Mercedes-Benz OM 615 / OM 616 / OM 621 diesel engines

Mercedes Benz
OM 615, OM 616, OM 621
Production period:	1958-1995
Manufacturer:	Mercedes Benz
How it works:	diesel
Engine Type:	In-line
displacement:	1897, 1988, 2194, 2399, 2404 cm 3
Fuel supply:	indirect injection
Engine charging:	none
Power:	37-53 kW
torque:	108-137 N · m
Previous model:	OM 636
Successor:	OM 601

The OM 621 engine as well as its slightly modified successors OM 615 and OM 616 are diesel engines with prechamber injection and four cylinders in series , developed and produced by Mercedes-Benz .

These engines have been installed in cars, vans and Unimogs of Mercedes since the late 1950s to 1996, and after the participation in Hanomag-Henschel from 1970 here too, over about four decades in millions of units. These engines are still on the streets of the world in hundreds of thousands of copies today.

The predecessor of the OM 621 was the OM 636 . Successor of the OM 615, OM 616 and OM 617 (which differs from the OM 616 only by an additional cylinder) were the completely newly developed engines OM 601 , which was introduced in 1983 in the 190 D , and the OM 602 and OM 603 in the Built in 1985, the 124 series .

The abbreviation "OM" stands for "oil engine" (engine, which is operated with light oil / diesel) and designates until today the diesel engines of Mercedes-Benz.

History

First came out the OM 621 1958 for the pontoon model 190 D W 121 series , with an output of 50 hp and a displacement of 1897 cc. Compared to the still offered until 1961 parallel model 180 D ( W 120 ), which still used the slightly improved OM 636 from the 170 D ( W 136 ) with 43 hp, he offered a significant improvement in performance. The OM 621 engine was a state-of-the-art design at its inception, with an overhead camshaft ( OHC ) instead of the lower ( OHV ) of the OM 636.

The design of the OM 621 was based on the gasoline engine M 121 , which was also installed in the 121 series. With the M 121, the engine divided the crankshaft with its bearings , the crankcase, the bore pattern of the cylinder head, and many other small parts. Even otherwise, the diesel engine had many design features of the M 121, such as the chain-drivenoverhead camshaft and the valve actuation via cam followers . Only the camshaft, cylinder head, pistons, connecting rods and injection equipment had to be redeveloped. As a result, the production could be rationalized, resulting in a cost savings of 250 DM compared to the OM 636.

For the appearance of the tail fin model W 110 in 1961, the capacity was increased to two liters, but the sales name 190 D initially maintained. The engine power grew to 55 hp, which now for two decades the minimum driving performance of German cars (together with the VW Beetle with 34 hp) formed. In 1965, the engine was changed to five crankshaft bearings (designation OM 621 VIII), and henceforth offered as 200 D, with unchanged 55 hp.

The versions of the OM 621 up to the Index / III had only three crankshaft bearings: before the first and after the last cylinder, and a center bearing between the 2nd and 3rd cylinder. Their engine run is quite rough and noisy. With the conversion to five main bearings, the engine was much quieter. This was the most profound of all changes made to the entire OM 621/615/616 engine family.

The engine OM 615 came out 1968 in the model 200 D of the series W 115 out. The OM 615 in its two-liter version for the 200 D is just a minor development of the predecessor OM 621 from the tail fin models, the difference being essentially a changed oil filter position and a lower, shorter intake manifold due to the flatter front end. The most important innovation was the version of the OM 615 with extended stroke, with a displacement of 2.2 liters and a power output of 60 hp in the Model 220 D - the best-selling W 115 diesel model.

The engine OM 616 came out in 1973: based on the extended stroke of the 220 D, the bore was also expanded, the capacity increased to 2.4 liters and the power to 65 hp. This engine was offered as part of the model care ("MOPF") in the "dash-eight" series under the model name 240 D.

The engine OM 617 in the type 240 D 3.0, which in turn was released one year later, in 1974, is merely an OM 616 extended by a fifth cylinder, see also the article OM 617 .

Mercedes also used the same engine types OM 615 to 617 in the successor models of the "dash-eight", the 123 series .

The previous engines all had a "start-stop train", which took over not only the electrical control of the preheat and the starter, but also at the injection pump an accumulation of injection quantities to start, and the position of the injection pump to zero flow to stop the engine took over. This somewhat cumbersome, needy handling ended in 1980 with the introduction of quick-start glow plugs and key start-stop. As part of this, the engine power of the OM 615 (200 D) was increased to 60 hp, the OM 616 (240 D) made 72 hp, and the model 220 D was omitted.

Long construction time 

The engine OM 615, its predecessor OM 621 and its later sister models OM 616 (220 D, 240 D) and the five-cylinder OM 617 for the 300 D are proof of the mostly decades of largely identical motorized drives for cars that - with light Modifications and revisions - have a significantly longer life cycle than the shorter-lived body styles of different series.

The decisive reason for the long-term use of engine concepts is the huge investment that an engine manufacturer must make when planning a complete engine redesign in terms of production technology and then implementing it in the factory.

Both the facilities of a highly automated foundry for the engine blocks and cylinder heads and the mechanical processing of large castings as well as the transport and interlinking facilities to final assembly each represent high eight-digit investment, which only over very long periods, ideally just over three decades, can pay off. As a rule, engines of different designs can not be built mixed in the same production line until today.

At some point, however, even the longest-lived conception has reached its usable end; This was the case with the diesel engines of the OM 621, 615, 616 and 617 series in 1984, when the launch of the new mid-range W 124 series brought lighter and higher-revving diesel engines to the design of the "small" Mercedes W 201 (190 D) the middle class stopped. However, the OM 616 was again revised in 1991 (55 kW / 75 hp) and built into the MB 100 D until 1995. Even today, this engine is still being produced in India under license from Force Motors , now as a more powerful turbocharged version. For the current model (2016) of the Force Gurkhathe capacity was increased to 2.6 L and replaced the antechamber injection by a modern common rail injection system. 

Technical data 

OM 621 

• W 121 190 D (pontoon) 1956-1959,
• W 110 190 D  1959-1965,
• W 110 200 D  1965-1968,
• Mercedes Unimog ,
• Hanomag low loader F20 Diesel,
• Built-in motors for
  • Electricity generators ,
  • fork-lift truck
  • and marine propulsion .

Car models

OM 615/616 

• W 115 200 D ("Dash Eight") 1968-1976,
• W 115 220 D ("Dash Eight") 1968-1976,
• W 115 240 D ("dash-eight") 1972-1976,
• W 123 200 D 1976-1984,
• W 123 220 D 1976-1980,
• W 123 240 D 1976-1984,
• W 460 240 GD 1979-1987,
• Hanomag-Mercedes "Harburger Transporter" L206D / L306D series or Hanomag F20-F36 series (until 1977)
• Pickup truck T 1 ,
• Pickup truck T 2 ,
• MB 100 ,
• Mercedes-Benz Unimog ,
• Built-in motors for
  • Electricity generators ,
  • fork-lift truck
  • and marine propulsion .

Car models