Airflow.

The wind tunnel puts one trade-off in your hands: more downforce can come with more drag. Move the wing-angle control and compare the two force readings.

Try a controlled experiment

Hold speed at 250 km/h. Increase the wing angle a few degrees at a time and watch the lift-to-drag ratio. Then keep the angle fixed and change speed.

Look for the turning point

This model deliberately includes a simplified stall region above 20 degrees. More angle does not always produce a better result.

Model notes

The animated streamlines are illustrative. The force equations are simplified and do not represent computational fluid dynamics or a real car setup.