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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.
Depending on the application, stretch bolts are used to fix the TVD to the crankshaft. During installation the bolt will deform so it MUST be replaced during a repair. Failure to replace a used stretch bolt can cause the new TVD to fail due to incorrect torqueing or the bolt may snap during installation. To assist the installer, FAI have added a range of TVD kits which include the torsional vibration damper and any bolts and washers required for the installation. An air tool must never be used to remove or install crankshaft bolts and manufacturer instructions must be followed to ensure correct installation.
We recommend that only a pulley with a harmonic damper is fitted.