[olddog]

I took Anthony's advise and read on DYNOmite Dynamometers web site. In an artical I found this paragraph.

"Even if you select a low inertia brake remember that the engine's moving components still have there own inertia. If you take readings while the engine is accelerating or decelerating, inertial energy is being subtracted or added, respectively, to what your gauges indicate. Disappointingly, unscrupulous dynamometer operators use inertia to display impressive flash power readings by suddenly cranking on the brake load. Obviously such "inertial energy augmented" numbers have nothing to do with the true horsepower capabilities of the engine. After you run a dynamometer for awhile, you can spot such shenanigans in other's printed dyno data. This is another reason engine builders get their own dynamometers."

In summary, I think they are saying that yes I am right. However they do talk about doing what I called a static test at every 250 rpm, and they did mention when talking about flywheel type dynamometers and I quote "Fortunately, high end computerized data acquisition systems provide composition algorithms to back out the effects of absorber (and crank-train) inertia from acceleration data. On a high inertia dynamometer, compensation is required even for fairly low rate sweep testing." So maybe some dyno operators are correcting for this.

I have noticed that on TV some of these dyno runs are as short as 3 seconds while others are 8 seconds or longer. This can impact the numbers. I think when considering big block engines, these errors can get very missleading.

I have read on here many times about someone very confused at how they lost so much HP from the engine dyno to the chasses dyno. When you consider the large inertia of a 4+" stroke FE, large diameter flywheel and clutch, large wheels and tires, and heavy duty rear end and tranny, a 3 second chasses dyno run is going to measure much lower numbers. This is due to so much power going into accellerating all this enertia. Let's face it your car is not going to go from 40 mph to 120 mph in 3 seconds, at a 1:1 gear ratio.

Sorry about the head ache Power Surge.