Eighth-Gen Mercedes-Benz SL Gets Core Workout

STUTTGART, Germany –Mercedes-Benz finalizes plans to base the upcoming eighth-generation SL on the same platform as its AMG performance-car division’s GT models in a move aimed at providing the new roadster with added performance potential and greater dynamic flair.

The platform switch comes on the heels of dwindling sales of recent generations of the traditional open-top model and a decision by German automaker to hand lead engineering responsibilities for the new SL to AMG, which secretly has been developing the upmarket roadster at its headquarters on the outskirts of Stuttgart. The program runs parallel to its own GT roadster, which first bowed at the Paris auto show in September.

The shared platform will provide AMG with greater economies of scale in development, production procurement and engineering operations, according to sources familiar with Mercedes’ future model plans. They say the decision to twin the SL with the GT allows AMG to channel resources into further derivatives of the GT, including a planned hardcore Black Series edition that will sit above the recently introduced GT R atop AMG’s line when it launches later this decade.

Scheduled for introduction in 2019, the new rear-wheel-drive SL adopts the same underpinnings as the 2-year-old GT coupe and the more recent roadster with a front, longitudinally mounted engine and transaxle fixed at the rear for optimal weight distribution.

The new driveline layout replaces the more conventional E-Class-based setup used in the past two generations of the SL.

In further synergies between the SL and the GT lines, the new upmarket roadster is set to feature a specially tuned version of its AMG sibling’s largely aluminium double-wishbone suspension system, with the likelihood of an optional Air Body Control set-up with multi--chamber air plungers available on selected models.

Despite the common mechanical base, the SL is planned to receive a less dramatic cab-backwards silhouette than the GT roadster. The A-pillars instead will set farther forward to provide it with a longer and more versatile interior.

WardsAuto also confirms the SL, codenamed R233, will receive an aluminum body structure and the carbon-fibre torque tube from the GT. The technical decision should compel a substantial reduction in curb weight and yield vastly improved performance and efficiency.

Additional weight saving will come from a decision to replace the existing model’s folding aluminum roof structure with a more traditional fabric hood. The switch also is part of an extensive restyle for the eighth incarnation of the classic, whose roots can be traced back to the original SL in 1954.

Along with the SL roadster, Mercedes planners are mulling a resurrection of the SL coupe. If approved, the eighth-generation SL would be the first to feature such a model since the fourth-generation SL in 1981.  

In a nod to the fourth-generation model launched in 1971, Mercedes bosses in Stuttgart also have greenlighted plans to provide the new SL with a 2+2 interior layout. Sources say the space behind the front seats will add a pair of small rear seats complete with 3-point harnesses, a move aligning the SL more closely with the rival Porsche 911 cabriolet for load-carrying capability. 

New Engines, Too

The new SL will come with the choice of two GDI engines in varying states of tune. Included is Mercedes’ new M256 inline 6-cyl. with an integrated electric motor with up to 15kW that acts as a starter/generator for mild-hybrid properties.

Featuring an electrically driven turbocharger powered by a 48V electrical system, as well as a conventional exhaust-gas driven turbocharger, the recently unveiled 3.0L unit kicks out 402 hp in standard tune. That’s some 40 hp more than the older turbocharged 3.0L V-6 gas engine used by the existing SL400.

A racier version of the new inline-6 is planned for a midrange SL50-badged AMG Performance version of the new SL packing in the region of 450 hp.

Also earmarked to power the new SL is Mercedes’ M176 gas engine. A development of the twin-turbocharged 4.0L V-8 originally unveiled in the GT, it is planned to replace the twin-turbo 4.6L V-8 M278 designated engine used by the existing SL500. Set to make its debut in a facelifted version of the S-class in April, the new unit is claimed to deliver more than 470 hp.

Further up the SL line will be the M177 engine recently unveiled underneath the hood of the E63. As with the less-heavily tuned M176, it features two twin-scroll turbos and AMG’s cylinder-management system allowing it to close down four cylinders on part-throttle loads to save fuel. Set to replace the twin-turbo 5.5L V-8 in the SL63, the new engine, which is assembled by hand at AMG’s Affalterbach operations near Stuttgart, develops 603 hp in the new E63.

The future of the range-topping SL600 and SL65 remains unclear. Mercedes officials tell WardsAuto the high-power output of the latest twin-turbo 4.0L V-8s combined with ever-tightening emission regulations raises doubts over whether the German automaker will provide the new SL with an updated version of its existing twin-turbo 6.0L V-12.

“From an image standpoint, it would be a great loss to the SL to go without the V-12. However, the new V-8 provides outstanding performance and economy, and there is still more to come from it in the future,” a spokesman says.