Lightweight construction is an increasingly pivotal element of automotive R&D, and an absolute must have at the upper end of the premium segment. While Audi continues to reap the benefits of its aluminum spaceframe approach, BMW is putting a clear emphasis on carbon fiber. For its project i cars, BMW has teamed up with SGL Carbon, a leading systems supplier that recently also attracted the interest of the VW group. For its part, Mercedes-Benz has signed a cooperation deal with Toray, a Japanese carbon fiber provider. Both SGL and Toray are seasoned material specialists that have also acquired strong know-how in terms of vehicle architectures, manufacturing processes, and cost-cutting methods.
Mercedes started to explore the higher output potential of the lightweight black gold back in 2010. Although they had gained some experience when working together with McLaren on the SLR, the Germans needed a credible answer to the BMW i3 and i5, they needed a solution that met their cost and volume targets, and they needed it fast. While Audi is still hesitating to jump on the synthetic bandwagon, the VW group is also trying to make up for lost time and has selected Lamborghini as the interim carbon fiber flagship brand.
Well advised by their trend spotters, MB’s Dieter Zetsche and his chief engineer Thomas Weber understood the significance of this fuel-saving, eco-friendly and potentially brand-shaping trend early on in the game. In the course of last year, Mercedes compiled three alternative carbon fiber vehicle projects:
- B Clever, a high-roof four-door hatchback, much like the new B-class, but far more sophisticated as far as design and engineering. To be equipped with a diesel hybrid (for the European market) and with a plug-in hybrid (for the rest of the world), B Clever was aimed squarely at the upcoming BMW i3 and i5.
- SCS, a brand-new front-engine two-seat supercar positioned one full notch above the SLS. This racy low-drag showpiece would outshine the BMW i8, and it would be an unmistakable gesture towards McLaren. (The former allies from the UK were at one point meant to partner with Mercedes for a three-piece sports car portfolio of which the MP4 is the first chapter.)
- E Superlight, a four-door notchback loosely based on the footprint of the next-generation E-class. A sedan may not have the marketing impact of a supercar or the deep green luster of a subcompact, but the E-class segment is Mercedes heartland and it harbors all the core brand values.
The B car approach was quite clever indeed, but it would have been very expensive to produce, and with no Quandt family to personally carry the financial and entrepreneurial risks (as at BMW), the proposed Golf-plus-size hatchback was first to fall through the grid. While the SCS had the potential for greatness, it was feared to be the wrong message at the wrong time. It also might have gotten lost in the barrage of upcoming MB sports cars, which starts with the new 2013 SL, followed by an SLS facelift, then the smaller SLC coupé/roadster, and finally an SLS replacement that will also be carbon-fiber intensive but positioned well below the McLaren. That left the E Superlight, which is close to the CLS in size and is close to the S-class in price.
Getting the Look
Although E Superlight is said to borrow elements from ho-hum concepts like F800 (C-class-size) and F125 (S-class-size), we can only hope that the recent flamboyantly decorative shapes, questionable proportions, and over-the-top detailing will soon give way to a trend-setting architecture that is aerodynamically efficient, functional and versatile, pretty to look at, and sufficiently exciting to match the revolutionary content.
While we don’t know yet what visual theme, we do hear that the E Superlight features a radical door concept with relatively short rear pantograph panels that swing out and back. Thanks to the stiff and strong carbon fiber structure, there is no need for B-pillars, which should make entry and egress a truly grand experience. Although the suicide doors draw a certain parallel to BMW’s project i, Mercedes will go one step further by creating a full carbon fiber architecture that does without an aluminum chassis. This is said to not only reduce cost and complexity, it also brings the weight down further. In all, the E superlight is said to undercut the current steel-bodied E-class by nearly 800 pounds.
Powertrain and Production
The sole initially intended source of propulsion is a 150-hp fuel cell that drives the rear wheels in sync with a 50-hp electric motor. At a later stage, Mercedes may add a conventional gasoline or diesel engine, or a plug-in hybrid application.
Although the timing is still provisional, low-volume production is expected to commence in late 2015. By then, Mercedes will have gained plenty of carbon fiber experience by manufacturing body panels, suspension elements, and structural parts from the new material. By 2017, insiders expect an annual output of close to 20,000 E Superlight units, which is remarkably similar in volume to what the crew in Munich has in mind.
The biggest question mark seems to concern the feasibility of the fuel cell, for which the optimistic product planners have set a best-case scenario of 100,000 Mercedes passenger cars and vans for the same timeframe. But apart from some unresolved engineering issues (membrane, valves, connectors), the main markets also have still to establish a hydrogen infrastructure, and so far neither the politicians nor the manufacturers seem to be able to agree on maximum on-board tank pressures and on filling procedure norms. Having said that, the E superlight of course can fly without a fuel cell. After all, its main asset is light weight, and that is a benefit no matter what the powertrain.