Aerodynamics: Sleek, silent type

May 15, 2013
For almost three decades, the aerodynamic specialists at Mercedes-Benz have been breaking one record after another. At present the brand's models occupy the top position for aerodynamics in practically every vehicle segment. The new S-Class is likewise at the top of its segment in terms of aerodynamics and aeroacoustics.
The drag coefficient of the new S-Class (cd=0.24) undercuts the previous model's figure by two hundredths and sets a new benchmark in this segment. The
S 300 BlueTEC HYBRID is set to go even lower still with a cd figure of 0.23 thanks to additional aerodynamic optimisation measures.
A number of features and details have been aerodynamically optimised to achieve this result:
  • Aerodynamically optimised front and rear apron with perfectly matched rear spoiler
  • All-new aerodynamically and aeroacoustically optimised exterior mirrors
  • Complete sealing of the front end with sealing of the headlamp section, improved sealing of the radiator section and airflow guidance to make efficient use of the available cooling air
  • Use of a cooling air metering system (adjustable louvre)
  • Water drain channels with optimum flow
  • Lowering of the vehicle by up to 20 mm when the speed exceeds 120 km/h
  • Spoiler lip on the tail lights
  • Aerodynamically optimised underbody with extensive engine compartment and underbody panelling up to a point below the tank to also further minimise the penetration of road noise
  • Aerodynamically shaped multi-purpose recess cover
  • Special wheel spoilers ahead of the front wheels
  • Aerodynamically optimised wheels and tyres
  • Large area of cladding on the rear axle
Barely perceivable noise level in the interior
The aeroacoustic specialists took specific measures to counter wind noises during their aerodynamic development work. To reduce high-frequency wind noise, the sealing systems around the windows and door handles were above all improved considerably. The newly designed exterior mirror and the correspondingly shaped A-pillar with a minimised shoulder height ensure the efficient drainage of water and spray hitting the windscreen, prevent the airflow from breaking off at this point and therefore avoid noises that might enter the interior via the windscreen and side windows. The roof structure and the automatic tilting/sliding roof module were subjected to further aeroacoustic development to improve noise comfort in this area as well. In the case of the panoramic sliding sunroof, numerous air deflection measures, covers and seals with the appropriate geometry ensure the same high level of noise comfort as in the preceding model, despite the larger opening aperture. The combined effect of these measures allows the new S-Class to achieve the desired aim of being the quietest vehicle in its segment.
A subdued, scarcely perceptible level of noise in the interior of the S-Class was the objective when configuring and coordinating the sound insulation measures. Particular attention was paid to transmitted engine noise and road roar. During the acoustic optimisation work, the focus was both on lowering the sound pressure level and on achieving the well-balanced and comfortable overall sound perception that is a hallmark of the S-Class.
To ensure that engine noise is perceived as refined and unobtrusive in the interior, the firewall insulation was extended into the side areas of the A-pillars. Additional sealing levels were also added in the form of high-quality injection-moulded components.
A major contribution to the reduction in transmitted engine noise was made by improved insulation in the transmission tunnel area, as well as a modular engine partition made of plastic. The different noise characteristics of the engines are taken into account by the use of different weights per unit area.
The electrically adjustable rear seats available as an optional extra are free-standing. High-frequency tyre noise was reduced by a large area of insulation extending from the seat surface to the rear panel and parcel shelf. Breakthroughs are kept to a minimum. An intelligent air ducting system inside the parcel shelf allows the necessary ventilation while reducing noise transmission via the parcel shelf. The textile underbody and wheel arch cladding has an insulating and absorptive effect which reduces high-frequency tyre noise in the interior.
222 model series Mercedes-Benz S-Class (2013 to 2020), aerodynamics test in the wind tunnel. Photo from 2013.
222 model series Mercedes-Benz S-Class (2013 to 2020), aerodynamics test in the wind tunnel. Photo from 2013.