Mercedes-Benz SLK (R171) AMG SLK 55 V8 (360 Hp) 7G-TRONIC

Mercedes-Benz SLK (R171) AMG SLK 55 V8 (360 Hp) 7G-TRONIC: A Compact Powerhouse

The Mercedes-Benz SLK (R171) AMG SLK 55 V8 (360 Hp) 7G-TRONIC represents a formidable entry in the luxury compact roadster segment, combining Mercedes-Benz’s signature refinement with the raw, unadulterated performance prowess of AMG. Produced from September 2004 to December 2007, this specific variant of the second-generation SLK-Class (R171) was a testament to AMG’s philosophy of stuffing large, potent engines into smaller, agile platforms. Designed as a two-seat, two-door roadster, the SLK 55 AMG offered an exhilarating driving experience, distinctive styling, and the innovative retractable hardtop that defined the SLK lineage. It carved out a unique niche, appealing to enthusiasts seeking a visceral, open-air performance machine with the prestige of the Mercedes-Benz badge and the thunderous soundtrack of a naturally aspirated AMG V8.

Engine and Performance: The Heart of the Beast

At the core of the Mercedes-Benz SLK (R171) AMG SLK 55 V8’s appeal was its magnificent powertrain. Under the hood resided the legendary M 113.989 engine, a naturally aspirated 5.4-liter (5439 cm³ or 331.91 cu. in.) V8, positioned longitudinally at the front. This powerplant was a marvel of engineering for its time, featuring a V-engine configuration with eight cylinders, each boasting three valves (SOHC valvetrain). With a bore of 97 mm and a piston stroke of 92 mm, combined with an 11:1 compression ratio, the engine was tuned for robust power delivery and instant throttle response.

The M 113.989 generated a substantial 360 horsepower at 5750 rpm, translating to an impressive 66.2 horsepower per liter. Even more remarkable was its torque output: a colossal 376.16 lb-ft (510 Nm) available at a relatively low 4000 rpm. This ample torque ensured that power was readily accessible across a broad rev range, providing potent acceleration from almost any speed. Power was channeled to the rear wheels via Mercedes-Benz’s advanced 7G-TRONIC automatic transmission, a seven-speed unit renowned for its smooth shifts and ability to handle high torque loads.

The combination of a powerful V8 and a sophisticated automatic gearbox resulted in blistering performance figures. The SLK 55 AMG could sprint from 0 to 60 mph in a mere 4.7 seconds (0-100 km/h in 4.9 seconds), positioning it firmly among serious sports cars of its era. Its top speed was electronically limited to 155 mph (250 km/h), a common practice for German performance vehicles. Despite its performance orientation, the engine adhered to the Euro 4 emission standard, and its fuel economy, while not a primary concern for buyers, was rated at a combined 19.6 US mpg (12 l/100 km) under the NEDC cycle, with CO2 emissions of 288 g/km. The car’s weight-to-power ratio of 4.1 kg/Hp (245.7 Hp/tonne) further underscored its impressive athleticism.

Design and Features: Form Meets Function

The R171 generation of the SLK-Class, upon which the AMG 55 V8 was based, marked a significant evolution in design from its predecessor. It adopted a more aggressive and aerodynamic aesthetic, prominently featuring a distinctive “F1-nose” inspired by Mercedes-Benz’s Formula 1 racing cars of the time. The AMG variant further enhanced this sporty appearance with unique body styling, including more aggressive front and rear bumpers, sculpted side skirts, and quad exhaust outlets that hinted at the power within.

As a roadster, the SLK 55 AMG offered the best of both worlds with its iconic “Vario-roof” – a power-retractable hardtop that transformed the car from a sleek coupe into an open-air convertible in a matter of seconds. This innovative feature provided the security and refinement of a coupe with the exhilaration of a convertible, all within one compact package. The interior was a blend of luxury and performance, with AMG-specific touches such as bolstered sports seats, an AMG-branded steering wheel, and unique trim elements. Despite its compact dimensions, the cabin was driver-focused, offering a comfortable and engaging environment for two occupants.

Standard equipment included a robust braking system featuring ventilated discs at both the front and rear, ensuring excellent stopping power commensurate with its performance capabilities. Assisting systems like ABS (Anti-lock Braking System) were standard, enhancing safety and control. The car featured an independent McPherson-type front suspension and an independent multi-link rear suspension, both complemented by transverse stabilizers, providing a balance of agile handling and comfortable ride quality. Hydraulic power steering, a rack and pinion system, offered direct and communicative feedback to the driver. The vehicle rode on staggered wheel and tire setups: 225/40 ZR 18 92 Y XL tires on 7.5 J x 18 H 2 rims at the front, and wider 245/35 ZR 18 92 Y XL tires on 8.5 J x 18 H 2 rims at the rear, optimizing grip and handling dynamics.

Technical Specifications

Legacy and Market Impact

The Mercedes-Benz SLK (R171) AMG SLK 55 V8 carved out a significant legacy as a high-performance roadster during its production run. It was a unique proposition in the market, offering a blend of open-top motoring, luxury, and the raw, unadulterated power of a large displacement, naturally aspirated V8. It quickly gained a reputation for its thrilling acceleration, muscular exhaust note, and surprisingly agile handling for a car of its weight and engine size. Enthusiasts often fondly refer to it as a “baby Black Series” due to its potent engine and aggressive demeanor.

In the competitive landscape, the SLK 55 AMG faced rivals such as the Porsche Boxster S and, to some extent, the BMW Z4 M Roadster. While the Boxster S offered exceptional balance and handling, and the Z4 M Roadster brought its own high-revving inline-six character, the SLK 55 AMG distinguished itself with its charismatic V8 engine, which delivered a level of torque and aural drama that its six-cylinder competitors couldn’t match. It appealed to buyers who desired a more traditional, big-engine performance car in a compact, luxurious package.

The SLK 55 AMG also played a role in further cementing AMG’s integration into the mainstream Mercedes-Benz lineup, demonstrating that the performance division could infuse even smaller models with its high-octane spirit. Its robust performance and distinctive character ensured a loyal following. Today, the Mercedes-Benz SLK (R171) AMG SLK 55 V8 remains a highly sought-after modern classic, particularly appreciated for being one of the last naturally aspirated AMG V8 models in a compact roadster. Its combination of a powerful engine, retractable hardtop, and AMG pedigree continues to make it a compelling choice for collectors and driving enthusiasts alike, solidifying its place as a memorable chapter in Mercedes-Benz and AMG history.