Crankshaft Pulley

[redlightningsvx]

Originally Posted by ensteele

Will this one fit the SVX? Same size etc?

I'm pretty sure it will Earl as i've had my eye on this for a while.

[Crazy_pilot]

Originally Posted by ensteele

Will this one fit the SVX? Same size etc?

Any of the pulleys meant for the 4-cylinders will fit our cars.

[LetItSnow]

My SVX has had an Agency pulley on it for nicely over a year now. It spent time on a WRX before I got it for cheap.

[Trevor]

Originally Posted by LetItSnow

Certainly don't take this the wrong way, but it does also stand to question just how many miles the particular car is anticipating seeing in its lifetime.

If so, can it be predicted as to exactly when the crank might fracture?

[Trevor]

Originally Posted by alia176

Makes sense, hence the specific weight of the unit tuned to a specific freq.

Thanks.

No, the pulley has no specific weight. It is a damper, a soft drive which irons out or absorbs any vibrations/peeks in the rotational speed of the crank, and the parasitic loads driven by the pulley are very much part of the equation. There is no movement of the frequency, the object is to eliminate same.

[alia176]

Originally Posted by Trevor

No, the pulley has no specific weight. It is a damper, a soft drive which irons out or absorbs any vibrations/peeks in the rotational speed of the crank, and the parasitic loads driven by the pulley are very much part of the equation. There is no movement of the frequency, the object is to eliminate same.

The item does have some weight to it and I'd like to think that it didn't come to this weight by accident

From Wikipedia

A harmonic balancer (also called crank pulley damper, crankshaft damper, torsional damper, or vibration damper) is a device connected to the crankshaft of an engine to reduce torsional vibration.

Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.

To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass and an energy dissipating element. The mass resists the acceleration of the vibration and the energy dissipating (rubber/clutch/fluid) element absorbs the vibrations.

Additionally the energy transferred from the piston to the crankshaft can induce as much as 2 degree's of twist in the crankshaft, which has many follow-on effects on all engine elements that require adequate timing such as valve opening, cam timing, ignition timing etc.

Over time, the energy dissipating (rubber/clutch/fluid) element can deteriorate from age, heat, cold, or exposure to oil or chemicals. Unless rebuilt or replaced, this can cause the crankshaft to develop cracks, resulting in crankshaft failure.

Performance enthusiasts have been known to remove harmonic balancers, usually when the balancer is attached to the crank pulley, deciding that they aren't necessary and their mass reduces the performance of the engine. However, this is unproven and potentially very risky because the danger of damage to the engine from the vibrations the damper is intended to prevent is too high.

Certain cars, however, do not come equipped with an external balancer on the crank pulley, and as such, can have the pulley replaced with a performance oriented product which counter-act these resonance frequencies.

[Trevor]

Originally Posted by alia176

The item does have some weight to it and I'd like to think that it didn't come to this weight by accident

What is your point?

The original pulley certainly has some weight, but no specific weight in respect of a design requirement. The weight is dictated by mechanical considerations relative to the damping mechanism.

Wikipedia confirms my statement in all respects, but does not cover aspects of the driven load, this being in their description, a secondary item.

Why do you emphasise this point, which does not cover the SVX? ---

“Certain cars, however, do not come equipped with an external balancer (integral balancer?) on the crank pulley, and as such, can have the pulley replaced with a performance oriented product which counter-act these resonance frequencies.” What is your point? The original pulley certainly has some weight but no specific weight in respect of a design requirement. The weight is dictated by mechanical considerations relative to the damping mechanism.

Wikipedia confirms my statement in all respects but does not cover aspects of the driven load, this being in their instance a secondary item.

Why do you emphasise this point, which does not cover the SVX? ---

“Certain cars, however, do not come equipped with an external (integral?) balancer (Damper?) on the crank pulley, and as such, can have the pulley replaced with a performance oriented product which counter-act these resonance frequencies.”
(N.B. A plain pulley, within itself, can in no way counteract resonant frequencies.)