The Mercedes Sls Amg, a modern icon celebrated for its breathtaking design and exhilarating performance, owes much of its legendary status to its meticulously engineered engine and drivetrain. As a high-performance grand tourer, the SLS AMG distinguishes itself with an exclusive, naturally aspirated eight-cylinder front-mid engine coupled with a dual-clutch transmission in a transaxle configuration. This article delves into the intricate details of this powertrain, exploring the features that position the Mercedes SLS AMG as a pinnacle of automotive engineering.
At the heart of the Mercedes SLS AMG lies the formidable AMG 6.3-liter V8 engine, designated as the M159. This powerplant is not merely an adaptation of existing AMG engines; it’s a bespoke creation engineered to deliver unparalleled performance. Boasting eight cylinders and a displacement of 6.3 liters, the engine adopts a front-mid configuration, a high-revving concept, dry sump lubrication, and a power-optimized intake and exhaust system. AMG’s dedication to performance is evident in this engine, propelling the Mercedes SLS AMG into the upper echelons of super sports cars. With a peak output of 420 kW (563 hp), this engine proudly holds the title of the world’s most powerful naturally aspirated eight-cylinder engine in series production. Despite its immense power, the engine achieves a commendable fuel consumption of approximately 13 liters per 100 kilometers (NEDC combined), a testament to targeted fuel-efficiency measures. The responsibility of power transfer in the SLS AMG falls to a newly developed AMG dual-clutch transmission with seven gears. This advanced transmission is strategically mounted at the rear in a transaxle configuration and is rigidly connected to the engine via a torque tube, ensuring optimal weight distribution and responsiveness.
The Mercedes-Benz SLS AMG’s engine, producing 420 kW/563 hp at 6800 rpm and a robust 650 Nm (479 lb-ft) of torque at 4750 rpm, showcases the full potential of the AMG 6.3-liter V8 engine family, initially unveiled in 2005 with the M156 designation. While building upon the foundation of the M156, which already delivered impressive figures of 386 kW (525 hp) and 630 Nm in models like the SL 63 AMG, the new M159 naturally aspirated eight-cylinder engine underwent significant enhancements. These improvements focused primarily on the intake and exhaust systems, oil supply, and crank mechanism. Over 120 parts and components were meticulously redesigned, drawing upon AMG’s extensive experience and insights accumulated from over four decades of motor racing.
From a design perspective, the M159 engine, much like its sibling the M156, stands as an entirely independent development. It masterfully blends the high-revving concept with a large displacement, capturing the best attributes of both worlds. This combination results in exhilarating high-revving agility complemented by substantial pulling power even at lower engine speeds. The AMG V8 engine in the Mercedes SLS AMG delivers an impressive 545 Nm of torque to the crankshaft at just 2500 rpm. The peak torque of 650 Nm (479 lb-ft) becomes fully available at 4750 rpm – a figure unmatched by any other naturally aspirated engine in this power and displacement class. This translates to dynamic acceleration, immediate throttle response, and pure driving enjoyment at the highest level, without compromising the relaxed driving experience suitable for everyday use in the Mercedes SLS AMG.
Mercedes SLS AMG Engine: Key Performance Data
| 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 at 6800 rpm |
| Output per Liter | 67.6 kW/92.0 hp |
| Max. Torque | 650 Nm (479 lb-ft) at 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 |
Optimized Cylinder Charging for Enhanced Power
A critical factor in achieving the enhanced output and torque in the Mercedes SLS AMG engine is optimized cylinder charging. The intake airflow system was meticulously recalculated and aerodynamically improved to minimize pressure losses. Simultaneously, a completely redesigned valve train enhances gas dynamics. The intake manifold, crafted from magnesium, features precisely calibrated variable resonance tube lengths. Eight velocity stacks, each 290 millimeters long and 51.5 millimeters in diameter, guide fresh air into the combustion chambers. Positioned behind new air filters with a volume of just under 9500 cubic centimeters are two electronically controlled throttle flaps, each measuring 74 millimeters in diameter. These flaps can achieve maximum opening in a mere 150 milliseconds, resulting in exceptional engine responsiveness in the Mercedes SLS AMG. Two hot-film air mass sensors, located downstream of the air filters, provide the engine electronics with crucial data regarding the temperature and density of the intake air.
Another distinctive aspect of the V8 engine is its sophisticated valve train, which draws inspiration from AMG’s potent racing engines. The 32 valves within the cylinder heads are actuated by bucket tappets. Their space-saving design enables a rigid valve train and consequently, high engine speeds with substantial valve opening cross-sections, ultimately boosting both output and torque. The intake valves boast a diameter of 40 millimeters, while the exhaust valves measure 34 millimeters. Unlike racing engines, the Mercedes SLS AMG engine employs a maintenance-free valve train with hydraulic valve clearance.
Continuously Variable Overhead Camshafts and Advanced Exhaust System
The Mercedes SLS AMG engine features four continuously variable overhead camshafts, each adjustable across a range of 42 degrees. Both intake and exhaust camshafts are adjusted based on engine load and speed, ensuring optimal output, torque, smooth idling, and minimized exhaust emissions. Variable valve overlap, controlled electrohydraulically and monitored by the engine management system, optimizes the fuel/air mixture supply to the combustion chambers and efficient exhaust gas venting across the engine speed range.
Further enhancing performance, the exhaust system of the Mercedes SLS AMG has been redesigned. Headers with precisely tailored tube lengths, derived from motor racing technology, significantly increase output and torque by optimizing gas cycles. The newly developed, twin-pipe exhaust system incorporates large tube cross-sections to effectively reduce exhaust gas backpressure. Two relatively compact center silencers located under the body and a large, transverse-mounted rear silencer contribute to optimal weight distribution within the Mercedes SLS AMG.
Emission control is handled by two backpressure-optimized bulkhead ceramic catalytic converters positioned directly on the headers and two metal catalytic converters located under the body. This system ensures compliance with stringent emission standards such as EU 5, LEV 2, and ULEV. The AMG engine comfortably meets the specific requirements of the U.S. market, including On-Board Diagnosis II and oxygen sensor diagnosis.
Dry Sump Lubrication and Optimized Engine Position
Engine placement was a critical consideration in the Mercedes SLS AMG’s design. Specifications dictated that the engine be positioned as low and as far back as possible to achieve a low center of gravity and balanced weight distribution between the front and rear axles. The solution was to mount the eight-cylinder front-mid engine behind the front axle, combined with a transaxle configuration. This results in a front-to-rear weight ratio of 48 to 52 percent, contributing to the car’s exceptional handling dynamics.
The significantly lower engine position is achieved through the adoption of a dry sump lubrication system. This system eliminates the conventional oil pan, allowing for a lower engine mounting. The dry sump lubrication system in the M159 engine comprises a suction pump, a pressure pump, and an external 5-liter oil reservoir positioned in front of the engine. The entire system circulates 13.5 liters of engine oil. The oil suction pump draws oil directly from the crank chambers and cylinder heads, pumping it to the external reservoir at a rate of up to 700 liters per minute. By efficiently removing engine oil, the dry sump system prevents churning losses associated with crankshaft immersion in the oil pan, further enhancing the engine’s efficiency.
A hydraulic oil pump, designed as a pendulum-slide vane pump, ensures reliable engine lubrication even under high lateral acceleration experienced on a racetrack. This demand-driven pump adjusts oil flow based on engine revs, temperature, and load maps stored in the control unit, minimizing power loss within the engine and contributing to fuel consumption reduction in the Mercedes SLS AMG. Two large radiators located in the front wheel arches, each with an integrated blower fan, effectively cool the engine oil.
Lightweight Design and High-Tech Materials
The Mercedes SLS AMG engine incorporates numerous lightweight design features without compromising strength. 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 highly stressed piston crowns. Further weight reduction is achieved by eliminating steel liners for the crankshaft main bearings. The M159 crankcase is constructed entirely from aluminum, weighing approximately 4 kilograms less than its M156 counterpart. Extensive use of aluminum bolts throughout the M159 engine saves an additional 0.6 kilograms compared to steel bolts. 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 utilizes a rigid bedplate design based on the closed-deck principle, a feature commonly found in motor racing engines. The engine block and cylinder heads are cast from advanced aluminum-silicon alloys (AlSi7 and AlSi17), selected for their optimal balance of weight, thermal and mechanical resistance, and long-term durability. Mercedes-AMG employs a sophisticated twin wire arc spraying (TWAS) process, patented by AMG and also used in the M156, to create tribologically optimized surfaces on the eight cylinder walls of the M159. This TWAS technology results in extremely low friction and wear, coupled with exceptional long-term durability. The cylinder walls of the AMG V8 engine achieve twice the hardness of conventional cast iron liners, representing a significant advancement in engine technology.
Other high-tech components and systems carried over from the M156 engine include:
- A finely balanced crankshaft made from forged steel.
- A water cooling system for the cylinder head using the highly thermal-efficient cross-flow principle derived from racing engines.
- Variable coolant control for optimized efficiency.
- A computer-controlled fuel supply with the fuel pump integrated within the tank.
Advanced Cooling and Engine Management Systems
Water cooling in the Mercedes SLS AMG is provided by a large cooling module positioned behind the radiator grille. This module integrates the air conditioning condenser and the power-steering oil cooler, resulting in a weight reduction of approximately 4 kilograms compared to separate components, while simultaneously enhancing performance. A large suction-type fan positioned directly behind the cooler expels hot air as needed.
The Bosch ME 9.7 AMG engine management system not only controls engine functions but also manages the generator, further contributing to fuel efficiency in the Mercedes SLS AMG. Sensors continuously monitor the vehicle battery’s charge status and reduce generator output once the battery is sufficiently charged. To recharge the battery, the system strategically utilizes the engine’s overrun phases, converting braking energy into electrical energy through recuperation.
Through the intelligent combination of these fuel-efficiency measures, the Mercedes SLS AMG achieves an impressive NEDC combined fuel consumption of approximately 13 liters per 100 kilometers, positioning it as one of the most powerful yet relatively efficient super sports cars in its segment.
Handcrafted Engine Production and AMG Dual-Clutch Transmission
The Mercedes SLS AMG’s V8 engine is meticulously produced at AMG’s state-of-the-art engine workshops in Affalterbach, adhering to the “one man, one engine” philosophy. Each engine is assembled entirely by hand, from start to finish, by a single, highly skilled engineer. The AMG engine manufacturing facility, spanning three floors and 9950 square meters, produces approximately 100 high-performance engines daily for various AMG vehicle models.
Complementing the powerful engine is the AMG seven-speed dual-clutch transmission, featuring four driving modes and a RACE START function. This transmission technology, originating from motor racing, is perfectly suited to the high-revving characteristics of the AMG 6.3-liter V8 engine. Its strengths include lightning-fast gearshifts without power interruption, a tailored control strategy, and effortless shifting ease. Designed with a close-ratio configuration, the dual-clutch transmission optimizes gear ratio adjustments, providing the Mercedes SLS AMG driver with even more dynamic acceleration and maximum driving pleasure.
AMG DRIVE UNIT and RACE START Function
The AMG DRIVE UNIT serves as the central control interface for the dual-clutch transmission and all dynamic handling control functions in the Mercedes SLS AMG. Located to the left of the selector lever is the electronic rotary switch, allowing drivers to select from four driving modes and activate the RACE START function. RACE START enables maximum acceleration potential and ensures optimal traction to the drive wheels. The system automatically sets the ideal start-off engine speed, and the Mercedes SLS AMG accelerates instantly with electronically controlled wheelspin, optionally reaching top speed. The transmission handles gearshifts with incredibly short shift times, eliminating the need for manual gear changes during maximum acceleration.
Four Driving Modes and Automatic Double-Declutching
The dual-clutch transmission supports upshifts under full load in both automatic and manual modes. Manual gear changes can be executed using the AMG shift paddles on the steering wheel. Four distinct driving modes cater to various driving preferences in the Mercedes SLS AMG: “C” (Controlled Efficiency), “S” (Sport), “S+” (Sport plus), and “M” (Manual). In “C” mode, the car always starts in second gear and prioritizes highly efficient gearshifts. “S” mode allows for higher engine speeds in each gear and provides more spontaneous downshifts, with gearshifts occurring approximately 20 percent faster than in “C” mode. “S+” mode further reduces shift times by another 20 percent. “M” mode represents the sportiest setting, where the AMG 6.3-liter V8 engine delivers even sharper response, and the dual-clutch transmission shifts gears an additional 10 percent faster – a 50 percent reduction compared to “C” mode, achieving gearshifts in under 100 milliseconds.
An automatic double-declutching function is active in “S,” “S+,” and “M” modes, enhancing both driver engagement and vehicle stability. Every manual or automatic downshift is accompanied by precisely metered double-declutching, with intensity increasing incrementally from “S” to “M.” This feature not only enhances the auditory experience but also minimizes load-change reactions during downshifts, particularly beneficial when braking into corners on a racetrack or enhancing safety in wet or icy conditions in the Mercedes SLS AMG.
Compact and Lightweight Transmission with Torque Tube
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 in the Mercedes SLS AMG. The transmission casing also integrates a mechanical differential lock with a sporty setup, further pushing driving dynamics to the limit.
The dual-clutch transmission forms a fixed unit with the V8 engine via a torque tube. Engine and transmission, mounted at the rear axle in a transaxle configuration, are rigidly connected to each other, providing flexural and torque rigidity and mutual support. This sophisticated solution results in a backlash-free drivetrain, delivering significant advantages in driving dynamics and ride comfort in the Mercedes SLS AMG. The 1.64-meter-long torque tube is constructed from a one-piece aluminum sand-cast casing and weighs less than 25 kilograms. A driveshaft rotates within the tube at engine speed. Mirroring the technology used in the Mercedes-Benz C-Class DTM racing touring car, the shaft is made from carbon fiber. Despite its high strength, the carbon-fiber shaft weighs only 4 kilograms, making it approximately 50 percent lighter than a steel equivalent. The 1.71-meter-long driveshaft transmits 650 Nm (479 lb-ft) of torque from the engine to the dual-clutch transmission. The torque tube also houses a specially developed torsion damper, effectively minimizing noise and vibration, optimizing ride and noise comfort within the Mercedes SLS AMG.
Suspension and Braking System: Racing-Derived Technology
The Mercedes SLS AMG’s commitment to uncompromising performance extends beyond its engine and drivetrain to its suspension and braking systems. The aluminum double-wishbone suspension is designed for lightweight construction and exceptional driving dynamics. An AMG high-performance braking system is standard, with an optional high-performance ceramic composite version available for even greater braking capabilities.
The double-wishbone suspension system, utilized at all four wheels, is a technology proven in motor racing, including Formula 1. This configuration separates wheel location and suspension functions, with spring/damper struts supported on the lower wishbone. The double-wishbone concept, with its high camber and track rigidity, precisely locates the wheel with minimal elastic movements, providing the driver with optimal feedback and road contact, especially at the limits of performance in the Mercedes SLS AMG.
The kinematics are determined by the varying lengths of the wishbones, the position of the wishbone link points on the chassis, and the placement of the steering knuckles or hub carriers. The wide base of the wishbones effectively channels wheel forces to the rigid steel subframe at the front and to the compact, rigid bodyshell cast nodes in the rear structure of the Mercedes SLS AMG.
Wishbones, steering knuckles, and hub carriers at both the front and rear axles are manufactured entirely from forged aluminum, significantly reducing unsprung masses and notably improving suspension response in the Mercedes SLS AMG.
Optimized Wheelbase, Track Width, and Wheels
The Mercedes SLS AMG features a long wheelbase of 2680 millimeters, contributing to outstanding straight-line stability and reduced wheel load shifts, minimizing the vehicle’s tendency to dive and squat under braking or acceleration. The broad track width – 1679 millimeters at the front and 1649 millimeters at the rear – ensures reduced wheel load shifts from the inner to the outer wheel during cornering, maximizing tire grip. A large caster angle of 11.5 degrees significantly increases negative wheel camber during cornering, further enhancing tire grip and ensuring exceptional stability even during heavy braking while cornering in the Mercedes SLS AMG.
AMG light-alloy wheels, manufactured using an innovative flow-forming process, complement the weight-optimized suspension design. Hot forming in the rim well area during production compresses the structure, improving durability and allowing for reduced wall thicknesses. This results in a weight saving of approximately 1.1 kilograms per wheel compared to conventional light-alloy wheels, further reducing unsprung masses and optimizing driving dynamics and suspension comfort in the Mercedes SLS AMG.
The Mercedes SLS AMG is fitted with AMG light-alloy wheels measuring 9.5 x 19 inches at the front and 11.0 x 20 inches at the rear, shod with 265/35 R 19 front tires and 295/30 R 20 rear tires. These tires, developed exclusively for the AMG super sports car, provide optimal dry performance comparable to today’s ‘Cup’ tires, without their inherent disadvantages in wet and cold conditions. A standard tire pressure monitoring system continuously monitors tire pressure in all four wheels, displaying individual tire pressures on the instrument cluster in the Mercedes SLS AMG.
In conclusion, the Mercedes SLS AMG’s engine and drivetrain are a masterpiece of automotive engineering. From the handcrafted, naturally aspirated V8 engine to the advanced dual-clutch transmission and racing-derived suspension, every component is designed and engineered for maximum performance and driving pleasure. This detailed examination of the Mercedes SLS AMG powertrain reveals the depth of engineering and technological innovation that underpins its iconic status and exhilarating driving experience.
