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Old 03-25-2010, 04:21 PM   #7 (permalink)
Piwoslaw
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Join Date: Oct 2008
Location: Warsaw, Poland
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Svietlana II - '13 Peugeot 308SW e-HDI 6sp
90 day: 58.1 mpg (US)
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Quote:
Originally Posted by NeilBlanchard View Post
I thought that the new Bug had a Cd of 0.45? The curve in the rear is way too steep. I doubt it has attached flow as far down the back as the picture shows...
In this case, the sooner the airflow detaches the better.

EDIT: The following in red isn't exactly true, see post #10 for details.

I saw a chart somewhere (can't find it right now, grrrr). Pretty much it showed that as the rear angle gets steeper (starting from 0°=flat) lift decreases until 12°-14°, then it increases again until 26°-28° when airflow detaches and lift goes down again.

So, if you can find the spot where the tangent is 12° and make a small "step", then the airflow will detach there, reducing lift at the best point. Many new cars already have this small "step" around the top of the rear window.

Quote:
Originally Posted by aerohead View Post
While it has good penetration,once it gets to the frontal area cross-section,the curves rapidly approach those that cannot support attached flow,creating a significantly large wake,'poison of mpg'.
If you extend this "step" into a Kammback, you keep the angle right while reducing wake area, and keeping Aerohead happy at the same time
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Piwoslaw's Peugeot 307sw modding thread


Last edited by Piwoslaw; 03-26-2010 at 11:36 AM..
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