The Mercedes-Benz M156 engine stands as a monumental achievement in automotive engineering, marking the first engine developed entirely in-house by AMG. This naturally aspirated 6.3-liter V8 powerhouse, delivering between 451 and 518 horsepower depending on the specific model application, became the driving force behind a range of iconic AMG vehicles. From the C63 AMG and E63 AMG sedans to the exhilarating CL63 AMG coupe and the robust ML63 AMG SUV, the M156 solidified its place as a benchmark for high-performance V8 engines.
From Racing Pedigree to Road Dominance: The M156 Engine’s Design
The M156 engine is more than just raw power; it’s a testament to AMG’s deep-rooted racing heritage and commitment to engineering excellence. Drawing heavily from AMG’s successful motorsport endeavors, this 6.3-liter V8 is packed with advanced features designed for both breathtaking performance and remarkable durability. Constructed primarily from a high-strength silicon-aluminum alloy, the engine block boasts impressive strength while minimizing weight. Key features contributing to its exceptional performance include four valves per cylinder for optimal breathing, variable valve timing to enhance power and efficiency across the RPM range, bucket followers for a robust valve train, and a variable-length intake manifold to optimize airflow.
Bedplate Crankcase: Enhancing Engine Rigidity and Reliability
Unlike conventional engines that utilize individual main bearing caps, the Mercedes-Benz M156 engine incorporates a rigid one-piece bedplate at the base of the engine block. This innovative design significantly enhances engine strength and reliability, particularly at high RPMs. The aluminum bedplate, reinforced with cast-in steel inserts, effectively sandwiches the crankshaft between sections of the engine block, providing superior crankshaft support and minimizing distortion or loosening of components under extreme stress. This robust construction is crucial for maintaining engine integrity and performance during demanding driving conditions.
Forged Crankshaft and Optimized Rotating Assembly for High Performance
The heart of the M156 engine features a high-quality forged steel crankshaft made from 42CrMo4V alloy. This meticulously balanced crankshaft, supported by five main bearings, rotates with exceptional smoothness and precision. A notable detail, typically reserved for racing engines, is the inclusion of heavy metal plugs within the crankshaft counterweights. This sophisticated approach allows for smaller counterweights, reducing rotational inertia and oil drag, ultimately contributing to increased engine power and responsiveness.
Each forged connecting rod in the M156 is precisely “cracked” using a laser beam, a technique that creates an irregular fracture surface. This unique fracture enhances the strength of the connection when the two halves are clamped around the crankshaft. Furthermore, the connecting rods are carefully weight-matched with lightweight pistons to achieve extremely tight tolerances. This meticulous balancing of the rotating assembly minimizes vibrations and ensures smooth, high-revving performance. To manage heat effectively, small nozzles integrated into the engine block spray cooling oil directly onto the underside of each piston crown, helping to maintain optimal operating temperatures under demanding conditions.
TWAS Cylinder Coating: Innovation for Reduced Friction and Enhanced Durability
A standout feature of the Mercedes-Benz M156 engine is its innovative twin-wire-arc-sprayed (TWAS) cylinder coating. This advanced process results in cylinder bores with remarkably low friction and exceptional wear resistance. The TWAS coating creates running surfaces that are twice as hard as traditional cast-iron cylinders, contributing to increased engine longevity and efficiency.
The engine block and cylinder heads themselves are constructed from cast aluminum silicon alloys (AlSi7 and AlSi17), representing state-of-the-art materials for strength, lightweight design, and thermal management. The TWAS process begins with roughening the cylinder bores using a high-pressure water jet. Then, two electrode wires and an atomizing gas are used to generate plasma under high voltage. This plasma spray melts metal from the wires and propels it onto the cylinder walls, where it solidifies into an incredibly hard coating. Finally, a honing process refines the cylinder bores, creating micro-pores in the hard coating. These micro-pores are crucial for retaining oil and ensuring optimal lubrication of the pistons and piston rings, minimizing friction and wear.
Vertical Intake and Exhaust Ports and Variable Intake Manifold for Optimized Airflow
Inspired by racing engine designs, the M156 engine features a vertical intake and exhaust port layout. This design promotes a straight, unimpeded airflow path through the engine, from the intake manifold into the hemispherical combustion chambers and out through the exhaust passages. This optimized airflow contributes to enhanced engine breathing and performance.
A patented dual-length intake manifold is an integral component of this vertical intake and exhaust system. This variable intake manifold, controlled by the Bosch 9.7 engine management system, utilizes two electrically operated internal flaps within a magnesium manifold. At lower engine speeds, intake air is directed through longer runners, maximizing torque output. As engine speed increases, the flaps adjust to allow intake air to flow through shorter pipes, optimizing the engine for maximum horsepower at higher RPMs. Two hot film air mass sensors, positioned behind the air cleaners, provide the engine electronics with precise data on the density and temperature of the incoming air, further optimizing engine management. It is important to note that the M156 engine shares no components with standard Mercedes-Benz V8 engines, highlighting its unique and dedicated AMG engineering.
Bucket Followers and Variable Valve Timing: Sophisticated Valve Train for Performance and Efficiency
The valve train of the Mercedes-Benz M156 engine showcases further AMG racing-derived technology. Each cylinder bank features twin overhead camshafts that actuate the 32 valves via bucket-type followers. Unlike rocker arms, bucket followers feature a flat surface that directly contacts the cam lobes, offering a more rigid and space-efficient valve train design. This robust design enables larger valve openings and reliable high-speed operation, crucial for maximizing horsepower and torque. While employing racing-inspired bucket followers, the M156 engine also integrates hydraulic lifters within each bucket. These lifters automatically maintain valve clearance, ensuring long service intervals and reduced maintenance costs, making this high-performance engine surprisingly practical for everyday use.
Variable valve timing is another key technology employed in the M156 engine. Both intake and exhaust valve timing are adjustable within a 40-degree range using electro-hydraulic vane-type adjusters on each camshaft. This variable valve timing optimizes engine performance and efficiency across a wide RPM range. During part-throttle operation, the valve timing system induces valve overlap, where exhaust valves remain open as intake valves begin to open. This creates internal exhaust gas recirculation, reducing emissions and improving fuel economy. However, as the engine approaches full throttle, the camshaft adjustment shifts to optimize valve timing for maximum power output. A double chain driven from the crankshaft drives the intake camshafts, and small gears on the intake cams then drive the exhaust camshafts, ensuring precise and reliable valve train operation.
AMG Supercharged V8 Options: Expanding the Performance Spectrum
While the naturally aspirated M156 engine is a performance marvel, AMG also offered supercharged V8 variants based on earlier engine architecture. The G55 AMG, for instance, was powered by a supercharged V8, distinguished by its dual side-pipe exhaust system and impressive 500 horsepower output. A naturally aspirated 355-hp version of this 5,439-cc V8 was also utilized in the SLK55 AMG model. These AMG V8 engines deliver exhilarating acceleration, propelling the SLK55 AMG from 0-60 mph in just 4.9 seconds and the G55 AMG in 5.4 seconds.
The supercharged AMG Kompressor V8 in the G55 AMG achieves its remarkable power thanks to a belt-driven “Lysholm” or screw-type supercharger. This advanced supercharger design generates approximately 30 percent more intake pressure compared to other comparable supercharging systems. Each Teflon-coated rotor within the supercharger can spin at speeds exceeding 23,000 rpm, forcing up to 4,000 pounds of air per hour into the engine’s combustion chambers at maximum boost pressure of 0.8 bar (11.6 psi).
The engine management system intelligently engages the supercharger based on engine speed and load. Under light loads and partial throttle, the Kompressor V8 operates as a naturally aspirated engine. However, the supercharger engages instantly when the driver demands more power. Below 2,700 rpm, the supercharger activates only when the throttle is open and the engine is under load. Above 2,700 rpm, the supercharger operates continuously. This intelligent, load- and rpm-dependent operation offers significant advantages in thermal efficiency, fuel consumption, noise reduction, and exhaust emissions. An electromagnetic clutch, controlled by the Bosch ME 2.8.1 engine management system, manages supercharger engagement seamlessly, ensuring smooth torque delivery throughout the RPM range, imperceptible to the driver.
Compact Water-Cooled Intercooler for Enhanced Supercharger Efficiency
To further enhance the efficiency of the supercharged V8, a compact water-cooled intercooler is positioned between the cylinder banks. This air-to-water heat exchanger effectively cools the compressed intake air, transferring heat to the coolant. A dedicated pump circulates coolant through a special low-temperature cooler located between the air conditioning condenser and the radiator. This independent cooling system ensures consistent intercooler performance, regardless of engine coolant temperature.
Unlike air-to-air intercooler systems, which may require reduced ignition timing and engine power under high thermal loads, this advanced water-to-air intercooler allows the supercharged V8 to deliver its full power and torque output at all times. An oil cooler, located in the front apron, further contributes to maintaining optimal engine temperatures.
The Signature AMG Sound and Hand-Built Craftsmanship
The exhaust system of both naturally aspirated and supercharged M156 engine variants is meticulously engineered to complement the engine’s high-performance character. With the exception of the exhaust manifolds, each Mercedes-AMG model features a bespoke exhaust system designed specifically for its application. All four catalytic converters utilize thin-wall ceramic material with a large surface area, minimizing exhaust back pressure for optimal performance and reduced emissions. The result is the distinctive, throaty AMG sound emanating from the twin-oval AMG tailpipes, a signature element of these high-performance vehicles.
Each Mercedes-Benz M156 engine is hand-assembled by a single expert craftsman at the Mercedes-AMG facility in Affalterbach, Germany, adhering to the “one man, one engine” philosophy. A technician is responsible for the complete assembly of an AMG high-performance engine, from initial component installation to final testing. With meticulous care, the craftsman installs every part, from the crankshaft and pistons to the intake system and wiring harness. Each completed engine undergoes rigorous bench testing to ensure consistent quality and maximum performance before being installed in an AMG vehicle. This hand-built approach underscores AMG’s dedication to precision and quality, ensuring that every M156 engine delivers exceptional performance and reliability.
AMG: The Pinnacle of Mercedes-Benz Performance
AMG has been the high-performance division of Daimler AG since 1999, located in Affalterbach, Germany. With over 600 specialists, AMG is responsible for developing complete vehicle models, including the engine, transmission, chassis, brakes, aerodynamics, and interior. AMG engines embody a unique blend of cutting-edge technology, computer-aided design, and traditional hand craftsmanship. AMG vehicles deliver exhilarating performance while maintaining remarkable everyday driving refinement. AMG engines are produced and tested at their Affalterbach headquarters, while AMG vehicles are assembled at Mercedes-Benz main manufacturing plants.
The United States is the top global market for AMG, accounting for over 50 percent of AMG sales. While all authorized Mercedes-Benz dealers offer AMG vehicles, select dealerships operate as AMG Performance Centers, featuring specially trained staff and unique AMG branding. AMG also hosts driving events like the “AMG Performance Tour,” Driving Academy, and AMG Challenge programs, providing enthusiasts with opportunities to experience the full potential of AMG vehicles.
Mercedes-Benz USA: Delivering Luxury and Performance
Mercedes-Benz USA (MBUSA), headquartered in Montvale, New Jersey, is responsible for the sales, marketing, and service of Mercedes-Benz and Maybach vehicles in the United States. MBUSA is committed to providing superior luxury vehicles and exceptional customer support. Further information about MBUSA and its products is available at www.mbusa.com and www.maybachusa.com.
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