The 2012 Mercedes-Benz SLK55 AMG stands as a testament to high-performance engineering, embodying the most potent iteration of the SLK class ever conceived up to that point. At its heart lies a revolutionary AMG 5.5-liter V8 engine, ingeniously equipped with cylinder shutoff technology. This powertrain masterfully blends exhilarating performance with an unprecedented level of fuel efficiency for its class. Delivering a peak output of 415 horsepower and a formidable 398 lb-ft of torque, the 2012 SLK55 AMG is engineered to surpass its competitors, offering a driving experience that is both thrilling and refined. The vehicle’s high-performance capabilities are further enhanced by the inclusion of an AMG sports suspension system featuring Direct-Steer, Torque Vectoring Brakes, and a 3-stage ESP®, all working in concert with the AMG high-performance braking system to ensure unparalleled control and responsiveness on the road. The arrival of the 2012 SLK55 AMG in U.S. showrooms in early 2012 marked a significant moment for enthusiasts seeking top-tier performance in a compact roadster.
As part of the third generation of the SLK, which debuted in June, the AMG model immediately captures attention with its distinctive visual enhancements. Exclusive AMG light-alloy wheels and bespoke AMG body styling, complete with an AMG spoiler lip and dual chrome-plated twin tailpipes at the rear, accentuate the classic roadster silhouette while injecting a pronounced athletic flair. The expressive design of the 2012 SLK55 AMG is both captivating and instantly recognizable, setting it apart in the realm of high-performance vehicles.
The SLK55 AMG perfectly embodies AMG’s “Driving Performance” ethos. Within the compact high-performance Roadster category, it presents an unmatched synthesis of dynamic driving capabilities, superior sportiness, cutting-edge technology, and optimized fuel economy. The SLK55 AMG achieves a 0 to 60 mph acceleration in a mere 4.5 seconds, reaching an electronically governed top speed of 155 mph.
| 2012 SLK55 AMG | |
|---|---|
| Displacement | 5,461 cc |
| Bore x stroke | 3.86 in x 3.56 in |
| Compression ratio | 12.6 : 1 |
| Output | 415 hp at 6,800 rpm |
| Max. torque | 398 lb-ft at 4,500 rpm |
| Engine weight (dry) | 412 lbs |
| Acceleration | 0 – 60 mph 4.5 s |
| Top speed | 155 mph** |
| * provisional figures; ** electronically limited |
Setting new benchmarks for fuel efficiency among V8 engines, the 5.5-liter powerplant combines reduced fuel consumption with robust power delivery, all while maintaining the signature deep exhaust note characteristic of a large-displacement eight-cylinder engine.
Aligned with AMG’s “Performance 2015” strategy, this new V8 engine exemplifies the ongoing commitment to decrease fuel consumption and emissions across new models in the coming years, reinforcing the brand’s dedication to “Driving Performance”. The M152 engine underscores AMG’s dedication to social responsibility, demonstrating that high performance and environmental consciousness can coexist.
The Innovative Naturally Aspirated V8 Engine
The newly developed M152 engine shares a close lineage with the AMG M157 5.5-liter V8 biturbo engine introduced in 2010, which powers models such as the E63 AMG, CLS63 AMG, S63 AMG, and CL63 AMG. Numerous design parallels exist between these engines, including displacement, bore/stroke dimensions, cylinder spacing, ECO stop/start system, and direct gasoline injection technology. However, key distinctions of the M152 include a redesigned intake air ducting system, new cylinder heads, a modified valve drive mechanism, a refined oil supply system, and an optimized crankcase, all contributing to its unique performance characteristics.
Advanced Technologies for Unrivaled Performance
The M152 engine showcases an unparalleled combination of advanced automotive technologies. It stands out as the only gasoline engine to integrate direct injection at an exceptionally high pressure of 2,900 psi, spray-guided combustion, and piezo injectors, alongside map-controlled cylinder shut-off, an all-aluminum crankcase with “spectacle” honing, four-valve technology with continuous camshaft adjustment, a high 12.6:1 compression ratio, a stop/start system, and generator management, all while capable of revving beyond 7,000 rpm. These features collectively enhance thermodynamic efficiency, crucial for achieving both superior fuel economy and reduced exhaust emissions. The utilization of a large-displacement, naturally-aspirated eight-cylinder engine with cylinder shut-off effectively addresses the inherent trade-off between high power and torque output and fuel efficiency.
AMG Cylinder Management System
The AMG Cylinder Management system, an in-house development by Mercedes-AMG, significantly boosts efficiency by deactivating cylinders two, three, five, and eight under partial load, markedly reducing fuel consumption. This technology shares conceptual similarities with systems used in Formula 1’s 750-hp V8 engines, where cylinder deactivation is employed to enhance efficiency during slow cornering, safety car periods, or pit stops.
This cylinder shut-off feature operates across a broad engine speed range from 800 to 3,600 rpm, provided the driver selects “C” (Controlled Efficiency) transmission mode. The AMG main menu, displayed in the instrument cluster, provides real-time feedback on whether cylinder shut-off is active and if the engine is running in four or eight-cylinder mode. Even in four-cylinder mode, a substantial 170 lb-ft of torque remains available, ensuring ample power for diverse driving scenarios. When increased power is demanded and the driver moves beyond the partial load range, cylinders two, three, five, and eight are seamlessly reactivated. The transition between four and eight-cylinder operation is instantaneous and virtually imperceptible, preserving passenger comfort. At 3,600 rpm, the activation process is completed in a mere 30 milliseconds.
Mechanism of Cylinder Shut-off
Cylinder shut-off is enabled by an intelligent engine management system, incorporating 16 hydraulically compensating actuators and a sophisticated oil supply system within the cylinder head. These actuators, integrated into the cylinder head, maintain the closure of intake and exhaust valves for cylinders two, three, five, and eight when cylinder shut-off is engaged. Concurrently, fuel supply and ignition to these cylinders are deactivated. This approach not only minimizes load-change losses from the deactivated cylinders but also improves the efficiency of the operational cylinders by shifting their operating point to a higher load range. The compact and lightweight design of the actuators ensures precise valve train operation and supports engine speeds up to 7,200 rpm.
Advanced Crankcase and Cylinder Technology
The engine block of the AMG 5.5-liter V8 is constructed from a die-cast all-aluminum alloy. The engine’s light dry weight of 412 lbs is a result of rigorous lightweight design principles. Main crankshaft bearing covers are made from grey cast iron and are bolted to the crankcase, including laterally, enhancing overall rigidity.
Piston rings are coated with carbon to reduce internal friction and wear, while cast-in Silitec cylinder liners minimize friction for the pistons. “Spectacle” honing is another innovative technique used to further reduce friction and improve fuel economy. This sophisticated process involves mechanically treating the cylinder liners after they are bolted into place. Since conventional honing is not feasible with the cylinder head installed, a “spectacle”-like jig is used to simulate the distortion caused by the cylinder head, allowing the cylinder liners to be honed in a state that mimics their operational condition. This eliminates any static distortion caused by tightening the cylinder head bolts.
Further efficiency-enhancing measures include:
- Weight-optimized cast aluminum pistons with a special piston skirt coating.
- Purpose-designed ventilation holes in the crankcase.
- An oil pump with electrically controlled pressure regulation.
- A dedicated, controllable, low-friction vane cell oil pump for the cylinder shut-off system.
- Engine cooling employing a high-efficiency cross-flow principle.
- Electronically regulated fuel pressure, variably adjustable between 1,450 and 2,900 psi based on demand.
The forged crankshaft, crafted from high-grade 38MnS6BY steel alloy, rotates on five main bearings and features eight counterweights, optimized for torsional stiffness, inertia, low rotating mass, and durability. A dual-mass viscous damper at the front effectively dampens vibrations. Each connecting rod journal on the crankshaft supports two forged, cracked connecting rods.
Four-Valve Technology and Variable Camshaft Adjustment
Optimal combustion chamber charging is achieved through large intake and exhaust valves, four per cylinder. The exhaust valves, exposed to high thermal stress, are hollow and sodium-cooled. Four overhead camshafts actuate the 32 valves via low-maintenance, low-friction cam followers. Infinitely variable camshaft adjustment, within a 40-degree range on both intake and exhaust sides, adapts to engine load and speed, maximizing power and torque. This system also ensures consistent idling at low speeds. Valve overlap can be adjusted based on engine speed to optimize the air-fuel mixture in the combustion chambers and efficiently expel exhaust gases. Hydraulic pivoting actuators control the variable camshaft adjustment, electromagnetically activated and managed by the engine control unit. The camshafts are driven by three low-noise, high-performance silent chains, offering superior noise comfort compared to cylinder roller chains.
Controlled Efficiency Stop/Start Function
The Controlled Efficiency stop/start function further reduces fuel consumption. Standard on the SLK55 AMG, it is active in “C” mode. When the vehicle stops, such as at a traffic light, the V8 engine automatically shuts off. Releasing the brake or pressing the accelerator instantly restarts the engine for a quick departure. Intelligent technology ensures a smooth restart: a crankshaft sensor detects rotation direction and piston positions. The cylinder with the most favorable position receives fuel for immediate start-up, aided by precise piezo-electric injectors for rapid starts. The M152 engine always restarts in eight-cylinder mode.
An “ECO” symbol in the AMG menu indicates stop/start function is active. “ECO4” signifies four-cylinder operation during cylinder shut-off, while “ECO8” denotes eight-cylinder mode. In “S” (Sport) and “M” (Manual) modes, stop/start is deactivated. Drivers can also manually deactivate it in “C” mode, in which case neither “stop/start” nor “ECO” symbols appear.
Alternator Management for Fuel Efficiency
An alternator management system further enhances fuel efficiency by using kinetic energy during engine overrun or braking to charge the battery, instead of wasting it as heat. In other modes, a combination of onboard network and alternator management maintains a low voltage electrical system.
AMG Sports Exhaust System with Integrated Flaps
AMG introduces a new sports exhaust system with an exhaust flap on each side, balancing emotional exhaust notes during spirited driving with a more subdued sound at partial load. The sound design prioritizes a synthesis of performance audibility and Mercedes-Benz’s hallmark long-distance comfort.
Each rear silencer has a flap variably activated based on power demand and engine speed. Below 2,000 rpm at low loads, flaps remain closed, directing exhaust gases through a longer path and additional damping, resulting in a mellow, quiet tone, especially in four-cylinder mode.
Upon acceleration, flaps open progressively to 15, 30, and 50 degrees, allowing some exhaust gases a shorter path while others take the longer, dampened route, creating a sonorous engine note. Under full load at high speeds in eight-cylinder mode, both flaps fully open, unleashing the signature muscular AMG V8 sound, emphasizing the 415 hp engine’s performance.
The two-pipe AMG sports exhaust system, with chromed twin tailpipes, has a 2.56-inch pipe diameter from manifolds to pre-silencer, reduced to 2.36 inches from pre-silencer to rear silencers.
Advanced Emissions Technology
Meeting stringent emissions standards, the 2012 SLK55 AMG complies with Euro-5 and US market (LEV-III, On-Board Diagnosis II) standards. Air gap-insulated manifolds ensure quick catalytic converter response. For efficiency and space, tandem catalytic converter housings are used, integrating two thin-walled ceramic substrates per housing, eliminating the need for underbody catalytic converters. The substrates differ: the front is palladium-coated, the rear bimetal (palladium and rhodium). Lambda sensors are positioned pre and post each catalytic converter housing for precise emissions control.
AMG SPEEDSHIFT PLUS 7G-TRONIC Transmission
Power is delivered to the rear wheels via the AMG SPEEDSHIFT PLUS 7G-TRONIC automatic transmission, offering “Controlled Efficiency” (C), Sport (S), and Manual (M) modes. Automatic rev-matching during downshifts and brief ignition/injection interruption during upshifts enhance shift times and driving excitement. A dual turbine torsional damper with centrifugal pendulum adapts to engine speed, minimizing vibrations in four-cylinder mode and improving comfort.
Driving Dynamics and Handling
The AMG sports suspension with Torque Vectoring Brakes and AMG Direct-Steer system offers both dynamic handling and comfortable cruising. Whether seeking aggressive driving or relaxed touring, the SLK55 AMG adapts. Independent suspension struts, stiffer spring/damper tuning, torque strut bearings, stiffer stabilizers, and increased rear axle negative camber contribute to high cornering speeds and reduced body roll.
Torque Vectoring Brakes selectively apply brakes to the inner rear wheel during cornering, creating a rotational force for precise turn-in. AMG Direct-Steer enhances handling and agility over standard steering, reducing parking effort. A new power steering pump saves fuel by operating only when steering input is needed. The AMG Direct-Steer system’s parameters are tuned to complement the AMG sports suspension, providing optimal response, road feel, and sharp handling in all conditions.
The AMG-exclusive 3-stage ESP® offers driver-selectable control: “ESP ON,” “SPORT Handling Mode,” and “ESP OFF.” The AMG high-performance braking system features ventilated and perforated discs (14.2 in. x 1.4 in. front, 13 in. x .9 in. rear) for responsiveness, short stopping distances, and fade resistance.
Optional AMG Handling Package
The optional AMG Handling Package further elevates sportiness with AMG Performance suspension (stiffer tuning), an AMG rear axle differential lock, two-piece front brake discs, and an AMG Performance steering wheel in premium leather with Alcantara® grips.
Exterior Design and Styling
The 2012 SLK55 AMG’s design blends classic roadster proportions with AMG styling cues and inspiration from the SLS AMG. AMG designers enhanced the long hood, rear-set greenhouse, and crisp rear with AMG-specific front, side, and rear styling. The new AMG front apron features large air inlets and AMG LED daytime running lights. The wide radiator grille, inspired by the SLS AMG, prominently displays a central Mercedes star. On the SLK55 AMG, front apron slats and the lower cross strut are finished in high-gloss black. Darkened clear-lens headlamps and bicolor tail lamps are exclusive to the V8 model. Optional Bi-Xenon headlights with Active Curve Illumination are available.
Vent grilles with chrome-plated fins on the front fenders echo the SLS AMG and Mercedes-Benz 300 SL Roadster from the 1950s. “V8 AMG” lettering highlights the top-tier model. AMG side sill panels connect the front to the rear apron, which features a unique shape, black diffuser insert with three fins, and chrome-plated twin tailpipes. A trunk lid spoiler lip, body-colored, reduces rear lift and improves high-speed stability.
Interior Design and Features
The SLK55 AMG interior, functional, stylish, and high-quality, also draws inspiration from the SLS AMG Roadster. Jet-engine-style air vents and a brushed aluminum center console evoke the super sports car. An AMG-specific analog clock with IWC design is centered on the dashboard. The AMG Performance steering wheel, with flattened top and bottom, features metal trim, aluminum shift paddles, and perforated leather grips. The clear AMG instrument cluster offers four circular gauges, distinctive dials, and the AMG main menu, positioned for optimal driver visibility. The transmission mode selector (C, S, M) is on the center console.
AMG sports seats offer enhanced lateral support and premium leather upholstery with AMG badges and standard AIRSCARF neck-level heating.
MAGIC SKY CONTROL Panorama Roof
The standard retractable hardtop opens/closes in under 20 seconds, converting the roadster to a coupe. Optional panorama roof in tinted polycarbonate is available. The MAGIC SKY CONTROL panorama roof, a world-first, switches between light and dark at the touch of a button, offering an open-air feel even when closed, and shading/cooling when darkened. Magnesium frames make each roof variant about 13 lbs lighter than prior models, lowering the center of gravity for improved agility. AIRGUIDE pivoting wind-stop, an alternative to standard wind-stop, features pivoting transparent plastic wings on rollover bars, requiring no installation/removal.
Advanced Assistance and Safety Systems
The 2012 SLK55 AMG sets safety standards with advanced assistance systems, including fiber-reinforced roll-over bar, two-stage airbags, headbags, thorax airbags, knee airbags, seat belt tensioners with limiters, NECK-PRO head restraints, 3-stage ESP®, and ATTENTION ASSIST.
Optional systems include:
- DISTRONIC PLUS: adaptive cruise control maintaining set distance, capable of stopping and restarting the vehicle.
- PRE-SAFE® Brake: detects imminent rear-end collisions, preparing for autonomous braking between 19 and 124 mph when approaching vehicles are detected.
AMG SLK Heritage
The 2012 SLK55 AMG is the third generation of AMG-enhanced SLK Roadsters, starting with the 2001 SLK32 AMG. The SLK32 AMG featured a supercharged AMG V6 (349 hp, 332 lb-ft torque), leading its class in power. In late 2004, the SLK55 AMG followed, with a 5.5-liter V8 (355 hp, 376 lb-ft torque), further cementing its segment leadership with a large-displacement eight-cylinder engine, a philosophy Mercedes-AMG continued with the 2012 model. The 2012 SLK55 AMG launched in the U.S. market in early 2012, continuing this legacy of performance and innovation.
