The sixth-generation SL is based on an all-new platform, but apart from that it diverts from the proven recipe of the outgoing model only among the details.
As is the class norm, and like the R230 model, the new R231 SL uses longitudinal V6 and V8 petrol engines and rear-wheel drive. But unlike many direct competitors, it has a folding metal ‘vario-roof’ that takes less than 20 seconds to convert, and a strictly two-seat cabin.
Featuring cleaner surfaces and bolder styling lines than the outgoing car — none more so than the unbroken shoulderline running from headlight to tail-lamp — the new SL’s aesthetic references are to the 1960s ‘pagoda’ SL and 1970s R107. However, Mercedes hasn’t wasted the chance to update the car with the SLS-inspired upright radiator grille used by its sports car family, and some familiar body-side sculpting.
The exterior form is functional as well as elegant. Mercedes claims the SL is the most aerodynamically efficient car in its class and sets new standards for wind noise-based cabin refinement.
But the car’s biggest technological advancement is under the skin. This SL will be the first Mercedes in large-scale series production to use an almost exclusively aluminium construction.
Made from a mix of chill cast, vacuum die cast, stamped and extruded aluminium, this body-in-white superstructure allows the new SL to be between 125kg and 140kg lighter than the outgoing steel car, and 20 per cent more torsionally rigid.
The metal castings and tailored blanks of the SL’s body-in-white are connected via various techniques, depending on how much load they transmit. While some parts of the underbody are MIG welded, hemmed, bonded and bolted together, others are joined via state-of-the-art friction stir welding — a technique that allows for particularly stiff, precise joins.
With mainly aluminium body panels, the only significant parts that aren’t aluminium are its plastic ‘soft nose’ grille (for pedestrian protection), super-lightweight magnesium rear bulkhead, folding roof and tubular steel A-pillars and header rail.
Steel is chosen here for its extremely high strength in the event of a rollover.
Two direct-injection petrol engines contribute to fuel efficiency gains of between 22 and 29 per cent over previous models. The 3.5-litre V6 in the entry-level SL350 produces 302bhp and 273lb ft. Although less powerful than the outgoing SL350, it offers more torque, makes the SL350 0.3sec faster to 62mph (5.9sec) and promises to return 41.5mpg on the combined cycle.
The eight-cylinder engine in the SL500 is the twin-turbo 4.7-litre unit that also serves in Mercedes’ current S-class. It produces 429bhp and 516lb ft and sends the SL500 to 62mph in just 4.6sec. Both engines operate via a seven-speed automatic transmission.
Like the previous SL, suspension on the new one is by a multi-link set-up at both ends, and it will be tuned to suit the car’s uniquely laid-back dynamic character among its peers. A dash of dynamism will therefore be mixed into the generous baseline of compliance and refinement for which the SL is famed.
Steel springs with ‘semi-active’ dampers will be standard on the SL350. Mercedes’ self-levelling, height-adjustable, hydraulically controlled Active Body Control chassis will be an option. The steering features a new electro-mechanical ‘direct steer’ set-up with variable assistance levels and a variable ratio.
Mercedes will offer the same optional electro-chromic panoramic glass roof on the SL that features on the smaller SLK convertible. The Magic Sky Control system allows the driver to choose between transparent glass, light shade and dark shade.
The SL’s folding roof frame itself is made out of magnesium. It weighs 6kg less than that of the outgoing car and contributes to a lower centre of roll for the car.
The SL is credited with two further technological premieres. Its Frontbass audio system uses bass loudspeakers mounted in the front bulkhead rather than in its interior door panels.
The system takes advantage of the more rigid construction of the bulkhead for better sound resonance and less distortion than a conventional system, and the cone-like shape of the footwell acts as a natural amplifier.
The car’s other first is a high-precision windscreen wash-wipe system called Magic Vision Control. The system flushes water through jets integrated into the rubber of the wiper blade. It deploys water just ahead of the leading edge of the wiper, on both the upstroke and downstroke of the blades, to minimise wastage and mess and improve visibility.
Heated wiper blades, heated fluid supply lines and a heated washer fluid tank are also available as an option, for uncompromised performance in wintery conditions.