Mercedes-Benz OM651 engine

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Mercedes-Benz OM651
Manufacturer Mercedes-Benz
Production 2008-present
Combustion chamber
Configuration I4[1]

1,796 cc

2,143 cc
Cylinder bore 83mm
Piston stroke


Cylinder block alloy cast iron [1]
Cylinder head alloy aluminium
Valvetrain DOHC 16-valve
Compression ratio 16.2:1
Turbocharger turbo/twin-turbo
Fuel system common rail with piezo injectors. Fuel pressure 2000 bar.
Fuel type diesel
Cooling system intercooler
Power output 108-208 ps
Torque output 300-500 Nm
Predecessor OM646
Successor OM654

The OM651 is a family of inline-four cylinder Diesel automobile engines introduced by Mercedes-Benz in 2008. The chief goal was to create a common engine design that maximized the parts commonality between the engines manufactured by parent company, Daimler.

One requirement of the design was the ability of the engine to be mounted both longitudinally and transversely. Improved fuel efficiency and compliance with Euro 5 emission standards were also design objectives, by 2010 being updated to the Euro 6 standard; four piezo-electric injectors fed with very high pressure fuel from a common rail inject fuel directly into the combustion chambers to improve combustion compared to previous Mercedes Diesel engines and recirculated exhaust gas reduces the oxygen in the cylinders to "starve" any reactions that would produce NO(x).

Although all engines have the same 2,143 cc swept volume, engines with various power outputs are produced ranging from 120 ps (badged x180) through 170 ps (badged x220) to 204 ps (badged x250). The 170 ps and 204 ps versions employ a twin-turbo charger with a small, high pressure turbo providing quick boost at low RPM and a large, lower pressure turbo providing increased performance at higher RPM. The 100kW lower output version has only a single turbocharger.

Beginning of summer 2017 the engine, together with Mercedes-Benz OM642 is in discussion that depending if the engine is operated in laboratory emissions testing a different amount of diesel exhaust fluid is used than in real world operating scenarios.[2]

See also[edit]