2019 Mercedes-Benz SLK55 AMG

The 2012 Mercedes-Benz SLK55 AMG is the most powerful SLK of all time. Its new AMG 5.5-liter V8 engine featuring cylinder shutoff combines the ultimate in performance with the lowest possible fuel consumption. With a peak output of 415 hp and maximum torque of 398 lb-ft, the 2012 SLK55 AMG is poised to outperform all of its direct competitors. High-performance driving is ensured thanks to the AMG sports suspension with Direct-Steer system, Torque Vectoring Brakes and 3-stage ESP, as well as the AMG high-performance braking system. The 2012 SLK55 AMG will arrive in U.S. Helping to set new fuel efficiency standards for V8's, the 5.5 liter engine combines low consumption figures with superior power delivery and the typical exhaust growl which only a large-displacement eight-cylinder engine can produce. The new M152 is based on the AMG M157 5.5-liter V8 biturbo engine presented in 2010, which powers the E63 AMG, CLS63 AMG, S63 AMG and CL63 AMG.

Numerous design features are identical, such as the displacement, bore/stroke, distance between cylinders, ECO stop/start system and direct gasoline injection technology. Distinguishing features versus the M157 include the new intake air ducting, new cylinder heads, the modified valve drive, an adapted oil supply system and an optimized crankcase. The high-tech M152 motor dazzles with a combination of advanced technologies which is unequalled anywhere in the world. The AMG Cylinder Management cylinder shut-off system - developed completely by Mercedes-AMG - significantly improves efficiency: cylinders two, three, five and eight are cut off under partial load, which lowers fuel consumption considerably. The cylinder shut-off function is available over a wide engine speed range from 800 to 3,600 rpm if the driver has selected transmission mode "C" - Controlled Efficiency. The AMG main menu in the instrument cluster informs the driver whether cylinder shut-off is active, and whether the engine is currently running in four or eight-cylinder mode. No less than 170 lb-ft of torque is still available in four-cylinder mode - enough power to ensure plenty of acceleration in most driving situations.

As soon as the driver has a need for more power and leaves the partial load range, cylinders two, three, five and eight are activated. The switch from four to eight-cylinder operation is immediate and imperceptible, leading to no loss of occupant comfort. At an engine speed of 3,600 rpm the activation process takes no more than 30 milliseconds. Cylinder shut-off is made possible by the intelligent engine management system, with 16 hydraulically compensating actuators and a sophisticated oil supply system in the cylinder head. The compensating actuators are integrated into the cylinder head, and keep the intake and exhaust valves of cylinders two, three, five and eight closed when cylinder shut-off is active. At the same time their fuel supply and ignition are deactivated. This not only enables the loadchange losses of the four deactivated cylinders to be reduced, but also increases the efficiency of the four remaining cylinders.

This is because the operating point is transferred to the higher load range. The actuators are compact and lightweight, allowing taut valve train operation and engine speeds up to 7,200 rpm. The crankcase of the new AMG 5.5-liter V8 engine features a diecast allaluminum construction. The low (dry) engine weight of just 412 lbs is the result of uncompromising lightweight construction methods. The bearing covers for the main crankshaft bearings are grey cast iron, and are bolted to the crankcase, as well as on the sides, for high rigidity. The piston rings are carbon-coated to minimize internal friction and reduce wear. Cast-in Silitec cylinder liners ensure low friction for the eight pistons. Unique "Spectacle" honing is another measure to reduce friction and therefore fuel consumption: in this sophisticated and complex process, the cylinder liners receive their mechanical surface treatment when already bolted in place. As honing would no longer be possible with the cylinder head installed, a jig resembling spectacles is bolted to the crankcase. The cylinder liners distort as if the cylinder head were in place, and are only then given their mechanical surface treatment.

As a result, any static distortion of the cylinder liners caused by tightening the cylinder head bolts can be completely eliminated. Perfect charging of the combustion chambers is provided by large intake and exhaust valves, four per cylinder. The exhaust valves, which are subject to high thermal loads, are hollow and sodium-cooled. Four overhead camshafts operate the 32 valves via low-maintenance, low-friction cam followers. The infinitely variable camshaft adjustment within a range of 40 degrees on the intake and exhaust sides adapts to engine load and engine speed, leading to high output and torque values. This also provides consistent idling at a low speed. Depending on the engine speed, valve overlap can be varied for the best possible fuel/air supply to the combustion chambers and efficient removal of the exhaust gases. The variable camshaft adjustment is carried out hydraulically via four pivoting actuators. These are electromagnetically activated and controlled by the engine control unit.