EPA Road Load Coastdown Testing

[aerohead]

here's another article from the EPA which describes their coastdown testing,including data for the test vehicles sampled,coasting from 60-mph,down to 20-mph
Document Display | NSCEP | US EPA

[gumby79]

Nice read ...Duse any one know how to translate this information into total drag ?? Meaning CDa+crr=hp required @X speed.

[aerohead]

Originally Posted by gumby79

Nice read ...Duse any one know how to translate this information into total drag ?? Meaning CDa+crr=hp required @X speed.

With respect to streamlining and lower rolling resistance,these values are considered the total drag (actually the power absorption at 50-mph,under the test conditions and parameters of the coastdown test).
These values do not represent the powertrain losses (transmission and differential,although they do include U-joint losses if applicable) or accessory losses (reported at 2.2% of brake horsepower).
Under highway conditions,a non-GDI gasoline engine will be around 37.5% thermally efficient,greater for Diesels.
You might figure 94.6% mechanical efficiency for a standard powertrain.
If you know your cars CdA or mass and R-R power absorption coefficient,you can parse out aero and rolling resistance.
Here is a road load curve for one of the Tesla cars.You can see how the components of load vary with velocity

Here you can see how the load varied on my CRX for three different velocities