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Old 09-23-2010, 10:42 PM   #7 (permalink)
RobertSmalls
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Quote:
Originally Posted by Weather Spotter View Post
for a rough idea, the % longer of coast down is ~= to $ better Cd.

Example: you coast 5% longer now = 5% better Cd or a change from .32 to .304 Cd
Ehh.... I don't think that's accurate. Suppose I coast 50% farther. Does that mean I reduced my drag from 0.25 to 0.125? And if I coast 100% farther?

If you drive really fast so that aerodynamic drag dominates (see the calculator to determine exactly how fast), and hit the clutch, the rate at which you slow down (mph per second) should be fairly linear with CdA. But the mph disappear too quickly to accurately measure when you hit the clutch at 74mph.
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