The 2012 AMG Mercedes-Benz SLK55 marked a significant milestone in the celebrated SLK lineage, staking its claim as the most potent iteration ever produced. This roadster wasn’t just about open-top thrills; it was a symphony of raw power and refined engineering, all thanks to its groundbreaking AMG 5.5-liter V8 engine. This powerplant wasn’t just about brute force; it ingeniously incorporated cylinder shutoff technology, a feat that harmonized exhilarating performance with unprecedented fuel efficiency for its class. Boasting a formidable 415 horsepower and a commanding 398 lb-ft of torque, the 2012 SLK55 AMG was engineered to dominate its competitive landscape. Driving enthusiasts were treated to a high-performance experience, underpinned by the AMG sports suspension with Direct-Steer system, Torque Vectoring Brakes, and 3-stage ESP®, all working in concert with the AMG high-performance braking system to deliver unparalleled control and dynamism. The anticipation for the 2012 SLK55 AMG culminated in its arrival at U.S. showrooms in early 2012, ready to redefine the performance roadster segment.
Part of the SLK’s third generation, which debuted in June, the AMG variant immediately commanded attention. Its aesthetic was a clear departure, signaling enhanced athleticism and exclusivity. Distinctive AMG light-alloy wheels and bespoke AMG body styling, complete with an AMG spoiler lip, sculpted its profile. The rear was punctuated by two chrome-plated twin tailpipes, underscoring its potent performance capabilities. These elements amplified the classic roadster silhouette, injecting a palpable sense of athletic prowess. The design language of the 2012 SLK55 AMG was both striking and instantly recognizable, a testament to AMG’s commitment to visual distinction and performance-oriented design.
.jpg_Version_1500x1000.jpg)
AMG light-alloy wheels and exclusive body styling, enhancing the 2012 AMG Mercedes-Benz SLK55’s athletic appearance.
The 2012 SLK55 AMG wasn’t just a car; it was an embodiment of AMG’s new brand ethos: “Driving Performance.” Within the realm of compact, high-performance roadsters, it stood unchallenged, offering an unmatched synthesis of dynamic driving characteristics, superior sporting pedigree, cutting-edge technology, and surprisingly frugal fuel consumption. The raw figures spoke volumes: a sprint from 0 to 60 mph in a mere 4.5 seconds, and an electronically governed top speed of 155 mph. These statistics weren’t just numbers; they were a promise of exhilarating experiences behind the wheel of the 2012 AMG Mercedes-Benz SLK55.
To truly appreciate the engineering marvel beneath the hood, examining the key performance indicators is crucial:
| Feature | 2012 SLK55 AMG |
|---|---|
| Displacement | 5,461 cc |
| Bore x Stroke | 3.86 in x 3.56 in |
| Compression Ratio | 12.6 : 1 |
| Peak Output | 415 hp at 6,800 rpm |
| Maximum Torque | 398 lb-ft at 4,500 rpm |
| Engine Weight (dry) | 412 lbs |
| 0-60 mph Acceleration | 4.5 s |
| Top Speed | 155 mph** |
| * provisional figures; ** electronically limited |
These figures highlight the robust heart of the 2012 AMG Mercedes-Benz SLK55. The 5.5-liter engine was not just powerful; it was also designed with efficiency in mind, setting new benchmarks for V8 engines in terms of fuel economy. This achievement was all the more impressive considering the engine’s capacity to deliver both breathtaking power and the signature, resonant growl that only a large-displacement eight-cylinder engine can produce. The 2012 SLK55 AMG was a testament to the fact that performance and responsibility could coexist.
Aligned with AMG’s “Performance 2015” strategy, this new V8 engine was a clear indicator of the brand’s commitment to continuous improvement. The strategy aimed to progressively reduce fuel consumption and emissions across new models while simultaneously elevating driving performance – the core tenet of the AMG brand. The M152 engine in the 2012 AMG Mercedes-Benz SLK55 was a tangible demonstration of AMG’s dedication to both thrilling performance and environmental consciousness, showcasing a sense of social responsibility without compromising on the exhilarating driving experience that AMG is known for.
The M152 engine, a naturally aspirated eight-cylinder marvel, shared close familial ties with the V8 biturbo M157 engine, which had debuted in 2010 and powered other AMG powerhouses like the E63 AMG and CLS63 AMG. The two engines shared numerous fundamental design elements, including displacement, bore and stroke dimensions, cylinder spacing, ECO stop/start system, and direct gasoline injection technology. However, the M152 distinguished itself with unique features tailored for the SLK55 AMG, such as redesigned intake air ducting, bespoke cylinder heads, a modified valve drive, a specifically adapted oil supply system, and an optimized crankcase. These distinctions underscored AMG’s commitment to tailoring engine design to the specific performance characteristics and demands of each vehicle model, ensuring optimal performance in the 2012 AMG Mercedes-Benz SLK55.
Key components of the AMG M152 engine, showcasing the advanced engineering within the 2012 AMG Mercedes-Benz SLK55.
The M152 engine within the 2012 AMG Mercedes-Benz SLK55 was a showcase of cutting-edge automotive technology, boasting a combination of advanced features unparalleled in the global automotive landscape. Its direct injection system, operating at a pressure of 2,900 psi, worked in concert with spray-guided combustion and piezo injectors. These systems were further enhanced by map-controlled cylinder shut-off, an all-aluminum crankcase featuring “spectacle” honing, four-valve technology with continuous camshaft adjustment, a high compression ratio of 12.6:1, a stop/start system, and sophisticated generator management. All of these technologies allowed the engine to rev beyond 7,000 rpm, contributing to exceptional thermodynamic efficiency. This efficiency was crucial for achieving both remarkable fuel economy and low exhaust emissions. The utilization of a large-displacement, naturally-aspirated eight-cylinder engine equipped with cylinder shut-off ingeniously resolved the inherent conflict between delivering high power and torque and maintaining low fuel consumption, making the 2012 AMG Mercedes-Benz SLK55 a leader in its class.
A cornerstone of the 2012 AMG Mercedes-Benz SLK55’s efficiency was the AMG Cylinder Management system. This sophisticated cylinder shut-off technology, developed entirely by Mercedes-AMG, significantly enhanced fuel efficiency by deactivating cylinders two, three, five, and eight under partial load conditions. This clever system resulted in a substantial reduction in fuel consumption. Remarkably, this technology found its parallel in the high-performance 750-hp V8 engines used in Formula 1, demonstrating that efficiency was a priority even at the pinnacle of motorsport. In Formula 1 applications, cylinder shut-off was employed during situations like low-speed cornering, Safety Car periods, or pit stops.
The cylinder shut-off function in the 2012 AMG Mercedes-Benz SLK55 was operational across a broad engine speed range, from 800 to 3,600 rpm, provided the driver selected the “C” (Controlled Efficiency) transmission mode. The AMG main menu within the instrument cluster provided real-time feedback to the driver, indicating whether cylinder shut-off was active and whether the engine was running in four or eight-cylinder mode. Even in four-cylinder mode, the engine still delivered a substantial 170 lb-ft of torque, ensuring ample power for most everyday driving scenarios. When the driver demanded more power and moved out of the partial load range, cylinders two, three, five, and eight seamlessly reactivated. The transition between four and eight-cylinder operation was designed to be instantaneous and imperceptible, ensuring no compromise in occupant comfort. At an engine speed of 3,600 rpm, the activation process occurred in a mere 30 milliseconds, highlighting the system’s responsiveness.
Diagram illustrating the AMG Cylinder Management system, responsible for the 2012 AMG Mercedes-Benz SLK55’s fuel efficiency.
Cylinder shut-off in the 2012 AMG Mercedes-Benz SLK55 was enabled by an intelligent engine management system, incorporating 16 hydraulically compensating actuators and a meticulously designed oil supply system within the cylinder head. These compensating actuators, integrated directly into the cylinder head, played a crucial role in keeping the intake and exhaust valves of cylinders two, three, five, and eight closed when cylinder shut-off was engaged. Simultaneously, the fuel supply and ignition to these cylinders were deactivated. This dual action not only minimized load-change losses from the deactivated cylinders but also enhanced the efficiency of the remaining four cylinders by shifting their operating point into a higher load range. The actuators were engineered to be compact and lightweight, allowing for precise valve train operation and enabling engine speeds up to 7,200 rpm.
The crankcase of the 2012 AMG 5.5-liter V8 engine was constructed from diecast all-aluminum, contributing to a remarkably low dry engine weight of just 412 lbs. This achievement was a direct result of AMG’s commitment to uncompromising lightweight construction principles. For enhanced rigidity, the bearing covers for the main crankshaft bearings were made from grey cast iron and were securely bolted to the crankcase, both from below and laterally.
To minimize internal friction and reduce wear, the piston rings were coated with carbon. Cast-in Silitec cylinder liners further minimized friction for the eight pistons. “Spectacle” honing, a unique and sophisticated process, was employed to further reduce friction and, consequently, fuel consumption. In this complex procedure, the cylinder liners underwent mechanical surface treatment after being bolted in place. Since conventional honing was impossible with the cylinder head installed, a specialized jig resembling spectacles was bolted to the crankcase. This jig simulated the distortion that would occur with the cylinder head in place, allowing for precise mechanical surface treatment of the cylinder liners in their stressed state. This eliminated any static distortion of the cylinder liners caused by tightening the cylinder head bolts, ensuring optimal cylinder geometry and reduced friction.
Further measures implemented to optimize efficiency in the 2012 AMG Mercedes-Benz SLK55 engine included:
- Weight-optimized cast aluminum pistons with a special piston skirt coating.
- Special ventilation holes in the crankcase.
- An oil pump featuring an electrically controlled pressure stage.
- A dedicated oil pump for cylinder shut-off, employing a controllable, low-friction vane cell pump design.
- Engine cooling utilizing a highly efficient cross-flow principle.
- Electronically controlled fuel pressure, fully variable and demand-related between 1,450 and 2,900 psi.
The forged crankshaft, crafted from high-grade 38MnS6BY steel alloy, rotated smoothly in five main bearings. It featured eight counterweights and was meticulously optimized for torsional rigidity, inertia, low rotating masses, and extended operational life. A two-mass viscous damper, mounted at the front, effectively eliminated vibrations. Each connecting rod journal on the crankshaft supported two forged, cracked connecting rods.
Optimal combustion chamber charging was achieved through large intake and exhaust valves, with four valves per cylinder. The exhaust valves, subjected to high thermal stress, were hollow and sodium-cooled. Four overhead camshafts actuated the 32 valves via low-maintenance, low-friction cam followers. Infinitely variable camshaft adjustment, spanning 40 degrees on both the intake and exhaust sides, adapted to engine load and speed, optimizing both power and torque output. This system also ensured consistent idling at low speeds. Depending on engine speed, valve overlap could be varied to optimize the air-fuel mixture delivery to the combustion chambers and efficiently remove exhaust gases. Hydraulic actuation via four pivoting actuators controlled the variable camshaft adjustment, with electromagnetic activation and control handled by the engine control unit. The camshafts were driven by three high-performance silent chains, which offered significant noise reduction advantages compared to cylinder roller chains.
The Controlled Efficiency stop/start function, a standard feature on the 2012 AMG Mercedes-Benz SLK55, further contributed to its impressive fuel economy. This system was active in the fuel-efficient “C” transmission mode. When the driver brought the car to a halt, for instance, at a red traffic light, the V8 engine automatically shut off. Upon releasing the brake pedal or depressing the accelerator, the engine restarted instantly, allowing for prompt acceleration. Intelligent technology ensured a comfortable and immediate starting procedure: a crankshaft sensor detected the direction of rotation and registered the resting position of all eight pistons. For an automatic engine start, the cylinder with the most favorable piston position received a fuel injection into its combustion chamber. The precise piezo-electric injectors played a crucial role in facilitating especially rapid starts. The M152 engine always restarted in eight-cylinder operation.
An “ECO” symbol framed in the AMG main menu visually indicated to the driver that the Controlled Efficiency stop/start function was active. When cylinder shut-off was also engaged, the symbol changed to “ECO4,” while “ECO8” indicated eight-cylinder operation. In the more performance-oriented driving modes, “S” (Sport) and “M” (Manual), the stop/start function was automatically deactivated. Drivers could also manually switch it off while in “C” mode if desired, in which case neither the “stop/start” nor the “ECO” symbol would be displayed.
An alternator management system further enhanced fuel efficiency in the 2012 AMG Mercedes-Benz SLK55. During engine overrun or braking, kinetic energy was harnessed to charge the battery, rather than being dissipated as heat. In other operating modes, a combination of onboard network and alternator management kept the electrical system voltage at a low level, reducing parasitic losses and improving overall efficiency.
AMG debuted a new sports exhaust system with integrated exhaust flaps on the 2012 SLK55 AMG. This technology effectively balanced the desire for an emotive exhaust note during spirited driving with a more subdued engine sound during partial-load cruising. The sound design prioritized a perfect blend of perceptible performance and the long-distance comfort expected of a Mercedes-Benz.
Each of the two rear silencers incorporated a flap that was variably activated based on the driver’s power demand and engine speed. At low loads and engine speeds below 2,000 rpm, the flaps remained closed. This forced the exhaust gases to travel a longer path through an additional damping element, resulting in a pleasantly muted engine sound and effectively suppressing disruptive frequencies – particularly beneficial in four-cylinder operation with cylinder shut-off active.
When the driver accelerated, the flaps progressively opened, starting at a 15-degree angle, then 30, and up to 50 degrees. This allowed some exhaust gases to take a shorter path while the remainder followed the longer, acoustically dampened route, producing a sonorous engine note. Under full load and at higher engine speeds in eight-cylinder mode, both flaps fully opened, unleashing the distinct, muscular sound characteristic of an AMG V8 engine, emphasizing the performance potential of the 415 hp naturally aspirated engine.
The two-pipe AMG sports exhaust system, featuring two chromed twin tailpipes, had a pipe diameter of 2.56 inches from the manifolds to the pre-silencer. From the pre-silencer to the rear silencers, the diameter was reduced to 2.36 inches, optimizing both exhaust flow and sound characteristics.
The 2012 SLK55 AMG was engineered to meet stringent emissions standards, complying with the Euro-5 standard and all US market requirements (LEV-III standard, On-Board Diagnosis II). Air gap-insulated manifolds ensured rapid catalytic converter response. For efficiency and space optimization, a tandem catalytic converter housing was employed on each side of the vehicle. Located near the firewall, each housing contained two thin-walled ceramic substrates, eliminating the need for separate underbody catalytic converters. The two ceramic substrates differed in composition to ensure effective emissions control. The front substrate was coated with palladium, while the rear one featured a bimetal coating of palladium and rhodium. Lambda sensors, positioned upstream and downstream of each catalytic converter housing, provided precise emissions monitoring and control.
Power delivery to the rear wheels was managed by the AMG SPEEDSHIFT PLUS 7G-TRONIC automatic transmission, offering three distinct transmission modes: “Controlled Efficiency” (C), Sport (S), and Manual (M). Automatic rev-matching during downshifts and brief, precisely timed interruptions of ignition and injection during upshifts at full load reduced shift times and enhanced the driving experience. A double turbine torsional damper with centrifugal pendulum adapted to engine speed, minimizing vibrations during four-cylinder operation and improving overall comfort.
The AMG sports suspension, coupled with Torque Vectoring Brakes and the AMG Direct-Steer system, provided a harmonious blend of impressive lateral dynamics and agile handling. Whether the driver sought aggressive driving or comfortable cruising, the 2012 SLK55 AMG adeptly accommodated both. Independent suspension struts with firmer spring and damper tuning, torque strut bearings on the front axle with increased rigidity, stiffer stabilizers at all four corners, and increased negative camber on the rear axle contributed to high cornering speeds and minimized body roll during rapid directional changes.
In challenging cornering situations, Torque Vectoring Brakes subtly applied braking force to the inner rear wheel, creating a rotational moment around the vertical axis. This helped the 2012 SLK55 AMG steer into the turn with precision and control, without compromising performance. Complementing this was the AMG Direct-Steer system, which enhanced handling and agility compared to the standard steering while also reducing parking effort. A new power steering pump improved fuel efficiency by drawing power only when steering input was actually applied. The AMG Direct-Steer system also featured parameterization tailored to the AMG sports suspension, resulting in optimal responsiveness, exceptional road feel, and sharp handling in all driving scenarios.
The AMG-exclusive 3-stage ESP® system offered drivers customizable control. The ESP® button on the center console allowed selection between “ESP ON,” “SPORT Handling Mode,” and “ESP OFF.” The AMG high-performance braking system featured internally ventilated and perforated brake discs on all wheels, measuring 14.2 in. x 1.4 in. at the front and 13 in. x .9 in. at the rear. This system provided outstanding responsiveness, short stopping distances, and excellent fade resistance.
For drivers seeking even greater driving dynamics, the optional AMG Handling Package was available. This package included an AMG Performance suspension with stiffer tuning, an AMG rear axle differential lock, two-piece front brake discs, and a three-spoke AMG Performance steering wheel trimmed in premium leather with Alcantara® inserts in the grip areas.
The 2012 SLK55 AMG’s design was unmistakably AMG, blending classic roadster proportions with distinctive AMG styling cues and subtle hints of the SLS AMG supercar. AMG designers enhanced the already striking lines of the long hood, rearward greenhouse, and crisp rear section with signature AMG elements at the front, sides, and rear. The new AMG front apron featured large air inlets and AMG-specific LED daytime running lights. Inspired by the SLS AMG, the wide radiator grille prominently displayed a centrally-positioned Mercedes star. On the SLK55 AMG, the slats in the front apron and the lower cross strut were finished in high-gloss black. Darkened clear-lens headlamps and darkened bicolor tail lamps were standard, exclusive to this top-tier V8 model. Bi-Xenon headlights with Active Curve Illumination were also available as an option.
The vent grilles with chrome-plated fins on the front fenders not only echoed the SLS AMG but also recalled the iconic Mercedes-Benz 300 SL Roadster from the 1950s. “V8 AMG” lettering beneath the grilles proudly denoted the range-topping eight-cylinder model. AMG-specific side sill panels seamlessly extended the front apron’s design to the new rear apron, which featured a unique shape, a black diffuser insert with three fins, and the two chrome-plated twin tailpipes of the AMG sports exhaust system. The spoiler lip on the trunk lid, painted in body color, reduced rear axle lift, enhancing high-speed stability.
Exterior design elements emphasizing the sporty and luxurious aesthetics of the 2012 AMG Mercedes-Benz SLK55.
The interior of the 2012 SLK55 AMG mirrored its exterior in being functional, stylish, and high-quality, drawing inspiration from the SLS AMG Roadster. Jet-engine-style air vents and a brushed aluminum center console evoked the supercar connection. An AMG-specific analog clock, designed by IWC, was centrally positioned on the dashboard. The AMG Performance steering wheel, with flattened top and bottom sections, featured metal trim, aluminum shift paddles, and perforated leather grip areas. The clearly arranged AMG instrument cluster, positioned directly in the driver’s line of sight, included four circular instruments, distinctive dials, and the AMG main menu. The transmission mode selector for C, S, and M was conveniently located on the center console.
AMG sports seats, offering enhanced lateral support, were upholstered in premium leather and featured AMG badges in the backrests, along with the standard AIRSCARF neck-level heating system.
The standard retractable hardtop of the 2012 AMG Mercedes-Benz SLK55 transformed the roadster into a closed-top coupe in under 20 seconds. Optional roof choices included a tinted polycarbonate panorama roof panel and the innovative panorama roof with MAGIC SKY CONTROL. MAGIC SKY CONTROL allowed the glass roof to switch between light and dark at the touch of a button, offering an open-air feel even in cold weather or providing shade and heat reduction in its darkened state.
The frames of all three roof variants were constructed from magnesium, making each roof approximately 13 lbs lighter than the previous model, lowering the car’s center of gravity and improving agility. The new AIRGUIDE pivoting wind-stop, an alternative to the standard wind-stop, consisted of pivoting transparent plastic wings attached to the rollover bars, offering convenience and effectiveness without requiring installation or removal.
The 2012 SLK55 AMG set new benchmarks for safety, incorporating a suite of advanced assistance systems. Standard safety features included a new fiber-reinforced roll-over bar, two-stage driver and front passenger airbags, headbags, thorax airbags, knee airbags, seat belt tensioners with belt force limiters, NECK-PRO crash-active head restraints, three-stage ESP®, and ATTENTION ASSIST drowsiness detection.
Optional assistance systems included:
- DISTRONIC PLUS: Adaptive cruise control that automatically maintained a set distance from the vehicle ahead, even bringing the SLK55 AMG to a complete stop and resuming acceleration.
- PRE-SAFE® Brake: Detected imminent rear-end collision risks and prepared for autonomous braking, active between 19 and 124 mph when detecting moving vehicles ahead.
The 2012 SLK55 AMG represented the third generation of AMG-engineered SLK Roadsters. The lineage began in 2001 with the SLK32 AMG, powered by a supercharged AMG V6 engine producing 349 hp and 332 lb-ft of torque, then the most powerful in its class. In late 2004, the SLK55 AMG debuted, featuring an AMG 5.5-liter V8 engine with 355 hp and 376 lb-ft of torque, further solidifying its segment leadership. Mercedes-AMG remained committed to the large-displacement eight-cylinder philosophy with the 2012 successor, the new 2012 SLK55 AMG, which launched in the U.S. market in early 2012, continuing the legacy of performance and innovation.
