Beside smoke lances do you use pressure sensitive paint or other tools to validate CFD?
Alex: We are using specific pressure probes to validate CFD. Pressure sensitive paint is a great mess in a frequently used wind tunnel ;)
The clay model is a genius idea!! Does it vary with respect to the real model when you build it?
Alex: Yes, of course. There are minor differences with regards to missing gaps between body parts and the not completely accurate engine compartment within the clay model. We know the influence, therefore it is easy to interpret the results.
Why do you need clay models? Can't you do all the aerodynamic evaluations with the help of CFD?
Jonas und Alex: The target is to combine both tools in an efficient manner. Modifications in the wind tunnel are way quicker and more exact. Furthermore, you can touch and see the look of it immediately. CFD helps to assess the flow field in detail.
In the clay model is the tire also made out of clay?
Alex: No, axles and wheels are real parts.
What are the downforce numbers for different driving speeds (front and rear)?
Markus: M4 Coupé
@140kph: front axle 150N lift, rear axle 150N downforce
@200kph: front axle 300N lift, rear axle 300N downforce
@290kph: front axle 620N lift, rear axle 620N downforce
How does improved downforce affect the design of the suspension?
Markus: For a road going vehicle, we aim for low lift at the front axle and downforce at the rear axle. This works perfectly with our suspension so there is no need for further suspension adjustments.
Are the aerodynamics split evenly between the front and rear axles?
Markus: CZ1 = 0,07; CZ2 = -0,07
Was the M3 rear wheel arch designed to keep the standard rear door unchanged?
Markus: Yes.
Do the wing mirrors play an important role in the aerodynamics?
Markus: No.
Do turning vanes increase drag?
Alex: Yes, they do. But the aerodynamic efficiency is increased because of the significantly higher downforce though.
What is the break response at high speed?
Markus: The new M3/M4 is an easily controllable and stable car even at high speeds.
Did the larder size of the updated kidney grille pose a challenge to the aero design?
Jonas: The aim of our work is to combine aerodynamic requirements with regards to cooling airflow and design requirement. The bigger the surface, the better for cooling and the worse for drag. This had to be optimized.
Does the radar sensor in the kidney have no effect on cooling?
Jonas: Well, obviously the radar sensor in front of the radiators will have an influence on the air flow. However, you only notice the marginal effect under extreme conditions.
