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Old 01-03-2013, 01:10 AM   #4 (permalink)
13B_88FC
EcoModding Lurker
 
Join Date: Jan 2013
Location: Oregon, US
Posts: 43

ZoomFreakingZoom - '88 Mazda RX7 Convertible
90 day: 19.02 mpg (US)

Geo - '96 Geo Prizm Base
90 day: 32.42 mpg (US)
Thanks: 2
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Quote:
Originally Posted by wmjinman View Post
I always loved the aerodynamic look of those RX-7s. In fact, I have a friend who once had one. My understanding is that while the rotary engines have an amazingly high level of condensed power for their physical size, fuel economy was never their strong suite. Not sure why - something inherent with the design, I think.
If you think of the combustion chamber of a rotary engine compared to a piston engine, the rotary engine has a higher ratio or surface area to volume. A cylinder is a nice regular space with minimal heat loss through the inside surface area compared to it's volume while the rotary engine's combustion chamber is a more irregular space that loses more through it's inside surface relative to it's volume.
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1988 rx7 convertible. Streetported, racing beat header and presilencer replacing all 3 catalytic converters. Atkins 6 port sleeves. K&N cone filter intake. 22mpg average, 27mpg max. Spreadsheet (updated regularly):
https://dl.dropbox.com/u/5310442/198...%20mileage.xls
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wmjinman (02-18-2013)