The SL 55 AMG high-performance sports car comes with a 5-speed automatic transmission which sporty drivers can operate using a race car-style steering column gearshift. The Mercedes-AMG engineers have also adapted the brakes, axles, wheels, tyres and the entire power train of the Roadster to the high engine output. Visually, distinguishing features of the SL 55 AMG include bumpers with dy-namic AMG bodystyling, distinctive side skirts, 18-inch multi-spoke wheels and four chromed exhaust pipes.
The engineers at Mercedes-AMG GmbH have developed a sports car which, in terms of power delivery and torque characteristics, sets new standards in the eight-cylinder roadster class.
The new bodystyling, and classic AMG-style bumpers are clear indications of the phenomenal power contained within this car. Equally, the powerful sound produced by the newly developed engine, even when idling, unequivocally confirms that the eight cylinders form a powerpack of epic proportions.
A quick touch of the accelerator is all it takes to feel and experience this power. At a mere 1500 rpm, the driver can elicit no less than 500 Newton metres of torque from the V8 engine, rising to 650 Newton metres at 2000 rpm and 690 Newton metres at 2500 rpm. The rev counter still only displays 2650 rpm when maximum torque is reached: a massive 700 Newton metres.
The power curve is just as steep, reaching its peak of 350 kW/476 hp at 6100 rpm. No other current Mercedes passenger car can match the new SL 55 AMG in terms of pure power.
On-the-road performance is equally impressive: it takes the new AMG Roadster just 4.7 seconds to accelerate to 100 km/h from a standing start. And only a little over 16 seconds for the red speedometer needle to reach the 200-km/h mark. The speed is piled on until the microcomputer cuts in at precisely 250 km/h to electronically limit the power delivery. The scale on the speedometer goes up to 300 km/h, showing just what this exhilarating high-performance sports car is theoretically capable of.
The impressive power development in the eight-cylinder engine is largely down to a newly developed mechanical supercharger enthroned between the cylinder banks. It works on the principle of a Lysholm compressor and ensures about 30 percent more charge pressure than comparable, mechanical supercharging systems. The maximum charge pressure is 0.8 bar. The engine management unit calculates whether to use the scroll compressor depending on the engine speed and load. With lightning speed, the electronic system controls an electromagnetic clutch which drives the compressor by means of a separate poly-V-belt. The advantage of this direct link to the crankshaft is that the supercharger can spontaneously react when the driver presses the accelerator and provide powerful thrust at an engine speed barely above idle.
Nearly all the mechanical components in the original 5.0-litre standard production engine had to be modified when developing the V8 power plant. The AMG engineers’ experience of developing high-performance engines for motorsport stood them in good stead during this phase.
The new bore/stroke ratio (92 : 97 mm) means the displacement of the AMG engine is now exactly 5439 cc; 473 cc more than the engine in the SL 500.
In the SL 55 AMG, the standard-fitted automatic transmission as used in the new SL-Class receives a steering wheel gearshift and an additional manual transmission mode. This means that, for the first time in a series-produced Mercedes car, motorists who fancy themselves as racing drivers can opt for a Formula-1-style gearshift with two selector switches located behind the top two steering wheel spokes.