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Sunday, November 16, 2008
2004 Mercedes-Benz SL 600
(from Mercedes-Benz Press Release) Performance, luxury, refinement -- just three of the outstanding characteristics of the new SL 600 which will complete the successful Mercedes-Benz SL-Class Roadster model range from spring 2003.
A look under the bonnet reveals a technological tour de force in the shape of the newly developed Mercedes twelve-cylinder engine. Equipped with two turbochargers, an air/water intercooler, three valves per cylinder, twin-spark AC ignition and other high-tech innovations, the new unit is one of the most advanced car engines in the world. And one of the most powerful in its class, too: the V12 engine has an output of 368 kW/500 hp and maximum torque of 800 newton metres, which is available from just 1800 rpm and remains on tap at a constant level all the way up to 3600 rpm.
With figures like these, it is clear that the SL 600 has ample resources to cope with every driving situation. It accelerates from 0 to 100 km/h in only 4.7 seconds and polishes off the 60 to 120 km/h sprint in 4.9 seconds. The maximum speed is electronically limited to 250 km/h.
The twelve-cylinder unit combines its impressive performance with exemplary smoothness and extremely quiet operation -- ideal conditions for a refined, highly enjoyable driving experience.
Standard equipment: COMAND, CD changer and sound system
The theme of refinement and enjoyment is also picked up by the exceptionally high level of standard equipment in the new top-of-the-range SL-Class Roadster. Based on the features found in the already luxurious SL 500, it includes interior appointments such as ruffled leather, embossed V12 emblems on the head restraints, soft-texture floor mats with chrome-coloured lettering as well as an elegant wood/leather steering wheel and a wood/leather automatic transmission selector lever. The COMAND system, a CD changer and a sound system are also standard equipment in the new twelve-cylinder sports car from Mercedes-Benz.
The external cues which identify the SL 600 comprise a radiator grille with discreet chrome elements, silver-painted brake callipers, V12 emblems on the side air intakes and bi-xenon headlamps. The light-alloy wheels which are fitted as standard are distinguished by their exclusive rim design. At the front, the sports car is equipped with 255/40 R 18 tyres, while the rear wheels have 285/35 R 18 tyres.
Parking and manoeuvring is made more convenient by the PARKTRONIC system which also forms part of the standard equipment. Superb high-tech systems, such as Active Body Control (ABC), Sensotronic Brake Control (SBC™) (a new type of electrohydraulic brake system), the automatic climate control system which is equipped with advanced sensors, and the innovative vario roof add the perfect finishing touches to the driving experience and also reflect the special position which the SL 600 occupies among the sports cars in its class.
In addition to the new V12 model, SL-Class customers have a choice of three other engine versions: the six-cylinder SL 350 sports car with 180 kW/245 hp, the SL 500 with a 225 kW/306 hp V8 engine and the SL 55 AMG which develops
368 kW/500 hp.
V12 engine: state-of-the-art lightweight power plant features aluminium, steel and magnesium components
The newly developed twelve-cylinder engine of the SL 600 reflects the wealth of experience and expertise which Mercedes-Benz brings to the development of high-tech power plants. The Stuttgart-based automaker is the world's largest manufacturer of V12 engines for passenger cars.
Diecast aluminium is used for the crankcase of the twelve-cylinder engine while the two cylinder-head covers are made from diecast magnesium. Fracture-split conrods made from high-strength forged-steel alloy, pistons made from a high-quality aluminium alloy, hollow camshafts of induction-hardened forged steel, a weight-optimised forged-steel crankshaft and a diecast aluminium sump feature among the other lightweight components of the engine which weighs just 263 kilograms and has a power-to-weight ratio of 0.71 kg/kW.
This exemplary lightweight design is complemented by the engine's equally impressive credentials with regard to its noise emissions and vibration characteristics. These qualities are inherent in the design of the new V12 unit: the V-angle of 60 degrees balances inertia forces and moments at source, without the need for special balancer shafts.
Cylinder head: rapid warm-up of catalytic converters thanks to three-valve technology
A camshaft in each of the two banks of cylinders controls the three valves per cylinder via low-friction roller-type cam followers. Each valve has a cam follower and is adjusted hydraulically.
The three-valve technology reduces thermal losses at the exhaust stage and speeds catalytic converter warm-up after a cold start. In conjunction with two large ceramic catalytic converters positioned close to the engine this has a decisive influence on ensuring that the new V12 reliably complies with the strict EU-4 limits. Emissions are controlled by two catalytic converters which are arranged close to the engine and which contain two ceramic monoliths each.
Turbochargers: bi-turbo system with two water-cooled intercoolers
The space-saving positioning of the twin turbocharger turbines in the exhaust manifold maximises their efficiency. A wastegate control system enables the flow of exhaust gases to the turbines to be matched to the current operating point of the engine. Wastegate valves are integrated into each turbocharger and operate electropneumatically, receiving their commands from the engine control unit.
The compressed air flows through two engine-mounted water-cooled intercoolers located on the cylinder head covers. Depending on the engine load the air is cooled here by up to 100 degrees Celsius, so that its temperature and density are optimised for the combustion process.
The water-intercoolers are integrated in a special low-temperature circuit. A demand-controlled, electric circulation pump transfers the heat between the water-intercoolers and the low-temperature cooler located in front of the engine which passes the heat from the water to the cooling air.
Ignition: AC system with constant ionic current measurement
A powerful microprocessor controls all the engine functions, making use of various additional sensor data to control the two turbochargers:
• Pressure and temperature sensors in the charge air distributor are used to calculate the intake air mass.
• A sensor in front of the throttle valve actuator registers the charge pressure.
• Sensors upstream and downstream of the air filter monitor the pressure on the clean air side so that the speed of the turbochargers can always be adjusted to suit the situation.
In addition, the engine computer controls an advanced alternating-current twin-spark ignition system whose outstanding feature is constant ionic current measurement at the spark plugs. This recognises any misfires and therefore has a major role in protecting the catalytic converters -- should the ionic current fall below a certain value the fuel injection for the cylinder concerned is automatically interrupted at once. Ionic current measurement is supplemented with torsional vibration analysis at the crankshaft. The combination of both control signals in this way not only results in an unprecedented degree of accuracy in the detection of misfires, but also does so across the entire load and speed range of a twelve-cylinder engine for the very first time.
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