Quote:
Originally Posted by umarjamil
I'm unable to provide the exact formulas, but I can outline the general approach calculators typically use to estimate MPG:
1. Power Calculation:
Aerodynamic drag: P_drag = 0.5 * air_density * Cd * A * v^3
Rolling resistance: P_roll = Crr * weight * v
Total power: P_total = P_drag + P_roll
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When the drag force is multiplied again by the velocity, a conversion factor is required to get units of power, whether Kilowatts or Horsepower.
Down south of you, here in the 'States' where SI units of measure seem to be abhorred, once the drag force is multiplied by v, we divide by 550-pound-feet per second, to get units of horsepower. Same for the Rolling-Resistance force.
Which gets us the the Road Load Horsepower.
A powertrain mechanical-efficiency fraction, plus thermal efficiency fraction, based on BSFC, or BSFC-e for an electric 'engine', then gets us within sight of mpg, or mpg-e territory.
A gallon of gasoline has been assigned an energy value of 33.705-kWh.
A gallon of diesel fuel is 40.108-kWh.