The Mercedes Sls Amg, a modern icon, is celebrated for its breathtaking performance and striking design, most notably its gullwing doors. At the heart of this automotive masterpiece lies an exceptional engine and drivetrain, meticulously engineered by AMG to deliver a driving experience that is both exhilarating and refined. This article delves into the intricate details of the SLS AMG’s powertrain, exploring the high-performance V8 engine and the advanced dual-clutch transmission that work in perfect harmony.
The AMG 6.3-Liter V8: A Naturally Aspirated Marvel
The soul of the Mercedes SLS AMG is its hand-built AMG 6.3-liter V8 engine. This naturally aspirated powerhouse, designated M159, is a significant evolution of the M156 engine, renowned for its performance in other AMG models. However, the M159 is far from a mere upgrade; it’s a bespoke creation tailored specifically for the SLS AMG, pushing the boundaries of naturally aspirated engine technology.
AMG engineers focused on enhancing every aspect of the engine, from the intake and exhaust systems to the oil supply and crank mechanism. Over 120 components were redesigned, drawing upon decades of AMG’s motorsport expertise. The result is an engine that produces a staggering 420 kW (563 hp) at 6,800 rpm and 650 Nm (479 lb-ft) of torque at 4,750 rpm. These figures not only position the SLS AMG within the elite ranks of super sports cars but also establish its engine as the world’s most powerful naturally aspirated eight-cylinder in series production at the time of its release.
This immense power is accessible across a broad rev range. The engine delivers 545 Nm of torque as low as 2,500 rpm, ensuring potent acceleration and responsiveness in everyday driving situations, while the peak torque at 4,750 rpm unleashes its full dynamic potential. This duality makes the Mercedes SLS AMG equally adept at cruising comfortably and attacking apexes on a racetrack.
Key Engine Specifications of the Mercedes SLS AMG:
| Feature | Specification |
|---|---|
| Cylinder Arrangement | V8 |
| Cylinder Angle | 90° |
| Valves per Cylinder | 4 |
| Displacement | 6208 cc |
| Bore x Stroke | 102.2 x 94.6 mm |
| Compression Ratio | 11.3 : 1 |
| Peak Power | 420 kW (563 hp) @ 6800 rpm |
| Specific Output | 67.6 kW/liter (92.0 hp/liter) |
| Maximum Torque | 650 Nm (479 lb-ft) @ 4750 rpm |
| Specific Torque | 104.7 Nm/liter |
| Maximum Engine Speed | 7200 rpm |
| Dry Weight | 206 kg |
| Power-to-Weight Ratio | 0.36 kg/hp |
Optimized Airflow and Valve Train for Peak Performance
Achieving the remarkable output of the Mercedes SLS AMG engine required meticulous attention to detail, particularly in optimizing cylinder charging. The intake airflow system was redesigned with improved aerodynamics to minimize pressure losses. The valve train was also completely reworked to enhance gas dynamics.
The intake manifold, crafted from lightweight magnesium, features variable resonance tube lengths, precisely tuned for optimal performance. Eight velocity stacks, each meticulously dimensioned, guide fresh air into the combustion chambers. Responsiveness is further amplified by two electronically controlled throttle flaps, each 74 millimeters in diameter, capable of opening fully in a mere 150 milliseconds. Hot-film air mass sensors provide the engine electronics with real-time data on intake air temperature and density, ensuring precise engine management.
Drawing inspiration from AMG’s racing engines, the valve train incorporates 32 valves operated by bucket tappets. This space-saving design facilitates a rigid valve train, enabling high engine speeds and large valve opening cross-sections, ultimately boosting both power and torque. The intake valves measure a substantial 40 millimeters in diameter, while the exhaust valves are 34 millimeters. Unlike a pure racing engine, the SLS AMG engine features a maintenance-free valve train with hydraulic valve clearance adjusters, ensuring long-term reliability and reduced maintenance.
Variable Camshaft Adjustment and Redesigned Exhaust System
The Mercedes SLS AMG engine features four continuously variable overhead camshafts, adjustable over a 42-degree range. Both intake and exhaust camshafts are dynamically adjusted based on engine load and speed. This sophisticated system optimizes valve overlap, ensuring an ideal air-fuel mixture in the combustion chambers and efficient exhaust gas expulsion. The electrohydraulic control of the variable camshaft adjustment is managed by the engine management system, contributing to both performance and reduced emissions.
Complementing the optimized intake is a redesigned exhaust system engineered for maximum output. Headers with precisely calculated tube lengths, derived from motorsport technology, significantly enhance power and torque through improved gas flow dynamics. The twin-pipe exhaust system, with its large tube cross-sections, minimizes exhaust gas backpressure. Two center silencers and a large rear silencer contribute to balanced weight distribution.
Emission control is handled by two ceramic catalytic converters positioned close to the headers and two metal catalytic converters further downstream. This system ensures compliance with stringent emissions standards such as EU 5, LEV 2, and ULEV.
Dry Sump Lubrication and Lightweight Construction
A crucial element in the Mercedes SLS AMG’s design is the low and rearward positioning of the engine. This was achieved through the adoption of dry sump lubrication, eliminating the need for a conventional oil pan and allowing the engine to sit lower in the chassis. This contributes to a lower center of gravity and a balanced 48:52 front-to-rear weight distribution, enhancing handling and agility.
The dry sump system utilizes a suction pump, a pressure pump, and an external 5-liter oil reservoir. 13.5 liters of oil circulate through the system, with the suction pump drawing oil directly from the crank chambers and cylinder heads at a rate of up to 700 liters per minute. This efficient oil scavenging minimizes churning losses and further improves engine efficiency. The demand-driven hydraulic oil pump ensures reliable lubrication even under high lateral acceleration experienced during spirited driving.
Weight reduction was a paramount concern in the engine’s design. Forged pistons, lighter than those in the M156 engine, contribute to reduced reciprocating mass. The crankcase is constructed entirely from aluminum, saving approximately 4 kilograms compared to its M156 counterpart. Extensive use of aluminum bolts further reduces weight. The engine’s dry weight of 206 kg results in an exceptional power-to-weight ratio of 0.36 kg/hp.
The crankcase employs a rigid bedplate design and closed-deck principle, typical of racing engines. The cylinder walls utilize AMG’s patented twin-wire arc spraying (TWAS) coating, creating an exceptionally durable and low-friction surface.
AMG Speedshift DCT 7-Speed Transmission: Precision and Speed
Power from the V8 engine is channeled through the AMG Speedshift DCT 7-speed dual-clutch transmission. This advanced transmission, mounted in a transaxle configuration at the rear of the car and connected to the engine via a torque tube, is engineered for lightning-fast gear changes and optimal power delivery.
The dual-clutch technology enables seamless gear shifts without interrupting traction. The transmission offers four driving modes: “C” (Controlled Efficiency), “S” (Sport), “S+” (Sport plus), and “M” (Manual), selectable via the AMG DRIVE UNIT. Each mode progressively sharpens throttle response and shift speeds. In “M” mode, gear changes occur in under 100 milliseconds.
The RACE START function, activated via the AMG DRIVE UNIT, optimizes launch control for maximum acceleration. The transmission also features an automatic double-declutching function in “S,” “S+,” and “M” modes, enhancing both the auditory experience and stability during downshifts.
The transmission’s lightweight aluminum housing and the absence of a traditional torque converter contribute to efficiency and reduced fuel consumption. It also incorporates a mechanical differential lock for enhanced traction and handling.
Transaxle Configuration and Torque Tube: Optimized Dynamics
The transaxle configuration, with the transmission located at the rear axle, contributes to the balanced weight distribution of the Mercedes SLS AMG. The connection between the engine and transmission is facilitated by a torque tube, a rigid aluminum structure housing a carbon-fiber driveshaft.
The carbon-fiber driveshaft, a technology derived from the Mercedes-Benz C-Class DTM racing car, is significantly lighter than a steel equivalent, reducing rotational inertia and improving responsiveness. A torsion damper within the torque tube minimizes noise and vibration, enhancing refinement.
Suspension and Braking: Motorsport-Derived Technology
The Mercedes SLS AMG’s suspension and braking systems are equally rooted in motorsport technology. The aluminum double-wishbone suspension ensures precise wheel control and exceptional handling. Forged aluminum wishbones, steering knuckles, and hub carriers minimize unsprung masses, further enhancing suspension responsiveness.
Optional AMG high-performance ceramic composite brakes provide exceptional stopping power and heat resistance, befitting the car’s high-performance capabilities.
Conclusion: An Engineering Masterpiece
The engine and drivetrain of the Mercedes SLS AMG represent a pinnacle of automotive engineering. The hand-built AMG 6.3-liter V8 engine, combined with the advanced AMG Speedshift DCT 7-speed transmission and transaxle configuration, delivers a driving experience that is both visceral and technologically sophisticated. This powertrain is a testament to AMG’s commitment to performance, innovation, and the pursuit of driving perfection, solidifying the Mercedes SLS AMG’s place as a true automotive legend.
