The new Mercedes-AMG SL: aerodynamics

Oct 28, 2021

A key development focus of the new SL was high aero efficiency. This means a perfect balance between low drag and reduced lift. Here, the luxurious roadster benefits from Mercedes-AMG's wide-ranging motorsport expertise. The extensive active aerodynamic elements at the front and rear are seamlessly integrated into the exterior design. Further detailed measures reduce the drag coefficient to Cd 0.31 - an excellent figure for open-top sports cars. The good aerodynamics reduce consumption and stabilise handling.

Driving stability, drag, cooling and wind noise: The SL's aerodynamics meet complex requirements. An even aerobalance can defuse critical driving situations, such as a sudden evasive manoeuvre at high speed. At the same time, it contributes to easier drivability, high efficiency and low wind noise.

The particular challenge with a roadster is to keep the aerobalance even, regardless of whether the top is up or down. The vehicle character and driving characteristics are to remain unchanged. In addition, the noise level should not vary too much when lowered side windows or the use of a wind deflector change the conditions.

The three-dimensionally modelled front apron with jet wing and front splitter not only reduces lift to the desired level, it also helps with the targeted inflow and outflow of the cooling modules. In addition, the cooling airflow from the aerodynamically shaped brake air ducts brings about a targeted improvement in braking performance. The large area of underbody cladding ensures an optimum exhaust airflow from the oil cooler in the underfloor area, and effective airflow to the rear diffuser.

Two-piece AIRPANEL air control system for the first time

Another technical highlight also improves the aerodynamics: the two-piece, active air control system AIRPANEL. The first piece operates with vertical louvres hidden behind the lower air intake in the front apron. The second piece is located behind the upper air intake and has horizontal louvres. All louvres are electronically controlled and can be opened and closed with actuators to direct the airflow as needed, improving aerodynamic performance.

Normally the louvres are closed - even at top speed. This position reduces drag and allows air to be directed specifically towards the underbody to further reduce front lift. Only when certain temperatures are reached on predefined components and the demand for cooling air is particularly high do the louvres open (the second piece only from 180 km/h) and allow maximum cooling air to flow to the heat exchangers. This calls for highly intelligent and fast control.

Active rear spoiler with intelligent operating strategy

The same applies to another active component of the aerodynamics: the retractable rear spoiler seamlessly integrated into the vehicle silhouette. It changes its position depending on the driving status. In doing so, the control software takes into account numerous parameters: It factors the driving speed, the longitudinal and lateral acceleration and the steering speed into the calculation.

The spoiler assumes five different angular positions from 80 km/h to either optimise handling stability or reduce drag. If the system detects driving dynamics, the spoiler moves to the steepest position, ensuring a driving experience that is both dynamic and safe.

  • Position 0 (retracted), -11-degree angle, 0-80 km/h: The rear spoiler, fully integrated into the design of the rear lid, enables the clean look when stationary and at low speeds. When parked, the positioning mechanism is protected against dirt and foreign bodies.
  • Position 1, +6-degree angle, 80-140 km/h: In this position, the new SL has the lowest drag (lower than in position 0), for the best possible efficiency and low consumption.
  • Position 2, +11-degree angle, 140-160 km/h: optimal balance between low drag and handling stability from the medium road speed range.
  • Position 3, +17-degree angle, 160 km/h - top speed: optimal balance between low drag and handling stability right up to the vehicle's top speed.
  • Position 4, +22-degree angle, Dynamic Position, 120 km/h - top speed, with high dynamic driving recognised by the vehicle: maximum lateral dynamics with greatest possible downforce providing for the best-possible road-holding. Simultaneously the greatest driving stability. The spoiler can also extend into this position independently of the driving situation when the driver presses the display button on the steering wheel.

Added downforce and efficiency: the optional Aerodynamics Package

This package not only sharpens the look: Larger flics on the front and rear bumpers, a larger rear diffuser and an active aerodynamic profile in the underbody in front of the engine significantly improve the aerodynamic characteristics - both downforce and drag. This improves driving characteristics at high speeds, especially lateral acceleration, handling stability, braking stability and efficiency. The speed thresholds of the rear spoiler vary with the Aerodynamics Package. The rear spoiler extends 10 km/h earlier in positions 1 and 2 and offers improved balance with a steeper angle of 26.5 degrees in the Dynamic Position.

Active aerodynamics profile in the underbody

As part of the optional Aerodynamics Package, the active aerodynamic profile, which is almost invisibly hidden in the underbody in front of the engine, contributes significantly to improved handling. The carbon element, which weighs only around two kilograms, reacts to the position of the AMG DYNAMICS and automatically extends downwards by around 40 millimetres at a speed of 100 km/h in Basic/Advanced or 80 km/h in Pro/Master. This significantly changes the airflow at the underbody. This process results in what is known as the Venturi effect, which additionally "sucks" the car onto the road and reduces the front-axle lift by around 50 kilogrammes at 250 km/h. The driver feels this positively in the steering even at lower speeds: The SL can be steered even more precisely into bends and tracks even more stably. Especially when turning in quickly and under high lateral acceleration, the roadster delivers far more agile response and always remains easy to control. In addition, the drag coefficient is improved.

When the electrically driven profile extends, the exhaust air opening of the engine radiator in the front opens at the same time and directs the airflow specifically toward the rear diffuser. This means that the flow to it is optimised. This also increases the driving stability of the rear axle and reduces the temperature level of the hotspots in the rear area. At the same time, the aerodynamic refinements of the new SL ensure optimised brake cooling by directing the cold air specifically to the wheel discs. To protect against damage, the active component is spring-mounted and can therefore easily deflect upwards in the event of bumps.

In addition, the active element enhances the effect of the AIRPANEL active air control system: if the adjustable shutters are closed, the lift at the front axle is further reduced. The aerodynamic profile on the underbody can be extended when the vehicle is stationary (to clean it of leaves, for example) and is then automatically retracted when the vehicle moves off. When the speed threshold is reached, the profile extends again automatically.

Aero wheels reduce drag and weight

There is also a choice of aerodynamically optimised 20 or 21-inch diameter alloy wheels for the SL, which reduce drag through less turbulence. Particularly sophisticated are 20-inch wheels with plastic aero rings that also save weight.

The SL's low wind noise contributes significantly to the hallmark Mercedes long-distance comfort. Effective sealing systems and sophisticated aero-acoustics ensure a high level of day-to-day suitability. The anti-soiling measures for the exterior mirrors, side windows and rear window make an important contribution to active safety.