Mercedes-Benz launches all-ally 4-cylinder diesel

Mercedes-Benz has joined the ranks of JaguarLandRover and others with its OM 654, its first all-aluminium  four-cylinder diesel engine which it says marks the debut of a “ground-breaking” family.

The company claims that “exemplary efficiency and emissions” ensure that the premium diesel is “future-proof” while underlining the key role to be played by the diesel engine in achieving the challenging global climate targets.

The first all-aluminium four-cylinder diesel engine will debut in the new low volume E-Class E 220d this spring.

"The new family of engines embodies over 80 years of Mercedes-Benz diesel know-how. The new premium diesels are more efficient and powerful, lighter and more compact - and they are designed to meet all future global emissions standards," claims Prof. Dr. Thomas Weber, member of the Daimler Board of Management with responsibility for group research and head of Mercedes-Benz Cars Development. "In our opinion, the diesel engine is indispensable in trucks and cars if we want to further reduce the CO₂ emissions from traffic."

Mercedes-Benz says it attaches “key importance to the optimisation of modern internal combustion engines alongside hybrid and electric vehicles” and the new diesel will make an “important contribution to the further reduction of fleet consumption”.

In the two decades since 1995, the average consumption of the passenger car fleet has fallen by almost half from 9.2 l/100 km (230 g CO₂ /km) to 5.0 l/100 km (125 g CO₂/km). Today, Mercedes-Benz Cars says it has 68 models that emit less than 120 g/km – and 108 models with the efficiency label A+ or A.

The modular family of engines will find broad application across the entire range of Mercedes-Benz cars and vans.

There are plans for several output variants as well as longitudinal and transverse installation in vehicles with front-, rear- and all-wheel drive. This, too, makes the new engine significant, because the improvements in efficiency have a direct impact on Mercedes-Benz's fleet consumption.

One objective behind the new generation of engines is the need to reduce the number of variants. The compact engine offers more flexibility in adapting to different vehicle models.

The interfaces between drive unit and vehicle have been standardised across all model series. More especially, all the elements of the exhaust after-treatment system are now configured directly on the engine itself and no longer on the vehicle.

The new engine delivers around 13 percent lower fuel consumption and CO₂ emissions along with a further increase in output (143 kW instead of 125 kW).

The most important innovations of the new engine:

·    first Mercedes-Benz all-aluminium four-cylinder diesel engine

·   steel pistons with stepped combustion bowls, NANOSLIDE^® cylinder coating, fourth-generation common rail injection

·    all exhaust treatment technologies configured directly on the engine

·    significantly lighter and more compact: 168.4 kg vs. 202.8 kg (-17 per cent),
two-litre displacement instead of 2.15 litres, cylinder spacing 90 mm vs. 94 mm

·   lower noise level and outstanding vibration comfort thanks to a raft of measures

The new diesel engine is designed to meet future emissions legislation (RDE – Real Driving Emissions).

In contrast to the current NEDC measurement cycle, the WLTP (Worldwide harmonized Light vehicles Test Procedure) cycle is aimed at ensuring that the figures for standard and real-world consumption are close together in future. In addition, it is planned in Europe to introduce a measuring procedure for Real Driving Emissions (RDE), a move backed by Mercedes-Benz.

Supported by insulation measures and improved catalyst coatings, Mercedes-Benz claims “there is absolutely no need for engine temperature management during cold starting or at low load”.

Engineers add that with “near-engine configuration”, exhaust after-treatment has a low heat loss and optimal operating conditions.

The new engine has multiway exhaust gas recirculation (EGR). This combines cooled high-pressure and low-pressure EGR.

Exhaust gases from the turbocharger are sent first to a diesel oxidation catalyst. It next passes the downdraft mixer, in which AdBlue^® is added by means of a water-cooled dosing module. Thanks to a specially developed mixing area, the AdBlue^® evaporates and is distributed uniformly on the surface of the downstream sDPF (particulate filter with coating to reduce nitrogen oxides).

Positioned behind the sDPF is an SCR catalyst for further catalytic reduction of the nitrogen oxides. Only then does the treated exhaust gas enter the exhaust system.