Quote:
Originally Posted by CigaR007
Stumbled upon this video of the 2012 Subaru Impreza. At the 30 seconds mark, the guy talks about the roof rack and its design. The added "tab" at the end of the roofrails added 1 MPG to the highway fuel economy as per their aerodynamic testing. Apparently it smooths the airflow. I find that aerodynamic tweak amazing given its small size and its correlating impact on fuel economy.
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The tail end of the rack ends just where attached longitudinal vortices might form off the roof.
The tail of the rack sections are just like a Mitsubishi Lancer roofline (very steep!) and the 'bump' should act just like a vortex generator to help the flow follow that steep incline.
Also,EPA Mobile Sources certification testing includes faster speeds ( up to 70 or 75 mph) than in past decades,so drag is more important than ever before and 'small' differences would matter.