I have to be careful. There are a lot of police around today," said Jurgen Weissinger. He's the chief engineer for the complete Mercedes-Benz sports car line -- and specifically for the highly camouflaged SL550 in which I was a passenger, the model to be revealed at the 2012 Detroit show. That we were rocketing uphill on a winding two-lane mountain road at about 110 mph made his words slightly inappropriate, but since the car felt as if we were proceeding quietly at half that speed, I was relaxed and just enjoyed the ride.
When the SL series started some six decades back with sports racing cars, the chief engineer for the project was Rudolf Uhlenhaut, who had been responsible for engineering Mercedes grand prix cars in the 1930s. He was famously known to be an exceptionally capable driver, as fast as -- or even faster than -- the drivers of the racing team, although he never competed in motorsports. Born in London, he spoke English like a native. Weissinger very much reminds me of the great man, in that he's fluent in English and is as reassuringly masterful on the road as any of the world-champion racing drivers I've ridden with over the years. Weissinger knows the roads in the Swabian Alps south of Stuttgart like a native because he is one, born and raised in the area he likes to use for testing, so his local knowledge removes one more variable from exploration of a car's ability. And this SL's ability is considerable. The ride is amazingly comfortable, worthy of a limousine yet dead flat and free of any hint of wallow or sogginess. "The springs are soft, the damping firm," Weissinger offered, but he had no need to explain; the chassis spoke for itself. The SL is completely new, with a cutting-edge chassis made entirely of aluminum. Massive chilled-cast aluminum structural members are joined with extruded sections by bonding, bolting, MIG welding, and friction-stir welding to make an enormously rigid structure to which all-new suspension elements are fixed. They're aluminum, too.
You'd expect a considerable reduction in total weight from the change of principal structural material, and the savings is 240 pounds for the body-in-white, despite a more than 20 percent increase in torsional rigidity. The engineering goal seems to have been to make the SL feel as though it's machined from a huge billet, and if that was the intent, it was attained.
The direct-injected aluminum V-8 engine is familiar from the CL550, a twin-turbocharged affair from which 429 hp and an impressive 516 lb-ft of torque is drawn. It sounds wonderful, which is not accidental. "We worked on the sounds the engine makes, tuning the exhaust system so that it is sporty but not loud," said Weissinger, putting his foot down to demonstrate the point. With the seven-speed automatic, ratio changes are extremely smooth, and the sounds tell you what you can't really feel since there are no abrupt changes of thrust as the car accelerates -- smoothly, to 60 mph in only 4.5 seconds.
It was a brisk fall morning, but we were comfortable in the open car, the heating and ventilation system ensuring proper conditions in the cockpit no matter what was happening outside. To that everyday-usability point, the SL is the first to receive Mercedes' new Magic Vision Control windshield wipers. Two separate washer-fluid circuits feed laser-drilled holes on either side of the wiper. When washing the windshield, fluid is sprayed only on the leading edge of the wiper. The result is no glare, very little wasted water, and, since the system sprays only on the downstroke with the top down, there are no unwanted showers for the passengers. The system automatically determines the amount of fluid to use, too -- more in cold, snowy conditions and less in the dry and dust. As an option for cold climates, the entire system can be heated, the reservoir using engine coolant and the hoses and wiper blades warmed by 270 watts of electric heat.
Thoughtful space utilization compelled Mercedes to locate the SL's two 8.5-inch subwoofers in the footwells, using as resonating chambers space that would have otherwise gone unused. In addition to moving the sound stage in front of the passengers, removing the largest speakers from the doors eliminates rattles and allows for a wider cabin.
An optional photochromic glass roof can vary from transparent to opaque at the driver's command, and Mercedes claims that the top takes up a relatively small percentage of rear body volume by the standards of a retractable hardtop. The result is increased luggage space and room for the proverbial set of golf clubs. This is decidedly an all-season, everyday roadster.
If at first the SL line of production cars was sharply separated into the fast, racing-derived 300SL Gullwing coupe and the sluggish 190SL boulevard tourer in 1955, by 1963 the two were replaced by a single model that combined sporting ability -- the 230SL won the difficult Spa-Sofia-Liege long-distance rally from Belgium to Bulgaria and back -- and comfort. That combination has been the policy for almost fifty years now. In this R231 iteration, "every comfort and safety feature of the S-class, standard or optional, is available on the SL," says Weissinger.
That the Mercedes-Benz SL continues to combine, in one model, the performance of a supercar with all the attributes of a luxury car is an extraordinary achievement. The SL is unique in these attributes among today's roadsters, and as the most iconic vehicle of the entire Mercedes lineup, the switch to aluminum construction and direct-injected turbocharged engines helps put the SL back at the leading edge of technology -- something that was missing from the car it's replacing. How and whether that translates to an exhilarating driving experience, we'll find out for ourselves in a few months.
2012 Mercedes-Benz SL
Base price $105,000 (est.)
Engine 32-valve DOHC twin-turbo V-8
Displacement 4.7 liters (285 cu in)
Power 429 hp @ 5250 rpm
Torque 516 lb-ft @ 1800 rpm
Transmission 7-speed automatic
Length 182.0 in
Width 73.9 in
Wheelbase 101.8 in
Track F/R 63.0/64.0 in
0–60 MPH 4.5 sec