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Something that AeroHead alluded to in his post, is that wind tunnel testing numbers do not relate exactly to real world numbers.
Let me give you an example...
I have been performing coast down testing for the last two months. One thing that gave way to the research was that:
At 55mph, 65% of the drag is due to air resistance
35% of the drag is due to Crr
The faster you go, the more the ratio shifts to air drag.
If one sees a 20% air drag benefit in the wind tunnel, then the only way that this will show a 20% benefit on a test track is to be going about 200 mph were the air drag portion swaps out the Crr portion.
As you slow down from this speed then Crr starts to become are larger factor again, and reduces the affect of the aero gains from the mods.
Jim
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