The Torsional Vibration Damper (TVD) pulley is the pulley on the end of the crank that drives the accessories – alternator, water pump, and air conditioning compressor.
The O.E. TVD pulley has a built-in harmonic damper, in the form of a split design, with a thick rubber pad sandwiched between two steel sheets. The damper is designed to absorb torsional and vertical vibrations from the crank, as a result of the engine combustion process. All FAI Torsional Vibration Dampers are manufactured to meet or exceed OE specifications.
Torsional vibration is a twisting vibration caused by the firing of each piston. The force of the piston causes the crank to deflect ever so slightly in the direction of the force, and when that force goes away the crank ever-so-slightly springs back. At certain frequencies the crank can resonate, making the vibration much worse. This is where the harmonic damper comes into play.
Some product found in the aftermarket does not include the rubber part of the damper and as a result almost certainly increases crank bearing wear, and could lead to early failure of the crankshaft or crankshaft bearings.
We recommend that only a pulley with a harmonic damper is fitted.