March 13, 2009 For the first time in its 40 year history, the Mercedes-Benz performance brand AMG has developed a vehicle completely in-house: the Mercedes-Benz SLS AMG. This "super sports car" takes an AMG 6.3-litre V8 front-mid engine developing 420 kW/571 hp peak output, seven-speed dual-clutch transmission and sports suspension with aluminum double wishbones, wraps it in an aluminum spaceframe and throws in a set of always-in-style gullwing doors. The combination of the company's first ever use of an aluminum chassis and body frame coupled with lightweight, high-strength components such as a carbon-fiber driveshaft delivers a kerb weight of just 1620 kilograms and a power-to-weight ratio of 2.84 kg/hp. Provisional performance figures put acceleration at 0 to 100 km/h in 3.8 seconds with a top speed of 315 kmh.
SLS AMG features an aluminum chassis and body
Compared with the traditional steel design, the aluminum chassis and body results in a significant weight saving illustrated by the planned DIN kerb weight of 1620 kilograms, as well as meeting requirements in terms of passive safety. The car's design also delivers an ideal front/rear weight distribution of 48 to 52 percent and a low center of gravity according to Mercedes Benz.
AMG 6.3-litre V8 engine
The AMG 6.3-litre V8 engine achieves a peak output of 420 kW/571 hp at 6800 rpm. A power-to-weight ratio of 2.84 kg/hp comes courtesy of the low vehicle weight and the eight-cylinder, naturally-aspirated engine delivers maximum torque of 650 Nm at 4750 rpm. The Gullwing accelerates from 0 to 100 km/h in 3.8 seconds, before going on to a top speed of 315 kmh (all figures are provisional).
The principal measures to increase output include the all-new intake system, the reworked valve train and camshafts, the use of flow-optimized tubular steel headers and the de-throttling of the exhaust system. This results in much better cylinder charging, which feeds through into an increase in output to 420 kW/ 571 hp with maximum torque of 650 Nm. Mercedes-Benz says that the eight-cylinder engine responds swiftly to movements of the accelerator pedal, demonstrating much more pronounced high-revving flexibility across the entire rev range. They go onto to say that the switch to dry sump lubrication translates into a much lower position of the engine in the vehicle and lowering the vehicle's center of gravity has also paved the way for high lateral acceleration and exhilarating driving dynamics.
The use of high-strength components compensates for the increased engine load associated with the higher output. Forged pistons, a reinforced crankshaft bearing, optimized crankcase structure, along with improved lubrication with an on-demand high-performance oil pump ensure optimum durability. The engine weight has been further reduced resulting in a kerb weight of 206 kilograms and, in turn, a power-to-weight ratio of 0.36 kg/hp.
The improved catalytic converter should enable current and future exhaust emission standards such as EU 5, LEV 2 and ULEV to be met. The friction-optimized twin-wire-arc-sprayed (TWAS) coating on the cylinder walls – a process exclusive to AMG – also reduces fuel consumption, as does the on demand, map-optimized oil supply along with the regulated generator management. Mercedes-Benz says the fuel consumption for the SLS AMG is around 13 litres of Super Plus per 100 kilometers (NEDC combined, provisional figure).
Dual-clutch transmission with transaxle configuration and torque tube
The AMG 6.3-litre V8 engine delivers its power via a light weight carbon-fibre driveshaft at the rear axle – similar to the set-up used on the DTM C Class racing touring car. The transmission is mounted at the rear (transaxle principle) and is connected to the engine housing via a torque tube. A carbon-fiber shaft rotates at engine speed in the torque tube and Mercedes-Benz says the advantages of this sophisticated solution are associated with the rigid link between the engine and transmission and, in turn, the optimum support for the forces and torque generated. A new AMG dual-clutch transmission with seven gears takes care of power transfer and the transmission boasts fast gear changes with no loss of tractive force, says Mercedes-Benz. The driver has a choice of four different driving modes, ranging from comfortable to sporty, as well as a RACE START function. Optimized traction comes courtesy of the mechanical differential lock, which is integrated in the compact transmission casing.
The chosen solution with a front-mid engine plus transaxle configuration ensures what's said to be an ideal front/rear weight distribution of 48 to 52 percent. Further, mounting the engine behind the front axle has created the ideal conditions for consummate driving dynamics with precise steering, first-class agility, low inertia with spontaneous directional changes and outstanding traction according to Mercedes. Wheel location comes via double wishbones and hub carriers made of lightweight forged aluminum. The 'Gullwing' comes with 3-stage ESP® as standard, providing the driver with access to the three "ESP ON", "ESP SPORT" and "ESP OFF" modes at the push of a button.
Ceramic composite brakes, innovative flow-forming wheels
Braking is provided by either AMG high-performance composite brakes or the newly developed, optional ceramic composite brakes with larger brake discs. The ceramic brake discs will perform reliably at even higher operating temperatures thanks to their greater hardness; all combined with an impressive weight reduction of around 40 percent. Further to this, light-weight design was also a key consideration with the wheels: weight-optimized AMG light-alloy wheels – 9.5 x 19 inch (front) and 11.0 x 20 inch (rear) – based on the flow-forming principle reduce the un-sprung masses while increasing driving dynamics and suspension comfort. 265/35 R 19 (front) and 295/30 R 20 (rear) tires developed exclusively for AMG provide the grip.
The design and development phase for the SLS AMG got underway in the last quarter of 2006 and the intensive vehicle testing program will be completed by the end of 2009. The reinterpretation of the legendary Gullwing is scheduled to be launched in spring 2010.
David Greig
