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Old 12-06-2009, 08:45 PM   #256 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.07 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)
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I did A-B testing only on the undertray (because it was difficult to re-install, as you said).

It showed about a 2% improvement.

The numbers I have from the undertray + the boat tail suggest the combination of the two is greater than the sum of their individual effects taken separately.

Meaning: if I were to leave the boat tail on, and test just the undertray, we'd see greater than a 2% improvement from it (because the best maximum performance of the boat tail depends on the smooth flow provided by the undertray).
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