Under the microscope: aerodynamics, wind noise, protection from soiling: Less drag and substantially quieter

Oct 4, 2010
Aerodynamics are a key contributory factor to the outstanding efficiency of the new Mercedes-Benz CLS. Although the new model is wider than its predecessor and thus offers the wind a larger frontal area, drag has been reduced by up to ten percent. As a result of fine-tuning measures on the body and the application of technical measures such as a cooling air louver and aerodynamically optimised wheels, the Cd value – which defines the drag coefficient – has been reduced by 13%, to 0.26. Other focuses of aerodynamic development have been on reducing wind noise and keeping all surfaces which contribute to visibility free of soiling – a key element of perceptual safety.
Specifically, the key focuses of aerodynamic development work were as follows:
  • New exterior mirrors, optimised in terms of aerodynamics, aeroacoustics and dirt deflection, positioned expediently on the beltline
  • Aerodynamically efficient design of the front and rear aprons and the boot lid
  • Improved sealing of the radiator section and utilisation of air flows to make efficient use of the available cooling air, deployment of a cooling air louver
  • Flow-optimised drip rails in the area of the A-pillars
  • Optimum coordination between the taper of the C-pillars and the shaping of the vehicle's rear end
  • Aerodynamically optimised underbody with wheel spoilers and extensive engine compartment and main floor panelling
  • Aerodynamically optimised wheels; Aero Wheel used for the first time on the CLS 250 CDI BlueEFFICIENCY
  • When the CLS is fitted with AIRMATIC air suspension, the body is lowered by 15 millimetres at speeds of over 140 km/h
Wind noise: a highly refined driving experience even at high speeds
In order to improve comfort and in the interests of a more refined driving experience at high speeds in particular, the aerodynamics and body experts have tweaked a number of details to attain a further reduction in the noise level in comparison to the predecessor model.
The following measures result in reduced wind noise:
  • Optimised sealing of joints between bonnet and radiator grille
  • Positioning of the exterior mirror on the beltline, optimised joint sealing between head and base of mirror
  • Elaborately designed wind deflector for the tilting/sliding sunroof
  • Sophisticated system of seals between the frameless doors and the body; improved sealing of door handles; increased rigidity of the doors themselves
  • Damping package at many points of the body to reduce low-frequency noise
Protection from soiling: further improvement in vision and visibility
The areas of the side and rear windows of relevance to safety remain free of soiling when driving in rain at between 80 and 160 km/h, thanks to effective channelling and drainage of the incoming water. A water runnel with continuously diminishing height and an optimised roof trim strip channel water which lands on the front windscreen along the roof. The mirror positioned on the beltline additionally helps to keep the side window free of soiling more effectively than a traditional bridge mirror.
The water flowing over the roof is diverted away from the rear window by means of a coordinated water management system comprising channels to the left and right of the rear window through which the water flows down.