Quote:
Originally Posted by Thenorm
Why does the sedan get a better Cd?
if we look at a contemporary model, say the 2014 mazda 3.
Cd: 0.275 for hatch, 0.255 for sedan.
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The reason is because the template is an optimum and or maximum air adhesion concept. Whereas wind tunnels and CFD models will illustrate (
some) air flow over truncated or scaled down shapes and slopes.
Just because it doesn't match the template it don't mean it's a complete fail.
I would argue that the hatchback may perform better in real life with such things as cross winds over it's sedan counterpart. The air should be flowing over the hatchback with a little more stickiness than over the sedan (my current theory).
My other theory is the template works scaled down, but in a percent of efficiency scaled down. This particular example would put a big crack in this theory, and seem to indicate that scaling down the template has no adverse affects and in fact could be an improvement. Hard to draw wide conclusion off just one example, must use many examples to see a pattern.
Aerodynamics Photos by kach22i | Photobucket
EDIT:
2013 not 2014 model below
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