[JulianEdgar]

I have been doing some maths and I realise I made an important mistake earlier.

Looking closely at the Chrysler paper, the equation they use for their K value is in fact:

K = drag force (lb) / [frontal area (square feet) * (mph)^2]

That makes much more sense, as it's the standard drag equation with air density missing (but obviously assumed for a standard atmosphere).

I have now been trying to convert that to drag force (newtons), frontal area (square metres) and speed (metres/second) so that we can convert to our normal Cd values.

Using an air density of 1.2 kg/m^3, and taking into account the 0.5 multiplier on the bottom of the Cd equation, I get a conversion factor of 398.746 (ie multiple Chrysler's K value by that number to get Cd).

But math is not my strong point so it would be great if someone can check.

(Addition: I've been checking that against probable Cd values from the cars shown in the paper, and it seems to largely make sense. I've asked a few of the experts I know to check my calculation, so we'll see how wrong I am!)