Quote:
Originally Posted by gascort
I've been looking around on the EPA and fueleconomy.gov websites the past day or so and as far as I can tell, the EPA tests completely disregard the fact that different vechicles have different aerodynamic profiles (different frontal area and different Cd).
Someone please correct me if I'm wrong, but they just run their lab test with the exhaust analysis with the vehicle on the dyno at a higher speed for highway, then subtract a flat percentage from all vehicles' fuel economy to represent aero drag. I think 22% is the number I saw, but I can't locate a link anymore.
Thoughts?
Mine is that if this is true, where's the motivation for automakers to make their cars more efficient with regard to aerodynamics / the highway? Most people purchase based on the sticker rather than looking at aero themselves.
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I called the EPA a couple years ago.I talked with Dave Good,EPA Mobile Sources,Ann Arbor,Michigan,where they do all the new car certification testing.Dave told me that the carmakers provide CdA and R-R data for each make to the EPA.This data is "plugged-in" to the resistive loading on the twin-roller dynos used in testing each inertia weight class,so the dyno can simulate the dynamic loading of the vehicle as it drives the cycle map.The EPA is "aware" of aero-related stuff,however they don't set policy,they only enforce what's on the books.Those laws are the play thing of auto makers,politicians,lobbyists,The UAW,The U.S.Chamber of Commerce,good ol' boys,etc.,far beyond any authority of EPA.