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Old 03-16-2008, 06:33 PM   #19 (permalink)
mazdaspeed3 - 27 mpg
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Join Date: Feb 2008
Location: Georgia
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MS3 - '07 Mazda Mazdaspeed3 mazdaspeed
90 day: 27.85 mpg (US)

speedy3 - '07 Mazda Mazda 3 mazdaspeed3
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Originally Posted by GenKreton View Post
Let's stick to the metric system since it seems to use it, mostly?

1/2C_d is unit-less
A in m^2
rho is density, so kg/m^3
v is m/s, so v^3 is m^3/s^3

so we have kg*m^2/s^3
1 N is kg *m / s^2 -> Nm/s
1 J is Nm -> J/s
1 W is J/s, so we are left with pure watts
1 hp is 0.7457 kW

Essentially we take the result of the first part and *10^-3 / 0.7457, or multiply by 0.01341.

I'm not sure what the second part of the equation is, the addition, but in order to add numbers, the units MUST match. Pmotive=1/2*Cd*A*rho*v^3 is normal for a flat surface. What is Crr1?
Apologies for the long time to respond. Crr1 is the rolling resistance of the tires. Thank you for the detailed formula breakdown. I also looked at the updated spreadsheet boxchain provided. All this information provides a much clearer picture.

Thanks again!
power, performance, and fuel economy - can't they all just get along
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