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Innlegg av: ZaloUltra (27.07.17 19:42 ), lest 274 ganger

OM 656 kvantespranget for dieselbiler starter nå!

With the new six-cylinder in-line diesel engine OM 656, the next member of the ground-breaking family of premium diesel engines from Mercedes-Benz will follow in 2017. Its features include the stepped-bowl combustion process, a combination of aluminium engine block and steel pistons as well as further-improved NANOSLIDE® cylinder wall coating.

The new family of premium diesel engines from Mercedes-Benz celebrated its world premiere with the four-cylinder E 220 d in spring 2016. In 2017, another important representative of this modular family will follow with the six-cylinder in-line engine OM 656. Although there is a significant increase in output compared with the previous OM 642 (over 230 kW/313 hp instead of 190 kW/258 hp), the new engine consumes more than seven percent less fuel.

A special feature of the family of premium diesel engines is the combination of steel pistons with an all-aluminium engine block. The lower expansion of steel as operating temperatures rise ensures an increasing clearance between piston and aluminium block, thereby reducing the friction by 40 to 50 percent. At the same time, the fact that steel is stronger than aluminium allows very compact, lightweight pistons that even offer additional strength reserves. Finally, the lower thermal conductivity of steel leads to higher component temperatures, thereby improving the thermodynamic efficiency, increasing combustibility and reducing combustion duration.

The combination of innovative steel pistons and the optimised piston ring package with the further-improved NANOSLIDE® coating of the cylinder walls results in benefits in terms of fuel consumption and CO2 emissions, especially in the lower and medium engine-speed ranges, which are of relevance for day-to-day vehicle use.

Stepped-bowl combustion process

The new OM 656, too, employs the Mercedes-Benz stepped-bowl combustion process – named after the shape of the combustion bowl in the piston. The stepped bowl has a positive effect on the combustion process, the thermal loading of critical areas of the pistons and the introduction of soot into the engine oil. The efficiency is increased by the higher burning rate in comparison with the previous omega combustion bowl. The characteristic feature of the specifically configured combination of bowl shape, air movement and injector is its very efficient utilisation of air, which allows operation with very high air surplus. This means that particulate emissions can be reduced to an especially low level.

Exhaust emissions: all set for the future

The new diesel engine is designed to meet future emissions legislation (RDE – Real Driving Emissions). All the components of relevance for efficient emissions reduction are installed directly on the engine. Supported by insulation measures and improved catalyst coatings, there is no need for engine temperature management during cold starting or at low load. In addition to the advantages in terms of emissions, this results in fuel savings, especially on short journeys. Thanks to the near-engine configuration, exhaust aftertreatment has a low heat loss and extremely favourable operating conditions. This is reinforced by the CAMTRONIC switchable exhaust camshaft, which supports the consumption-neutral heating of the exhaust system.

The new engine is equipped with multi-way exhaust gas recirculation (EGR). It combines cooled high-pressure and low-pressure EGR. This makes it possible to significantly further reduce the untreated emissions from the engine across the entire engine map, with the centre of combustion being favourable for fuel economy.

The data of the new engine in comparison with its predecessor:

Engine

OM 656
OM 642
No. of cylinders/arrangement

6/in-line
6/V
Valves per cylinder

4
4
Displacement per cylinder
cc
488
498
Displacement
cc
2927
2987
Cylinder spacing
mm
90
106
Bore
mm
82
83
Stroke
mm
92.4
92
Rated output
kW/hp
over 230/313
190/258
Peak torque
Nm
over 650
620
Compression ratio
1:
15.5
15.5
Emissions standard

EU 6/RDE
EU 6