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Re: Yes, I had thought of that... Posted by JimBlake [Email] ![]() ![]() ![]() In Reply to: Yes, I had thought of that..., Mr. Science, Thu, 19 Sep 2002 16:41:24 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Torque would be measured on an engine dynamometer. Constant speed, so rotational acceleration is zero. Or slowly sweep the speed so acceleration is negligible. There is some kind of brake to hold the engine at a constant speed (wide-open-throttle), then the engine (or the brake) is mounted with load cells to measure force (torque). Power would be calculated from torque & rpm.
I believe that they have the accessory drives in place, maybe even OEM air filters & exhaust systems. That was part of the difference vs. "gross" HP numbers from the '60s.
I'm not sure about a chassis dynamometer. Does it run at constant speed? If so it has some kind of brake keeping your wheels from accelerating. Again, there isn't any angular acceleration. Maybe in this condition your wheels would spin... Somebody out there has probably gotten their car measured on a chassis dyno.
You could put a transmission in some kind of dynamometer, measure rpm & torque both at the input shaft & at the output shaft. Difference in power should be due to internal friction & Joule heating of the oil. (& windage losses, etc.) Again, constant speed. I don't know if they actually do this, or if they add up drag forces that are calculated separately.
Other drivetrain losses would be drag in the wheel bearings, brakes, tires, anywhere else you can imagine. I always thought those losses didn't include rotational acceleration.
posted by 131.184.14...
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