The 2012 SLK Benz, specifically the SLK55 AMG, represents the pinnacle of performance within the SLK lineup. This model year marked the arrival of the most potent SLK ever created, boasting a brand-new AMG 5.5-liter V8 engine. This engine wasn’t just about raw power; it cleverly integrated cylinder shutoff technology to balance exhilarating performance with surprising fuel efficiency. With a robust 415 horsepower and 398 lb-ft of torque at its command, the 2012 SLK55 AMG was engineered to dominate its class. AMG sports suspension, featuring a Direct-Steer system, Torque Vectoring Brakes, and 3-stage ESP®, along with the AMG high-performance braking system, ensure that this power translates to exceptional driving dynamics. The 2012 SLK55 AMG made its debut in US showrooms in early 2012, ready to redefine the compact high-performance roadster segment.
Part of the SLK’s third generation introduced in June, the AMG variant immediately distinguishes itself. Exterior enhancements such as unique AMG light-alloy wheels and exclusive AMG body styling, including an AMG spoiler lip, immediately signal its performance pedigree. The rear is punctuated by two chrome-plated twin tailpipes, adding an aggressive touch to the classic roadster silhouette. The 2012 SLK55 AMG’s design is both striking and instantly recognizable, a testament to AMG’s commitment to visual dynamism.
The SLK55 AMG perfectly embodies AMG’s “Driving Performance” philosophy. In the realm of compact, high-performance roadsters, it stands unmatched in its fusion of driving dynamics, superior sportiness, cutting-edge technology, and optimized fuel consumption. The SLK55 AMG achieves a 0 to 60 mph sprint in just 4.5 seconds and reaches an electronically limited top speed of 155 mph, showcasing its impressive capabilities.
| 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 |
Pioneering fuel efficiency for V8 engines, the 5.5-liter powerplant balances economical operation with potent power delivery and the signature V8 exhaust note. Aligned with AMG’s “Performance 2015” strategy, this engine exemplifies the brand’s commitment to reducing fuel consumption and emissions while simultaneously enhancing driving performance. The M152 engine underscores AMG’s dedication to both performance and environmental responsibility.
This new naturally aspirated eight-cylinder engine is closely related to the V8 biturbo found in other high-performance AMG models. The M152 shares numerous design elements with the AMG M157 5.5-liter V8 biturbo, including displacement, bore/stroke, cylinder spacing, ECO stop/start system, and direct gasoline injection. Key differentiators include redesigned intake air ducting, new cylinder heads, a modified valve drive, an adapted oil supply system, and an optimized crankcase, all tailored for the naturally aspirated application in the Slk Benz 2012.
The M152 engine showcases an unparalleled combination of advanced technologies. Its high-tech design features direct injection at an impressive 2,900 psi, spray-guided combustion, and piezo injectors. These are integrated with 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. Capable of revving beyond 7,000 rpm, these features contribute to exceptional thermodynamic efficiency, crucial for both fuel economy and reduced emissions. The utilization of a large-displacement, naturally-aspirated eight-cylinder engine with cylinder shut-off effectively bridges the gap between high power and torque and responsible fuel consumption.
AMG Cylinder Management, developed in-house, is central to the SLK55 AMG’s efficiency. This system deactivates cylinders two, three, five, and eight under partial load, significantly reducing fuel consumption. This technology mirrors systems used in Formula 1 V8 engines, where cylinder shut-off enhances efficiency during cornering, safety car periods, and pit stops.
Cylinder shut-off operates across a broad engine speed range, from 800 to 3,600 rpm, when the driver selects “C” – Controlled Efficiency transmission mode. The AMG main menu in the instrument cluster visually indicates cylinder shut-off activity, displaying whether the engine is running in four or eight-cylinder mode. Even in four-cylinder mode, a substantial 170 lb-ft of torque remains available, providing ample power for typical driving situations. Upon demand for greater power, cylinders two, three, five, and eight seamlessly reactivate. This transition between four and eight-cylinder operation is instantaneous and virtually imperceptible, maintaining occupant comfort. At 3,600 rpm, the activation process completes in a mere 30 milliseconds.
Valve closure, fuel delivery, and ignition are deactivated in the cylinders shut off by the intelligent engine management system, which utilizes 16 hydraulically compensating actuators and a sophisticated cylinder head oil supply system. These actuators, integrated into the cylinder head, maintain closure of the intake and exhaust valves for cylinders two, three, five, and eight during cylinder shut-off. Simultaneously, fuel and ignition are disabled for these cylinders. This not only minimizes load-change losses from the deactivated cylinders but also boosts the efficiency of the remaining active cylinders by shifting their operating point to a higher load range. The actuators’ compact and lightweight design ensures precise valve train operation and allows for engine speeds up to 7,200 rpm.
The crankcase of the AMG 5.5-liter V8 is constructed from diecast all-aluminum, contributing to a low dry engine weight of just 412 lbs, a result of rigorous lightweight engineering. Grey cast iron bearing covers for the main crankshaft bearings are bolted to the crankcase and laterally for enhanced rigidity.
Carbon-coated piston rings minimize internal friction and wear, while cast-in Silitec cylinder liners reduce friction for the pistons. “Spectacle” honing, a unique and intricate process, further reduces friction and fuel consumption. This method involves mechanically treating the cylinder liners after they are bolted into place. A jig, resembling spectacles, is used to simulate the distortion caused by the cylinder head being installed. The cylinder liners are then honed in this distorted state, ensuring that any static distortion from tightening the cylinder head bolts is eliminated, leading to optimal cylinder geometry and reduced friction.
Additional efficiency-enhancing measures include weight-optimized cast aluminum pistons with special skirt coatings, ventilation holes in the crankcase, an electrically controlled pressure stage oil pump, a separate low-friction vane cell oil pump for cylinder shut-off, an efficient cross-flow engine cooling system, and electronically controlled, fully variable fuel pressure between 1,450 and 2,900 psi.
The forged crankshaft, made from high-grade 38MnS6BY steel alloy, rotates on five main bearings and features eight counterweights. Optimized for torsional rigidity, inertia, and low rotating mass, it ensures durability. A two-mass viscous damper at the front effectively minimizes vibrations. Each connecting rod journal on the crankshaft supports two forged, cracked connecting rods.
Four-valve technology with variable camshaft adjustment optimizes combustion chamber charging. Large intake and exhaust valves, four per cylinder, facilitate efficient gas flow. Exhaust valves, subjected to high thermal stress, are hollow and sodium-cooled. Four overhead camshafts actuate the 32 valves via low-friction cam followers. Infinitely variable camshaft adjustment, over a 40-degree range on both intake and exhaust sides, adapts to engine load and speed, enhancing both power and torque. This system also ensures consistent idling at low speeds. Valve overlap is adjusted based on engine speed to optimize the air-fuel mixture in the combustion chambers and efficiently remove exhaust gases. Hydraulic pivoting actuators, electromagnetically activated and controlled by the engine control unit, manage the variable camshaft adjustment. The camshafts are driven by three low-noise silent chains, improving noise comfort compared to roller chains.
The Controlled Efficiency stop/start function, standard on the SLK55 AMG, further reduces fuel consumption. Active in “C” mode, it automatically shuts off the V8 engine when the vehicle 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 rapid restart: a crankshaft sensor detects rotation direction and piston positions. The cylinder with the most favorable piston position receives immediate fuel injection via precise piezo-electric injectors for quick starts. The M152 engine always restarts in eight-cylinder mode.
An “ECO” symbol in the AMG main menu indicates stop/start function activity. “ECO4” signifies four-cylinder operation during cylinder shut-off, while “ECO8” indicates eight-cylinder mode. In “S” (Sport) and “M” (Manual) modes, the stop/start function is deactivated. Drivers can also manually deactivate it in “C” mode.
Alternator management contributes to fuel efficiency by using kinetic energy during overrun or braking to charge the battery, reducing alternator load during other driving phases.
AMG introduces a new sports exhaust system featuring exhaust flaps on each side, balancing emotional sound during spirited driving with quieter operation at partial load. The sound design prioritizes a synthesis of performance audibility and Mercedes-Benz’s hallmark long-distance comfort.
Each rear silencer incorporates a flap, variably controlled based on power demand and engine speed. Below 2,000 rpm and at low loads, flaps remain closed, directing exhaust gases through a longer, more dampened path, resulting in a subdued engine sound, particularly in four-cylinder mode.
During acceleration, flaps progressively open, from 15 to 50 degrees, allowing exhaust gases to take a shorter path while some still follow the dampened route, producing a sonorous engine note. Under full load and at higher engine speeds in eight-cylinder mode, both flaps fully open, unleashing the characteristic muscular AMG V8 sound, emphasizing the 415 hp engine’s potential.
The two-pipe AMG sports exhaust system with chrome twin tailpipes has a 2.56-inch pipe diameter from manifolds to pre-silencer, reducing to 2.36 inches from pre-silencer to rear silencers.
Effective emissions technology includes new catalytic converter boxes. The 2012 SLK55 AMG meets Euro-5 emission standards and US market requirements (LEV-III, On-Board Diagnosis II). Air gap-insulated manifolds ensure quick catalytic converter activation. Tandem catalytic converter housings, positioned close to the firewall, each contain two thin-walled ceramic substrates, eliminating the need for underbody converters. The substrates differ: the front is palladium-coated, the rear is palladium and rhodium-coated. Lambda sensors are positioned pre and post each catalytic converter housing for precise emissions control.
The AMG SPEEDSHIFT PLUS 7G-TRONIC automatic transmission delivers power to the rear wheels, offering “Controlled Efficiency” (C), Sport (S), and Manual (M) modes. Automatic rev-matching during downshifts and brief ignition/injection interruption during upshifts shorten shift times and enhance driving emotion. A double turbine torsional damper with centrifugal pendulum adapts to engine speed, minimizing vibrations in four-cylinder mode and improving comfort.
AMG sports suspension with Torque Vectoring Brakes and AMG Direct-Steer provides both dynamic handling and comfortable cruising. The SLK55 AMG accommodates both aggressive driving and relaxed touring. Independent suspension struts with stiffer tuning, torque strut bearings on the front axle, stiffer stabilizers, and increased rear axle negative camber enhance cornering and reduce body roll.
Torque Vectoring Brakes improve cornering by applying selective braking to the inner rear wheel, inducing rotation around the vertical axis for precise turn-in. AMG Direct-Steer enhances agility and reduces parking effort, with a new power steering pump that saves fuel by operating only when steering input is needed. The system’s parameter function is tuned to the AMG sports suspension for optimal response and road feel.
AMG-exclusive 3-stage ESP® offers driver-selectable modes: “ESP ON”, “SPORT Handling Mode”, and “ESP OFF”. The AMG high-performance brake system features internally 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.
The optional AMG Handling Package further enhances sportiness with AMG Performance suspension, AMG rear axle differential lock, two-piece front brake discs, and an AMG Performance steering wheel in premium leather with Alcantara® inserts.
The 2012 SLK55 AMG’s design, inspired by the SLS AMG, features classic roadster proportions with AMG-specific styling. AMG front apron with large air inlets and LED daytime running lights, a wide radiator grill with a central Mercedes star, high-gloss black slats and cross strut, darkened headlamps and bicolor tail lamps, vent grilles with chrome fins reminiscent of the 300 SL Roadster, “V8 AMG” lettering, AMG side sill panels, a unique rear apron with black diffuser insert, and chrome twin tailpipes all contribute to its distinctive appearance. A body-colored spoiler lip reduces rear axle lift at high speeds.
The interior of the SLK55 AMG mirrors the SLS AMG Roadster, featuring jet-engine-style air vents, a brushed aluminum center console, and an AMG-specific IWC-design analog clock. The AMG Performance steering wheel has a flattened top and bottom, metal trim, aluminum shift paddles, and perforated leather grip areas. The AMG instrument cluster is clear and driver-focused, with four circular instruments and the AMG main menu. The center console houses the transmission mode selector. AMG sports seats offer enhanced lateral support, premium leather upholstery, AMG badges, and standard AIRSCARF neck-level heating.
The standard retractable hardtop opens/closes in under 20 seconds. Optional panorama roof or the MAGIC SKY CONTROL roof are available. MAGIC SKY CONTROL switches the glass roof from light to dark at the touch of a button, offering open-air feel even when closed and shade when needed. Magnesium roof frames reduce weight and lower the center of gravity. AIRGUIDE pivoting wind-stop is a comfortable alternative to standard wind-stops.
The 2012 SLK55 AMG includes advanced safety systems: fiber-reinforced roll-over bar, two-stage airbags, headbags, thorax airbags, knee airbags, seat belt tensioners with force limiters, NECK-PRO head restraints, 3-stage ESP®, and ATTENTION ASSIST. Optional systems include DISTRONIC PLUS proximity control and PRE-SAFE® Brake collision preparation.
The 2012 SLK55 AMG is the third generation of AMG-developed SLK Roadsters, following the 2001 SLK32 AMG and the 2004 SLK55 AMG, continuing AMG’s legacy of high-performance roadsters with powerful V8 engines. The new 2012 SLK55 AMG solidified its position as a leader in its segment upon its US launch in early 2012.
