Optimised internal combustion engines trucks Because every drop counts for trucks as well

Fuel accounts for about one third of a truck's total cost of ownership. That is the reason why the engineers at Daimler Trucks are constantly working on the optimisation of the internal combustion engines to always offer our customers the most efficient powertrains.

As the world's largest manufacturer of commercial vehicles, we have a global footprint. Because the emissions standards vary greatly from region to region, Daimler Trucks offers a host of different engine variants. But that doesn't mean that we design a different engine for each country: We create synergies wherever possible. For instance, the heavy-duty engine family from Daimler Trucks was designed to be used for different applications: it powers the heavy-duty trucks from Mercedes-Benz, FUSO, Freightliner and Western Star as well as the buses and coaches from Mercedes-Benz and Setra.

OM 470 and OM 471: More driving dynamics, lower consumption

The Mercedes-Benz OM 470 and OM 471 truck engines for heavy-duty operations undergo continuous further development. The result is even lower CO2 emissions but more power.

 

Even more economical, and now even more powerful with a new output variant: the latest generation of the Mercedes-Benz OM 470 and OM 471 achieves an all-round increase in performance.

The OM 470 is available in five output variants. In its new, top variant with 335 kW (456 hp), the OM 470 with a maximum torque of 2200 Nm even reaches the power band of the larger OM 471 with a displacement of 12.8 l. In turn, the top engine variant of the OM 471 achieves an output of 390 kW (530 hp) and a maximum torque of 2600 Nm. This means that the OM 471 enters output and torque levels that were the preserve of much larger and eight-cylinder engines just a few years ago.

One major feature of the new engine generations is the latest generation of the injection system X-Pulse, the unique common-rail system with pressure boost in the injector and free configurability of the injection system. The maximum rail pressure has been increased from 900 to 1160 bar. This leads to a maximum injection pressure of 2700 bar.

Though the maximum figures remain unchanged, one typical characteristic of the latest-generation OM 470 is a very steep increase in torque and output in the medium engine speed range. This results in a reduction in rated speed from 1800 rpm to just 1600 rpm. This means that the engine delivers maximum output over a wide engine speed range from 1450 rpm to 1900 rpm. The torque curve is similar: maximum torque is nominally delivered at 1100 rpm, however it is almost constantly available from around 900 to 1400 rpm.

In the latest generation of the OM 471, the output and torque curves rise much more steeply in the lower rpm range. All the output variants now deliver a torque of at least 2000 Nm at just under 800 rpm. Depending on the output variant, maximum torque is already achieved between around 800 and 950 rpm.

Instead of the previous EGR flap in the EGR tract, an EGR flap located well forward has been integrated into the exhaust manifold in the OM 470 and OM 471.

One special feature of both engines is the asymmetrical turbocharger. For a rapid increase in boost pressure with a corresponding fast rise in output and torque, the exhaust gases of cylinders four to six are conducted directly into the turbine. A defined proportion of the exhaust gases from cylinders one to three is diverted for exhaust gas recirculation (EGR) to reduce NOx emissions.

Instead of the previous EGR flap in the EGR tract, there is now an EGR flap located well forward in the exhaust manifold, well before the exhaust gases enter the turbocharger. Both the EGR rate and the flow of exhaust gases to the turbocharger can be regulated according to the engine's characteristic map thanks to the new position of the flap. By virtue of the variably controllable EGR flap in its new position, between zero and 100 percent of the exhaust gases from the three supplying cylinders can be fed to the combustion process as required – a unique feature in engine technology. The EGR flap therefore not only controls the exhaust flow for exhaust gas recirculation, but also the turbocharger.

The asymmetrical turbocharger ensures precise adaptation to the requirements of the engine, and impresses with its outstanding efficiency.

The asymmetrical turbocharger for the latest generation of the OM 470 and OM 471 was developed in-house by Mercedes-Benz, and is produced at the engine plant in Mannheim. It thus ensures precise adaptation to the requirements of the engine, and impresses with its outstanding efficiency. As before, the asymmetrical turbocharger has a fixed turbine geometry and is therefore very robust.

In the latest generation of the OM 470 and OM 471, Mercedes-Benz not only dispenses with a wastegate valve for the turbocharger, but also with boost pressure control. Together with elimination of the EGR sensor and EGR control, this means that the engines are in purely pre-controlled operation and therefore operate even more efficiently.

The sophisticated emissions control strategy, for example, supersedes the previous individual control of exhaust gas recirculation and boost pressure, making for much more efficient operation. Thus there are no longer any diversions of the exhaust flow necessary to separate control systems and combinations of them. At the same time the engine is even more robust thanks to the elimination of numerous components and parts.

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