The 2.0 liter OM621 engine belongs to the second generation of lightweight diesel engines. Introduced in 1956 and later replaced by a new engine family in 1968. It is based on the M121 gasoline engine but has redesigned camshafts, cylinder head, pistons and fuel injection system.
It is a lower shaft, prechamber, with a gear drive. The camshaft and injection pump are driven by a 2-row chain with a hydraulic tensioner. It should be noted that the chain drive is used on all Mercedes engines, without exception, because reliability is paramount for them. This engine is not very powerful, but it demonstrates solid torque at low revs. Without turbocharging.
Mercedes diesel R4 family: OM636, OM621, OM615, OM616, OM601, OM661, OM604, OM611, OM668, OM640, OM646, OM651, OM654.
Specifications
| Production years | 1956-1968 |
| Displacement, cc | 1897 – 2197 |
| Fuel system | prechamber injection |
| Power output, hp | 47 – 55 |
| Cylinder block | cast iron R4 |
| Block head | aluminum 8v |
| Cylinder bore, mm | 87 |
| Piston stroke, mm | 83 |
| Compression ratio | 21.0 |
| Timing drive | chain |
| Turbocharging | no |
| Fuel type | diesel |
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 |
The engine was installed on:
- Mercedes W121 (Ponton) in 1958 – 1959 (190 D), W110 (Fintail) in 1961 – 1968 (190 Dc, 200 D), W120 (Ponton) in 1961 – 1962 (180 Dc);
- Mercedes Unimog 421 in 1966 – 1988.
Frequently asked questions about the Mercedes OM621
How much power does the Mercedes OM621 make?
The Mercedes OM621 develops 47 - 55 hp.
Does the Mercedes OM621 have a timing belt or chain?
The Mercedes OM621 uses a timing chain.
Is the Mercedes OM621 turbocharged?
No, the Mercedes OM621 is naturally aspirated.
What cars was the Mercedes OM621 installed on?
Mercedes W121 (Ponton) in 1958 - 1959 (190 D), W110 (Fintail) in 1961 - 1968 (190 Dc, 200 D), W120 (Ponton) in 1961 - 1962 (180 Dc); Mercedes Unimog 421 in 1966 - 1988.
