I've just saw the latest press releases for Opel Vectra GTS mentioning also that they manage to design her with a Cx=0.28 which is great.
Does anyone know which will be those values for Mazda 6 Hatch/Sedan/Wagon?
Replying to Topic 'Mazda 6 Cx? aerodynamic coefficient (factor)'
There was a discussion on this a month ago I think. Anyway, I think the M6 is in the low 0.3-0.35 range.
That said, Cd is meaningless without knowing the reference area for the vehicle. For autombiles it's the frontal area, for aircraft it's the planform area (the area the aircraft covers as seen from above).
The equation for drag force is D=1/2*(density of air)*Cd*Area*velocity^2.
Common values to plug in would be: density=1.22 kg/meter^3, Area = 2.2meter^2, Cd = 0.33, velocity = 24.587 meters/sec.
This would mean that the aerodynamic drag is exerting a force of 267.72N on the body of the car at 88.56kph (55mph). If you want to know power lost to aerodynamics, multiply again by velocity and you loose 6564.7W (8.75hp) to aerodynamics. This all assumes that there is no wind and the aerodynamics of the car don't change with pitch or yaw.