12 Jan 2022
Aerodynamics, or the science of how air flows around and inside objects, serve multiple purposes in road vehicles. It helps to reduce drag and wind noise, and even fuel consumption. Good aerodynamics can also help make a car go faster since there is less air resistance or drag, which is measured by the drag coefficient (cd) — the lower the number, the better it is (less drag).
Since the 1980s, Audi has been at the forefront of innovation in aerodynamics. Some of the brand’s most celebrated car models boasting outstanding aerodynamics through the years include the 1982 Audi 100 (cd 0.30), 1999 Audi A2 (cd 0.25), 2015 Audi A4 (cd 0.23), and the latest 2021 Audi e-tron GT (cd 0.24).
Having good aerodynamics, while important for all vehicles, is even more important for electric vehicles such as the Audi e-tron GT. Since EVs run on whatever charge there is in the car’s battery, the car has limited amount of energy on board. With good aerodynamics and low air resistance, EVs can maximise their power consumption to achieve more mileage.
Audi’s innovation in aerodynamics is more than just giving its cars designs that can ‘cut’ through the air — it’s in every detail from head and toe. Here are some of the key features.
Audi cars have always had streamlined profiles, and good aerodynamics are present across all models from its most aerodynamic model — the Audi e-tron GT to its biggest SUV, the Audi Q8 that has a drag coefficient of cd 0.36.
The Audi e-tron GT has an advantage as it has done away with the car’s exhaust system, allowing Audi designers to create an enclosed and very smooth profile from nose to tail. According to Dr Moni Islam, Head of Aerodynamics/Aeroacoustics Development at Audi, components that usually give cars more drag, such as the tunnel, fuel tank and exhaust system, are designed differently in EVs such as the Audi e-tron range — a tremendous plus point for aerodynamics.
Audi’s first fully electric sports car also has smart designs that contribute to the car’s overall aerodynamics. One example is the Audi e-tron GT’s singleframe grilles located at the front end of the car. These are controlled by a highly intelligent thermal management system that automatically opens the grilles only when the car needs to be cooled. For aerodynamics, having the grilles closed most of the time is important as it allows the air to flow over and under the car — having air flow through the car contributes to drag.
Air curtains are the small tunnels at the sides of the car’s nose that guide airflow across the front wheels. These help to reduce drag ensuring that the air flows smoothly along the sides of the car. This is particularly important when the car is going at high speeds as the air curtains guide the airflow closer to the vehicle body improving the car’s overall aerodynamics.
Even the wheels of the Audi e-tron GT has aerodynamic design features. The sports car’s optional aero blades on the 20- and 21-inch wheels (standard on the RS model), covers majority of the fender to help improve the airflow. These are made from lightweight high-performance plastic that are only 2 to 3 mm thick.
The design of the tail and rear lights also contributes to the car’s overall aerodynamics. “Our Audi designers love making a nice curved transition from the side to the rear of the vehicle. However, that’s a real challenge in aerodynamic terms because the air current doesn’t really know where it should separate,” explained Dr Islam. To help the Audi e-tron GT achieve better aerodynamics, the team designed the rear lights to have integrated edges to ensure a clean break in the air flow by following the same contours as the interior graphics of the lights. Not only does this achieve a more harmonious appearance, it also helps avoid unpleasant refractions of light.
In aerodynamics, the rear is the most important zone as it is where low pressure forms which is responsible for creating resistance and causing drag. The trick is to keep the rear of the vehicle as small and compact as possible. In the case of the Audi e-tron GT, Audi incorporated a narrow track width, recessed wheels, and a slim luggage compartment. The addition of the extendable rear spoiler also helps correct the direction of the airflow to maximise aerodynamics.
“So is there a limit to how far we can reduce the cd value? My personal take is that designing a production car that is both a practical workaday vehicle and attractive to customers with a drag coefficient of under 0.20 won’t be possible for the foreseeable future,” said Dr Islam. “Ultimately, automotive engineering is constrained by the laws of physics.”
However, the aerodynamics team at Audi is continually working to optimise the brand’s aerodynamics to work seamlessly with customers’ needs, who are, afterall the consumers. “Let’s not forget: It’s our customers’ needs that define function,” he said.