Aerodynamics: Aerodynamically efficient

Jul 15, 2014
The new C-Class Estate also owes its high efficiency to its low Cd value – the lowest in its segment.
The new C-Class Estate also follows in the Mercedes-Benz tradition as the trendsetter in the aerodynamics discipline: the best variant achieves a drag coefficient of Cd = 0,27 and is thus the benchmark in this premium estate segment. However, the new Estate has larger exterior dimensions than its predecessor; its frontal area has been increased by 0.05 square metres to 2.23 square metres compared with the preceding series. This is, however, more than offset by the improved drag coefficient. The drag area (vehicle cross-section multiplied by Cd value) was reduced as a result by as much as five percent to 0.60 (predecessor 0.63).
Intensive detail work for Cd-benchmark
The aerodynamics engineers achieved the top Cd-an extensive bundle value with of measures. In concert with the designers, the intensive use of computer-based airflow simulations allowed them to find a basic aerodynamic shape already in the early design phase, which was the prerequisite for further optimisation in the wind tunnel. The optimum ratio between rear width and rear roof height had to be found when optimising the Estate. The wind resistance could only be reduced substantially compared with the predecessor thanks to the graduated sweeping momentum of the roof, combined with an extended roof spoiler and the associated side spoilers.
A host of other detailed optimisation measures provide the new Estate with the lowest Cd-value in its vehicle segment. For instance, the A-pillar was optimised in many details and ensures a flow around the vehicle with little turbulence. In concert with the aerodynamically and aeroacoustically optimised mirrors it contributes to a reduction in drag and wind noise. Specially shaped front and rear wheel spoilers optimise airflow around the wheels.
EXCLUSIVE line vehicles even make aerodynamic measures visible for everyone. Depending on the engine, they come as standard or as an option with the AIRPANEL. Its louvres open and shut the radiator trim depending on the cooling demand. On the C 180 BlueTEC and C 200 BlueTEC variants the flow of cooling air is controlled by the annular shutters behind the radiator. With savings of 2 to 3 grams of CO2 per kilometre both measures for controlling the cooling air are effective – and in the case of the AIRPANEL even visible – aerodynamics measures.
Wind noise minimised
Special attention during the aeroacoustic development was on further improving wind noises caused by the air flowing around the vehicle and its detachable body parts compared with the preceding model. In particular the impact of the air flowing over the side windows, i.e. the associated acoustic excitation, play an important role in near-field acoustics and have been decisively minimised. The low-frequency noise characteristics were also improved right from the simulation phase through a host of detail optimisations – such as on the main floor of the bodyshell and the new aluminium doors.
The fine-tuning of the door seals, whose concept was taken from the S-Class, was finally conducted on the actual vehicle in the wind tunnel in order to fully meet the aspirations of the C-Class as a premium estate. Windows with laminated safety glass are available as an option for the front doors, which can then reduce the wind noise penetrating the passenger compartment to virtually the same level as the E-Class.