lacking a bit lar!

[Modeldriver]

power never enough one lah...

[Vtim]

well said

[Hattee]

I suppose most of the potential damages have been well covered here that can be sustained with loss in essential dampening on a mechanical system.

 

But I am not sure if really OEM crank pulley serves such a critical purpose in every car if we were to look at it a little closer on how it affects dampening at various conditions of operation.

 

Perhaps, most of us already notice the pitch at a given rpm, particularly up from idling, is always alot higher at N than at D or with gear. This might suggest the drive-train, design couplings, structural rigidity, precision, absorbers and even the gross weight are far more important dampers than just crank pulley. For some older cars and probably lighter ones, engine noise readily shows up when driving at higher rpm. Maybe this can differentiates a well-balanced (dampened), stable and probably quieter car from those lighter, vibration-prone and noisier ones as the rpm moves away from idling (interesting to hear some associating quiet idling with assurance of quality ride).

 

To understand how little the pulley can do on dampening, just remove the belt to the compressor, alternator and various pumps, the sound of idling becomes significantly sharper (even exhibiting vibration) and not proportional to the slight rise in idling rpm. It again shows many other anciliaries contribute more significant dampening than crank pulley. Assumption here is potentially damaging harmonics are always audible. Or are there other damaging higher harmonics? Even if there are ultrasonics for some very exceptional case, can crank pulley be of any use?

 

Having said this, heavier crank pulley does reduce potential damages whenever the engine is ram up at N for whatever reasons. The caveat for marginal reduction in inertia of crank pulley not causing damages is when the engine does not exhibit increase noise loaded at the higher rpm. Otherwise many among us using lighter crank pulley for more 2-3 years would have said something by now. They sure testify noticeable gain in pickup and even FC. Of course there are cars designed with meagre dampening, further reduction of inertia might not always be wise.

 

Like many things in life, gain some will lose some. If there is nett 50% inertia reduction at the crank linkages, got to avoid ramming at N (3000 can sustain equiv wear of 6000). Also, shedding 3-5 kg from the pulley might be translated to 2-3% loss in drive train inertia resulting in a little lethargy in reaching the max speed, particularly uphill. Using incorrect pulley radius or requiring use of different size belt would soon lead to other problems related to a/con, hydraulic power, coolant circulation and battery.

 

I think what ICERAIN is trying to say in longer technical terms is as listed. Just be careful ... I was also considering the aftermarket pulleys till I read this.

 

http://www.toyotacelicaonline.com/pulleys.htm

 

The Danger of Power Pulleys & Understanding the Harmonic Damper

By Steve Dinan of Dinan BMW

 

 

I have been threatening for a long time to write a series of technical articles to educate consumers and to dispel misconceptions that exist about automotive after-market technology. Motivated by problems with customer's cars resulting from the installation of power pulleys, I wish to explain the potential dangers of these products and address the damage they cause to engines.

 

The theory behind the power pulley is that a reduction in the speed of the accessory drive will minimize the parasitic losses that rob power from the engine. Parasitic power losses are a result of the energy that the engine uses to turn accessory components such as the alternator and water pump, instead of producing power for acceleration. In an attempt to minimize this energy loss, many companies claim to produce additional power by removing the harmonic damper and replacing it with a lightweight assembly. While a small power gain can be realized, there are a significant number of potential problems associated with this modification, some that are small and one which is particularly large and damaging!

 

The popular method for making power pulleys on E36 engines is by removing the harmonic damper and replacing it with a lightweight alloy assembly. This is a very dangerous product because this damper is essential to the longevity of an engine. The substitution of this part often results in severe engine damage.

 

It is also important to understand that while the engine in a BMW is designed by a team of qualified engineers, these power pulleys are created and installed by people who do not understand some very important principles of physics. I would first like to give a brief explanation of these principles which are critical to the proper operation of an engine.

 

1) Elastic Deformation

 

Though it is common belief that large steel parts such as crankshafts are rigid and inflexible, this is not true. When a force acts on a crank it bends, flexes and twists just as a rubber band would. While this movement is often very small, it can have a significant impact on how an engine functions.

 

2) Natural Frequency

 

All objects have a natural frequency that they resonate (vibrate) at when struck with a hammer. An everyday example of this is a tuning fork. The sound that a particular fork makes is directly related to the frequency that it is vibrating at. This is its "natural frequency," that is dictated by the size, shape and material of the instrument. Just like a tuning fork, a crankshaft has a natural frequency that it vibrates at when struck. An important aspect of this principle is that when an object is exposed to a heavily amplified order of its own natural frequency, it will begin to resonate with increasing vigor until it vibrates itself to pieces (fatigue failure).

 

3) Fatigue Failure

 

Fatigue failure is when a material, metal in this case, breaks from repeated twisting or bending. A paper clip makes a great example. Take a paper clip and flex it back and forth 90