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Old 01-03-2008, 09:58 PM   #31 (permalink)
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Harold - '94 Honda Civic CX
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Clarifying some terms. Cd, A, CdA and such.

Originally Posted by AndrewJ View Post
Sure, this will increase the CdA of my car, but it will also take care of two (or three) nasty areas of aerodynamic drag, thereby decreasing my Cd.
What I *should* have said was:
"Sure, this will increase the frontal area (A) of my car, but it will also take care of two (or three) nasty areas of aerodynamic drag (Cd), thereby decreasing my coefficient of drag (CdA).

Basically the coefficent of drag is CdA which is comprised of the Cd multiplied by A. See wikipedia for further detail.

So the big idea behind airdams is that they will improve your aerodynamics IF you can improve your Cd without adding to much A. If you tip the balance the other direction, by adding a lot of frontal area without streamlining the shape much then you will actually be hurting your aerodynamics.

This is why an airdam like mine would actually be a bad idea for basjoos's CX. He has a full belly pan, so adding an airdam wouldn't improve his Cd any, and it would add a bit to his A, thereby raising his CdA.

As for the original post, "You have to hear what I'm thinking."

"I got 350 heads on a 305 engine. I get 10 miles to the gallon. I ain't got no good intentions." - The Drive By Truckers.

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