World premiere in the new E-Class.
The completely newly developed OM 654 four-cylinder diesel engine was launched as the E 220 d in the new E-Class. Installed in a comparable vehicle, the new engine consumes around 13 percent less fuel than its predecessor. Besides the optimised air ducting on both the intake and exhaust sides, and the use of fourth-generation common-rail injection with pressures up to 2,050 bar, the approximately 25-percent reduction of internal friction forces also played a major role in achieving this. The new OM 654 is the first member of a modular-construction engine family which will be used across the entire Mercedes-Benz product portfolio. Several power stage variants are planned as well as longitudinal or transverse mounting in vehicles with front, rear or 4MATIC all-wheel drive systems.
E 220 d: Fuel consumption combined: 4.3–3.9 l/100 km; combined CO₂ emissions: 112–102 g/km.*
Aluminium housing and steel pistons.
The combination of aluminium housing and steel pistons may at first appear a little unusual. That’s because steel expands less than aluminium when heated, it is also a worse conductor of heat and is heavier. That’s why aluminium pistons were previously used. The engineers of the power unit used these seemingly disadvantageous aspects to their advantage. For example, the lower expansion of steel when the operating temperature rises ensures greater play between the pistons and the aluminium housing, thus reducing friction.
In comparison with aluminium, the greater rigidity of steel allows for a very compact, lightweight piston construction. After all, the lower heat conductivity of steel leads to increased component temperatures and improves the thermodynamic efficiency with greater ignition quality and a reduced combustion duration.
Stepped recess combustion process.
This is the first time the stepped recess combustion process is used in the diesel engine of a passenger car. Its name refers to the shape of the combustion pocket in the piston. The combustion process is an entirely new development. The stepped recess has a positive effect on the combustion process, the thermal stress on the components in critical piston areas and soot accretion in the engine oil. Increased combustion speed also increases the overall efficiency.
Innovative cylinder wall coating.
Besides the stepped recess combustion process and the combination of an aluminium housing with steel pistons, another innovation was the further improvement of the NANOSLIDE cylinder wall coating. Wires made of an iron-carbon alloy are fused to it using an electrically created arc. The melted material is sprayed onto the cylinder wall using a gas stream and deposited there as a lamellar, ultra-fine to nano-crystalline layer. Very fine finishing of the resulting nano-crystalline iron layer creates an almost mirror-like surface with fine pores, which reduce the friction and wear between the piston group and the cylinder wall. Further advantages are reduced engine weight, extremely high wear-resistance and lower consumption and emissions.
Emissions: Ready for the future.
The new OM 654 is designed to fulfil future emissions regulations (RDE – Real Driving Emissions). All components relevant in reducing emissions are directly mounted to the engine and temperature management for cold starting and operating at low loads has been omitted. Besides the advantages in terms of emissions, there is also reduced consumption, particularly on short journeys.
Production in Untertürkheim and Kölleda.
The new engine features multi-way exhaust gas recirculation (AGR). It combines the cooled high-pressure and low-pressure AGR. Thus, already the engine's untreated emissions were again able to be drastically reduced across the entire characteristic curve whilst maintaining a consumption-optimised position for the centre point of combustion. The OM 654 production will be carried out in the base plant Untertürkheim as well as at the 100-percent Daimler subsidiary MDC Power in Kölleda, Thuringia.