Aerodynamics and aeroacoustics: Shaped by the wind
The lowest aerodynamic drag of any SUV in its segment, and even less wind noise than in the preceding model – this was the development goal for the new GLE. This was achieved with Cd figures from 0.29 – a significant improvement over the preceding model (Cd = 0.32). The good aerodynamic properties make a key contribution to low fuel consumption under everyday conditions. A host of details were optimised with numerous computation loops, CAE simulations (computer-aided engineering) and measurements in the wind tunnel in Sindelfingen.
Major measures include an active cooling air control system behind the radiator grille for need-related metering of the airflow (AIRPANEL), so that only as much air as is absolutely necessary flows through and as much as possible flows around the vehicle. To ensure that it meets little resistance, wheel spoilers with aerodynamically shaped deflectors ahead of the front wheels were developed, with additional wheel spoilers ahead of the rear wheels. The exterior mirrors were optimised, as the turbulence they create not only increases drag, but also noises that are very close to the driver's ears. Acting together with the airflow around the A-pillars, this airflow substantially ensures that the side windows remain clean even when driving in the rain. The roof spoiler and the side spoilers, which are sealed against the D-pillar on the tailgate, as well as rear lights with special spoiler lips, ensure reduced turbulence at the rear end.
The high ground clearance of SUVs makes detailed improvements to the underbody particularly beneficial to the aerodynamics. In the new GLE, a large area of cladding on the underbody and propshaft tunnel is used to good effect. A flush fuel tank cladding, aerodynamic cladding at the rear axle and an aerodynamically optimised diffuser cladding reduce drag and noisy turbulence at the underbody, where particularly low-frequency wind noise occurs. The wheels, a constant thorn in the side for aerodynamics engineers, have also been optimised to the extent that they could almost be called aero-wheels. The detailed work even went as far as to recess the lettering on the tyre sidewalls.
The large panoramic sliding sunroof, an item that takes pride of place in the list of optional equipment, is not exactly welcomed by the engineers working in the wind tunnel, as its unavoidable joints and apertures are always sources and opportunities for wind noise. However, the aerodynamicists dedicated themselves to the task and used numerous air deflection measures, specially shaped seals and facings to ensure a level of noise comfort corresponding to that of a much smaller sliding sunroof. Indeed a special programme was developed for the panoramic sliding sunroof to adapt the tilted position of the roof to the vehicle speed, so that the wind noise presumably desired by the driver always remains pleasant without becoming intrusive.
The good aeroacoustics of the new GLE are also the result of painstaking attention to detail in other areas which can only be seen if one knows what to look for. Numerous examples are revealed in the form of joint and seals that become apparent when the bonnet or doors are opened.