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Old 05-19-2008, 01:51 PM   #5 (permalink)
amateur mech. engineer
Join Date: May 2008
Location: New York City
Posts: 112

Sporty Accord - '88 Honda Accord LX-i
90 day: 23.25 mpg (US)

Dad's Camry - '01 Toyota Camry CE
90 day: 22.81 mpg (US)

Artie's Camry - '98 Toyota Camry
90 day: 37.3 mpg (US)
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Thanked 17 Times in 4 Posts
You wanted to know how many MPG you get when you floor the accelerator. Try this formula I made. It is for engines running on gasoline.

MPG=74000 x VE/(ER x R x L)

VE: Volumetric efficiency, normally varies from 0.3 to 1, depending on RPM and throttle position. It could exceed 1 if the engine has a turbocharger or supercharger.
ER: Equivalence ratio, equivalent to 14.7/(A/F ratio). Should be close to 1.
R: engine revolutions per mile or revolutions per minute at 60 MPH in this gear
L: Liters of engine displacement

It should be close. Adding ethanol to gasoline would reduce the result because more of it is needed to mix with a certain amount of air.

For the MPG while coasting, try this one.


GPH=L/6 when idling at about 700 RPM

MPG=6 x MPH/L at 700 RPM idle


MPG=4200 x MPH/(L x RPM) to calculate at any idle speed

This is only an approxamation. If you have an unusual engine configuration (like a racing camshaft for example) this may not be accurate.

If you have a 2.0 L engine you should expect your coasting MPG to be about three times your speed in MPH.
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