Mercedes-Benz has unveiled its new 2-liter four-cylinder OM654 unit that will launch with the new E-Class, the first engine in its next-generation diesel range.
The German OEM says that the all-aluminum unit a first for a four-pot diesel has a higher power output than its predecessor, but 13% lower fuel consumption and emissions. The engine in the E220d has a power rating of 195ps instead of 168ps.
Mercedes is counting on the high-volume engine to lower its average fleet emissions.
Changes in detail
The key changes on the new motor are a move from 2,143cc displacement to 1,950cc, steel pistons with stepped combustion bowls, Nanoslide cylinder coating (which contributes to a 25% reduction in friction losses), fourth-generation common rail injection (with pressures up to 2,050 bar), and exhaust treatment technologies built directly on the engine. Mercedes says that the flat pistons and cylinder alone account for a 4% cut in emissions and fuel consumption.
Mercedes says that the motor is significantly lighter and more compact than its predecessor at 168.4kg versus 202.8kg, a 17% reduction. Cylinder spacing has also been reduced to 90mm from 94mm. Bore/stroke of 82 x 92.3mm result in an advantageous individual cylinder volume of just under 500cc.
Real-world driving tests
Mercedes says that the OM654 unit and other engines in the new range have been designed with new real-world emissions tests in mind.
The German OEM says that all components of relevance for efficient emissions reduction are installed directly on the engine, and supported by insulation measures and improved catalyst coatings, it means that 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 optimal operating conditions.
The new engine is equipped with multiway EGR, which combines cooled high-pressure and low-pressure EGR. The company says that it makes it possible to significantly further reduce the untreated emissions from the engine across the entire engine map, with the center of combustion being optimized for fuel economy.
Exhaust gas from the turbocharger is sent first to a diesel oxidation catalyst. It then passes the downdraft mixer, where 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 gas enter the exhaust system.
Most-produced engine
Manufactured from 2008, the 2.2-liter OM651 unit was Mercedes’s most-produced engine ever, finding itself in applications from the A-Class to the Sprinter van.
The components for the new engine will be built in Stuttgart at the Untertürkheim plant, while the units will be assembled at Mercedes’s factory in Kölleda, Thuringen, in central Germany.
February 24, 2016