Thanks for posting that information Aerohead,
Take a look at your data below. The data is curve fit with a second order polynomial so we can fill in more points.
The data shows several interesting things:
As expected, the aero portion of the drag is not linear, but rises sharply since it is a cube function (velocity ^3).
The road drag is linear and directly related to the velocity!! This means that my initial hunch about rolling friction of moving components in the drive train was correct. Apparently how this relates to my coast down testing was misinterpreted and needs to be looked at further.
I did notice that the dV/T or deceleration while coasting was essentially a constant when it came to rolling friction. But did not tie this in with velocity at the time.
With this in mind, I will reword the apology about the Instructables posting regarding Crr in an earlier post.
Notice also the total drag at 55 mph. See that the aero portion consumes about 70% of the total drag. This very close to the data generated for the Insight, and essentially collaborates my coast down numbers. Apparently that old GPS unit doesn't do too bad of a job for this application.
This is also good news for anyone making aero mods to their vehicles, as it shows that the vast majority of drag is due to the air portion of the overall drag.
Yes, using low rolling resistance tires and such will help, but the low hanging fruit will continue to be anything related to smoothing the airflow over the body.
Thanks again Phil !!
Jim.