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- Jul 21, 2020
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- Mach-E wannabuy
Vehicle weight (inertia) and all force losses (bearing drag, brake drag, driveline loss, aero drag, etc.) are measured on an actual vehicle and transfered to the dynamometer system. There are even corrections for the non-spinning wheels, i.e. all 4 wheels spin in actual driving conditions, but on a RWD dyno test only the rear wheels are spinning. Aero measurements are taken both into the wind and with the wind, and averaged.When I found out that EPA tests are done on a dynometer, I was (and still am) puzzled. Seems like all that could measure is the fuel it takes to turn the wheels with the weght of the vehicle pushing down. With zero regard for aerodynamics. Doesn't that just treat a Ferrari and a Hummer the same?? Even though there's clearly a dramatic difference in aerodynamics?
The more I find out about EPA ratings, the more worthless they appear. I'm beginning to think our anxiousness to get the EPA range for the Mach-e is misplaced.
EDITED: I just remembered that (IIRC) vehicle manufactures also have to report results of an aerodynamic test too, that's used to set the resistance on the dyno rollers to mimic wind resistance.
Still though, seems ripe for inaccuracies.
Bottom line, as far as the vehicle is concerned, when it is on a chassis dynamometer it thinks and feels like it is being driven on an actual flat road. All the forces are simulated within ~ 1%. Almost all modern dynamometers can also simulate other things, like hills, if so desired.