Mercedes-AMG has developed a new 5.5-litre V8 engine which combines powerful eight-cylinder performance with the decidedly economical fuel consumption of a four-cylinder. Unrivalled efficiency is achieved thanks to the AMG Cylinder Management cylinder shut-off system newly developed by Mercedes-AMG. This new technology exclusively developed by AMG is inspired by Formula 1 racing. In the eight-cylinder racing engines developing around 750 hp, cylinder shut-off is likewise used primarily to save fuel.
Thanks to a fuel saving of around 30 percent compared to the existing AMG 5.5-litre V8 engine, the naturally aspirated, high-revving eight-cylinder demonstrates the great innovative strength of AMG. At the same time it is AMG’s demonstration of the potential still residing in the naturally aspirated eight-cylinder engine.
The distinctive AMG 5.5-litre V8 engine with AMG Cylinder Management and direct petrol injection will find exclusive use in the new SLK 55 AMG, which celebrated its world premiere at the International Motor Show (IAA) in Frankfurt/Main in September 2011. This means that the latest version of the SLK 55 AMG will remain the only roadster in its segment with an eight-cylinder engine.Even with peak output increased by 45 kW (62 hp) to 310 kW (422 hp) and torque increased from 510 to 540 Nm, (376 to 398 lb-ft) the fuel consumption of 8.5 l/100 km (27.67 mpg/US, 11.76 km/l) (NEDC combined, provisional figure) is 3.5 litres less than that of the preceding model – a real quantum leap of around 30 percent which places the new SLK 55 AMG among the top performers in its segment. CO2 emissions have likewise been considerably reduced, as witness the figure of 199 grams per km (NEDC combined, provisional figure).
New naturally aspirated eight-cylinder closely related to the V8 biturbo
In line with its “AMG Performance 2015” strategy, Mercedes-AMG is meeting its promise to continuously reduce both the fuel consumption and emissions of new models over the next few years with the new V8 unit – while reaching new heights with the central brand claim of “Driving Performance”. Moreover, the performance brand within Mercedes-Benz is also demonstrating its social commitment with the M152.The new M152 is based on the AMG M157 5.5-litre V8 biturbo engine presented in 2010, which powers the E 63 AMG, CLS 63 AMG, S 63 AMG and CL 63 AMG. Numerous components and systems are basically identical, e.g. the displacement, bore/stroke, distance between cylinders, stop/start system and direct petrol 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 optimised crankcase.
“Top performer for fuel economy and maximum output: with the new 310 kW (422 hp)AMG 5.5-litre V8 engine we have once again created a real masterpiece. The M152 sets an outstanding example for efficiency, while demonstrating the creativity and expertise of our engineers, who took their inspiration from Formula 1 when developing the cylinder shut-off system. This makes the new, naturally aspirated eight-cylinder the perfect power unit for the new SLK 55 AMG, which celebrated its premiere at the International Motor Show in Frankfurt/Main in the autumn 2011,” says Ola Källenius, Chairman of Mercedes-AMG GmbH.
“Thanks to the innovative AMG Cylinder Management system and other high-tech components, our newly developed AMG M152 naturally aspirated eight-cylinder engine achieves the fuel economy of a four-cylinder with the muscular power delivery and emotional sound experience of a V8. A sports car engine with technology taken from Formula 1 – I am convinced that the new SLK 55 AMG will meet the high expectations of all sports car fans,” says Friedrich Eichler, head of powertrain development at Mercedes-AMG GmbH.
The high-tech M152 powerpack not only enthrals with its extraordinary power delivery and torque, but also thanks to a combination of advanced technologies which is unequalled anywhere in the world. No other petrol engine features direct injection at a pressure of 200 bar (2900 psi), spray-guided combustion and piezo-injectors in conjunction with map-controlled cylinder shut-off, an all-aluminium crankcase with “spectacle” honing, four-valve technology with continuous camshaft adjustment, a high compression ratio of 12.6 : 1, a stop/start system and generator management – while revving to a maximum of over 7000 rpm. All these design features lead to high thermodynamic efficiency, which is in turn the precondition for high fuel efficiency and low exhaust emissions. Moreover, deciding in favour of a large-displacement, naturally aspirated eight-cylinder unit with cylinder shut-off resolves the conflict of aims between high output/torque delivery and decidedly low fuel consumption figures.
It is the AMG Cylinder Management cylinder shut-off system in particular, completely newly developed by Mercedes-AMG, which significantly improves efficiency: cylinders two, three, five and eight are cut off under partial load, which considerably lowers fuel consumption. In similar form this technology is also used in the approx. 750 hp V8 engines used in Formula 1. As efficiency also plays a major role at the pinnacle of motor racing, two or four of the eight cylinders are cut off e.g. when cornering at slow speed, in the Safety Car phases or for pit stops. With a fuel consumption of 8.5 l/100 km (27.67 mpg/US, 11.76 km/l) and CO2 emissions of 199 grams per kilometre (NEDC combined, provisional figures), the naturally aspirated AMG V8 engine comes in at or below the level of its competitors, however these are unable to match either the output or torque of the SLK 55 AMG – and above all, they do not use large-displacement eight-cylinder engines.The cylinder shut-off function is available over a wide engine speed range from 800 to 3600 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 230 Nm (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 whatever. At an engine speed of 3600 rpm the activation process takes no more than 30 milliseconds.