Detroit show: Benz reveals all-alloy SL roadster

MERCEDES-BENZ has revealed full official details and images of its sixth-generation SL roadster, which will be 20 per cent more torsionally rigid despite weighing at least 125kg less than its predecessor.

The engineering feat is due to the fact the next SL, which goes on sale in Australia in June, will be the first large-scale series production Mercedes in the brand’s 125-year history to feature a bodyshell comprised almost entirely of aluminium, joining the likes of Audi’s R8 supercar.

First official images of the redesigned SL two-seater, which will make its public premiere at the Detroit motor show on January 9, confirm as legitimate the multitude of leaked images circulating the internet in recent days.

They reveal a much more aggressive demeanour that retains the long bonnet and low-slung silhouette of its forebears but is dominated by a wide front grille opening and larger headlights and tail-lights, while a far bolder surface treatment completes the more dynamic look.

Mercedes’ first all-new SL since 2002 also features a more curvaceous iteration of the folding hard-top roof system pioneered by the model it replaces and since mimicked by a ride range of coupe-convertibles.

The result is the most aerodynamically efficient vehicle in its class, says Benz, which also claims its latest SL sets new standards for noise-based cabin refinement.

Despite this, the new SL will surrender its station as the German luxury giant’s most expensive convertible.

That honour now goes the soft-top SLS AMG Roadster, which arrives here in January priced at $487,500 plus on-road costs, although the outgoing SL65 AMG flagship still eclipses that at $513,760, making it the second least affordable Mercedes behind the CL65 AMG ($519,250).

Mercedes is yet to reveal pricing, but the outgoing range opens with the six-cylinder SL350 at $242,780, and also includes the 5.5-litre V8-powered SL500 ($334,840), twin-turbocharged SL600 ($422,255) and the 6.2-litre V8 SL63 AMG ($418,670).

All models will be more efficient than before due to the SL’s lighter chassis, the rear wheels of which continue to be powered by longitudinal Vee engines.

The 2013 SL350 is powered by a new (but still 3499cc) direct-injection petrol V6 that consumes just 6.8 litres per 100km – almost 30 per cent less than before.

However, the new SL350 delivers 7kW less peak power than before at 225kW (down 7kW), while torque is up 10Nm to 370Nm. But because it has less to haul, the SL V6 now sprints to 100km/h in 5.9 seconds – three-tenths quicker than before.

Also fitted as standard with an optimised 7G-Tronic Plus seven-speed automatic transmission and fuel-saving idle-stop function is the only other new SL variant revealed so far, the SL500 (badged the SL550 in the US).

The SL500’s new twin-turbo 4.7-litre (4663cc) V8 produces 320kW and a meaty 700Nm of torque - up a respective 12 and 32 per cent over the 285kW/530Nm 5.5-litre naturally aspirated V8 it replaces, despite being downsized by 0.8 litres.

Combined with its lighter body, the new SL500 sprints to 100km/h in 4.6 seconds (eight-tenths quicker than before) and consumes 9.4L/100km - 22 per cent less than the existing SL500.

Based on those impressive performance and efficiency gains, the new twin-turbo V8-powered SL63 AMG and twin-turbo V12-powered SL65 AMG performance leaders should offer both outrageous acceleration and family-car economy.

The body of the SL – a model that dates back to the legendary 300SL ‘Gullwing’ model of the early 1950s – is comprised of a mix of chill-cast, vacuum die-cast, stamped and extruded aluminium, resulting in an overall torsional strength of 19,400Nm per degree.

Mercedes says 89 per cent of the next SL’s new body structure – which is 110kg lighter than before - is aluminium. Exceptions are the tubular steel A-pillars and header rail, and the magnesium rear bulkhead, while the only plastic body panel is the ‘soft nose’ pedestrian-friendly grille.

The result is that the new SL500 is 125kg lighter than the model it replaces, while the SL350 is some 140kg lighter than before.

Final kerb weights have not been revealed, but the current SL350’s kerb weight tips the scales at a hefty 1825kg, meaning the new model should dip under the 1700kg mark, while the current SL500 is a hefty, meaning it should drop to about 1785kg.

“The effect is rather as if a heavyweight-class passenger had got out of the car,” said Dr Thomas Rudlaff. “The result is perceptible and measurable. Less weight means more dynamism and less consumption. In other words: the motoring enjoyment increases, the environmental burden sinks.”

The weight and consumption reductions would have been greater had the SL now grown significantly in all directions. Compared with the old SL, its is 50mm longer and 57mm wider, liberating 37mm more shoulder room and 28mm more elbow room.

The new R231-series SL also employ a high proportion of aluminium in its suspension set-up to reduce unsprung weight, including all rear-end wheel location components and the front axle’s steering knuckles and spring links.

Two suspension systems will be offered, including the standard layout with steel springs and semi-active adjustable damping, and the optional self-levelling, height-adjustable hydraulic Active Body Control (ABC) system, both linked to Direct Steer - a new variable-ratio speed-sensitive electromechanical power steering system.

The next SL will usher in at least two more new technologies, including the Magic Vision Control windscreen washer/wiper system that channels water directly in front of the wiper blade – which along with the washer fluid bottle can also be heated to negate snow/ice build-up - to eliminate splash.

Benz says the car can also be driven to its electronically limited top speed of 250km/h with the roof down - without dirtying its side windows.

Then there is the FrontBass sound system, which Mercedes says uses free spaces in the car structure ahead of the foot wells as resonance chambers for the woofer speaker system, resulting in better sound with the roof up or down while freeing up space in the doors and interior.

The SL will continue to be available with a retractable hard-top that opens or closes in less than 20 seconds – this time mounted on a 6kg lighter magnesium frame and available in either glass or with the electro-chromic Magic Sky Control coating, which debuted on the new SLK and switches between light and dark at the push of a button.

Cutting-edge safety systems are a give, including radar-based adaptive cruise control with automatic braking, six airbags, electronic stability control and an active bonnet reduce pedestrian injuries.

Convenience features include a hands-free boot-opening system operated by placing a foot below the rear bumper. Like similar systems, the proximity key must be close by, but the SL’s boot can also be closed in the same way.

In the US, the new SL will be launched as an ‘Edition 1’ model with standard 19-inch AMG wheels, an upgraded interior, special exterior paint and a top-end surround sound system.

SL sales are down by more than half so far this year in Australia, with just 23 examples sold to November, despite the most recent model refresh here in 2008.

The Mk6 SL will be one of three new models from Benz next year, including the all-new SLS AMG Roadster, the new M-class SUV and the redesigned GL-class seven-seat SUV.