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MERCEDES-AMG ENGINES ESTABLISH BENCHMARK PERFORMANCE
Supercharged V8s Offer League-Leading Power, Craftsmanship

This is a reprint from press information supplied by Mercedes-Benz in 2005

Mercedes-AMG, the highly specialized integral part of the Mercedes-Benz family, has overall responsibility for sales and marketing of AMG-badged cars including, transmission, chassis, brakes, aerodynamics, interior, design and - most importantly - the engine.

Each AMG engine is the product of a surprising combination of cutting-edge technology, computer-aided design and old-fashioned hand craftsmanship. While AMG engines benefit from hours of computerized dynamometer testing and merciless hours of test-track torture, they perform with every bit of the industry-leading smoothness and refinement expected from standard Mercedes-Benz engines. No automobile capable of equal flat-out performance also displays such a docile nature under every-day driving.

Already establishing an industry benchmark with the normally aspirated 5,439-cc V8 used in the new C55 AMG and SLK55 AMG models as well as the current CLK55 AMG, Mercedes-AMG also makes a supercharged V8 for the SL55 AMG, S55 AMG and CL55 AMG that belts out 493 hp. While the supercharged V8 also powers the E55 AMG and G55 AMG, their smaller exhaust systems reduce power slightly - to a mere 469 hp. In four models, the AMG Kompressor V8 engine makes easy work of the 0-60 mph sprint in well under 5 seconds (5.5 seconds for G55 AMG).

One Man - One Engine

Every new AMG engine is hand-assembled one at a time by expert technicians at Mercedes-AMG in Affalterbach, Germany and is bench-tested to ensure maximum performance. Mercedes-AMG follows a philosophy of "one man, one engine." This means that a single technician - identified by the signature plate affixed to the engine - is responsible for the complete assembly of an AMG high-performance engine from start to finish. With the utmost care, the craftsman installs each and every part, from the crankshaft, connecting rods and pistons to the supercharger, ensuring the closest possible tolerances. Individual workmanship and skill still count here.

V8 Kompressor - Powerful Supercharger Between Cylinder Banks

The impressive power of the AMG Kompressor V8 comes through a newly developed belt-driven supercharger. This "Lysholm" or screw-type supercharger achieves about 30 percent more charge pressure than other comparable belt-driven supercharging systems. Each Teflon-coated rotor spins at a maximum of over 23,000 rpm and, in doing so, can push up to 4,000 pounds of air per hour into the engine's combustion chambers (at 70 degrees F, sea level). The maximum boost pressure is 11.6 pounds per square inch, or 0.8 bar.

The engine management unit determines whether to engage the supercharger depending on the engine speed and load. In this instance an electromagnetic clutch engages the supercharger via its drive belt. The advantage of this direct link to the crankshaft is that the supercharger can spontaneously react when the driver presses the accelerator and provide powerful thrust even just off idle.

Further special technical features in the supercharged V8 engine include a fuel distribution system controlled by a computer that ensures the right amount of fuel is delivered every time, depending on the engine speed and load. A sophisticated exhaust system with two ceramic-firewall catalytic converters upstream and two powerful metal catalytic converters downstream enables the car to qualify as a low emission vehicle.

Compact Intercooler Located Between Cylinder Banks

To improve efficiency even further, Mercedes-AMG specialists have developed an innovative intercooler, or "charge cooler." The intercooler sits between the cylinder banks, operating as an air-to-water heat exchanger, extracting heat from the compressed air and transferring it to the coolant. A pump allows the water to flow through a special low-temperature cooler located up front between the air conditioning condenser and the radiator. The low-temperature system for charge air works independently of the primary coolant circuit for the V8 engine. In contrast to conventional air-to-air systems, where ignition timing and therefore engine power must be reduced under certain thermal load conditions, this sophisticated counterflow water-to-air cooler enables the full output and torque potential of the supercharged V8s to be exploited at all times. Also, an oil cooler is housed in the front apron.

Intelligent, Electromagnetic Supercharger Activation

Unlike in many other systems the supercharger - jointly developed with the Japanese company IHI - is not continuously driven. Under light loads when the throttle is open only slightly, the Kompressor V8s operate purely as a naturally aspirated engine. However, the supercharger goes into instant action when the driver wishes to accelerate. Under 2,700 rpm, the supercharger runs only when the throttle is open and the engine is under load, but above 2,700 rpm, the supercharger is engaged full-time. This strategy nets many advantages - thermal efficiency, fuel consumption, noise and exhaust emissions all benefit.

The load- and rpm-dependent operation is carried out by an electromagnetic clutch that gets its signals directly from the fully electronic Bosch ME 2.8.1 engine management system. The driver feels and hears nothing of the supercharger activation. Torque build-up is extremely smooth, and the supercharged V8 shows its muscle evenly throughout the rpm range.

Long Service Life Typical of Mercedes

To achieve exceptional performance and long operating life, Mercedes-AMG engineers also made significant modifications to the mechanics of the engine. Nearly all the mechanical components from the basic 5.0-liter V8 engine are modified significantly. Mercedes-AMG's vast experience in high-performance engines gained during three decades of motor racing shows through:

• crankcase using special cross-bolted main bearing connections.
• long-stroke crankshaft (92 millimeters) adapted to the high torque of the supercharged engine using modified bearings and more durable material
• pistons specially forged to resist heat and pressure
• oil supply with a new sump and more powerful, higher-volume oil pump
• cylinder heads with larger intake and exhaust runners to accommodate higher airflow rate
• camshafts with longer valve opening duration to improve charging of the combustion chambers
• valve train uses double valve springs and lightweight retainers
• engine ECU performs additional tasks, such as using electronic maps to activate the supercharger

The Sound of Power

The AMG engine's exhaust system is just as sophisticated as the rest of the car. With the exception of the two exhaust manifolds, the complete exhaust systems of each Mercedes-AMG model have been designed specifically for that application. All four catalytic converters are of ceramic material and feature thin-wall technology. Large surface area in the catalytic converters ensure reduced exhaust backpressure and more rapid heating on cold starts, benefiting both performance and exhaust emissions. The sound emanating from the characteristic, twin-oval AMG tailpipe is also exciting, for the supercharged engine produces a sound with a very special resonance.

The Normally Aspirated Mercedes-AMG V8: Silken Brawn

Like the Kompressor V8s, the normally aspirated 5.5-liter V8s in the CLK55 AMG, C55 AMG and SLK55 AMG use a pressure-cast aluminum cylinder block. It uses innovative cast in silicon aluminum cylinder sleeves and low friction surfaces that allow a reduction in piston ring spring tension by 50 percent. Thanks to a number of such friction reducing measures, the internal "drag" of this engine is 45 percent lower than most, which translates to both fuel savings and increased power.

The sleeves are cast separately, but rather than being pressed into the block, the block is cast around them. In the process, the outer 20 percent of each sleeve melts, bonding each to the block. This process provides exceptional block stiffness while minimizing weight. Also, these sleeves are over a pound lighter. Engine displacement is reached with 97-mm bores and an AMG-designed and manufactured forged billet steel crankshaft with a stroke of 92 mm. As a result, the cylinders of the 5,439-cc engine are close to "square" in dimensions, with nearly equal bore and stroke measurements.

For road cars, many engineers consider this type of square design as striking an ideal balance between piston speed (largely a function of stroke) and allowable valve size (primarily determined by bore diameter). The forged crankshaft is dynamically balanced, and connecting rods and pistons are selected for each engine in equal weight-matched sets. This attention to detail ensures that the V8 produces smooth, low-vibration power. An aluminum oil pan also contributes to block rigidity.

The AMG V8 uses hollow, forged steel rods which are made in one piece, then "cracked" hydraulically, instead of being machine cut and reground. This irregular, one-in-a-million fit results in unusual strength and durability. It actually shortens the production process as well, since regrinding isn't necessary. Aluminum pistons are fitted to the connecting rods and inserted in the silicon aluminum sleeves. Oil jets driven by a high-volume pump cool the underside of each piston, enhancing durability.

Top-Shelf Hardware for the Top End

One key to the broad torque band of the Mercedes-AMG V8s is a dual-resonance intake manifold. AMG alters the magnesium intake manifold from the production 5.0-liter V8, netting a wider cross-section to increase airflow. As in the standard Mercedes manifold, the AMG piece features long intake passages which spiral around to each cylinder. This manifold incorporates active flaps (one for each cylinder) that remain closed below about 3,700 rpm. This forces intake air to take the longer of two routes through the manifold, building up advantageous pressure waves that actually boost the intake flow and improve low and mid range torque. At higher speeds, the active flaps close off the longer runners while opening shorter ones that lead more directly to each cylinder, netting greater high rpm power. The electronic engine control unit determines precisely when the flaps are open and closed.

Modular Camshafts Reduce Reciprocating Weight

Each cylinder head houses a single, hollow camshaft driven by double roller chains and silent, rubber coated sprockets. Twin rocker shafts in each head hold low friction, roller tip aluminum rocker arms to actuate the valves, and housed in the end of each rocker arm is a small hydraulic lifter that ensures quiet, maintenance free valve operation.

AMG engineers designed higher-tension valve springs and replaced the standard camshafts with new cams of modular construction. The stock hollow camshafts are lightweight, but the AMG cams are lighter still. While valve head size is the same as the standard 5.0-liter Mercedes-Benz V8, the AMG cams provide longer valve opening duration for increased power.

To make the camshafts, AMG starts with a precision seamless welded tube, and individually forged cam lobes are placed onto the tube. When all cam lobes are degreed and positioned axially, an expansion lance is pressed into the tube. The lance expands the tube hydraulically at each lobe position, fusing the lobes to the shaft. This modular process simplifies designing and manufacturing camshafts.

© 2005 Marcus Blair Fitzhugh

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