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Old 11-30-2008, 02:16 PM   #141 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,530

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 54.46 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car Mirage - '14 Mitsubishi Mirage ES (base)
90 day: 62.14 mpg (US)
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Quote:
Originally Posted by Christ View Post
I'm pretty sure you're better off blocking the lowest grilles over the higher ones, especially if the lower ones are perpendicular to the ground... they would present a higher open area for air to flow into.
All else being equal (size of the openings), some people say it's better to block upper grille openings if they're likely above the stagnation point (where airflow "splits" between flowing up & over the car vs. underneath).

The thought is that it's better to permit that upward flowing air to continue over the relatively smooth body of the car than to redirect it through the aerodynamically dirty engine compartment & exit underneath the car.

Might as well use air that was already going to end up there (below the stagnation point - probably lower openings) to take care of cooling.

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Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
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Ecodriving test: Manual vs. automatic transmission MPG showdown



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