21 March 2011
Daimler Trucks announced the launch of the Mercedes-Benz OM 47x, a redesigned range of heavy-duty truck engines marketed under the name “Blue Efficiency Power”. The Blue Efficiency Power generation of Mercedes-Benz engines has been specifically developed for use in Europe and is the first of its type to meet the Euro VI (2013) emission standards. However, Euro V versions of the engines will be available as an option.
The engines have been designed from scratch, without consideration to engines that already existed. The development work was started five years ago in Stuttgart. The new generation comprises three model series of six-cylinder in-line engines with varying displacements. The three series share a common basic design, but the technical details vary according to the differing requirements.
The first member of the new engine generation is the Mercedes-Benz OM 471, with a 12.8 L displacement, a power output range of 310 kW (421 hp) to 375 kW (510 hp) and maximum torque of 2100 to 2500 Nm. The OM 471 is the first engine in its class to have received Euro VI type approval.
The engines feature a new, X-PULSE amplified common-rail fuel injection system. In the X-PULSE common-rail system with pressure booster, the twin-piston high-pressure pump produces a maximum pressure of around 900 bar in the common rail. This pressure is boosted within the individual injectors to up to 2100 bar. The X-PULSE pressure boost varies according to the engine mapping and adjusts continuously to the the actual operating conditions of the engine.
Unlike in conventional common-rail systems, the X-PULSE system also allows for both the pressure and the pressure distribution to be freely adjusted during the main injection with the help of two solenoid valves. Each injection process is made up of a series of separate injections. Up to two pilot injections precede a gradual increase of pressure to reduce noise and ensure smooth running characteristics. The flexible rate shaping of the subsequent main injection ensures low fuel consumption and emissions. A post-injection ensures in-cylinder combustion of particulates. A further post-injection can also be made, as necessary, to regenerate the particulate filter. The Mercedes-Benz OM 471, however, has a separate injection valve—known as the HC doser—located in the exhaust system, which is used to control the active regeneration of the filter.
The Mercedes-Benz OM 471 utilizes a fixed geometry turbocharger featuring an asymmetric turbine casing. With the asymmetric turbine, the exhaust gases from the first three cylinders flow directly through the exhaust gas recirculation (EGR) system to the turbine, without any losses. Only three of the cylinders are linked with the exhaust gas recirculation duct, and the asymmetric design of the turbine means that a higher pressure level can be maintained in them for the recirculation process. As a result, the engine can be operated across a broad range of parameters with an economical, positive scavenging gradient, despite the exhaust gas recirculation. A wastegate valve is used to limit the charge pressure and further improve engine response during acceleration.
Euro VI emissions are met through the use of a cooled EGR system, urea-SCR technology and a particulate filter. The optional Euro V version of the engines has no particulate filter, a reduced EGR rate and a smaller EGR cooler.
In spite of the added complexity to meet Euro VI emissions, “the fuel consumption on these models is excellent and will produce top figures in everyday vehicle use”, said Daimler, but no fuel consumption figures were provided.
The new Mercedes-Benz engines are built at the company’s Mannheim plant. This plant also produces key components for the Detroit Diesel engines and complete engines for Fuso.