The future of the diesel engine.

In its road map towards sustainable mobility, Mercedes-Benz attaches key importance to the optimisation of modern internal combustion engines alongside hybrid and electric vehicles. In particular, the economical, clean and, especially in Europe, highly popular diesel engine makes an important contribution to the further reduction of fleet consumption.

Mercedes-Benz is on the right track. In 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). Already today, Mercedes-Benz Cars 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 so significant, because the improvements in efficiency have a direct impact on Mercedes-Benz's fleet consumption.

Another of the objectives behind the new generation of engines was to reduce the number of variants as far as possible. The engine's compact dimensions allow even 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 aftertreatment system are now configured directly on the engine itself and no longer on the vehicle.

• first all-aluminium construction of a 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. 203.8 kg (-17%), 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). This, too, is actively supported by Mercedes-Benz.

All components of relevance for efficient emissions reduction are installed directly on the engine. Supported by insulation measures and improved catalyst coatings, there is absolutely 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 optimal operating conditions.

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

The exhaust gas from the turbocharger is 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 over the shortest possible distance in the exhaust gas stream and is distributed very 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.