- Published in News.
A drag co-efficient of 0.26 should make the the new Mercedes B-Class the most aerodynamic model in its segment – most compact cars struggle to get below 0.30.
An optional aero pack lowers that figure to just 0.24, equaling the E-Class coupe's Cd value, which Daimler claims is the lowest of any series production vehicle.
Most of the development work was performed digitally but vehicle models and prototypes logged around 1,100 hours of wind tunnel testing. Achieving such low drag factors is more difficult with a two-box bodystyle than with a three-box sedan and meant optimising every part of the vehicle.
Daimler's head of aerodynamics, Dr Teddy Woll, said: “The 0.26 is revolutionary because that's the figure that our sedans reach today. The front bumper's smooth form leads the air over the wheel houses. In addition, the wheelhouses are slotted.
“The slots lead part of the cooling airflow out over the wheel – it works like a virtual cover, separating the smooth outer flow from the highly-turbulent inner flow. And we have a completely covered underbody, including rear axle cladding – normally only supercars have this.”
Other refinements include the shape-optimised air deflectors in front of the wheels. Instead of using a straight moulded feature, Daimler's engineers developed a tooth-form, like those used on sunroof wind deflectors. The small turbulent wakes they generate create a virtual barrier to the airflow, preventing it from entering the wheelhouses.
A pneumatically-operated adjustable radiator grille cover controls airflow into the engine compartment, reducing drag when cruising. Tier One Brose supplies the module.
A rear roof spoiler and a diffuser under the rear bumper help the airflow to remain attached to the vehicle before forming a tapering, three-dimensional closed wake. “The air comes together very quickly and the wake collapses a few metres behind the car,” said Woll.
According to Daimler, every 0.01 reduction in the Cd figure can cut fuel consumption by up to 0.4-litres/100km at 130km/h.