The second generation of lightweight diesel engines includes the 2.0-liter OM621 engine. A new engine family took its place in 1968 after it was first introduced in 1956. Although the camshafts, cylinder head, pistons, and fuel injection system have been redesigned, it is based on the M121 gasoline engine.
It is a prechamber, lower shaft with a gear drive. A two-row chain with a hydraulic tensioner powers the camshaft and injection pump. It should be mentioned that because Mercedes places a high value on dependability, the chain drive is utilized on all of their engines. Despite its lack of power, this engine produces good torque at low revs. not using a turbocharger.
Specifications
| Engine’s type | diesel |
| Tradename | OM 621 |
| Power, hp / kW | 50 / 37 |
| Displacement, cc | 1990 |
| Number of cylinders | 4 |
| Number of valves | 8 |
| Compression ratio | 21:1 |
| Cylinder bore, mm | 87 |
| Piston stroke, mm | 83 |
| Crankshaft bearings | 5 |
| Configuration | inline |
| Fuel type | diesel fuel |
| Turbine | suction pump |
| Cylinder head | SOHC/OHC |
| Timing mechanism | chain |
| Timing | rocker arm |
| Cooling | water |
Generations of OM621 engines
| Also called | Displacement | Power | Torque output | Production years |
|---|---|---|---|---|
| OM621 I | 1.9 l. (1897 cc) | 37 kW (50 hp) @ 4000 rpm |
108 Nm @ 2200 rpm |
1958–1959 |
| OM621 IV | 2.0 l. (1988 cc) | 35 kW (47 hp) @ 3800 rpm |
1961–1962 | |
| OM621 III / VIII | 40 kW (54 hp) @ 4200 rpm |
118 Nm @ 2400 rpm |
1961–1968 | |
| 2.2 l. (2197 cc) | 40 kW (54 hp) @ 3000 rpm |
1966–1988 |