Mercedes-Benz introduces new generation OM 470 diesel engine
25 June 2016
Mercedes-Benz announced a new generation of the OM 470 diesel engine with new developments to achieve a further reduction in fuel consumption. A new top-of-the-range variant with a power output of 335 kW (456 hp) is also being introduced. The engine will be exhibited in the Mercedes Actros truck at the IAA show in Hannover.
The six-cylinder in-line Euro VI engine with a displacement of 10.7 L benefits both from technical refinements of the larger OM 471 (12.8 L) which were introduced last year and from technology specific to the compact model series.
The OM 470 is the most compact of the heavy-duty engines from Mercedes-Benz. It features all the major characteristics of the bigger OM 471, such as steel pistons, two overhead camshafts, asymmetric exhaust-gas turbocharger, powerful engine brake and the X-Pulse common rail injection system with pressure booster.
With the addition of the new top-of-the-range variant, the OM 470 family includes five engine variants, from 240 kW (326 hp) at 1600 rpm / 1700 Nm at 1100 rpm to 335 kW (456 hp) at 1600 rpm / 2200 Nm at 1100 rpm. The OM 470 is intended for such applications as tank vehicles, rigid trucks or construction transport, while the larger OM 471 engine is designed for long-haul transport.
Some of the key design features of the OM 470 (some shared with the OM 471) are:
- Higher injection pressure—Fuel injection continues to be based on the X-Pulse injection system with pressure boosting in the injector. As in the OM 471, the maximum rail pressure has been raised from 900 to 1160 bar. This results in a maximum injection pressure of 2700 bar. In contrast to the OM 471, the principle of the seven-hole injection nozzle has been retained, due to the compact design. A new injection nozzle with a higher flow capacity is employed, however. The shape of the combustion chamber is also new, with an omega-shaped recess in the piston. The compression ratio has been increased by one bar to 18.5 bar.
- Asymmetric injection system—During normal driving, all six cylinders are supplied with the same quantity of fuel. Depending on the load and the EGR percentage, the quantity of fuel in cylinders one to three can be continuously reduced, while at the same time increasing the quantity in cylinders four to six. In extreme cases, the quantity of fuel injected into the first three cylinders may drop to zero, while the other three cylinders operate at full load. This strategy prevents incomplete combustion with high soot emissions.
- Fixed geometry turbine—A new asymmetric turbocharger, developed by Mercedes-Benz and manufactured at the Mannheim engine plant. The turbocharger has a fixed turbine geometry and utilizes no wastegate.
- Variable donor cylinder EGR—The exhaust gases from cylinders four to six are channelled directly into the turbocharger. A defined quantity of the exhaust gases from cylinders one to three is branched off for exhaust gas recirculation. Using an infinitely adjustable EGR flap, the quantity of exhaust gases directed from the three donor cylinders to the combustion process can be varied exactly as required between zero and 100 percent. The EGR flap thereby controls not just the flow of exhaust gas for EGR, but also the turbocharger. The technology was first introduced in the OM 471.
- Control system—The engine control system uses fewer sensors and is less complex. The engine apparently requires no boost pressure or EGR control and uses no EGR sensor. Instead, the engine is operated exclusively in “pre-controlled” mode. The meaning of this term is unclear; it seems to suggest more reliance on engine map based control.
- New SCR catalytic converter—AdBlue consumption is on a par with earlier Euro V engines, at around 5% of fuel consumption.
Source: Daimler