Engine Mercedes OM668

Engine Mercedes OM668

The Mercedes OM668 engine is a transverse in-line 4-cylinder diesel engine produced from 1997 to 2004 for a single Mercedes-Benz A168. This is the first engine in the history of Mercedes, which received the CDI prefix – diesel with direct injection. The engine has a kinship with the gasoline counterpart, but at the same time it has a serious difference – 4 valves per cylinder. Despite the small displacement, the OM 668 has a turbocharger, an intercooler and, as already mentioned, direct fuel injection.

The engine is equipped with a turbocharger, a common rail fuel injection system and an intercooler. The timing is driven by 2 chain-driven overhead camshafts. The first chain engages the intake camshaft, and is connected to the exhaust camshaft by means of a gearbox. A similar chain drive from the crankshaft drives the oil pump. A transitional intercooler is responsible for cooling.


Engine’s type diesel
Start of release 1997
Power, kW at rpm 55-67 at 3600
Power, hp at rpm 75-91 at 3600
Displacement, cc 1689
Number of cylinders 4
Number of valves 16
Torque output, Nm at rpm 160 at 3600
Compression 19.5:1
Cylinder bore, mm 80
Piston stroke, mm 84
Crankshaft bearings 5
Configuration inline
Fuel type diesel fuel
Combustible mixture supply direct injection
Turbine turbocharger
Cylinder head DOHC
Timing mechanism chain
Cooling water

OM 668 was produced with one single displacement – 1689 cc, but had three modifications and four power options:

  1. Version 668.940 (OM 668 DE 17 LA) with 90 HP at 4200 rpm. and was installed on Mercedes Benz A170 CDI until 2001.
  2. Version 668.941 (OM 668 DE 17 A) with 60 HP at 3600 rpm., was installed on the Mercedes Benz A160 CDI until 2001. This modification was notable for the absence of an intercooler.
  3. Version 668.942 (OM 668 DE 17 LA) with 95 HP at 4200 rpm., was installed on the Mercedes Benz A170 CDI since 2001.
  4. Version 668.940 (OM 668 DE 17 LA Red) with 75 HP at 3700 rpm., was installed on the Mercedes Benz A160 CDI since 2001. “Red” means reduced (reduced) power.

Engine Mercedes OM668 under the hood
In 2001, the OM668 series engines underwent changes – the camshaft and turbocharger were modified. Improvements made it possible to increase the rated power. However, due to the weak grip, the torque remained untouched. The engine power can be increased to 118 hp. by reprogramming the software of the electronic control unit. At the same time, the reliability and durability of the engine will not be affected in any way.

Explanation of marking

OM Heavy Fuel Oil (Diesel) ICE
668 Engine type: in-line

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