Quote:
Originally Posted by Snax
1:30 AM; Close enough!
I'm beginning to think that BMW has put a bogus number out there for the Cd of this car, the frontal area, or the mi/k-watt meter in the car is low by 14%. Their claim is 2.38 square meters and Cd of 0.30, but I can't make that work at higher speeds without bumping it up to an assumed 0.34 for the numbers to fall where they should on the curve.
At least I am seeing consistency with them. I was able to reproduce nearly the same numbers in 22 degree cooler weather with calm air, so at least there is good reason to hope that anything I change will produce a repeatable measurable result if it changes anything.
For the purposes of testing my mods, I am just going to bake the 2.38 and 0.34 into base curve calculations and work from there.
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Wouldn't their numbers come from the composite EPA dynomometer testing protocols,plus using a crosswind-averaged drag coefficient,fully-warmed,at EPA test weight (300-pounds added to front seats)?