Mercedes-Benz M 123 six-cylinder petrol engine
|Engines:||2.5 liters (2525 cm³)|
|Previous model:||M 180|
The M 123 is a six-cylinder in - line engine from Daimler-Benz . The gasoline engine with chain-driven overhead camshaft (OHC) and countercurrent cylinder head was used from 1976 to 1985 in the models 250 and 250 T of the 123 series use. This replaced the engines M 180 of the type 230.6 and M 130 of the type 250 2.8 of the series 114 . Successor was the M 103 , which was introduced in 1984 in the 124 series.
The engine still has essential features of the precursor. Thus, the crankshaft is mounted only four times and oil pump, fuel pump and ignition distributor are driven by a slanted shaft at the front end of the engine, which in turn is driven by a sprocket and a pair of helical gears. On the other hand, the cylinders are no longer cast together in pairs, but the cylinder spacings are uniform. There are no cast-in cooling channels in the dividing walls between the cylinders, but slots are cut in, through which the cooling water flows.
The vertically suspended valves are operated by drag levers and are arranged in two rows. Like the M 115, the intake and exhaust are on the right side of the engine, and on the left side there is a recessed combustion chamber in the cylinder head (with a flat piston crown) containing the exhaust valve and the spark plug. The remaining cylinder cross section forms a pinch surface, which swirls the mixture in the combustion chamber.
While the rest of the engine range was taken over by its predecessor, the M 123 was the only new development that could not quite convince customers. In 1979, the engine was revised, with the power increased from 95 kW (129 hp) to 103 kW (140 hp). Especially after the presentation of the new four-cylinder M 102 in the models 200 and 230 E, the interest of the public dropped sharply. The M 102 could do almost anything better, and the fuel consumption was much cheaper. The station wagon (250T) was canceled in 1982, in the sedan (250), the engine was available until 1985, but played in the sale no major role.
The Solex -double carburetor type 4A1 with its four air funnels ( venturi) is considered relatively difficult to control today. It is identical to the carburettor of the Mercedes 280 of the predecessor series W 114. In each case three cylinders are supplied by a set of mixing systems (air funnel). A single set consists of a relatively small air vent for idle and medium speeds and a larger sized second hopper for full load operation. At idle and up to about a third load only the two smaller systems are addressed mechanically by the accelerator pedal; The two full-load systems are additionally opened at high load and speed by a vacuum box. A central float chamber supplies all four mixing systems with fuel. In this double register carburettor, as is usual with injection engines, the fuel supply with flow and return line is designed;
Shortly before introduction of the first, working together with a catalyst and electrically controlled by the lambda probe data gasifier (ca. 1986/87) was this model the most complex of four pipe carburetor roughly what of the invention, the spray nozzles carburetor of Wilhelm Maybach after 80 years of development had become. However, when the lambda probes came in, which are needed for the three-way catalyst to control the mixture fatness, this elaborate carburettor type has already been history and has been replaced by port injection , which is simpler in design and easier to maintain.
The joy of the quiet run was clouded by a high fuel consumption, but this engine was quite noticeably more economical than the 280 carburetor models (which often consumed more than 17 liters in city traffic) and thus reached its most important development goal. Better in every respect, however, this made the successor type M 103 from 1984, which was cheaper to produce in the variant with 2.6 liter displacement, was lighter and considerably more economical, with increased engine power of initially 122 kW (166 hp) or with cat 118 kW (160 hp) and better revving compared to the comparatively sluggish M 123. The smoothness of the M 103 was again significantly better, especially in the 2.6 l variant.
- 1976-1985 250th
- 1976-1985 250 long
- 1976-1982 250 T
- Bore 86 mm, stroke 72.45 mm, displacement 2525 cm 3
- Compaction 8,7: 1
- Power 95 kW (129 hp) at 5500 rpm
- Torque 196 Nm at 3500 rpm
- Top speed: 175 km / h
In 1979 the engine was redesigned:
- Compaction 9.0: 1
- Power 103 kW (140 hp) at 5500 rpm
- Torque 200 Nm at 3500 rpm
In October 1981, the M 123 was revised again to reduce consumption. The compression was increased by changing the combustion chambers in the cylinder head to 9.4: 1; the remaining data remained the same. The internal type designation of the engine was simultaneously changed from M 123.920 to M 123.921.