Formulas
The horsepower needed to overcome aerodynamic drag at a given speed is: HP = k*A*Cd*v^3
Where HP is horsepower, k is the density of air, A the frontal (cross-sectional) area, Cd the coefficient of drag, and v the velocity. The density of air depends on conditions but is nominally .08 lb/ft^3.
Aerodynamic drag is calculated as: F = 1/2 CDAV^2
Where: F - Aerodynamic drag force, C - Coefficient of drag, D - Density of air (nominally about 0.08 pounds per cubic foot.. yes I know that's not a technically accurate mass but it saves converting to and then back from metric), A - Frontal area, V - Velocity of object
To estimate engine HP from 1/4 mile run: HP = ((trapspeed/234)^3) * weight
Tire Diameter in inches = ( ( Tire Width * Aspect Ratio ) / 25.4 ) * 2 + Wheel Diameter
Example: 245/40-17 would be ( ( 245 * .40 ) / 25.4 ) * 2 ) + 17 = 24.71653543307
MPH = ( RPM * Tire Diameter ) / ( ( gear ratio * final drive ) * 336 )
Example: ( 8000 * 24.71653543307 ) / ( ( .771 * 4.062 ) * 336 ) = 187.9074535627 MPH
Of course the tires expand at high speeds so this isn't totally accurate.
VERY Rough Rules Of Thumb
Each 10 degree F drop in temperature = 1 % gain in HP
Each 10 lbs. removed from the vehicle = 1 HP for acceleration (top speed is not noticably affected)
Each 10 HP added = 0.1 second in the 1/4 mile
Conversions
Volume |
|
|---|---|
| 1 Imperial Gallon = | 4.5461 liters (l) |
| 1 liter (l) = | 0.2200 Imperial Gallons |
| 1 US Gallon = | 3.7854 liters (l) |
| 1 liter (l) = | 0.2642 US gallons |
| 1 Imperial Gallon = | 1.2009 US Gallons |
| 1 US Gallon = | 0.8327 Imperial Gallons |
| 1 liter = | 61 Cubic Inches (ci) [approximate] |
Distance |
|
| 1 mile (mi) = | 1.6093 kilometers (km) |
| 1 kilometer (km) = | 0.6214 miles (mi) |
Fuel Consumption |
|
| 1 Mile/Imp. Gallon = | 0.354 kilometers/liter (km/l) |
| 1 kilometer/liter (km/l) = | 2.825 miles/Imp. Gallon |
| 1 mile/US gallon (mpg) = | 0.425 kilometers/liter (km/l) |
| 1 kilometer/liter (km/l) = | 2.352 miles/US gallon (mpg) |
Mass |
|
| 1 kilogram (kg) = | 2.2046 pounds (lbs) |
| 1 pound (lb) = | 0.4536 kilograms (kg) |
| 1 gram (g) = | 0.0353 ounces (oz) |
| 1 ounce (oz) = | 28.35 grams (g) |
Pressure |
|
| 1 pound/square inch (PSI) = | 0.0689476 bars |
| 1 bar = | 14.5037681 pounds/square inch (PSI) |
Power |
|
| 1 PS = | 0.98632 HP |
| 1 HP = | 1.01387 PS |
| 1 kgm = | 7.23 lb. ft. |
| 1 lb. ft. = | 0.14 kgm |