Optimum aerodynamics have long been an important consideration in automotive design and when it comes to the Audi e-tron it takes on a new importance.
8 October, 2020
Even at a glance, the Audi e-tron is all Audi. The brand’s first all-electric vehicle also bucks the trend adopted by many manufacturers who have sought to create wild, futuristic designs for their electric vehicles, a fact that many automotive journalists have praised, questioning why an e-vehicle needs to look as if it has arrived from an other planet.
Of course the Audi e-tron has plenty of unique design cues and identifying factors, such as the distinctive sill area, the yellow brake callipers and specific daytime running light signature and there are obviously no exhausts on an e-tron. Then there are items like the virtual exterior mirrors which a technology highlight, design element and aerodynamic aide all in one.
But while these all stand out to a degree, there are myriad less obvious design elements that have been painstakingly developed in the wind tunnel to ensure the Audi e-tron has the best aerodynamic form to slip through the air with least resistance and in turn, deliver the very best range possible as a result.
The drag coefficient for the Audi e-tron is almost 0.07 less than for a comparable, conventionally powered vehicle, and in regular day to day usage, this equates to an increase in range of around 35 kilometres per battery charge in the WLTP cycle. To achieve the same result simply by cutting weight, the engineers would have had to shed a half a metric tonne.
Fitted with conventional exterior mirrors, the Audi e‑tron achieves a drag coefficient of 0.28, but fit the optional virtual side mirrors and that value becomes 0.27 which puts it right at the top in the SUV segment. Compared to the standard mirrors, the camera mirrors reduce the vehicle width by 15 centimetres and, thanks to their new shape, not only reduce drag, but also noticeably cut the already low wind noise.
Another less obvious aerodynamic factor is the fully lined underbody of the Audi e‑tron, made up primary ofan aluminium plate underneath the high-voltage battery. What sets this plate apart though are the bolting points which are recessed into bowl-shaped indentations, similar to the dimples on a golf ball. These ‘dimples’ create stabilising vortices that help the flow much better than a totally flat surface, and makes the e-tron ‘slipperier’ through the air.
The electric motors on the axles and the wheel suspension are covered with paneling made from pressed fibre-fleece material, which at the same time absorbs noise. Ahead of the front wheels, wheel spoilers mounted on the underbody use air baffles to reduce irritating swirl in the wheel arches. These baffles specifically channel the airflow past the wheels. The transverse links on the rear axle of the Audi e-tron are located under separate paneling and a variable diffuser below the rear skirt ensures that the accelerated air returns to ambient speed and creates as little swirl as possible.
The standard adaptive air suspension also contributes to the low drag coefficient, lowering the body by as much as 26mm from its normal height of 172 millimetres from speeds of 120km/h. This means that the rectangle that the tyres represent for the airflow is partially covered by the wheel arch and also improves handling.
Then there is the controllable cool-air intake that sits behind the Singleframe front grille. Although the traditional front grille is not required to cool a conventional engine, this system is made up of two two electrically operated louvres which, when shut allows the air in this area float flow with virtually no swirl.
But as soon as the drivetrain components need cooling or the air conditioning condenser needs ventilation, the top Louvre opens first and then both louvres. When the hydraulic wheel brakes are subject to high loads, the controllable cool-air intake 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 also incorporate additional ducts, which are clearly visible from outside. These channel the airstream so that it flows past the outside of the standard aerodynamically optimised 19-inch wheels which feature a design that is flatter than with conventional wheels, thus reducing the aerodynamic drag. The 255/55 tyres are also optimised for low rolling resistance, and their flanks are aerodynamically designed with the lettering recessed rather than raised.
The combination of all of these factors and of course the e-tron’s larger capacity battery and outstanding ability to recoup energy result in a vehicle that can deliver over 400km of range on a full charge –without compromising comfort, ride or performance.
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