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The Deep Dive: Next Mercedes-Benz SL Loses Weight, Gains a Ragtop

Mercedes-Benz is about to reinvent its roadster twins, the SL and SLK (the current versions are pictured), on a new lightweight sports car architecture. While the SLK will retain its retractable hardtop, the SL replacement is to feature a classic soft-top. Both will go on a strict diet. The new Mercedes roadsters are still about six years out, but many details have emerged.

Back to the roots

The aluminum-body, six-cylinder W198 Mercedes 300SL, offered as a gullwing coupe and fabric-top roadster, was the purest two-seater ever to wear the famous three-pointed star. The 190SL that followed turned out to be an unremarkable anti-climax. The pagoda-roofed W113 was, in essence, a lady's car. The chrome-laden R107 looked and drove like a shortened, topless two-door S-class. Bruno Sacco's R129 recovered a dash of the roadster feel, but the overweight, quad-headlamp SL that replaced it introduced the space-consuming retractable hardtop. The current model, launched in 2012, likewise targets well-to-do gentlemen drivers, but is neither Sporty nor Light. Although the current generation still has a lot of life left in it, Mercedes decided late last yea rto replace it with a hardcore, back-to-the-roots concept. In an even more significant move aimed at cutting costs, the next SL will be paired with the new SLK.

New Sports Car Architecture

Global demand for open-top two-seaters is steadily declining, which has Mercedes and its competitors scrambling to reduce development and production costs. (The BMW-Toyota sports car venture is one such example, the Mazda-Fiat partnership is another.) Mercedes' solution is an all-new components set called MSA, for Modular Sports car Architecture. It will underpin both the next SLK (R173, out in early 2020) and the all-new SL (R232, due in March 2021). Although the changeover is still almost six years away, the MSA plan is said to be irrevocable,an integral part of the grand scheme of things in Stuttgart, which also includes MRA (Modular Rear-wheel drive Architecture, for C-class and up)and MHA (Modular High-floor SUV Architecture, for GLK and up). All three architectures aim to cut costs through greater standardization and to offer greater flexibility in vehicle dimensions, materials, drivetrains, and body styles.

Lower Center of Gravity, Better Dynamics

Why invest in a separate sports car architecture, rather than building both the SLK and SL off of the architecture used for rear-wheel-drive sedans? All previous SLKs have, in fact, been C-class derivatives while the SL has been, toa varying degree, genetically linked to the E-class. Cutting that umbilical cord allows both roadsters to gain better balance and proportions. MSA will have its engines and transmissions mounted much lower than in Mercedes passenger cars to push down the center of gravity. The firewall will sit further back to create a better-balanced front-mid-engine layout.

MSA will be very flexible. The only fixed parameter is the distance between the aforementioned firewall and the front axle. All other dimensions are fully scalable. The main modules will includea choice of steel suspension or Airmatic, a variety of brake setups, and the 4Matic all-wheel-drive system, a firstfor both the SL and SLK. The SL bodyshell will likely be made of aluminum with some reinforcing carbon fiber and magnesium accents here and there. The lower-priced SLK remains steel-intensive, but will wear lightweight body panels,sources say. Weight-saving targets are more than 330 pounds for the SL and about 220 pounds for the SLK.

Classic cloth

All that still doesn't explain the decision to ditch the hardtop in the SL, especially considering that the car has been relatively popular: global SLK sales dropped from 30,000 to 24,000 units from 2012 to 2013, but SL sales increased from 10,000 to 12,000 in the same period. Why would Mercedes change the roof treatment on the more expensive, more successful car?

"It's a complex issue,"explains a board member intimately familiar with the issue. "Differentiation is the key driver.The SLK and SL are too close in application, appearance and appeal. Design is another important factor. We are quickly moving away from the old wedge-shaped silhouette, which entailed a tall and boxy rear that was perfect for accommodating a big and heavy roof."

Design of the New SL

For better styling and aerodynamics, the new Mercedes brand language, under the direction of Gorden Wagener, is undergoing a dramatic change. Compare, for example, the outgoing C-class sedan with the new one. The next SL is a butch, almost mean-looking sports car with a big mouth grille, aggressively styled headlamps, a prominent Mercedes star framed by two chrome bars, large secondary air intakes feeding brakes and intercoolers, subtle drag-cutting aids, small waffle-shaped side vents, and two narrow power bulges on the engine cover. The rear will be low but muscular, rounded yet sporty, and aerodynamically efficient and yet distinctive. You'll be able to spot it from afar by its neatly integrated horizontal taillights.

The next SL's classic-looking, tight-fitting fabric top takes up so little space when folded that it barely exceeds the bulk of a wind deflector. "The appearance is so much more in line with the dynamic character we want to re-emphasize," the board member explains.

Despite those ragtop advantages, the next SLK will again feature a roof composed of solid panels, though they will be lighterand more space efficient. For the SLK, too, Mercedes takes a good look back at the first generation model, whichwas crisp and clean instead of decorative and ornamental. Expect a more homogenous whole—rather than a front and rear end that seem to belong to two different cars—along with a sportier and more sculptured shape.Priorities are aerodynamic efficiency, substantial weight reduction, and superior driving dynamics. The SLK promises to become, at last, a sharply focused Cayman/Boxster rival instead of a laid back GT.

New SL Engines

Theoretically, Mercedes could launch an ultra-efficient, superlight SL powered by an uprated four-cylinder CLA engine good for about 400 hp. But such an extreme specification would likely confuse customers and hurt brand image, which is why we expect the all-new 3.0-liter straight six to become the mainstay powerplant. The twin-turbo engine should develop 365 hp in the SL300 and atleast 435 hp in the SL400.

Those in the know predict an SL63 AMG equipped with a 570hp, 4.0-liter V-8. What about a V-12 and a diesel? There will certainly be enough room under the lid for the 5.5-liter twelve-ender, but how much longer will there be a market for a very expensive SL65 AMG rated 630 hp? As far as the oil burner option goes, product planning is reportedly looking at a six-cylinder SL400 CDI good for 315 hp and 490 lb-ft.

When the new smaller SLK, expect a 230 hp SLK300, a 335 hp SLK350 and, for Europe, at least, a 230 hp SLK250 CDI diesel. The AMG model will be a 435 hp SLK55, and there may even be a Black Series edition rated at 465 hp waiting in the wings.