Mercedes Breaks New Ground to Lighten CL Coupe

GENEVA - Mercedes-Benz has never been known as a maker of lightweight cars, but it has taken a very serious stab at weight reduction with its new flagship CL Coupe: It's smaller and about 750 lbs. (340 kg) lighter than its hulking predecessor, which weighs almost 5,000 lbs. (2,300 kg).

Set to go on sale late this year in Europe and early next year in the U.S., Mercedes forecasts global sales of 3,500 in 1999 and 9,000 units in 2000. Mercedes believes the new coupe will help it grab a 30% share of the worldwide 30,000-unit exclusive luxury coupe market.

Because it will be produced in low volumes - and likely be priced at more than $90,000 - Mercedes can afford to implement some innovative materials strategies, including a hybrid body construction that incorporates not only high-strength steel and aluminum but magnesium and plastic as well.

The car's construction is so unique that it actually now has to be built on its own separate production line where aerospace assembly techniques, such as riveting and adhesive bonding, are used along with more conventional welding. Mercedes dedicated an area of its Sindelfingen, Germany, plant and invested $195 million (DM350 million) in new buildings and equipment to accommodate this new process.

The hood, rear fenders, roof and other major exterior parts are aluminum. So is the roof frame, the support structure for the engine and transmission, and front suspension components. The front fenders and trunk lid are made of thermoplastic. The door inner panels are made of magnesium.

Steel is used in zones that are highly stressed in a crash, such as roof pillars, side members, crossmembers, and bulkheads as well as the front underbody, front-end structure and rear floor.

Mercedes claims to be the first in the world to use die-cast magnesium for large shaped products such as the inner shells of the Coupe's doors.

Compared with conventional steel door inners, this method permits the numerous brackets and fixing points for the window lift, door lock and other components to be integrated into a single process with much better formability. Subsequent welding no longer is required.

A special powder coating is used for corrosion protection and at the same time meets the requirements for adhesively bonding the magnesium inner shells with the aluminum sheet of the outer door.

The aluminum/magnesium construction of the doors chops the CL's weight by 34% compared with steel while meeting strict safety requirements, Mercedes says.

Plastic components were used not only to save weight but lower damage costs as well. Mercedes says the thermoplastic front fenders show no trace of damage after collisions of up to 9 mph (15 km/h) and trims 4.4 lbs. (2 kg) from the car.

The plastic trunk lid has another advantage: antennas for the phone and navigation system can for the first time be built into the trunk lid because plastic - unlike steel - does not interfere with reception.

Despite the unusual mix of materials, the CL body is 37% stronger than its predecessor and withstands the toughest crash tests in the world, Mercedes says.

And the new coupe still retains the vehicle's trademark performance and luxurious trimmings, the carmaker adds.

Both the CL 500 and CL 600 are designed with several goals in mind: exemplary safety, maximum comfort and low fuel consumption, the company says.

The CL coupe is loaded with technology, including bi-xenon headlamps, electronic stability program (ESP) with brake assist, automatic climate control with sensor monitors, parktronic, side impact door-mounted airbags, Speedtronic and head protection curtain airbags.

The CL 600 also gets a new 367-hp

V-12 engine that achieves 17 mpg (13.8L/100 km) in the new European driving cycle, 20% more fuel efficient than the automaker's previous 12-cyl. coupe. This engine also can switch off six cylinders when they are not in demand achieving about a 20% reduction in fuel. The CL 500's 306 hp V-8 also can be optionally fitted with the cylinder cutout. - Andrea Wielgat and Drew Winter