Engine Mercedes OM651

Engine Mercedes OM651

Mercedes-Benz OM651 is a family of in-line four-cylinder internal combustion diesel engines from Mercedes-Benz, first introduced in October 2008. It was created as a replacement for the OM646 and OM642 series. Production took place at a plant in Stuttgart, Germany.

Available in versions DE18 LA (1796 cc) and DE22 LA (2143 cc). Despite the fact that most of the variations of the power unit have a working volume of 2143 cubic meters. see, nevertheless, its power varies in the range from 107 hp. up to 204 HP Versions over 125 kW (170 hp) are equipped with a twin-turbo system, below 100 kW with a single turbocharger.


Manufacturer Mercedes-Benz
Also called OM 651
Production years 2008
Fuel system direct injection
Configuration inline
Number of cylinders 4
Piston stroke, mm 99
Cylinder bore, mm 83
Compression ratio 16.2
Displacement, cc 1796
Power output, hp 107/3200-4600
Torque output, Nm / rpm 250/1400-2800
Fuel type diesel
Euro standards Euro 6
Engine lifespan, thousand km
— official information
1 000

OM 651 engine block head

  1. Chain guide;
  2. Chain;
  3. Stars;
  4. Intake camshaft;
  5. Exhaust camshaft;
  6. Sensor;
  7. Roller rocker arm;
  8. Hydraulic compensator;
  9. Chain tensioner;
  10. Leading asterisk.


The compact, low design, thanks to the rear camshaft drive, contributes to the fulfillment of legal requirements for pedestrian protection.

The 4th generation common rail direct injection with piezo injectors (which Mercedes replaced with conventional ones as part of the service program, because they turned out to be problematic) provides an injection pressure of up to 2000 bar. Direct control of the injector needle creates the conditions for high flexibility in injection timing and smooth engine operation, as well as high performance with low fuel consumption and low exhaust emissions.

The geometry of the flat combustion chamber and the lower compression pressure reduce the emission of raw exhaust gases, especially nitrogen oxides. The maximum cycle pressure of up to 200 bar increases engine performance and contributes to the reduction of harmful emissions.

The compact two-stage boost module (not on the GLK) consists of a small high-pressure turbocharger and a large low-pressure turbocharger. Each of them consists of a turbine connected in series and a compressor driven from it. The combustion air supply is regulated as required using both turbochargers. This ensures a better filling of the cylinders and, as a result, a higher torque already at low revs.

Explanation of OM651 marking

OM Heavy Fuel Oil (Diesel) ICE
651 Engine type: 4-cylinder in-line.

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