Drag race winner

| Environmental Testing

Wind tunnel testing at the Mercedes Sindelfingen test facility

Slippery Mercedes A-Class surpasses previous records for low drag coefficients by combining CAE and wind tunnel validation. Jonathan Newell takes a closer look.

The reputation for being the smoothest operators in the automotive industry is usually reserved for exotic models and vehicles destined for the race track but now Mercedes-Benz is claiming it mid-market family car, the A-Class saloon, is amongst the best in terms of low drag.

A track record of drag reduction

Whilst the German car maker isn’t making any comparisons with equipment in the motor racing world or with low volume luxury car manufacturers, it is claiming that the A-Class has the lowest drag of any production vehicle in the world, a record previous held by the company’s CLA Coupé.

The latest generation of the A-Class saloon has come a long way from its first incarnation produced in 1997, having gained a complete redesign incorporating the new Mercedes signature design elements that allowed significant work to be done on improving aerodynamics whilst keeping the brand identity intact.

The result is a car that has a Drag Coefficient (Cd) value of 0.22 and a frontal area of 0.49 m2 compared with a Cd value from 0.26 and a frontal area of 2.20 m2 for the CLA Coupé, continuing the trend for Mercedes-Benz of setting aerodynamics records, which it has been doing since the 1980s.

Computation & Simulation

To achieve this significant 15% reduction in drag, Mercedes-Benz turned to Computer Aided Engineering (CAE) in the design, prototyping, simulation and testing of the car. Using a series of computational loops, the company optimised the new A-Cass down to the smallest of details.

CAE simulations were complemented by repeated measurements taken whilst undertaking wind tunnel testing at the enormous Mercedes Sindelfingen plant near the company’s home in Stuttgart.

It was here that the overall exterior shape of the car was optimised for reduced drag before adding a number of small measures, including a reduction of the frontal area and an extensive review and modification in the way the car is sealed, such as the sealing of the headlamp surrounds. Additionally, the underside of the car was almost completely panelled, including the engine bay, the main floorpan, parts of the rear axle and the diffuser.

The front and rear wheel spoilers were optimised specifically to route the air around the wheels as efficiently as possible. The rims and tyres also underwent aerodynamic fine-tuning. Depending on the market, an optional two-part shutter system behind the radiator grille is available, which minimises the airflow through the engine bay.

Technology democratisation

The new generation of A-Class is a good example of the way that high end advances in automotive technology created as concepts or for high-specification luxury vehicles are being filtered through to cars which are affordable to a wider community.

The company has maintained the proportions demanded by the hatchback and small saloon market whilst achieving the kind of aerodynamic properties usually reserved for cars that don’t have the same accommodation and volume capacity of the A-Class. These aerodynamic properties make a key contribution to low fuel consumption under everyday conditions.

In addition, the high end technology has been further democratised by delivering high efficiency clean engines as well as the latest Mercedes driver assist systems that are also used on the S-Class, which is the company’s flagship for ADAS and autonomy development.

Jonathan Newell
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