Originally Posted by C_Plunkett
If you are using the speed of the car in your calculations, you will probably get more downforce than you are calculating. The downforce should be calculated based on the local velocity of the air in front of the wing. As the air accelerates over the car, the air velocity near the wing should be higher than the speed of the car.
The only way the car is going to be able to accelerate air is by changing the direction of the velocity vector...it's not going to be able to increase its magnitude.