Audi e-tron prototype achieves a drag coefficient of 0.28

How difficult the topic of aerodynamics can be for SUVs, Audi recently experienced with the e-tron: The electric vehicle achieves a drag coefficient of 0.28 – but Audi already achieved a cW value of 0.30 with the 100 C3 back in 1982. In 1986, they managed 0.29 with the Audi 80 B3. Currently leading is the still recent Mercedes CLA with 0.22. Audi had to painfully experience again in over 1000 (!) wind tunnel hours that such values are not given for free, because the e-tron's 0.28 required several tricks. Audi focused on long distances, as one hundredth of the cw value stands for about five kilometers of range in everyday driving.

On long distances, aerodynamic drag forms the decisive driving resistance – much more important than rolling resistance and inertia, which is why Audi engineers developed various aerodynamic measures in all body areas. Some of these technical solutions are visible at first glance, while others serve their purpose hidden away. These innovations enable the Audi e-tron prototype to save nearly 0.07 on the cw value compared to a comparable conventionally powered vehicle. This results in a range advantage of around 35 kilometers per battery charge in the WLTP cycle for a typical usage profile.

In the production version of the Audi e-tron prototype, "virtual exterior mirrors" make their world premiere, which can be ordered as an option. Compared to the standard mirrors, they are significantly narrower: They reduce the vehicle width by 15 centimeters and not only lower aerodynamic drag but also reduce wind noise levels noticeably. Their flat mounts each integrate a small camera. The images they capture appear on OLED displays between the instrument panel and the door. The virtual exterior mirrors can be adjusted for different driving situations, thereby increasing safety. The MMI system offers three views – for highways, turning, and parking.

Standard is the "Adaptive air suspension," the air suspension with controlled damping: From 120 km/h, it lowers the body by up to 26 millimeters below the normal level and thereby reduces aerodynamic drag. The underbody of the purely electrically driven SUV is fully covered, with the front and rear areas completely shielded. An aluminum plate under the passenger cell protects the high-voltage battery from damage from below, for example from stone chips or curb edges. Its attachment points are bowl-shaped, similar to the "dimples" on a golf ball. They allow the air to flow even more easily than a completely flat surface.

Additionally, there are further "classics" such as the controllable cooling air inlet – a frame behind the Singleframe that houses two electrically operated shutters. When closed, the air flows almost without turbulence in this zone. As soon as it becomes necessary to cool the drive components or ventilate the air conditioning condenser, the upper, and then both shutters open. Even under heavy load on the hydraulic wheel brakes, the SKE opens and releases two channels that lead cooling air into the front wheel housings towards the brakes. Channels to the wheel housings guide the airstream so that it flows past the aerodynamically optimized 19-inch wheels. Their design is flatter than that of conventional rims. The wide 255/55 tires feature low rolling resistance. Even the tire flanks are aerodynamically designed – the inscriptions are recessed instead of raised.

What does that mean?

The aerodynamic drag of new cars could be so much lower if they weren't SUVs! Audi has to deploy a lot of effort to achieve values in their latest (having much more frontal area) product that are only marginally better than those from over 30 years ago.