The OM621 is an
inline-four
A straight-four engine (also called an inline-four) is a four-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.
The vast majority of automotive four-cylinder engines use a straight-four layout (with the ...
diesel engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...
produced by
Mercedes-Benz
Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...
, from 1956 to 1968. It was succeeded by the
OM615 engine.
Design
The OM621 is based on the petrol
M121 engine, but features revised
camshaft
A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...
s,
cylinder head
In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber.
In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...
,
piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...
s, and fuel injection system. In 1961, the engine capacity was increased to and power was uprated to for use in the newly introduced
W110 models. After being replaced by the OM615, a updated version of the OM621 engine was used solely in
Unimog
The Unimog (, ) is a range of multi-purpose tractors, trucks and lorries that has been produced by Boehringer from 1948 until 1951, and by Daimler Truck (formerly Daimler-Benz, DaimlerChrysler and Daimler AG) since 1951. In the United States and ...
vehicles until 1988.
Models
OM621 (37 kW version)
* 1958–1959
W121 190D, 190Db
OM621 (35 kW version)
* 1961–1962
W120 180Dc
OM621 (40 kW version)
* 1961–1965
W110 190Dc
* 1965–1968
W110 200D
* 1966–1988
Unimog 421
References
{{reflist, 30em
OM621
Diesel engines by model
Straight-four engines