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The Danger of Power Pulleys & Understanding the Harmonic Damper

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 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 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° or so. After about 10 oscillations the paper clip will break of fatigue failure.

The explanation of the destructive nature of power pulleys begins with the two basic balance and vibration modes in an internal combustion engine. It is of great importance that these modes are understood as being separate and distinct.

1) The vibration of the engine and its rigid components caused by the imbalance of the rotating and reciprocating parts. This is why we have counterweights on the crankshaft to offset the mass of the piston and rod as well as the reason for balancing the components in the engine.

2) The vibration of the engine components due to their individual elastic deformations. These deformations are a result of the periodic combustion impulses that create torsional forces on the crankshaft and camshaft. These torques excite the shafts into sequential orders of vibration, and lateral oscillation. Engine vibration of this sort is counteracted by the harmonic damper and is the primary subject of this paper.

Torsional Vibration (Natural Frequency)

Every time a cylinder fires, the force twists the crankshaft. When the cylinder stops firing the force ceases to act and the crankshaft starts to return to the untwisted position. However, the crankshaft will overshoot and begin to twist in the opposite direction, and then back again. Though this back-and-forth twisting motion decays over a number of repetitions due to internal friction, the frequency of vibration remains unique to the particular crankshaft.

This motion is complicated in the case of a crankshaft because the amplitude of the vibration varies along the shaft. The crankshaft will experience torsional vibrations of the greatest amplitude at the point furthest from the flywheel or load.

Harmonic (sine wave) Torque Curves
Each time a cylinder fires, force is translated through the piston and the connecting rod to the crankshaft pin. This force is then applied tangentially to, and causes the rotation of the crankshaft.

The sequence of forces that the crankshaft is subjected to is commonly organized into variable tangential torque curves that in turn can be resolved into either a constant mean torque curve or an infinite number of sine wave torque curves. These curves, known as harmonics, follow orders that depend on the number of complete vibrations (cylinder pulses) per revolution. Accordingly, the tangential crankshaft torque is comprised of many harmonics of varying amplitudes and frequencies. This is where the name "harmonic damper" originates.

Critical RPM's
When the crankshaft is revolving at an RPM such that the torque frequency, or one of the harmonic sine wave frequencies coincides with the natural frequency of the shaft, resonance occurs. Thus, the crankshaft RPM at which this resonance occurs is known a critical speed. A modern automobile engine will commonly pass through multiple critical speeds over the range of its possible RPM's. These speeds are categorized into either major or minor critical RPM's.

Major and Minor Critical RPM's
Major and minor critical RPM's are different due to the fact that some harmonics assist one another in producing large vibrations, whereas other harmonics cancel each other out. Hence, the important critical RPM's have harmonics that build on one another to amplify the torsional motion of the crankshaft. These critical RPM's are know as the "major criticals". Conversely, the "minor criticals" exist at RPM's that tend to cancel and damp the oscillations of the crankshaft.

If the RPM remains at or near one of the major criticals for any length of time, fatigue failure of the crankshaft is probable. Major critical RPM's are dangerous, and either must be avoided or properly damped. Additionally, smaller but still serious problems can result from an undamped crankshaft. The oscillation of the crankshaft at a major critical speed will commonly sheer the front crank pulley and the flywheel from the crankshaft. I have witnessed front pulley hub keys being sheered, flywheels coming loose, and clutch covers coming apart. These failures have often required crankshaft and/or gearbox replacement.

Harmonic Dampers
Crankshaft failure can be prevented by mounting some form of vibration damper at the front end of the crankshaft that is capable of absorbing and dissipating the majority of the vibratory energy. Once absorbed by the damper the energy is released in the form of heat, making adequate cooling a necessity.

It is also important to note that while the large springs of a dual mass flywheel absorb some of the torsional impulses conveyed to the crankshaft, they are not harmonic dampers, and are only responsible for a small reduction in vibration.

This is a simplified explanation meant to be comprehensible by those who are not automotive engineers.


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Supporting VIP
Jun 29, 2003
Luthersville Ga, Atlanta, Georgia
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Supporting VIP
Jun 29, 2003
Luthersville Ga, Atlanta, Georgia
This is the damper I purshased ati over Fluidampr also over oem.

ATI Damper Technology

The patented ATI Super Damper® is the only harmonic damper designed exclusively for high performance engines yet forgiving enough for everyday drivers. The proven elastomer design is actually two dampers in one: A 4" inner diameter and a 5-1/2", 6 3/8", 7", or 8" diameter outer damper in two shells that bolt to the crank hub.

All ATI Super Dampers® feature a replaceable bolt-in crank hub. Steel shells are black zinc chromate finished and Aluminum is Hard Anodized. All have computer controlled, laser engraved 360° timing marks.

All units are SFI manufacturer certified and exceed SFI spec. 18-1. The patented Super Damper® also gives you guaranteed performance. Your car will run as fast as or faster than with your present damper or your money back. Dyno tests have proven the Super Damper® will allow the engine to produce as much as 45 HP over a poorly sized Fluidampr at 7,500 RPMs and commonly 12 to 30 HP over OEM and other aftermarket brands on high performance engines.

For years, major manufacturers have used the elastomer-type damper design. These conventional, single-strip elastomer dampers have proven very effective on OEM applications operated at low RPM's. They were also surprisingly effective at high RPM's. Many engineering studies have shown that elastomer style dampers to be the far superior to the friction type and markedly better than the viscous type in controlling vibrations over a wide range.

Conventional single strip elastomer dampers are not re-buildable
. The main problem with this type of damper is a loss of certain controls inherent in the manufacturing process. An inertia weight pressed with a rubber insulator to the crank hub allows the possibility of the ring to move in its relation to the keyway. It is also impossible to maintain the concentricity of the inertia ring during manufacturing. The ring must be machined after it's pressed to the hub, and then balanced after machining. When it works loose with age or from multiple cycles, the ring will move, and the damper will be out of balance.

Hundreds of these OEM imitation SFI approved dampers have failed in service on high RPM engines.

Viscous fluid dampers are sealed and you don't know you have problem until it's too late. The inertia weight can become fixed (locked) by bearing failure or, more commonly, from the silicone turning to a solid mass. Your first warning of damper failure will probably be a broken crankshaft resulting in the replacement of your damper AND the engine. Viscous fluid dampers are not only ineffective but are actually detrimental at high RPM's.

The solution? The ATI Torsional Super Damper® - the unconventional, unbonded elastomer Super Damper™ that is actually 2 dampers in 1 diameter.

The ATI Super Damper® is the only damper designed exclusively for high performance engines. The proven elastomer design is actually two dampers in one and O-ring life has been tested to over 3.5 million race cycles in Sprint Cup competition (6500+ RPM, 600+ miles) and 10+ years (188 - 11 run weekends) in drag racing. The unit is re-buildable to new specifications by installing new O-rings and field serviceable. You can have a totally fresh Damper for as little as $40! Extensive dyno and on-the-track testing by ATI, GM, Toyota Racing Development (TRD), and all of the NASCAR engine builders have proven the Super Damper® far superior to all other designs, and is trusted by 100% of NASCAR engine builders and reputable engine builders around the world!


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Supporting VIP
Jun 29, 2003
Luthersville Ga, Atlanta, Georgia
Here is the competitor of ati I am posting this so you can make a sound decision on what you want to use. I chose ati because I have read to many crank failures with the fluidampr. have no experience with fluidampr but will post the imformation listed on their website.

Fluidampr performance harmonic dampers can increase torque, horsepower, reduce harmonics, and lengthen the life of your engine.

A new Fluidampr harmonic damper on your diesel truck will not only protect your engine from destructive torsional vibrations but will also increase TORQUE & HORSEPOWER output. Today's High Performance diesel engines can be easily modified to increase their power output levels. When a diesel programmer or chip is installed on your motor the torsional vibrations are increased leaving your motor vulnerable to torsional vibrations.
Save your crank & more by installing a new Fluidampr today.

Fluidampr® Performance Diesel dampers offer the best protection against torsional vibrations. Whether your Diesel motor is performance tuned or stock, your diesel engine will run more efficiently with a viscous Fluidampr® installed.

Fluidampr can increase torque, reduce harmonics, and lengthen the life of your engine.Torsional Vibrations or harmonics can destroy your engines crankshaft and bearings. These vibrations also rob horsepower and torque from the engine. Stock dampers utilize rubber or elastomer to control torsional vibrations. The rubbery material not only breaks down over time, but limits the capabilities for the damper to operate correctly throughout the entire RPM range. Fluidampr® Harmonic Dampers use a viscous silicone fluid, internal inertia ring and a laser sealed housing. The precision assembly used to construct a Fluidampr harmonic damper is the most effective way to control torsional twisting.

Fluidampr® performance harmonic dampers have been tested on both stock and performance tuned diesel pick-ups. Dynamometer tests have shown consistent increases in both horsepower and torque in the Cummins, Powerstroke and Duramax motors!

Each time the air/fuel mixture inside a cylinder is ignited, the combustion that occurs creates a torque spike that is applied to the crankshaft through the piston and rod. This torque spike is so severe that it not only turns the crankshaft, it actually twists the crankshaft ahead of its normal rotation and then the crankshaft rebounds. This twisting action is known as torsional vibration. When these torque spikes and forces get into phase with the natural frequency, critical torsional harmonic vibrations occur and can be seriously destructive to the bearings and the crankshaft. Fluidampr High Performance Harmonic dampers are designed to control those destructive vibrations.
Why do you need a Fluidampr High performance Diesel Damper?

Without a crankshaft damper, or with an improper design or worn out damper your engine will produce torsional vibrations. These vibrations induce a back and forth oscillation through the engines crankshaft.

When these oscillations begin to collide with other vibration frequencies of the same magnitude it amplifies and resonates a destructive force. When these destructive forces repeatedly happen it results in worn timing gears, timing chains, irregular valve train lash, destroyed main bearings, fractured accessory pulley mounts and even crankshaft failure. A worn out OEM damper is the leading cause of broken crankshafts. Protect yourself from catastrophic engine failure by installing a Fluidampr Performance Dampe


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Supporting VIP
Jun 29, 2003
Luthersville Ga, Atlanta, Georgia
About Fluidampr

Why Use Fluidampr's Harmonic Fluid Damper?

The Invisible Enemy of your engine and the most overlooked protector of your engine, the harmonic damper. Fluidampr can increase torque, horsepower, reduce harmonics, and lengthen the life of your engine.

Fluidampr Products and Fluidampr FAQs:

Why Use Fluidampr?
Fluidampr General Info
Fluidampr Cummins
Fluidampr Powerstroke
Fluidampr for Duramax
Fluidampr Diesel Accessories
Fluidampr FAQs
Heavy Duty Fluid Dampers

Why Use a Fluidampr Harmonic Fluid Damper?

The Fluid Damper Problem:

Fluidampr can increase torque, reduce harmonics, and lengthen the life of your engine.The stock harmonic damper on the majority of all personal vehicles and pick-up trucks is an elastomer (rubber) damper. Why? Because they are cheap to manufacture and usually do a marginal but adequate job of protecting your engine on stock applications under normal operating parameters; however, they are inadequate if performance enhancements are made to your engine.

Elastomer dampers are referred to as “tuned or frequency sensitive” devices, designed to function throughout only predetermined vibration frequency bandwidths associated with the RPM, torque and horsepower engineered for a particular engine application. The tuned or frequency sensitive stock dampers rely on a specific durometer of elastomer (rubber) to absorb the harmonic vibrations produced by the engine and are limited to the bandwidth of vibration frequencies that the particular elastomer can absorb.

Damper damage can hurt your engine!The stock or aftermarket elastomer damper cannot self tune beyond the bandwidth that it is designed for. When performance enhancements are made or added to a stock engine to increase horsepower and torque, whether for commercial, pleasure, or competition, the increase in performance overworks the stock damper because of its inherent inability to self tune to the increased harmonic vibration generated, resulting in diminished engine protection.

The reason the damper fails is that when the elastomer damper is overworked trying to compensate for the performance enhancements, excessive heat is generated which results in the rubber becoming hard and cracking, eventually causing the inertia ring to start slipping and risking the dangerous situation of the damper coming apart.

These pictures of stock elastomer dampers show the early stages of the elastomer ring starting to break down and separate from the heat drying out the rubber. This is the first warning sign that the stock or aftermarket elastomer damper has greatly diminished ability to protect your engine and failure is imminent, followed by engine damage or failure.

The Fluid Damper Solution

Fluidampr can increase torque, reduce harmonics, and lengthen the life of your engine.Fluidampr Performance Dampers for Gas and Diesel Engines are manufactured using viscous silicone fluids to shear harmful harmonic vibrations from gas and diesel engines.

Fluidampr’s design incorporates a totally sealed laser welded housing encasing the precision machined and balanced inertia ring. The viscous silicone fluid allows the inertia ring to shear the harmonic vibrations from the engine, regardless of performance enhancements (horsepower, rpm & torque) that have been made to the engine.

This is possible because Fluidamprs are frequency insensitive devises that self tune to the exact frequency bandwidth of the engine harmonics at any given range, unlike stock tuned dampers. This is why it is of the utmost importance to upgrade to a Fluidampr Performance Damper for Gas and Diesel Engines when making performance enhancements to your gas or diesel engines. When adding or using a programmer with your diesel engine it is critically important not to over look one of the most important parts of your engine, the damper.

The Fluidampr will self tune to the harmonics of your engine every time you select a new performance setting. Having the ability to tune your engine at your finger tips if your engine is not equipped with a Fluidampr Performance Damper is like playing “Russian Roulette” with your engine. Fluidampr is the performance product line of Vibratech TVD, the original inventor of viscous type dampers in 1946 and has continued their tradition of designing and manufacturing their superior line of viscous dampers in the U.S.A. Viscous dampers were designed for heavy-duty diesel applications because elastomer (rubber) dampers couldn’t and still can’t stand up to the punishment of diesel engines. 90% of all over-the road heavy-duty diesel engines use a viscous type damper to protect their engines.

In the early 80’s, performance gas engine builders requested a viscous damper to be designed for their applications thus the product name Fluidampr became the first choice of performance engine builders and after 60 years Vibratech TVD / Fluidampr still remains the first choice of major OEM diesel engine and gas performance engine builders. Vibratech TVD/Fluidampr is the only company that manufactures dampers for both performance and industrial heavy duty applications.

Fluidampr high performance replacement dampers are rated to -40 Degrees Farenhieght. Fluidampr viscous dampers can be found protecting engines in the frigid cold of the Alaskan oil fields to the blistering heat of the race track.
Viscous engine dampers are the preferred choice for premium engine builders and are stock equipment in supercars and custom built diesel drag trucks!

Each time the air/fuel mixture TORSIONAL VIBRATION inside a cylinder is ignited, the combustion event creates a torque spike that is applied to the crankshaft through the pistons and rods.

This torque spike is so severe that it not only turns the crankshaft, it actually twists the crankshaft ahead of its normal rotation and then the crankshaft rebounds.

This twisting action is known as torsional vibration. When these torque spikes get into phase with the natural frequency of the crankshaft assembly in the engine, critical torsional harmonic vibrations occur that are destructive to the bearings and crankshaft.


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Supporting VIP
Jun 29, 2003
Luthersville Ga, Atlanta, Georgia
The only other option for us dsmers is a brand new stock damper. I purchased two of them and both were toast in a relative short time frame. so its out of the question in this article!!
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