I look at the equation:
mx"+Crr*x'+0.5*CdA*rho*x'²=F
Of {m; Crr; CdA}, know two and you can calculate the third. It would seem to me, you would be able to tease m, Crr, and CdA out of the test data if you include some driving that highlights each term: Do some quick acceleration at low speeds (where aero is barely in play) to find your mass. Some very low speed cruising will get your Crr. High-speed driving will confirm your CdA.
As I understand it, this instrumentation plus careful analysis of the data *would* eliminate the need for A-B-A testing by producing CdA values that you can compare to other test configurations. Of course, Crr depends on factors extrinsic to the car, including pavement type and temperature, so back to back A-B-A testing is best when you want to work on your Crr. Using the same road each time is second best.
I was hoping for super-accurate bar graphs of energy consumption on the fly. Well, that would be nice, but due to the variable nature of rolling resistance and air density, and the effects of winds, what you display in real-time while commuting wouldn't be as accurate as values you manually comb out of a mountain of data.
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