Arriving in 2019
Scheduled for introduction in 2019, the new rear-wheel drive SL will adopt the same underpinnings as the two-year-old GT coupe and its more recent roadster with a front longitudinally mounted engine and transaxle mounted at the rear for optimal weight distribution.
The new driveline layout replaces the more conventional E-Class based set-up used in the past two generations of the SL.
In further synergies between the SL and the GT line-up, the new upmarket roadster is also 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 featuring on selected models.
Despite the common mechanical base, the new SL is planned to receive a less dramatic cab backwards silhouette than the GT roadster with the A-pillars set further forward to provide it with longer and more versatile interior.
Autocar can also confirm the new SL will also receive an aluminium body structure and the carbon fibre torque tube from the GT in a move, insiders suggest, will see a substantial reduction in kerb weight in an effort aimed at providing the new model, which goes under the internal codename R233, with vastly improved performance and economy.
Further weight saving has come from a decision to replace the existing model’s folding aluminium roof structure with a more traditional fabric hood as part of an extensive restyle for the eighth incarnation of the classic Mercedes-Benz model, whose roots can be traced back to the original SL launch in 1954.
Plans to resurrect the SL coupe
Along with the SL roadster, Mercedes is also mulling plans for resurrection of the SL coupe. If approved, the eighth-generation SL will be the first to feature such a model since the fourth-generation SL in 1981.
In a move that harks back to the fourth-generation model launched in 1971, Mercedes bosses have also provided the greenlight to plans to provide the new SL with a two-plus-two interior layout.
Autocar has been told the space behind the front row of seats will be used for the integration of two small rear seats complete with three-point harnesses – a move an AMG insider suggests is aimed at seeing the new SL more closely rival the Porsche 911 cabriolet for all-round load carrying ability.
The new SL will come with the choice of two direct injection petrol engines in varying states of tune. Included is Mercedes' new M256 in-line six-cylinder complete 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 48-volt electrical system as well as a conventional gas driven turbocharger, the recently unveiled 3.0-litre unit kicks out 402bhp in an initial standard tune, or some 40bhp more than the solder turbocharged 3.0-litre V6 petrol engine used by the existing SL400.
A more highly tuned version of the new in-line six-cylinder petrol engine is also planned to feature in a mid-range E50-badged AMG Performance version of the new SL with up to 450bhp.
Also earmarked to power the new SL is Mercedes-Benz’s M176 petrol engine. A development of the twin-turbocharged 4.0-litre V8 originally unveiled in the GT, it is planned to replace the twin-turbocharged 4.6-litre V8 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 over 470bhp in an initial state of tune.
E63 engine to be used further up the range
Further up the new SL line-up will be the M177 engine recently unveiled underneath the bonnet of the E63. As with the less heavily tuned M176, it features two twin-scroll turbochargers and AMG’s cylinder management system allowing it to close down four cylinders on part throttle loads for added fuel savings. Set to replace the twin-turbocharged 5.5-litre V8 in a replacement for the SL63, the new engine, which is assembled by hand at AMG’s Affalterbach operations near Stuttgart, develops 603bhp in the new E63.
Meanwhile, the future of the range topping SL600 and SL65 remains unclear. Mercedes-Benz officials contacted by Autocar suggest the high power output of the latest twin-turbocharged 4.0-litre V8 engines combined with ever tightening emission regulations has raised doubts on whether the German car maker will provide the new SL with an updated version of its existing twin-turbocharged 6.0-litre V12 petrol engine.
“From an image standpoint, it would be a great loss to the SL to go without the V12. However, the new V8 provides outstanding performance and economy – and there is still more to come from it in the future,” said an insider.
Read our review of the Mercedes-AMG E 63