The Mercedes-benz Sls AMG, a modern icon, owes much of its legendary status to its exceptional engine and drivetrain. This article delves deep into the engineering marvel that powers the “Gullwing,” exploring the high-performance eight-cylinder front-mid engine and the sophisticated dual-clutch transmission that work in perfect harmony to deliver an unparalleled driving experience.
The Heart of the Beast: AMG 6.3-Liter V8 Engine
At the core of the SLS AMG lies the formidable AMG 6.3-liter V8 engine, a naturally aspirated masterpiece that redefines high-performance engineering. Displacing 6.3 liters across eight cylinders in a front-mid configuration, this engine is a testament to AMG’s dedication to power and precision. Its high-revving concept, dry sump lubrication, and meticulously optimized intake and exhaust systems place the SLS AMG firmly in the realm of top-tier super sports cars. Producing a peak output of 420 kW (563 hp), it proudly holds the title of the world’s most powerful naturally aspirated eight-cylinder engine in series production. Despite its immense power, the engine also incorporates fuel-efficiency measures, achieving a combined fuel consumption of approximately 13 liters per 100 kilometers (NEDC provisional figure).
This engine, designated M159, is an evolution of the M156, which already impressed in models like the SL 63 AMG. However, the M159 takes performance to a new level through significant enhancements. Over 120 components have been redesigned, drawing upon AMG’s extensive motorsport experience spanning over four decades. The improvements focus primarily on the intake and exhaust systems, oil supply, and crank mechanism, resulting in a powerplant that delivers both exhilarating performance and refined driving dynamics.
The powerful AMG 6.3-liter V8 engine of the Mercedes-Benz SLS AMG, showcasing its front-mid engine configuration and advanced engineering.
The M159 engine embodies a design philosophy that blends high-revving capability with large displacement, offering the best of both worlds. It provides the thrill of rapid acceleration at high RPMs while maintaining substantial torque even at lower engine speeds. The engine delivers a remarkable 545 Nm of torque at just 2500 rpm, building to a maximum of 650 Nm (479 lb-ft) at 4750 rpm. This broad torque curve ensures dynamic responsiveness, instant power delivery, and exceptional driving pleasure in all conditions, from spirited track driving to relaxed daily commutes.
Key Engine Specifications:
| Feature | Specification |
|---|---|
| Cylinder Arrangement | V8 |
| Cylinder Angle | 90° |
| Valves per Cylinder | 4 |
| Displacement | 6208 cc |
| Bore x Stroke | 102.2 x 94.6 mm |
| Distance Between Cylinders | 109 mm |
| Compression Ratio | 11.3 : 1 |
| Rated Output | 420 kW/563 hp @ 6800 rpm |
| Output per Liter | 67.6 kW/92.0 hp |
| Max. Torque | 650 Nm (479 lb-ft) @ 4750 rpm |
| Torque per Liter | 104.7 Nm |
| Maximum Engine Speed | 7200 rpm |
| Mean Pressure | 13.16 bar |
| Weight (Dry) | 206 kg |
| Power-to-Weight Ratio | 0.36 kg/hp |
Optimizing Airflow for Enhanced Performance
A critical aspect of achieving the increased power and torque in the M159 engine is the optimized cylinder charging system. The redesigned intake airflow path minimizes pressure losses, while a completely new valve train enhances gas dynamics. The magnesium intake manifold, meticulously reworked, features variable resonance tube lengths that are precisely tuned. Eight velocity stacks, each 290 millimeters long and 51.5 millimeters in diameter, guide the fresh air into the combustion chambers.
Responsiveness is further amplified by two electronically controlled throttle flaps, each 74 millimeters in diameter, positioned after the new air filters. These flaps can achieve full opening in a mere 150 milliseconds. Dual hot-film air mass sensors, located downstream of the air filters, provide the engine management system with crucial data regarding the intake air’s temperature and density.
Drawing inspiration from AMG’s racing engines, the valve train is highly sophisticated. Bucket tappets operate the 32 valves within the cylinder heads. This space-saving design enables a stiff valve train and high engine speeds with large valve opening cross-sections, contributing to increased power and torque. The intake valves measure 40 millimeters in diameter, while the exhaust valves are 34 millimeters. Unlike racing engines, the SLS AMG engine employs a maintenance-free valve train with hydraulic valve clearance compensation, ensuring long-term reliability.
Variable Camshaft Adjustment and Exhaust System
The engine incorporates four continuously variable overhead camshafts, each adjustable across a 42-degree range. Both intake and exhaust camshafts are adjusted based on engine load and speed, optimizing power, torque, idle smoothness, and emissions. Variable valve overlap, controlled electrohydraulically and monitored by the engine management system, ensures an ideal air-fuel mixture supply and efficient exhaust gas expulsion across the engine’s operating range.
The exhaust system is also meticulously engineered for performance. Headers with precisely calculated tube lengths, another technology derived from motorsport, significantly boost power and torque by optimizing gas flow. The newly developed twin-pipe exhaust system features large tube cross-sections to minimize exhaust gas backpressure. Weight distribution is optimized through the use of two smaller center silencers and a large, transverse rear silencer.
Emission control is handled by two bulkhead ceramic catalytic converters positioned close to the headers and two metal catalytic converters under the vehicle floor. This system ensures compliance with stringent emission standards, including EU 5, LEV 2, and ULEV, as well as meeting specific U.S. market requirements and On-Board Diagnosis II standards.
Dry Sump Lubrication and Engine Positioning
The positioning of the engine in the SLS AMG was a critical design consideration. The objective was to mount the engine as low and as far back as possible to lower the vehicle’s center of gravity and achieve balanced weight distribution. Placing the front-mid engine behind the front axle, combined with a transaxle configuration, results in a near-perfect 48 to 52 percent front-to-rear weight distribution.
Achieving this low engine position is made possible by the dry sump lubrication system. This system eliminates the traditional oil pan, allowing for a lower engine mounting point. The M159’s dry sump system includes a suction pump, a pressure pump, and an external 5-liter oil reservoir located in front of the engine. The system circulates 13.5 liters of engine oil, with the suction pump extracting oil directly from the crank chambers and cylinder heads at a rate of up to 700 liters per minute. By efficiently removing engine oil, dry sump lubrication minimizes churning losses, which further enhances engine efficiency.
Diagram illustrating the dry sump lubrication system in the Mercedes-Benz SLS AMG, showcasing the external oil reservoir and pump system for optimized engine performance and positioning.
A demand-driven hydraulic oil pump, designed as a pendulum-slide vane pump, ensures reliable engine lubrication even under high lateral acceleration conditions experienced on a track. The pump’s output is regulated based on engine speed, temperature, and load maps, minimizing power loss and contributing to fuel efficiency. Engine oil cooling is managed by two large radiators located in the front wheel arches, each with an integrated blower fan.
Lightweight Design and High-Tech Materials
Lightweight design is a core principle in the SLS AMG, extending to the engine itself. Forged pistons, eight in total, are 0.5 kilograms lighter than the cast pistons used in the M156 engine. Pressure-controlled oil spray nozzles in the crankcase ensure optimal cooling of the piston crowns under high stress. Further weight reduction is achieved by eliminating steel liners for the crankshaft main bearings; the M159 crankcase is made entirely of aluminum, saving approximately 4 kilograms compared to the M156. Extensive use of aluminum bolts further reduces weight by around 0.6 kilograms. The AMG 6.3-liter V8 engine weighs a mere 206 kg (dry), resulting in an exceptional power-to-weight ratio of 0.36 kg/hp.
The crankcase employs a rigid bedplate design with a closed-deck principle, typical of motorsport engineering. The engine block and cylinder heads are cast from advanced aluminum-silicon alloys (AlSi7 and AlSi17), chosen for their optimal balance of weight, thermal and mechanical resistance, and long-term durability. AMG utilizes a patented twin wire arc spraying (TWAS) process for the cylinder walls, creating a tribologically optimized surface with extremely low friction and wear, along with exceptional long-term durability. This TWAS coating results in cylinder walls twice as hard as conventional cast iron liners.
Other advanced components and systems carried over from the M156 include:
- Finely balanced crankshaft made of forged steel.
- Cross-flow water cooling system for the cylinder head for efficient thermal management.
- Variable coolant control for optimized efficiency.
- Computer-controlled fuel supply with integrated fuel pump in the tank.
Advanced Cooling and Engine Management
Water cooling is provided by a large cooling module located behind the radiator grille, integrating the air conditioning condenser and power-steering oil cooler. This integrated design reduces weight by approximately 4 kilograms while enhancing performance. A large suction fan positioned behind the cooler expels hot air as needed.
The Bosch ME 9.7 AMG engine management system includes generator management, further contributing to fuel efficiency. Sensors monitor the battery’s charge status and reduce generator output when the battery is sufficiently charged, utilizing engine overrun phases for battery recharging through recuperation.
These fuel-efficiency measures contribute to the SLS AMG’s impressive fuel economy for a super sports car, achieving a combined NEDC fuel consumption of around 13 liters per 100 kilometers. The engine is meticulously hand-built at AMG’s Affalterbach facility following the “one man, one engine” philosophy, where a single engineer assembles each engine from start to finish.
AMG Seven-Speed Dual-Clutch Transmission: Seamless Power Delivery
Complementing the powerful V8 engine is the AMG seven-speed dual-clutch transmission, engineered for rapid, seamless gear changes and maximum performance. This transmission, with its roots in motorsport technology, offers instantaneous gearshifts without interrupting power flow, along with a finely tuned control strategy and ease of operation. Specifically designed for the high-revving characteristics of the AMG 6.3-liter V8 engine, it provides optimal gear ratio spacing for dynamic acceleration and driving enjoyment.
The AMG seven-speed dual-clutch transmission of the Mercedes-Benz SLS AMG, highlighting its transaxle configuration and advanced features like RACE START.
The AMG DRIVE UNIT serves as the central control interface for the dual-clutch transmission and dynamic handling functions. The rotary switch on the center console allows selection of four driving modes, including activation of the RACE START function. RACE START optimizes launch control for maximum acceleration and traction, automatically setting the ideal engine speed and managing wheelspin for rapid starts. The transmission executes gear changes with incredibly short shift times without requiring manual intervention.
Driving Modes and Double-Declutching
The dual-clutch transmission offers four distinct driving modes: “C” (Controlled Efficiency), “S” (Sport), “S+” (Sport plus), and “M” (Manual). “C” mode prioritizes fuel efficiency, starting in second gear and executing smooth, efficient shifts. “S” mode allows for higher engine speeds and more responsive downshifts, with gear changes approximately 20 percent faster than in “C” mode. “S+” mode further reduces shift times by another 20 percent, while “M” mode provides the sportiest experience with even more aggressive engine response and gear shifts that are 10 percent faster than “S+”, and a remarkable 50 percent faster than “C” mode, achieving shifts in under 100 milliseconds.
Automatic double-declutching is active in “S,” “S+,” and “M” modes, enhancing both driving exhilaration and stability. Each downshift, whether manual or automatic, is accompanied by precisely timed double-declutching, becoming progressively more pronounced from “S” to “M.” This feature not only adds to the auditory experience but also minimizes load-change reactions during downshifts, particularly beneficial when braking into corners on a track or in slippery conditions.
The AMG dual-clutch transmission is remarkably compact and lightweight, weighing just 136 kilograms including the differential. Its aluminum construction and the absence of a conventional torque converter improve efficiency and contribute to reduced fuel consumption. The transmission casing also houses a mechanical differential lock with a sporty setup, further enhancing driving dynamics.
Torque Tube and Carbon-Fiber Driveshaft
The dual-clutch transmission is rigidly connected to the V8 engine via a torque tube in a transaxle configuration. This arrangement provides exceptional flexural and torque rigidity, creating a backlash-free drivetrain that significantly benefits driving dynamics and ride comfort. The 1.64-meter-long torque tube is constructed from a one-piece aluminum sand-cast casing, weighing less than 25 kilograms.
Inside the torque tube rotates a driveshaft at engine speed. Inspired by the Mercedes-Benz C-Class DTM racing car, the driveshaft is made of carbon fiber. This high-tech material offers exceptional strength while weighing only 4 kilograms. The 1.71-meter-long carbon-fiber driveshaft, responsible for transmitting 650 Nm of torque from the engine to the transmission, is approximately 50 percent lighter than a steel equivalent.
A specially developed torsion damper within the torque tube effectively minimizes noise and vibration, optimizing ride refinement.
Suspension and Braking: Motorsport-Derived Technology
The Mercedes-Benz SLS AMG’s commitment to racetrack performance and Mercedes-Benz comfort extends to its suspension and braking systems. The aluminum double-wishbone suspension, designed for lightweight construction and exceptional driving dynamics, and the optional AMG high-performance ceramic braking system, exemplify this philosophy.
The double-wishbone suspension, a technology proven in motorsport including Formula 1, is employed at all four wheels. This design separates wheel location and suspension functions, with spring/damper struts supported on the lower wishbone. The double-wishbone concept ensures precise wheel control with minimal elastic movement, providing the driver with optimal feedback and road feel, especially at the limits of handling.
The double-wishbone suspension of the Mercedes-Benz SLS AMG, demonstrating its motorsport-derived technology and lightweight aluminum components.
Forged aluminum is used extensively for wishbones, steering knuckles, and hub carriers at both front and rear axles, significantly reducing unsprung masses and improving suspension response. The long wheelbase of 2680 millimeters contributes to straight-line stability and reduces pitching tendencies, while the wide track width (1679 mm front, 1649 mm rear) minimizes weight transfer during cornering, maximizing tire grip.
Weight-optimized flow-forming AMG light-alloy wheels further reduce unsprung mass. These wheels, measuring 9.5 x 19 inches at the front and 11.0 x 20 inches at the rear, are fitted with tires developed exclusively for the SLS AMG, providing exceptional dry performance comparable to “Cup” tires while maintaining wet and cold weather capability. A standard tire pressure monitoring system ensures constant monitoring of tire pressure at all four wheels.
In conclusion, the Mercedes-Benz SLS AMG’s engine and drivetrain represent a pinnacle of automotive engineering. From the hand-built, naturally aspirated V8 engine to the sophisticated dual-clutch transmission and motorsport-derived suspension, every component is meticulously designed and engineered for unparalleled performance and driving pleasure, cementing the SLS AMG’s legacy as a true automotive icon.
