The Technology Behind The New Mercedes-Benz SLS AMG

Engine and drive train

Exclusive high-performance eight-cylinder front-mid engine with dual-clutch transmission in transaxle configuration

Eight cylinders and 6.3 litres of displacement with a front-mid engine configuration, high-revving concept, dry sump lubrication and power-optimised intake and exhaust system: AMG has developed an impressive powerplant for the new 'Gullwing', which transports the super sports car into the top end of the output range. With peak output of 420 kW/563 hp, the AMG 6.3-litre V8 engine sets new standards, becoming the world's most powerful standard-fit eight-cylinder naturally-aspirated engine. Thanks to the targeted use of fuel-efficiency measures, fuel consumption of around 13 litres Super Plus per 100 kilometres (NEDC combined, provisional figure) has been achieved. Power transfer in the SLS AMG is handled by a new AMG dual-clutch transmission with seven gears, which is mounted at the rear in transaxle configuration and rigidly connected to the engine via a torque tube.

420 kW/563 hp peak output at 6800 rpm and 650 Nm  (479 lb-ft of torque) torque at 4750 rpm – the new high-performance eight-cylinder engine in the Mercedes-Benz SLS AMG impressively demonstrates the potential of the AMG 6.3-litre V8 engine unveiled in 2005 with the designation M156. Based on the M156, which develops 386 kW/525 hp and 630 Nm in the SL 63 AMG for instance, the new M159 eight-cylinder naturally-aspirated engine has been radically improved.

The principal changes relate to the intake and exhaust system, oil supply and crank mechanism. Over 120 parts and components have been redesigned – all based on the valuable insights gleaned from over 40 years of motor racing.

In design terms, the M159 – like its stablemate the M156 – is a completely autonomous development. The combination of high-revving concept and large displacement combines the best of both worlds: exhilarating high-revving flexibility accompanied by high pulling power at low engine speeds. The new AMG V8 for the 'Gullwing' delivers 545 Nm to the crankshaft as low down as 2500 rpm, while the maximum 650 Nm  (479 lb-ft of torque) is on tap at 4750 rpm – more than any other naturally-aspirated engine in this output and displacement class. This means the eight-cylinder engine promises dynamic acceleration, instantaneous pickup and sheer driving pleasure at the highest level, just as it does everyday relaxed motoring.

Key data at a glance: 

Optimised cylinder charging thanks to redesigned intake airflow

Optimised cylinder charging represents a key element in the increased output and torque. The recalculated, improved aerodynamic design of the intake airflow reduces pressure losses, while the all-new valve train improves the gas dynamics. The fully reworked magnesium intake manifold comes with perfectly matched variable resonance tube lengths. Eight velocity stacks, each 290 millimetres long and 51.5 millimetres in diameter, route the fresh air to the combustion chambers. Two electronically operated throttle flaps – each measuring 74 millimetres in diameter –, which are adjustable within fractions of a second, sit behind the new air filters with a volume just under 9500 cubic centimetres: they can be opened to their maximum in just 150 milliseconds. The result is exhilarating responsiveness. Two hot-film air mass sensors located behind the air filters provide the engine electronics with the necessary information about the temperature and density of the intake air.

Another special feature of the V8 engine is the sophisticated valve train, which is also derived from the powerful AMG racing engines. The 32 valves in the cylinder heads are operated by bucket tappets. Their space-saving design permits a stiff valve train and therefore high engine speeds with large valve opening cross-sections, which, in turn, boosts output and torque. The large intake valves have a diameter of 40 millimetres, while their opposite numbers on the exhaust side measure 34 millimetres. Unlike the racing engine, a maintenance-free valve train with hydraulic valve clearance is fitted.

Four continuously variable overhead camshafts

All four overhead camshafts are continuously variable over a range of 42 degrees. Both the intake and exhaust camshafts are adjusted as a function of engine load and engine speed, ensuring extremely high output and torque values and smooth idling, and especially low exhaust emissions. Depending on the engine speed, the valve overlap can be varied to ensure an optimal supply of fuel/air mixture to the combustion chambers and efficient venting of the exhaust gases. This variable camshaft adjustment is controlled electrohydraulically and monitored by the engine management system.

New exhaust system with two headers

The exhaust system has also been redesigned to optimise output: headers with precisely tailored tube lengths – likewise adopted from the world of motor racing – deliver a substantial increase in output and torque thanks to improved gas cycles. The large tube cross-sections in the newly developed, twin-pipe exhaust system effectively reduce the exhaust gas backpressure. Two relatively small centre silencers on the underbody and a large, transverse-mounted rear silencer help ensure optimum weight distribution.

Two backpressure-optimised bulkhead ceramic catalytic converters mounted directly on the header and two metal catalytic converters on the underbody ensure effective emission control and compliance with all current emission standards such as EU 5, LEV 2 and ULEV. The new AMG engine also comfortably meets the specific requirements of the U.S. market as well as On-Board Diagnosis II and oxygen sensor diagnosis.

Dry sump lubrication lowers the vehicle's centre of gravity

The engine position was a critical factor in the technical design of the SLS AMG. According to the specifications, the engine had to be as low and as far back as possible to keep the vehicle's centre of gravity low and ensure balanced weight distribution between the front and rear axle. The solution of fitting the eight-cylinder front-mid engine behind the front axle and combining it with a transaxle, results in a front/rear weight ratio of 48 to 52 percent.

The much lower position of the V8 engine results from the switch to the dry sump lubrication system, which does away with the otherwise necessary oil pan. The dry sump lubrication for the M159 comprises a suction pump, a pressure pump and an external 5-litre oil reservoir fitted in front of the engine. 13.5 litres of engine oil circulate throughout the entire system. The oil suction pump draws the oil directly from the crank chambers and the cylinder heads and pumps it to the external oil reservoir at a maximum rate of 700 litres per minute. The churning losses normally associated with immersing the crankshaft in the oil sump in the oil pan can be prevented by efficiently drawing off the engine oil, thus further improving the effectiveness of what is nonetheless a very efficient engine

The hydraulic oil pump, designed as a pendulum-slide vane pump, transports the oil from the external oil reservoir back into the engine, thus ensuring reliable engine lubrication even with the kind of high lateral acceleration commonly experienced on a private racing circuit. The demand-driven hydraulic oil pump takes its cue from the engine revs as well as temperature and load maps stored in the control unit. All of which lessens power loss within the engine, resulting in a substantial reduction in fuel consumption. The front wheel arches house two large radiators with a blower fan integrated on one side to effectively cool the engine oil.

Outstanding strength and optimum lightweight design also with the engine

Another innovation comes in the guise of the eight forged pistons that are 0.5 kilograms lighter than the cast pistons on the M156 entry-level engine. Pressure-controlled oil spray nozzles in the crankcase ensure optimal cooling of the highly stressed piston crowns. Another targeted weight reduction measure dispenses with steel liners to house the crankshaft main bearings. The crankcase on the M159 is made entirely of aluminium, weighing around 4 kilograms less than its counterpart on the M156. Aluminium bolts are also extensively used on the M159 to further reduce weight. Compared with steel bolts, this saves around 0.6 kilograms. The AMG 6.3-litre V8 engine weighs 206 kg (dry); this results in a first-class power-to-weight ratio of 0.36 kg/hp.

In typical motor racing fashion, the crankcase uses a rigid bedplate design on the closed-deck principle. The engine block and cylinder heads are cast from aluminium-silicon alloys (AlSi7 and AlSi17), which represent the state of the art in terms of weight, thermal and mechanical resistance and long-term strength. The engine specialists at Mercedes-AMG use a particularly advanced process for the eight cylinder walls on the M159 – as was also the case with the M156 – to produce a tribologically optimal surface, namely a coating applied by twin wire arc spraying (TWAS). The advantages of this TWAS technology patented by AMG are extremely low friction and wear, accompanied by outstanding long-term durability. A considerably harder surface is achieved compared to conventionally coated cylinder walls. In fact, the cylinder walls of the AMG V8 engine are twice as hard as conventional cast iron liners – a quantum leap for engine specialists.

Other high-tech components and systems adopted from the M156 include:

• the finely balanced crankshaft made out of forged steel;
• the water cooling system for the cylinder head using the highly thermal-efficient cross-flow principle familiar from racing engines;
• variable coolant control for optimum efficiency;
• the computer-controlled fuel supply with fuel pump integrated in the tank.

Powerful cooling module with weight-optimised design

Water cooling comes courtesy of a large cooling module mounted behind the radiator grille. The cooling module also includes the air conditioning condenser and the power-steering oil cooler. This innovation is particularly beneficial since it reduces weight by around 4 kilograms compared with previous components – while also increasing performance. A large suction-type fan placed directly behind the cooler expels the hot air as required.

Powerful control unit also provides generator management

The Bosch ME 9.7 AMG engine management system also provides generator management – another system that helps reduce fuel consumption. Sensors monitor the charge status of the vehicle battery and reduce the generator output as soon as the battery is sufficiently charged. To recharge the battery, the system specifically utilises the engine's overrun phases. The braking energy is converted into electric energy by means of recuperation.

Through the specific combination of fuel-efficiency measures, NEDC combined fuel consumption of around 13 litres Super Plus per 100 kilometres is achieved (provisional figure) – a first-class figure. Ultimately, the new SLS AMG is among the most powerful super sports car in its segment.

Engine production at the Affalterbach location

The new V8 powerpack for the 'Gullwing' is produced at the ultra-modern AMG engine workshops, according to the "one man, one engine" philosophy. That means the each complete engine is assembled by hand from start to finish by a single engineer. Every day the AMG engine manufacturing facility with its three floors covering 9950 square metres produces around 100 high-performance engines for a range of vehicle models.

AMG seven-speed dual-clutch transmission with RACE START

The new AMG dual-clutch transmission with seven gears, four driving modes and RACE START function is the ideal partner for the powerful eight-cylinder naturally-aspirated engine. The strengths of this technology, which originated from the world of motor racing, include spontaneous gearshifts with no loss of tractive force, the tailored-made control strategy and the supreme ease of shifting. Specially designed for the high-revving characteristics of the AMG 6.3-litre V8 engine, the dual-clutch transmission delivers optimum gear ratio adjustment with a close-ratio configuration. This means that the new transmission provides the 'Gullwing' driver with even more dynamic acceleration for maximum driving pleasure.

AMG DRIVE UNIT with fully automatic RACE START function

The AMG DRIVE UNIT is the central control unit for the dual-clutch transmission and all dynamic handling control functions. On the left next to the selector lever is the electronic rotary switch for selecting the four driving modes, including activating the RACE START function. This function allows the driver to call on maximum acceleration potential and ensures optimum traction to the drive wheels. The optimum start-off engine speed is set fully automatically and the 'Gullwing' accelerates instantly with its electronically controlled wheelspin – as an option also up to the top speed. The driver does not need to perform manual gearshifts; the transmission changes the gears with incredibly short shift times.

Four driving modes for maximum driving pleasure and ride comfort

The dual-clutch transmission supports upshifts under full load both in automatic mode, and manual mode where the gears can be shifted using the AMG shift paddles on the steering wheel. Four driving modes for maximum driving pleasure and ride comfort are available: "C" (Controlled Efficiency), "S" (Sport), "S+" (Sport plus) and "M" (Manual). In "C" mode, the car always moves off in second gear, while delivering highly efficient gearshifts. In "S" mode, the engine speed is allowed to reach a higher level in each gear; the downshifts also feel more spontaneous. The gearshifts are around 20 percent faster than in “C” mode. Switching to “S+” mode cuts another 20 percent off shift times, while “M” is the sportiest mode: here the AMG 6.3-litre V8 engine has even more bite, added to which the AMG dual-clutch transmission shifts gear another 10 percent faster – a reduction of 50 percent compared with “C” mode. In “M” mode, the transmission shifts gear in under 100 milliseconds.

Automatic double-declutching function for even more exhilaration

The automatic double-declutching function is active in "S" (Sport), "S+" (Sport plus) and "M" (Manual) modes. Every manual or automatic downshift is accompanied by precisely metered double-declutching – from “S” through “S+” to “M” incrementally. And this not only adds to the driver's emotional experience: the virtually load-free downshift minimises load-change reactions, which pays dividends particularly when braking into a bend on the racetrack and also enhances safety in the wet or on ice.

The new AMG dual-clutch transmission offers outstandingly compact dimensions and low weight of just 136 kilograms including the differential. The aluminium design and the absence of a conventional torque converter improve efficiency and help considerably reduce fuel consumption. The transmission casing also includes the mechanical differential lock with its decidedly sporty set-up that pushes driving dynamics to the limit.

Torque tube with carbon-fibre driveshaft between the engine and transmission

The dual-clutch transmission forms a fixed unit with the V8 engine via the torque tube. Engine and the transmission mounted at the rear axle – known as a transaxle – are connected to each other to ensure flexural and torque rigidity and to support each other. All of which translates into decisive advantages in terms of driving dynamics and ride comfort since this sophisticated solution provides a backlash-free drive train. The 1.64-metre-long torque tube comprises a one-piece aluminium sand-cast casing and weighs less than 25 kilograms. A driveshaft rotates inside the tube at the engine speed. As with the Mercedes-Benz C-Class DTM racing touring car, the shaft is made out of carbon fibre. A key advantage of this high-tech material: despite its high strength, the carbon-fibre shaft tips the scales at just 4 kilograms. Consequently, the 1.71-metre-long driveshaft, which has to transmit 650 Nm  (479 lb-ft of torque) torque from the engine to the dual-clutch transmission, is around 50 percent lighter than a steel equivalent.

The torque tube also accommodates a specially developed torsion damper, which reliably eliminates noise and vibration, thus optimising ride and noise comfort.

·                                                                                     Suspension and braking system

·                   Uncompromising high-tech from motor racing for consummate racetrack performance

Technology from motor racing – whatever applies to the complete drive train on the new Mercedes-Benz SLS AMG, holds equally true for the suspension and braking system. The aluminium double-wishbone suspension is tailored to consistent lightweight design and superb driving dynamics. The AMG high-performance braking system is also available as an option in an all-new, high-performance ceramic version.

The commitment of Mercedes-Benz and AMG to building an alluring super sports car that combines consummate racetrack performance with hallmark Mercedes long-distance comfort has given rise to an ingenious suspension layout. All four wheels are located on double wishbones with a track rod, a technology that has proven itself in motor racing, right through to Formula 1. With a double-wishbone axle, the wheel location and suspension function remain separate; the spring/damper struts are supported on the lower wishbone. The double-wishbone concept with its high camber and track rigidity positively locates the wheel with minimal elastic movements, providing the driver with an optimum sense of road contact when driving at the limits.

The kinematics is determined by the different length of the wishbones, the position of the wishbone link points on the chassis and the position of the steering knuckles or hub carriers. The wide base of the wishbones channels the wheel forces to the rigid steel subframe at the front and to the compact, rigid bodyshell cast nodes in the rear structure.

Wishbones, steering knuckles and hub carriers at the front and rear are made entirely from forged aluminium – substantially reducing the unsprung masses; this configuration also notably improves the suspension response.

Long wheelbase and broad track width

The long wheelbase of 2680 millimetres not only results in outstanding straight-line stability but also low wheel load shifts, significantly reducing the vehicle's tendency to dive and squat. The broad track width – front 1679, rear 1649 millimetres – ensures lower shifts in the wheel loads from the inner to the outer wheel when cornering, enabling the tyres to retain more grip. The large caster angle of 11.5 degrees significantly increases negative wheel camber when cornering and also improves tyre grip – this also ensures outstanding stability when braking heavily while cornering.

Weight-optimised flow-forming AMG light-alloy wheels

As befits the weight-optimised suspension design, AMG light-alloy wheels are used that are manufactured using the innovative flow-forming process. As part of the production process, so-called hot forming in the region around the rim well compresses the structure, thus improving durability. This enables reduced wall thicknesses to be used. A weight saving of around 1.1 kilograms per wheel compared with conventional light-alloy wheels reduces the unsprung masses and further optimises driving dynamics and suspension comfort.

The AMG light-alloy wheels measuring 9.5 x 19 inches (front) and 11.0 x 20 inches (rear) are shod with 265/35 R 19 (front) and 295/30 R 20 (rear) tyres. The tyres developed exclusively for the AMG super sports car provide optimum dry performance on a par with today's 'Cup' tyres – without demonstrating their inherent disadvantages in the wet and cold. A tyre pressure monitoring system is fitted as standard to permanently monitor tyre pressure in all four wheels; individual tyres are shown on the display.