Engine Mercedes OM646

The 2.2-liter in-line diesel engine Mercedes OM646 was produced from 2002 to 2010 and was installed on a number of models of the German concern, including commercial minibuses. In addition to the regular and derated modification, RED has been offering an improved EVO since 2006.

The engine was equipped with a Common Rail 2 fuel system. Such an injection is capable of delivering 1600 bar. The new nozzles are made with a smaller nozzle size, which improves the spray efficiency. Also, one of the features of Common Rail 2 injection is the ability to provide two injections – preparatory and main. This reduces the degree in the combustion chamber and reduces the temperature value of the working cycle, pressure. Thus, the indicator of environmental standards improves and the efficiency of the power unit increases.


Fuel type diesel
Configuration inline
Number of cylinders 4
Valves 16
Displacement 2.2 liters
Max power output, hp at rpm 150 / 4200 (170 / 3000 for turbo version)
Max torque output, Nm / rpm 340 / 2000 (400 / 2800 for turbo version)
Maximum crankshaft speed 4000 rpm
Cylinder bore 88 mm
Piston stroke 88,3 mm
Gas distribution system 4 valves per cylinder
Compression ratio 18.0:1
Fuel system direct injection
Engine location Engine compartment

The Mercedes OM 646 engine was equipped with a second generation Common-Rail fuel system with a maximum injection pressure of 1600 bar, with new 7-hole injectors. The smaller diameter of the nozzles allowed for better fuel atomization. The fuel system provided 2 pilot injections. Injection of fuel before direct injection, which causes the combustion of the fuel charge, allows the temperature in the combustion chamber to be reduced due to the evaporation of the fuel, correspondingly lowering the average operating cycle temperatures and pressures. Thus, NOx emissions are reduced, the diesel engine runs smoothly, and noise and vibration are reduced. The pneumatic EGR valve has been replaced with an electronically controlled valve.

In 2006, Mercedes-Benz upgraded the OM646 diesel. The updated OM646 EVO has 90 parts replaced. The compression ratio of the diesel engine was lowered from 18.0 to 17.5. Higher pistons and shorter connecting rods were used. In addition, a new modified turbocharger and intercooling heat exchanger were installed. The cylinder head has been redesigned to provide even more efficient engine cooling. Ceramic glow plugs were used to improve engine starting.

Compliance with environmental standards Euro-5 is the first characteristic feature of this engine. In order to improve environmental performance, the designers have revised the algorithms for the fuel supply of the engine control unit. Other changes were also made:

  • OM646 replaced the EGR valve, installed a new DPF and a catalyst;
  • increased the size of the intercooler heat exchanger;
  • all pressure and temperature regulators have been updated.


  • OM 646 DE 22 LA RED or 200 CDI;
  • OM 646 DE 22 LA or 220 CDI;
  • OM 646 DE 22 LA EVO RED or 200 CDI;
  • OM 646 DE 22 LA EVO or 220 CDI.

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