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Old 10-03-2013, 02:17 PM   #11 (permalink)
Otto
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Quote:
Originally Posted by MADMAC View Post
Got a question. I have a 2012 Chevy sonic turbo sedan. I was wondering if a air dam is better to have than full under body panels? I'm thinking underbody based off of knowledge I have gathered from this site and others. Could some confirm this for me?

Belly pan is most critical under the nose, then under the trunk, with the mid-section least critical, per Hucho. It's reportedly a fair amount of work.

Reportedly, you get more bang for the buck with an air dam under the front bumper. It's comparatively cheap and easy to install, i.e., a few bucks at Ace Hardware or Home Depot for a roll of garden edging, which would do two or three cars. In absolute terms, the air dam may not be quite as good as a full belly pan, but the difference in aerodynamic efficiency is marginal vs. cost and work involved. And, the air dam deflects air smoothly past the front wheels, which are effectively buckets of drag, given the oblique angle of airflow hitting them. (Previously on this website is a revealing wind tunnel picture from Hucho's book, where an Opel Calibra has the front wheels impacted by airflow at an angle of about 60 degrees:

http://www.google.com/imgres?hl=en&b...7&tx=132&ty=95

Anyhow, given such flow around the nose of an unfaired vehicle, the air dam seems a cheap and effective way to shunt a lot of draggy air past the wheels, and keep it from building up under the draggy underbody of the vehicle.

It might be even better to combine air dam and undertray, and/or fairings in front of and behind each wheel, per Prius et al.

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