NEW GENERATION MERCEDES-BENZ OM 470 ENGINES LOWERS EMISSIONS
At the upcoming IAA this fall, Mercedes-Benz Trucks will showcase the latest generation of the OM 470 six-cylinder in-line engine, used in trucks and buses, which incorporates numerous new developments to achieve a further reduction in fuel consumption of up to 5%.
The 10.7-liter, six-cylinder in-line engine benefits both from technical refinements relating to the ongoing development of the larger OM 471 which was 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 nevertheless features all the defining characteristics of its big brother, the OM 471, combining robust design, with sturdy steel pistons, two overhead camshafts with highly efficient gearing as the drive system, asymmetric exhaust-gas turbocharger, powerful engine brake and the X-Pulse common rail injection system with pressure booster.
The top model of the Mercedes-Benz OM 470 engine range is a variant generating an output of 335 kW (456 hp) and 2200 N·m (1,623 lb-ft) of peak torque. With a specific output of 31.4 kW per liter of engine capacity (42.7 hp/l) and specific torque of 206 N·m/l, the OM 470 is one of the most powerful engines in its size category.
Fuel injection continues to be based on the X-Pulse injection system with pressure boosting in the injector and unrestricted flexibility for modelling the injection system. As for the larger OM 471 engine, the maximum rail pressure has now 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, on account of 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. This shaping is adapted to the given conditions inside the compact engine.
The same applies to the compression ratio, which has been increased by one bar to 18.5 bar. All these measures—in conjunction with a reduction in the exhaust gas circulation rate—lead to a further improvement in efficiency across the entire range of the engine mapping. This in turn lowers fuel consumption significantly.
Rated engine speed lowered. A hallmark of the latest-generation OM 470 is a very steep rise in torque and output in the middle rev range, while the maximum rates remain unchanged. This results in a lowering of the rated engine speed from 1800 rpm to 1600 rpm. A look at the power curve shows that the engine attains its maximum output more or less constantly across a broad engine speed range from 1450 rpm to 1900 rpm.
The torque curve is configured along similar lines: maximum tractive power is attained nominally at 1100 rpm, but is available virtually constantly from around 900 to 1400 rpm. As a result of these two curves, the OM 470 offers excellent driveability. with high agility across a very broad usable rev range of around 1000 rpm.
With its optimized injection and combustion, the engine is systematically designed for low fuel consumption. The untreated NOx emissions are eliminated by means of proven SCR technology and a new SCR catalytic converter. AdBlue consumption is consequently on a par with earlier Euro V engines, at around five percent of fuel consumption.