Mercedes-Benz OM651 engine
The Mercedes-Benz OM651 is a family of inline-four diesel engines introduced by Mercedes-Benz in 2008.
Design
The main goal was to create a common engine design that shared parts across the line.One design requirement was that the engine could be mounted both longitudinally and transversely.
Improved fuel efficiency and compliance with Euro 5 European [emission standards|emission standards] were other design objectives, by 2010 updated to the Euro 6 standard. Four piezo-electric injectors fed with high pressure fuel from a common rail inject fuel directly into the combustion chambers to improve combustion compared to previous diesel engines while recirculated exhaust gas reduces the oxygen in the cylinders to "starve" any reactions that would produce NO.
Variants
Of the 6 variants, 4 have the same 2.2-litre swept volume, tuned to different power outputs , or , or to . The, and versions employ a 2-stage charging setup with a small, high pressure turbo providing quick boost at low rpm fed by a large, lower pressure turbo providing increased performance at higher rpm, then at highest rpm ranges and loads, both were active. The lower output versions have a single turbocharger.Two shorter stroke "square" variants had 1.8-litre displacement and . These two variants differ only in electronic tune, and have a single turbocharger.