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Old 01-02-2013, 10:58 PM   #12 (permalink)
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Lowering a vehicle will only decrease the frontal area a tiny bit - only the area of the wheels gets reduce by the reduction in height. If you drop the car an inch, then the width of two tires; say 8" X 1" X 2 = 16 sq in. The Cd is not likely to change one iota; or it might even increase the Cd because it compresses the air under the car somewhat.

If the vehicle frontal area is 25 sq ft and it has a Cd of 0.35 then the CdA is 8.75 sq ft. Take away the 16 sq in and the CdA is 8.71 sq ft - a net improvement of 5.76 sq in.

If you install video mirrors in place of both side mirrors, you reduce the frontal area by about 80 sq in *and* you reduce the Cd by say 0.03 or so. The resulting CdA is 8.482 sq ft - net improvement of 38.56 sq in which is 6.6X better than the lowering.

With a good grill block, smooth wheel covers, rear wheel skirts, a smooth bellypan, a partial Kamm back, and the video mirror swap, you could drop the Cd to 0.31 or so? That would be a CdA of 7.58 sq ft - a net improvement of 168.8 sq in which is 29.3X better.
Sincerely, Neil
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