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Validation Testing
“Computer modeling and rapid prototyping is fantastic,” comments Neyman. “The true test however is how well it functions. In motorsports it has to outperform and outlast the stock tuned elastomer crankshaft damper.” To validate the new Fluidampr performance damper the team partnered with the well-recognized speed shop, RT Tuning in Montgomeryville, PA.
“We want to get as close to a common real world set up as possible,” continued Neyman. “We know high power builds benefit extraordinarily well from a Fluidampr performance damper because you’re inducing much greater torsional vibration amplitudes and heat for what the stock tuned elastomer damper is designed for. For this validation test we went the other direction.” The car chosen was a 2013 Scion FR-S equipped with only a high flow air kit and exhaust, plus a mild tune. Initial peak torque and horsepower measured 141lb-ft and 149rwhp respectively on the Mustang Dynamometer chassis dyno. Torsional vibration control, along with horsepower and torque gains realized with the Fluidampr performance damper found here will only increase as future modifications are made.
The team developed a comparative test that would analyze crankshaft torsional vibration levels and its effect on performance between the Fluidampr performance damper (5.8lbs/3.8lbs rotating weight), the stock tuned elastomer style crankshaft damper (4.87lbs) and an un-damped lightweight pulley (1.195lbs). To conduct the testing, the OEM tuned elastomer damper was drilled and tapped with 4 holes to mount an aluminum trigger wheel. An optical sensor was installed to register off the timing strip. Steady state data was taken at idle to determine if the laser sensor was adjusted properly in order to provide clean data. This setup was also used on the Fluidampr performance damper to eliminate a possible variance due to dissimilar fixtures. For torsional vibration measurements, data sets were taken using speed sweeps from 2500rpm – 7500rpm over a time of 30 seconds in order to capture any resonance points in the operating range of the engine. Each speed sweep was conducted twice, back-to-back to verify consistency.
The laser sensor generates digital signals that are counted thousands of times per second and then run through a fast fourier transform (FFT) to calculate speed fluctuations of the crankshaft hub, across the engine frequency spectrum. The result plots the amplitude of each vibration order across the rpm range and determines system resonance frequencies. Figures 1, 2 and 3 show the overall torsional vibration map for each test.
FA20 engine torsional vibration map with the OEM tuned elastomer crankshaft damper. The first crankshaft resonance appeared at 88Hz and was almost below the testing rpm range. A second crankshaft resonance was also seen near 260 Hz.
FA20 engine torsional vibration map with Fluidampr performance damper. The Fluidampr performance damper effectively reduced all vibration amplitudes to less than 0.25 degrees peak across the testing range. Amplitudes also show a general reduction trend while approaching the upper limit of the rpm range.
FA20 engine torsional vibration map with an un-damped lightweight pulley. The lightweight pulley shifted a third crankshaft resonance into the operating range at 600Hz. The 600Hz resonance excited 5.5th and 6th order vibrations. High frequency amplitudes carry much more stress than equivalent low frequency amplitudes because they occur more times per revolution. In this case, even though the amplitudes were similar, without the proper crank pulley weight to keep the resonance point out of the rpm range, the frequency stress level felt by critical internal engine components rose three times. Crankshaft driven timing components and oil pump drives can be more susceptible to these high frequency vibrations.After reviewing the vibration overview waterfall plots some individual orders were examined to show the differences in detail. An order is how many times a vibration event occurs during one revolution.
