Over the past few years we have been asked by many users and dealers to explain the ATI advertising, which says Fluidampr® is inferior. We thought it might be useful to provide you with ALL the facts and let you decide.

The ATI chart leads the reader to believe that bad vibrations occur on the small block Chevy engine at over 7000 rpm. This is not always accurate. Depending on the mass elastics of a small block Chevy engine, generally the worst orders of vibration occur in the 4000 to 7000 rpm range with or without any damper installed.

We thought we would go back to the field and reapply our expertise and do more testing. After all, we developed the Fluidampr by actual torsional tests at 42 locations around the country with different engine combinations from June 1985 to January 1990. Some of these tests were conducted at the request of the engine factories at their designated facilities.

The actual torsional test results are from a slightly detuned 600 hp Winston Cup Chevy 350 engine which had many parts supplied by Hendrick Motorsport. We wanted to compare torsional vibrations using similar size dampers. For example, compare the 6 1/4" Fluidampr with the 6 3/8" ATI damper. The Fluidampr outperformed the ATI damper on all orders of vibration.

If you have ever bought or sold a damper, you will find the information in this bulletin extremely valuable when evaluating or confirming your choices. Vibration control is Vibratech's only business, and we are experts in the field.

A typical test run consisted of installing a particular damper and warming up the engine to meet requisite oil temperature and pressure followed by a 300 RPM per second constant rate acceleration ramp, under 100% engine load, over an RPM range of 4000 to 8400.

Each run was performed 3 times for verification.

Measuring Equipment:
The Vibratech torsional vibration analysis system consisted of an inductive 3030AN magnetic pickup mounted on a special bracket plate bolted to the engine block. A 60-toothed gear and adapter plate were mounted between the damper and the pulley. The probe and gear were mounted to permit the detection of the gear teeth passing under the center of the magnetic pole piece of the pickup.

The pickup signal was fed to a frequency modulation discriminator to separate the RPM pulse train signal from the torsional vibration signal. The output signals of the FM discriminator were sent to the Signal Processing Systems Model SPS-390 FFT (Fast Fourier Transform) Analyzer. The Analyzer was set up to acquire the data at 25 RPM increments from 4000 to 8000 RPM.

All torsional vibration data plots were generated using the SPS-390 FFT Analyzer.

FFT ANALYZER
These are actual charts from the FFT Analyzer that depict the amplitude of torsional vibration in degrees peak. When comparing the performance of the Fluidampr versus the ATI, you must compare amplitudes of the same order of vibration. It is most meaningful to compare the 4th order vibration with Fluidampr with the 4th order vibration with the ATI damper.

The charts show a dyno run with Fluidampr part number 620101installed and a dyno run with the ATI damper part number 917260 installed.

As you can see, Fluidampr is almost 50% more effective at reducing the 4th order vibration than the ATI damper of comparable size. In fact, Fluidampr was more effective in reducing torsional amplitudes at all three critical orders of vibration (4th, 3rd, and 2 1/2) in the operating range of the test engine (4800 to 8000 rpm).

COMPARISION CHARTS - The Fluidampr versus the ATI
4th Order Vibration Comparison Charts
3rd Order Vibration Comparison Charts
2 1/2 Order Vibration Comparison Charts

COMPARING APPLES TO APPLES
The greater the inertia mass of any given damper, the greater its potential is for countering the torsional twisting or harmonic vibrations of the crankshaft.

A typical damper with an 8" diameter will almost always be more effective at reducing torsional twisting than a 6" damper, simply because the 8" damper has a greater inertia mass.

For a meaningful comparison between different types of dampers, it's important to compare similar size dampers with similar inertia masses.

Comparing the 6 1/4" Fluidampr to the 6 3/8" ATI damper allows an objective look at two different dampers that have similar inertia masses. Meaningful and fair conclusions can be made using this type of comparison.