- Electric car with sophisticated aerodynamics concept: drag coefficient of 0.28
- Important factor particularly on long journeys
- For the first time in a volume-production car: virtual exterior mirrors as a high-end option
Ingolstadt, May 30, 2018 – The better an electric car's aerodynamics, the further it travels, and with a drag coefficient of 0.28, the Audi e-tron prototype achieves a top result in the SUV segment. This figure is a decisive factor in the everyday range of more than 400 km in the WLTP cycle. The virtual exterior mirrors constitute one highlight in the aerodynamics concept of the all-electric premium class model.
The scenario: endurance tests in the wind tunnel
In front of the low-noise rotor measuring around five metresin diameter, the Audi e-tron prototype stares into the eye of the hurricane. On the aeroacoustics test rig in the Wind Tunnel Centre in Ingolstadt, the world's quietest vehicle wind tunnel, the Audi engineers optimise drag and noise under extreme conditions. both crucial for a car's efficiency and comfort. With an output of 2.6 megawatts, the fan produces speeds of up to 300km/h and the Audi e-tron prototype was put through over 1,000 hours of testing here.
The result is a drag coefficient of 0.28. and customers benefit directly from this low figure as drag contributes decisively to the high range of more than 400 kilometres in the WLTP cycle. A hundredth of the drag coefficient figure represents a range of around five kilometresdriving under everyday conditions.
Drag: essential on long journeys
On long journeys where the Audi e-tron prototype is perfectly at home, the drag constitutes the key driving resistance – far more important than the rolling resistance and inertia. Energy is lost as the car works to overcome this resistance, demonstrating why good aerodynamics are so important. In urban traffic, however, other factors come into play. Here, an electric car can recover a large part of the used energy when braking, thereby reducing the importance of its mass.
To achieve the drag coefficient of 0.28, the Audi engineers developed a wide range of aerodynamics measures in all body areas. Some of these technical solutions are evident at first glance, while others fulfill their purpose hidden away from sight. Thanks to these solutions, the drag coefficient for the Audi e-tron prototype is almost 0.07 less than for a comparable, conventionally-powered vehicle. With a typical usage profile this set-up increases the range by around 35 kilometres per battery charge in the WLTP cycle.
Smart solutions: virtual exterior mirrors and dimples on the underbody
The optional virtual exterior mirrors will be making their world premiere in the volume-production version of the Audi e-tron prototype. They are much narrower than the standard mirrors: They reduce the vehicle width by 15 cmand, thanks to their new shape, not only reduce drag, but also noticeably cut the already low wind noise. Each of their flat supports integrates a small camera. The captured images appear on OLED displays in the transition between the instrument panel and door. The virtual exterior mirrors can be adapted for various driving situations, thus potentially improving safety. Three views are available in the MMI system – for highway driving, turning and parking.
Another important factor is the standard adaptive air suspension – a pneumatic suspension with adjustable damping. At speeds above 120km/h, it lowers the body by up to 26 mm below the normal position, thus reducing the drag. The underbody of the all-electric SUV is fully enclosed, with the front and rear area fully panelled. Underneath the passenger cell, an aluminium plate protects the high-voltage battery against damage from below, such as stone chipping or curbs. Its bolting points come with bowl-shaped indentations, similar to the dimples on a golf ball, which make the air flow much better than a totally flat surface.
The controllable cool-air inlet – a frame behind the Singleframe with two electrically operated louvres – also helps lower drag. When shut, the air in this area flows with virtually no swirl. As soon as the drivetrain components need cooling or the air conditioning condenser requires ventilation, the top louvre opens first and then both louvres. When the hydraulic wheel brakes are subject to high loads, the controllable cool-air inlet opens and releases two ducts which channel the cooling air into the front wheel arches to the brakes.
The side air inlets at the front of the Audi e-tron prototype incorporate clearly visible additional ducts to the wheel arches. These channel the airstream so that it flows past the outside of the standard aerodynamically optimised 19-inch wheels. Their design is flatter than conventional wheels. The 255/55 size tyres stand out with their ultralow rolling resistance. Even the tyre sidewalls add to the aerodynamic design, with the lettering negative instead of raised.
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The Audi Group, with its brands Audi, Ducati and Lamborghini, is one of the most successful manufacturers of automobiles and motorcycles in the premium segment. It is present in more than 100 markets worldwide and produces at 16 locations in twelve countries. 100 percent subsidiaries of AUDI AG include Audi Sport GmbH (Neckarsulm), Automobili Lamborghini S.p.A. (Sant'Agata Bolognese, Italy) and Ducati Motor Holding S.p.A. (Bologna, Italy).
In 2017, the Audi Group delivered to customers about 1.878 million automobiles of the Audi brand, 3,815 sports cars of the Lamborghini brand and 55,900 motorcycles of the Ducati brand. In the 2017 fiscal year, AUDI AG achieved total revenue of €60.1 billion and an operating profit of €5.1 billion. At present, approximately 90,000 people work for the company all over the world, more than 60,000 of them in Germany. Audi focuses on sustainable products and technologies for the future of mobility.