Quote:
Originally Posted by 3-Wheeler
And it's nice to explain in more detail why this is....
I have done numerous coast down tests with the Insight and Crr and Cd are about equal at 35 mph or so.
This means if you change the aero of your car and make it 100% more slippery to the wind, it will gain you 50% more gas savings, because while the aero part improved 100%, the Crr part stayed the same. Then when you add the new Cd and the old Crr, you have a 50% net gain.
Jim.
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Aero drag completely eclipses rolling resistance at higher speeds though. The reason is because the lower the load on your engine (generally, in the bottom 50-80% of torque output depending on forced induction or cams and stuff), the less efficiently it runs.