To put it simply: improved aerodynamics means improved efficiency. Already at a speed as low as 60 kilometres per hour, aerodynamic drag becomes the dominating factor in the drag and rolling resistance of a vehicle and has significant impact on fuel consumption.
There are two important metrics that determine the aerodynamic properties of a vehicle: its frontal area A (in square metres) and the drag coefficient Cd (c = constant, d = drag; dimensionless), which describes the quality of the aerodynamic shape of an object independent of its size. The total aerodynamic drag is calculated by multiplying Cd by A (Cd × A).Already at a speed as low as 60 kilometres per hour, aerodynamic drag becomes the dominating factor in the drag and rolling resistance of a vehicle and has significant impact on fuel consumption. By lowering the Cd value by 0.01, we can save one gram of CO₂ per kilometre in the NEDC. Based on the real-life fuel consumption average, the resulting savings are more than 2 grams less CO₂ per kilometre. Sophisticated aerodynamics pay even more significant dividends on the motorway. Here, a Cd value improved by 0.01 reduces CO₂ emissions by more than 4 grams per kilometre. But good aerodynamics also have a positive effect in the interior, for example an extremely low (wind) noise level. These are good reasons for Daimler to make our vehicles not just beautiful, but aerodynamic as well.
Top aerodynamics figures
With a Cd value of 0.22 and a frontal area of 2.19 m², the new A-Class Sedan has the lowest drag of any production vehicle worldwide and thereby defends the original world record of the CLA Coupé.
Aerodynamics also count for trucks
Aerodynamic, streamlined trucks consume less diesel fuel. Reductions in aerodynamic drag can achieve fuel savings of 1.5 percent in distribution transport and up to 3 percent in long-distance transport.
In 2015, Daimler Trucks demonstrates with the SuperTruck hybrid truck from Freightliner how fuel consumption can be reduced further with targeted measures regarding aerodynamics, energy management, the use of an intelligent powertrain and other levers. The SuperTruck improves transport efficiency by 115 percent (measured in tonne-miles per gallon) over a comparison truck from 2009. The fuel consumption of the SuperTruck is also phenomenal. During road tests, the truck consumed on average about 19 litres per 100 kilometres with a total weight of 29.5 tonnes and a speed of about 100 km/h. Standard fuel consumption in this weight class to date is about 39 litres. As a result, Daimler Trucks sets another technological benchmark for the North American truck market.
We also use high-efficiency engines and sophisticated aerodynamics in the new Western Star 5700XE to lower fuel consumption and CO₂ emissions. The aerodynamic drag was reduced considerably. In concert with the new integrated Detroit Diesel powertrain, this leads to a reduction in fuel consumption by almost 15 procent compared with the predecessor, the Western Star 4900 FE.
Aerodynamics for buses and coaches – Setra ComfortClass 500
The aerodynamic design forms the foundation for the good fuel consumption figures of the Setra ComfortClass 500. It lowered aerodynamic drag by 20 percent. This means fuel savings of up to five percent. In conjunction with other detailed measures, the ComfortClass 500 achieves a Cd value of 0.33, unprecedented in the industry. The goal of the engineers was to prevent a separation of the air stream at the front and rear as well at the sides of the new coaches.
The developers increased the radii of the roof vent at the front of the ComfortClass 500 and redesigned the A-pillar to significantly reduce drag at the front with the curved windscreen and ensure that the air stream hugs the vehicle body in this area. The previously rectangular profile of the mirror arm also has an aerodynamic shape on the new vehicles. The further advanced driver's window and the aerodynamic fit of the windows and doors reduce wind noise and inherent soiling.
The aerodynamics specialists and designers also implemented pioneering changes at the rear. A new design with a tapered rear section of the roof and side walls results in the air stream hugging the vehicle for as long as possible. The redesigned rear ensures a defined separation of the airflow behind the vehicle.