The twisting Provencal mountain road seemed better suited to a rally race than for an afternoon tour in a luxury car, but the new 2004 Mercedes-Benz SL 600 is no ordinary roadster. Its highly evolved suspension and powertrain are astonishing examples of automotive technology, which took the car over cratered pavement, through tortuous apexes and up steep inclines as if it were the proverbial magic carpet.
This awe-inspiring dynamic skill is even more impressive in that it's been artfully integrated into a car with such sybaritic levels of comfort. Rarely has outright speed been so well complemented by so much cosseting of the passengers. Joining siblings SL 500 and SL 55, this new 12-cylinder-engined model is a fitting capstone to the hardtop roadster lineup, though it might seem, at first glance, somewhat of a redundant model, so close in engine output and performance is it to the AMG-built SL 55. There are some detail and trim differences between the two models, but perhaps the best way to illustrate the ccntrast is to liken the SL 55 to an iron fist and the SL 600 to that same fist cloaked by a velvet glove. The accoutrements of the SL 600 are essentially 500 SL spec but with a number of refinements and model-specific trim. In the cockpit, you'll find ruffled leather, embossed V12 emblems on the head retraints, soft-texture floor mats with chrome-colored lettering and a wood/leather steering wheel and automatic transmission gear selector. Among the many standard features are Mercedes' COMAND system, a CD changer and high-zoot sound system.
Keys to recognizing the SL 600 from the outside include chrome elements on the radiator grille, silver-painted brake calipers, V12 emblems on the side air intakes and bi-xenon headlights. The 18-in. wheels are also exclusive to the 600, and they're mounted by 255/40Rs in front and 285/35Rs out back.
The car specifications certainly create high expectations: Under the hood is a bi-turbo 12-cylinder 5.5-liter engine, virtually identical to the twelve found in the new Maybach ultra-luxury sedan. The newly developed engine, one of the most sophisticated petro-burners on the planet, puts out 500 bhp at 5000 rpm and an almost unbelievable 590 lb-ft (800 Nm) of torque. This prodigious pull, moreover, is ready at the press of the accelerator pedal, from an almost unbelievable 1800 rpm through 3600 rpm. This is one car where keeping the traction control system switched on is preferred, even on dry pavement.
The factory performance figures underline the effects of the SL 600's thrust: 0 to 62 mph comes up in just 4.7 sec., and when you need to pass a slower car, the SL can jet from 37 mph to 75 mph in a mere 4.9 sec. Top speed would probably be well in excess of 180 mph, but like all Benzes, a governer kicks in at 155 mph (which my co-driver and I hit on an amazingly short stretch of straight asphalt we found at the base of the mountains).
In keeping with most new offerings from Stuttgart's biggest carmaker, a host of electronic aids help insulate stupid driver antics from serious consequences. And all of these systems came into play on that challenging road near Aix en Provence as we explored the limits of the car's forward and lateral motions. The heart of the car's intrepid stability is Active Body Control, first introduced on the CL 500 midyear in 2000 and now found throughout the Mercedes-Benz model lineup. ABC complements the front and rear multi-link suspension setups by a seemingly magical reduction of body roll, almost to the point of nonexistence. This includes squat or dive elicited by foot-to-the floor acceleration or braking.
Its "works" include two computers, four control valves and 13 sensors, which identify body movement almost as quickly as it begins and provide data to the computers, which then provoke an engine-driven oil pump to operate four servos, all within a few milliseconds, to control the Airmatic suspension's damping and spring rates. The SL line was also the first of Mercedes' ABC-equipped models to have a load adjustment element added to the system, which takes the car's actual load into account when initiaing the process of the active suspension.
In addition to the unequalled level of handling provided by the system, it enhances the SL's dynamic safety by keeping the car's center of mass under control. This was especially appreciated by the passenger during the test drive, who wasn't having to constantly fight to stay in his seat.
Also welcomed by the helpless right-seat occupant was Sensotronic Brake Control, Mercedes' new electronic, "by-wire" braking system. The SL 600 approached bends with such rapidity that, at first, the passenger couldn't help making a reflexive push of his right foot, but just for the first few corners. Once the capababilities of Sensotronic were revealed, virtually all fear factor was erased from the drive.
The system begins with four-piston fixed-caliper brakes with aluminum piston components and vented, drilled discs in front; in backare single-piston floating calipers with aluminum casings which clamp internally vented discs. The electronics interface between pedal and calipers is made up of a microcomputer, wheel pressure modulators, hydraulic pressure reservoir and an electrically driven hydraulic pump. Though hydraulics are still the driving force behind the calipers gripping the pads, the whiz-bang modern electronics add several layers of advantages over conventional systems.
The microcomputer, for instance, sends the correct amount of braking force to each wheel and more quickly, leading to better stability and quicker stops. The high-pressure reservoir also contributes to shorter periods between pedal application and braking, and it also allows full braking power even when the engine is off. The wheel pressure modulators, which regulate the braking at each wheel, which not only ensures optimum stopping but works with the ESP stability control to help stabilize a swerving car.
Assistance in effectively applying the brakes is also part of the system. For instance, if the driver tranfers his foot quickly from the accelerator pedal to the brake pedal, the sytem recognizes this as a potential emergency situation and readies the brakes by increasing pressure in the connectors and lightly pressing the pads against the discs. Full-power braking is then available as soon as the pedal is completely pressed. Mercedes says this decreases stopping distances from 80 mph by three percent.
And that's not all. If braking occurs during cornering, the system will increase pressure to the outside wheels and lower it to the insides, thus reducing the risk of locking the inside wheels. If it's wet, the system will apply short, transparent impules to the discs, wiping off any layer of water that might impede braking response. It works whenever the windshield wipers have been activated.
In the event of an electronic glitch in the system, a tandem hydraulic cylinder, which normally is decoupled from the system, will operate the front brakes. Also, pedal feel, an important aspect of a driver's response times, has been made more optimum, eliminating any of the pulses that otherwise might be felt from the ABS system. Simulator testing shows that stopping distances from 40 mph can be reduced by up to 6.5 ft in this way.
All of this technological wonderfulness, however, is virtually subsumed by the greatness of the V12. Mercedes-Benz makes more passenger-car V12s than any other manufacturer, this newest example is a sterling example of the firm's engineering prowess. Light weight and smooth operation are hallmarks of the mill, the 60* vee angle ideal for balancing intertial forces and moments at the source.
Highlights of the engine's architecture include a diecast aluminum crankcase; diecast magnesium cylinder-head covers; forged steel connecting rods, fracture-split for optimum fit; induction-hardened forged steel hollow camshafts; high-strength aluminum alloy pistons; a weight-optimized forged-steel crankshaft; and a diecast aluminum sump. Following Mercedes' recent valvetrain technology, each cylinder has three valves to reduce thermal losses at the exhaust stage and optimizing catalytic converter warm-up after a cold start. Twin catalytic converters, each with two ceramic monolith elements are situated close to the engine to further aid quick warm-up.
The pair of turbochargers are placed within the exhaust manifold, each controlled by a wastegate which is controlled electropneumatically by the ECU. Two watercooled intercoolers, mounted on the cylinder head covers cools the compressed air by up to 212* F (100*C). The intercoolers are themselves integrated in a low-temperature circuit, whereby an electric circulation pump transfer the heat between the intercoolers and a low-temperature cooler located in front of the engine. Combustion is handled by an advanced alternating-current twin-spark ignition system, which recognizes any misfires at the spark plugs through a constant ionic current measurement. Supplemented by torsional vibration analysis at the crankshaft, this unprecedented (for a 12-cylinder engine) combination guards against any damage to the catalytic converters via misfire.
The 600's release date in the U.S. is set for some time in the early fall. Pricing had not yet been determined as of this posting, but estimates put it in the mid $120,000s. Of the 8,000 to 10,000 SLs Mercedes expects to sell during the year, about 1,000 will be SL 55 AMGs and only 400 to 500 will be SL 600s.