The science of aerodynamics is a prime development tool in extending range, particularly for all-electric cars. Thanks to a number of technology and detail innovations, the prototype version of Audi’s sportier E-tron electric vehicle (EV), the S sportback, achieves a low drag coefficient figure of 0.26.
The sportback “coupé” gets a more sloped rear roof line and spoiler on trunk lid edge that improve drag coefficient compared with the sister model. The S models of the EV get sporty exterior details like wheel arch trim that is 23 mm (0.9 in) wider than that of the base version.
That special slotted trim of the prototype controls airflow at the front wheels, a fundamental part of the aerodynamics concept. The airflow through the wheel arch trim through the narrow horizontal bars in the recesses formed by the widened trims in the front channel the airstream to surround and encapsulate disruptive swirl in the wheel houses. Combined with side air inlets in the vehicle’s front fascia, and the design of the 20-inch wheels and tire tread/sidewalls, the resulting air curtain optimizes the airflow to and around the wheels and “cleaner” airflow along the vehicle flank with reduced flow losses. Audi intends to bring this patented solution to high-volume production on the future Audi E-tron S Sportback to help bring the stock E-tron S drag coefficient down from 0.28.
The prototype also features virtual exterior mirrors with exterior sensors and interior OLED (organic light-emitting diode) displays. They help improve aerodynamics by around the same amount as the airflow through the wheel arches and increase range by around 3 km (1.9 mi) in the WLTP cycle. The virtual exterior mirrors, a claimed world-first, went into volume production in the Audi e-tron quattro. Each of their external supports integrates a small camera at the ends, the captured images appearing on high-contrast OLED displays located inside at the transition between door and instrument panels. The field-of-view adjusts to driving situations such as when on the highway, turning, or parking.
The aerodynamic improvements of the prototype continue under the vehicle, where underfloor paneling with spoiler elements cleanly routes air around the vehicle. The underfloor integrates with the aluminum cover plate that encloses the high-voltage battery. The bolting points, with bowl-shaped indentations similar to the dimples on a golf ball, are said to make the air flow much better than a totally flat surface. The standard adaptive air suspension further aids aerodynamic drag at high speeds by lowering the body by up to 26 mm (1.0 in) from standard height in two stages.
Another important aerodynamic element of the prototype is a controllable cool-air inlet, which also acts as the thermal management control center. It comprises a frame behind the main grille with two electrically operated louvers. At speeds between 48 and 160 km/h (30 and 100 mph), the louvers are usually closed so that the air flows over the hood with virtually no swirl. If the air conditioning system or the drive components require more cooling air, the louvers open gradually. If the hydraulic brakes see extremely high loads, the system releases two channels that route air to the front wheel arches and, if necessary, the cooling fan is turned on.
In addition to aerodynamic improvements, the future e-tron S models will stand out by using three electric motors, two at the rear axle. They’ll produce a total 370 kW and up to 973 N·m (718 lb·ft) for 0- 100 km/h (62 mph) acceleration in 4.5 s. Their intelligent drive control raises vehicle safety, and dynamic handling, in particular, with fully variable torque distribution on the rear axle.