Mercedes-Benz M 103 Six-cylinder petrol engine

Mercedes Benz
M 103
Manufacturer:	Mercedes Benz
Production period:	1984-1995
Style:	Six-cylinder - inline engine
displacement:	2.6 liters (2599 cc)  3.0 liters (2962 cc)
Previous model:	M 110 , M 123
Successor:	M 104

The M 103 is a six-cylinder in-line engine from Daimler-Benz with a displacement of 2.6 or 3.0 liters

The engine has a cross-flow cylinder head and intake manifold injection . The petrol engine was of the M 123 (2.5 liters, a camshaft , counter-current cylinder head , carburetor ) and M 110 (2.8 liter, two camshafts, cross-flow cylinder head, carburetor or fuel injection).

The engine was presented at the end of 1984 by Mercedes-Benz together with the new W 124 passenger car series . The successor M 104 with four-valve technology appeared in 1989, however, the M 103 was used further, most recently until 1995 in the models with all-wheel drive ( 4MATIC ) W 124 series .

The M 103 engine was a fundamental redesign with similarities in design and manufacturing equipment to the 1983/84 introduced OM 601/602/603 diesel engines and the M 102 four-cylinder petrol engine . This was more compact and lighter than the two predecessors - so was z. For example, the 3-liter version, despite the higher displacement with oil and water 42 kg lighter than the 2.8-liter M 110. Compared with the M 123 with carburetor and countercurrent cylinder head was the specific fuel consumption of the M 103 with 2.6 liters Displacement by the cross-flow cylinder head and the intake manifold injection lower. At the same time, the maintenance effort was simplified because the adjustment of the valves by the same time in the M 102 Four-cylinder introduced hydraulic tappet accounted for and a finished filter cartridge replaced the old loose paper oil filter. Compared to the M 110 with the elaborate DOHC valve control , the M 103 with single camshaft (SOHC) was also able to produce significantly less expensive.

The M 103 had an engine block made of cast iron and a cylinder head from an aluminum alloy with two V-shaped arrangement of valves per cylinder. These were operated by a top-centrally located chain-driven camshaft via rocker arms and hydraulic tappets. Both displacement variants had from the beginning the KE-Jetronic - manifold injection from Bosch and an electronic ignition , with a matching plug in the engine room to adjust the ignition timing to different octane fuels.

The capacity of the M 103 was initially lower than that of the M 110. To achieve about the same performance, therefore, the capacity was increased from 2.8 to 3 liters. The 2.6-liter version was supposed to close the gap between the big 2.3-liter four-cylinder and the 3-liter six-cylinder. However, it did not prove to be a bestseller as the engine was nearly as expensive as the 3.0, with almost the same consumption and maintenance costs.

The reason for the change from DOHC - back to SOHC technology was, in addition to the lower weight and lower manufacturing costs, the achievement of new environmental and economic objectives, namely the introduction of regulated catalyst technology and the necessary reduction in gasoline consumption of the 6-cylinder in the face of the current oil crisis -Motorisierung. The latter was part of a major modernization program at Daimler-Benz in the mid-1980s, which had particular effects on the M 102, M 103 and M 117 engines and the newly designed diesel engines.

First class is the smoothness of this unit, especially the 2.6-liter version. The M 103 is one of the quietest 6-cylinder engines ever built.

Very interesting was this engine in the model 190 E 2.6 in the automatic version. In a civilized appearance (in contrast to the somewhat "krawalligen" appearance of the sixteen-valve 190 E 2.3 16V with spoilers) offered the "small" Mercedes with this engine very remarkable performance, at the same time comfortable drive design and still civilian consumption.

With these engines, a number of today still known tuning companies such as AMG , Brabus and Lorinser were great, although they were sometimes already active before. The usual measure was the boring of the engine and the use of a crankshaft with a longer stroke, so that 3.6 liters of displacement and about 165 to 180 kW, with the subsequent double camshaft cylinder head then resulted in about 195 to 205 kW. Occasionally, tuners even tried on turbocharged engine versions with well over 220 kW (300 hp).

The M 103 engines were among the most mature engines in Daimler-Benz history, as the sales figures show. In the early years until 1988, there were problems with the camshafts, these were partly a. Often they were later exchanged at the service, partly without the customers even knew about it. From 10/88 the M 103 was then largely flawless in the revised version. The camshaft production technology has been significantly redesigned, as well as the associated drag lever, so as to eliminate the main problem of the engine. But also injection system, ignition system, timing chain, etc. experienced some detail improvements which made this engine one of the most durable gasoline engines of the Daimler-Benz car engine series.

The ADAC statistics of the late 1980s are not a glorious glory for this engine, due to more frequent failures of the fuel pump control unit as well as deficiencies in the ignition system.

After the oil crisis was largely forgotten in the late 1980s, replaced Daimler-Benz from 1989, the M 103 by the M 104. The new engine with four-valve technology reached a power of 162 kW (220 hp), but with a higher fuel consumption and lower Torque in the lower speed range went along. This in turn meant that the engine was not accepted in all press tests and so the M 103 remained in the program until the end of 1992. Only then came the second version of the M 104 with new ignition and injection system and camshaft adjustment, which then largely replaced the M 103.

However, the M 103 with 3 liters of displacement was built in the W 124 4MATIC until 1995  , since it was not worthwhile to adapt the complex four-wheel drive technology, which in any case only sold in smaller numbers, to the new M 104 engine. Thus, the M 103 remained in the car program for 11 years (1984 to 1995) and, with several hundred thousand units, was one of the most successful engines in Daimler-Benz history.