[Adger Smith]

According to: Bob Szabo article

One method for ball-parking the size of a hood scoop is to look at the column of air that the hood scoop takes in from the speed of the vehicle. That amount is a function of the engine air demand, the velocity of the vehicle, and the inlet scoop area. The equation for that relationship is:

vehicle velocity = engine air demand / scoop area


Try this:
vehicle MPH = (engine cfm / scoop area in square inches) x (60 x 1/5280) / (1/144)

where:

60 = minutes (m) per hour (H)
1/5280 = miles (M) per foot (f)
1/144 = square feet per square inch
(60 x 1/5280) / (1/144) = 1.64
vehicle MPH = engine CFM x 1.64 / scoop area (square inches)