[Video] The new M4 DTM in the BMW Group Aero Lab Wind Tunnel

Aerodynamics experts at the BMW Group Aero Lab used the 50 times 15 formula to develop the new BMW M4 DTM for the 2017 season. The vehicle spends 50 days in the wind tunnel with a maximum 15 hours per day to keep the development costs manageable. Because of the limited time, airflow specialists waste no second in scrutinising their own processes and methods, which ultimately led to enormous success.

In modern motorsport, maximum efficiency is not only a key factor at race weekends, but also in the development process. Every minute counts. The planning of a wind tunnel session was completely adapted to the new regime for the BMW M4 DTM, and is similar to a test day at a racetrack. The engineers first define the initial configuration, then they set about creating a precise schedule for the subsequent tests. The focus was set primarily on the structure of the model car being tested in the wind tunnel. Compared with the development of the 2014 BMW M4 DTM, it is assembled in a more modular way to allow faster modification of the aerodynamic details. For example: the tests use a bonnet comprised of eight individual components that can be exchanged separately.

Depending on the complexity of the parts to be switched, the aerodynamicists at BMW were able to test, on average, three car configurations per hour. The model was prepared, mounted on a hexapod and precisely positioned with maximum tolerances of a hundredth of a millimetre to allow the simulation of different driving situations, such as fast corners, tight hairpins and straights. While a 60 percent scale model of the BMW M4 DTM was still under construction, work was already underway analysing the data gathered. Ultimately, no further test time could be wasted on a configuration that had not previously achieved the desired result.

All these steps followed each other faster than before, but with no less accuracy. An old motor racing adage still rings true: every tenth of a millimetre counts in the wind tunnel. These can then be converted into tenths of a second out on the racetrack.