The 2012 Mercedes-Benz SLK 55 AMG arrived as the pinnacle of the SLK range, embodying raw power and refined engineering. This high-performance roadster wasn’t just about open-top thrills; it was a statement of automotive excellence, packing the most potent engine ever fitted to an SLK – the naturally aspirated AMG 5.5-liter V8. With an intelligent cylinder shutoff system, the Mercedes-Benz SLK 55 AMG masterfully balanced exhilarating performance with surprising fuel efficiency, setting a new benchmark in its class. Prepare to delve into the details of a car that redefined driving dynamics in the compact, high-performance roadster segment.
Design and First Impressions of the SLK 55 AMG
The Mercedes-Benz SLK 55 AMG, part of the SLK’s third generation unveiled in June 2011, immediately commands attention with its aggressive yet elegant styling. AMG’s signature touch is evident throughout the exterior, starting with the distinctive AMG light-alloy wheels that hint at the performance prowess within. The exclusive AMG body styling further accentuates its sporty character, featuring an AMG spoiler lip that adds a subtle yet effective aerodynamic edge. At the rear, two chrome-plated twin tailpipes not only signal the potent V8 engine but also perfectly complement the classic roadster proportions, injecting a dose of athletic muscle into the SLK’s inherent elegance. The design of the 2012 Mercedes-Benz SLK 55 AMG is undeniably expressive, making it both instantly recognizable and deeply desirable.
Driving Performance: Unleashing the AMG V8 Engine
The Mercedes-Benz SLK 55 AMG is more than just a beautiful roadster; it’s a machine built for “Driving Performance,” AMG’s core brand promise. In the realm of compact high-performance roadsters, nothing quite matches its blend of dynamic driving capabilities, superior sportiness, cutting-edge technology, and surprisingly responsible fuel consumption. The heart of this beast is the AMG 5.5-liter V8 engine, delivering a staggering 415 horsepower and 398 lb-ft of torque. This power translates to breathtaking acceleration, propelling the Mercedes-Benz SLK 55 AMG from 0 to 60 mph in a mere 4.5 seconds. The electronically limited top speed of 155 mph confirms its status as a true performance machine.
Key Performance Specifications
| 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 @ 6,800 rpm |
| Maximum Torque | 398 lb-ft @ 4,500 rpm |
| Engine Weight (dry) | 412 lbs |
| 0-60 mph Acceleration | 4.5 seconds |
| Top Speed | 155 mph (electronically limited) |
This potent V8 engine not only provides exhilarating power but also sets new standards for fuel efficiency in its class. It achieves this remarkable balance by combining raw power with intelligent engineering, producing the signature AMG exhaust growl that only a large-displacement eight-cylinder engine can deliver.
AMG Performance 2015 Strategy and the M152 Engine
Aligned with AMG’s “Performance 2015” strategy, the new V8 engine in the Mercedes-Benz SLK 55 AMG represents a commitment to reducing fuel consumption and emissions across their model range while simultaneously enhancing driving performance. The M152 engine is a testament to this philosophy, showcasing AMG’s dedication to environmental responsibility without compromising on the thrilling driving experience expected from the marque.
A Naturally Aspirated Marvel: The M152 V8
The M152 engine is closely related to the formidable AMG M157 5.5-liter V8 biturbo, found in models like the E63 AMG and CLS63 AMG. Sharing numerous design elements such as displacement, bore/stroke, cylinder spacing, ECO stop/start system, and direct gasoline injection, the M152 distinguishes itself through new intake air ducting, redesigned cylinder heads, a modified valve drive, an adapted oil supply system, and an optimized crankcase. This naturally aspirated engine delivers power in a uniquely linear and responsive manner, offering a different character compared to its turbocharged counterpart.
Advanced Technologies in the M152 Engine
The M152 engine in the Mercedes-Benz SLK 55 AMG is a showcase of advanced automotive technology. It boasts a combination of features unmatched in the industry, including direct injection at an incredibly high pressure of 2,900 psi, spray-guided combustion with piezo injectors, map-controlled cylinder shut-off, an all-aluminum crankcase with “spectacle” honing, four-valve technology with continuous camshaft adjustment, a high compression ratio of 12.6:1, a stop/start system, and generator management. All these technologies work in harmony, allowing the engine to rev beyond 7,000 rpm while maintaining exceptional thermodynamic efficiency for both performance and fuel economy. The cylinder shut-off system is a key innovation, resolving the traditional trade-off between high power output and fuel efficiency in large-displacement engines.
AMG Cylinder Management: Efficiency Through Innovation
A standout feature of the Mercedes-Benz SLK 55 AMG is the AMG Cylinder Management system. Developed entirely by Mercedes-AMG, this system dramatically improves fuel efficiency by deactivating cylinders two, three, five, and eight under partial load. This technology, similar in concept to systems used in Formula 1 V8 engines, significantly reduces fuel consumption without sacrificing performance when power is needed.
How Cylinder Shut-off Works
The cylinder shut-off function engages between 800 and 3,600 rpm when the driver selects “C” (Controlled Efficiency) transmission mode. The instrument cluster clearly displays whether cylinder shut-off is active, indicating whether the engine is operating in four or eight-cylinder mode. Even in four-cylinder mode, the engine provides a substantial 170 lb-ft of torque, ensuring ample power for everyday driving. When more power is demanded, the transition from four to eight cylinders is instantaneous and seamless, taking only 30 milliseconds at 3,600 rpm, ensuring no compromise in driving comfort.
Deactivating Cylinders: Precision Engineering
Intelligent engine management makes cylinder shut-off possible, utilizing 16 hydraulically compensating actuators and a sophisticated oil supply system in the cylinder head. These actuators, integrated into the cylinder head, keep the intake and exhaust valves closed for cylinders two, three, five, and eight when deactivated. Simultaneously, fuel supply and ignition to these cylinders are cut off. This not only minimizes load-change losses but also increases the efficiency of the remaining four active cylinders by shifting their operating point to a higher load range. The compact and lightweight design of the actuators allows for high engine speeds up to 7,200 rpm and taut valve train operation.
Engine Construction and Efficiency Enhancements
The crankcase of the AMG 5.5-liter V8 engine in the Mercedes-Benz SLK 55 AMG is constructed from diecast all-aluminum, contributing to a low dry engine weight of just 412 lbs thanks to meticulous lightweight construction techniques. Grey cast iron bearing covers for the main crankshaft bearings, bolted to the crankcase and sides, ensure high rigidity.
Friction Reduction and Optimized Components
Carbon-coated piston rings minimize internal friction and wear, while cast-in Silitec cylinder liners further reduce friction for the pistons. “Spectacle” honing, a unique and complex process, mechanically treats the cylinder liners after they are bolted in place, eliminating static distortion caused by cylinder head bolt tightening. Other efficiency-enhancing measures include:
- Weight-optimized cast aluminum pistons with special skirt coating.
- Special ventilation holes in the crankcase.
- Oil pump with electrically controlled pressure stage.
- Separate, low-friction vane cell oil pump for cylinder shut-off.
- Efficient cross-flow engine cooling.
- Electronically controlled fuel pressure (1,450 to 2,900 psi).
The forged crankshaft, made from high-grade 38MnS6BY steel alloy, rotates in five main bearings and features eight counterweights, optimized for torsional rigidity, inertia, and longevity. A two-mass viscous damper at the front effectively eliminates vibrations. Each connecting rod journal supports two forged, cracked connecting rods.
Four-Valve Technology and Variable Camshaft Adjustment
Optimal combustion chamber charging in the Mercedes-Benz SLK 55 AMG is achieved through large intake and exhaust valves – four per cylinder. Sodium-cooled, hollow exhaust valves withstand high thermal loads. Four overhead camshafts control the 32 valves via low-maintenance, low-friction cam followers. Infinitely variable camshaft adjustment (40 degrees range on intake and exhaust sides) adapts to engine load and speed, maximizing output and torque while ensuring smooth idling. Valve overlap is adjusted based on engine speed to optimize fuel/air supply and exhaust gas removal. Hydraulic pivoting actuators, electromagnetically activated and controlled by the engine control unit, manage the variable camshaft adjustment. High-performance silent chains drive the camshafts, offering superior noise comfort compared to cylinder roller chains.
Controlled Efficiency Stop/Start Function
The Controlled Efficiency stop/start function further enhances fuel economy in the Mercedes-Benz SLK 55 AMG. Standard equipment and active in “C” mode, it automatically shuts off the V8 engine when the car comes to a stop, such as at traffic lights. Releasing the brake or pressing the accelerator instantly restarts the engine. Intelligent technology ensures a smooth and quick restart: a crankshaft sensor detects rotation direction and piston positions, injecting fuel into the cylinder with the most favorable piston position for immediate ignition. The M152 engine always restarts in eight-cylinder mode.
The instrument cluster displays “ECO” when stop/start is active, “ECO4” during four-cylinder operation, and “ECO8” in eight-cylinder mode. In “S” (Sport) and “M” (Manual) modes, the stop/start function is deactivated, but drivers can also manually disable it in “C” mode.
Alternator Management and Fuel Efficiency
An alternator management system further contributes to the fuel efficiency of the Mercedes-Benz SLK 55 AMG. During engine overrun or braking, kinetic energy is used to charge the battery, reducing wasted energy. In other operating modes, the system manages the electrical system to maintain a low voltage, optimizing fuel consumption.
AMG Sports Exhaust System with Integrated Exhaust Flaps
The Mercedes-Benz SLK 55 AMG features a newly developed AMG sports exhaust system with exhaust flaps on each side. This technology balances a thrilling exhaust note during spirited driving with a more subdued sound during relaxed cruising. The system is designed to provide a perfect blend of performance audibility and Mercedes-Benz’s signature long-distance comfort.
Variable Exhaust Sound Dynamics
Each rear silencer has a flap that variably activates based on driver input and engine speed. Below 2,000 rpm and at low loads, the flaps remain closed, forcing exhaust gases through a longer path and additional damping, resulting in a quieter and more refined sound, especially in four-cylinder mode. During acceleration, the flaps progressively open (15, 30, up to 50 degrees), allowing some exhaust gases to take a shorter path, creating a more sonorous engine note. Under full load and at higher engine speeds in eight-cylinder mode, both flaps fully open, unleashing the full muscular sound of the AMG V8, emphasizing the 415 hp engine’s performance potential.
The dual-pipe AMG sports exhaust system, with chrome-plated twin tailpipes, features a 2.56-inch pipe diameter from the manifolds to the pre-silencer, reducing to 2.36 inches from the pre-silencer to the rear silencers.
Emissions Technology and Catalytic Converters
The exhaust system of the Mercedes-Benz SLK 55 AMG is engineered to meet stringent emissions standards (Euro-5 and US LEV-III) while maintaining its characteristic AMG engine sound. Air gap-insulated manifolds ensure rapid catalytic converter response. For efficiency and space-saving, tandem catalytic converter housings are positioned on each side of the vehicle, close to the firewall. Each housing contains two thin-walled ceramic substrates, eliminating the need for underbody catalytic converters. The substrates differ: the front one is palladium-coated, and the rear has a bimetal palladium-rhodium coating. Lambda sensors are placed before and between the substrates in each cylinder row for precise emissions control.
AMG SPEEDSHIFT PLUS 7G-TRONIC Transmission
Power in the Mercedes-Benz SLK 55 AMG is delivered to the rear wheels via the AMG SPEEDSHIFT PLUS 7G-TRONIC automatic transmission, offering three modes: “Controlled Efficiency” (C), Sport (S), and Manual (M). Automatic rev-matching during downshifts and brief ignition/injection interruption during upshifts enhance shift times and driving emotion. A double turbine torsional damper with centrifugal pendulum adapts to engine speed, minimizing vibrations in four-cylinder mode and improving overall comfort.
AMG Sports Suspension and Handling Dynamics
The AMG sports suspension, combined with Torque Vectoring Brakes and AMG Direct-Steer system, provides the Mercedes-Benz SLK 55 AMG with exceptional lateral dynamics and agile handling. Whether seeking aggressive cornering or comfortable cruising, the SLK 55 AMG excels. Independent suspension struts, stiffer spring/damper tuning, torque strut bearings on the front axle, stiffer stabilizers, and increased negative camber on the rear axle contribute to high cornering speeds and reduced body roll.
Torque Vectoring Brakes and AMG Direct-Steer
Torque Vectoring Brakes enhance cornering by applying selective braking to the inside rear wheel, creating a rotational movement for precise and controlled turn-in. The AMG Direct-Steer system improves handling and agility compared to standard steering, while also reducing parking effort. A new power steering pump reduces fuel consumption by using energy only when steering. The AMG Direct-Steer system’s parameter function is specifically tuned to the AMG sports suspension, providing optimal response, road feel, and sharp handling.
3-Stage ESP® and AMG High-Performance Brakes
The AMG-exclusive 3-stage ESP® system offers selectable modes: “ESP ON,” “SPORT Handling Mode,” and “ESP OFF,” giving drivers greater control. The AMG high-performance braking system features internally ventilated and perforated discs on all wheels (14.2 in. x 1.4 in. front, 13 in. x 0.9 in. rear), providing outstanding responsiveness, short stopping distances, and excellent fade resistance.
Optional AMG Handling Package
For drivers seeking even greater driving dynamics, the optional AMG Handling Package for the Mercedes-Benz SLK 55 AMG enhances sportiness with an AMG Performance suspension featuring stiffer tuning, an AMG rear axle differential lock, two-piece front brake discs, and an AMG Performance steering wheel in premium leather with Alcantara® inserts.
Exterior Design and AMG Styling Cues
The Mercedes-Benz SLK 55 AMG boasts classic roadster proportions with distinctive AMG design elements, drawing inspiration from the SLS AMG. AMG designers have enhanced the SLK’s inherent lines with unique styling at the front, sides, and rear. The AMG front apron features large air inlets and AMG-specific LED daytime running lights. The wide radiator grille, inspired by the SLS AMG, prominently displays a central Mercedes star. The front apron slats and lower cross strut are finished in high-gloss black. Darkened clear-lens headlamps and bi-color tail lamps are standard, exclusive to the V8 model. Optional Bi-Xenon headlights with Active Curve Illumination are also available.
Vent grilles with chrome-plated fins on the front fenders recall the SLS AMG and the classic Mercedes-Benz 300 SL Roadster. “V8 AMG” lettering highlights the top-of-the-line model. AMG-specific side sill panels and a unique rear apron with a black diffuser insert, three fins, and chrome-plated twin tailpipes complete the distinctive look. A body-colored spoiler lip on the trunk lid reduces rear axle lift at high speeds, improving stability.
Interior Design: Inspired by the SLS AMG
The interior of the Mercedes-Benz SLK 55 AMG mirrors the functional, stylish, and high-quality design of 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 positioned in the center of the dashboard. The AMG Performance steering wheel, with a flattened top and bottom, features metal trim, aluminum shift paddles, and perforated leather grip areas. The AMG instrument cluster, with four circular instruments and distinctive dials, is driver-focused and includes the AMG main menu. The transmission mode selector (C, S, M) is located 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 Mercedes-Benz SLK 55 AMG offers a retractable hardtop that opens and closes in under 20 seconds, transforming the roadster into a coupe. Optional panorama roof panels in tinted polycarbonate are available. The groundbreaking panorama roof with MAGIC SKY CONTROL is also an option, allowing the glass roof to switch between light and dark at the touch of a button. In its transparent state, it provides an open-air feel, while in its dark state, it offers shade and reduces interior heat. Magnesium frames for all roof variants reduce weight by approximately 13 lbs compared to the previous model, lowering the car’s center of gravity and improving agility. The AIRGUIDE pivoting wind-stop, attached to the rollover bars, offers a comfortable alternative to traditional wind-stops without requiring installation or removal.
Advanced Assistance and Safety Systems
The Mercedes-Benz SLK 55 AMG sets high safety standards with numerous advanced assistance systems. Standard safety features include fiber-reinforced roll-over bars, two-stage airbags for driver and front passenger, headbags, thorax airbags, knee airbags, seat belt tensioners with force limiters, NECK-PRO crash-active head restraints, three-stage ESP®, and ATTENTION ASSIST drowsiness detection.
Optional assistance systems include:
- DISTRONIC PLUS: Adaptive cruise control that automatically maintains a set distance from the vehicle ahead, with stop-and-go capability.
- PRE-SAFE® Brake: Detects imminent rear-end collisions and prepares for autonomous braking at speeds between 19 and 124 mph.
The Legacy of SLK AMG Models
The 2012 Mercedes-Benz SLK 55 AMG represents the third generation of dynamic AMG roadsters in the SLK lineage. The journey began in 2001 with the SLK32 AMG, featuring 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 with a 5.5-liter V8 engine, delivering 355 hp and 376 lb-ft of torque, further solidifying its segment leadership. Mercedes-AMG has consistently maintained its V8 philosophy in this segment, culminating in the impressive 2012 Mercedes-Benz SLK 55 AMG, a testament to performance, innovation, and driving passion.
Conclusion: The Quintessential Performance Roadster
The 2012 Mercedes-Benz SLK 55 AMG stands as a remarkable achievement in automotive engineering. It successfully marries the thrilling performance of a naturally aspirated V8 engine with surprising fuel efficiency thanks to innovative technologies like cylinder management. Its striking design, luxurious interior, and advanced features solidify its position as the ultimate performance roadster. For enthusiasts seeking open-top driving exhilaration without compromise, the Mercedes-Benz SLK 55 AMG remains a compelling choice, representing the pinnacle of the SLK lineage and AMG’s unwavering commitment to “Driving Performance.”
