Audi e-tron prototype: an electric SUV with sports-car aerodynamics

The Audi e-tron prototype offers a drag coefficient of 0.28, a figure that gives it an extra 35 km of range over its combustion-engined rivals.

The Audi e-tron prototype is a true example of efficient aerodynamics and, above all, a benchmark for sustainable mobility thanks to its wide range: more than 400 km according to the WLTP cycle (much stricter than the permissive NEDC). The first 100% electric vehicle from Audi will reach the market at the end of 2018, and it does so with a drag coefficient of 0.28, a figure almost 7 hundredths lower than an equivalent combustion-engined SUV. Every hundredth in the drag coefficient figure translates into roughly five kilometres more real-world range, so the electric Audi SUV achieves, through its drag coefficient, around 35 kilometres of extra range over its conventional rivals.

Why is the drag coefficient so important for an electric car?

On long journeys, the aerodynamics of an electric car are key to resisting air drag, even more important than rolling resistance or inertia. The energy the car needs to overcome that resistance is energy lost. That is why a good drag coefficient matters so much, and it is an area where the Audi e-tron prototype stands out from other sports SUVs; its bodywork is closer to that of a sports saloon than to a conventional SUV, which gives it a clear advantage over the latter.

Why does the Audi e-tron prototype have such groundbreaking aerodynamics?

The virtual exterior mirrors are one of the most notable features of the Audi e-tron prototype and contribute to its cutting-edge aerodynamics. These elements are much narrower than conventional mirrors, which reduces the vehicle’s width by 15 cm and, thanks to their shape, not only improves aerodynamic drag but also noticeably reduces wind noise. Each of their flat supports integrates a small camera that shows up to three views on the car’s MMI system: for driving on the road, for turning and for parking.

Another feature that contributes to this car’s good aerodynamics is its standard adaptive air suspension, with adjustable damping. At speeds above 120 km/h, the Audi e-tron prototype lowers the body by up to 26 mm compared with the normal position, thereby reducing aerodynamic drag.

In addition, the underside of the electric SUV is fully covered by an aerodynamic undertray. Beneath the passenger cell, an aluminium plate protects the high-voltage battery from damage that could come from below. The points where this plate is attached to the chassis have cavities similar to the dimples of a golf ball, which make the airflow smoother than over a completely flat surface, further improving the car’s aerodynamics.

The cooling air intake includes electronically controlled louvres, which also improve aerodynamic drag. When closed, the air in that area flows practically without forming eddies. If the drivetrain components need cooling, or the air-conditioning condenser requires ventilation, the upper louvre opens first and then both open.