Much of the science behind dampers is based on theories in books, applied in a vacuum, not actual real world facts. Most people buy a damper because they herd they needed one or out of a fear of the unknown. The problem is people don't know why they do or don't need a damper. There is no mystery here, just cold hard facts based on real world use and need. So lets get started.
First what is a damper? The most basic definition comes from Websters, which says; a damper is a dulling or deadening influence. Now that's pretty simplistic but its a great start. A damper is designed to absorb motion and frequency (harmonics) created by the crankshaft and the rotating assembly (rods, cams, etc). The most important aspect/element of a damper is how it's mounted to the crankshaft. A damper must be interference fit to the crankshaft snout. This means the damper must be heated up to be pressed onto the crankshaft snout, making a fit so tight its like the parts were made from one piece of metal. Without being interference fit a damper cannot function according to the most basic law of physics, "every action must have an equal and opposite reaction." Without interference fit a damper moves on the crankshaft snout and loses all of its ability to counteract crankshaft torsional movement.
The purpose of a damper is to protect the crankshaft from cracking due to excessive torsional movement and harmonic frequencies. A damper has no effect on bearing wear, it is the engines balance and build tolerances that control bearing wear. Dampers are not necessary in most modern engines because of the many advances in engine design but more importantly the quality of the materials and machining tolerances. Factors such as shorter stroke lengths, short piston TDC dwell time, no piston pin off-sets, forged crankshafts and engines that are balanced to blue printing specs or better (Honda engines are 0 gram balanced). Another important factor is the actual tune of the engine, especially when modified. Poor tuning leads to detonation which is an engine killer and no damper can stop this damage.
Now that these important facts are out in the open you need to figure out if your engine does or doesn't need a damper. If your factory crank pulley is not interference fit onto the crankshaft you do not need a damper. A great example of this is the 4G63 engine (1990+ Eclipse, Evo, Laser & Taon) which has its crank pulley mounted to the engine with four small M8 bolts. The 420A SOHC/DOHC crank pulley (Chrysler Neon, etc.) is interference fit but not because it needs a damper but because there is no key or dowel pin to hold the pulley from spinning on the crankshaft. Still confused? If you unbolt your crank pulley and it slides off the crankshaft you do not need a damper. There are a few engines where the crank pulley is sometimes slightly tight (VG30DE & DETT) but these engine also do not need a damper.
Now lets cover some damper terminology mis-understandings. The term "Harmonic Balancer" is often used but is incorrect. This type of device does not exist but was created by putting two terms together. The words are harmonic damper and engine balancer. A harmonic damper is just a fancy name for a damper. The term engine balancer is for engines that are externally balanced and have a counterweight cast into or bolted to the crank pulley or damper. The proper way to describe the incorrect term above is Harmonic Damper or Damper with or without external balance weight.
Now many people will still have lingering confusion even after all the facts above. This is ok as we are changing people's understanding through real facts not urban myths and legends that have persisted for too long. As discussed above many of the pulleys on import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley making them look similar to a damper. The elastomer in the OEM pulley serves as an isolator, suppressing noise from the engine accessories; the A/C compressor, P/S pump, and alternator. This noise is what car manufacturers call NVH (Noise Vibration & Harshness) which they want to keep out of the passenger compartment. Its the same reason OEM's use of dual mass flywheels to quiet transmission noise and freewheeling alternator pulleys to quiet even more alternator noise.
Many earlier generation crank pulleys on domestic & import engines have no rubber at all. We have samples of many of these from Acura/Honda B & D Series engines, 2.4L Altima, 1.8L Eclipse, 2.3L Fords, 2.2L Chrysler's, and 1.8L VW's just to mention a few. Some people will now worry that because we remove the NVH damper they will start to hear more engine accessory noise. The type and amount of NVH is unique to every car. As an example NVH will increase with aftermarket intakes or exhausts. OEM intake and exhaust systems use baffles and resonators to quiet intake and exhaust noise. Aftermarket systems eliminate these baffles and resonators to increase HP but they also increase noise from the throttle opening and from the additional size of the freer flowing exhaust. To most people the increase of in NVH makes for a sportier driving experience not to mention more HP.
For engines that need dampers UR will finally be offering the most innovative new damper technology in 20 years. The Ultra Damper will be in a class by itself offering unmatched damping capability from idle to redline. Even more amazing is the Ultra Damper will be ligther than the factory damper and any other damper currently available. Once again UR is leading the industry in advanced light weight solutions helping increase engine efficiency, saving you the consumer money on fuel and maintenance costs.
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