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21-460: The block features an aluminium crankcase and cylinder heads . It uses aluminium sand casting in bedplate construction (divided at the height of the crankshaft ) with wet cylinder liners made of cast iron. The main bearings are reinforced, cast in GGG ductile cast iron . Rather than the usual 90° " vee " angle between the cylinder banks, a 75° angle was chosen due to the space available to install

42-623: A variable geometry turbocharger . The compressed air from these is cooled by an air to water heat exchanger with an additional cold water circuit. Compared to the OM628, the OM629 engine has an improved common-rail system, and higher boost from the turbochargers. It displaces 4.0 L (3,996 cc) and produces between 225 to 235 kW (306 to 320 PS; 302 to 315 hp) at 3600 rpm, and 700 to 730 N⋅m (516 to 538 lb⋅ft) of torque between 2000–2600 rpm. Crankcase A crankcase

63-411: A messy environment, because oil spray from the moving parts was not contained. Another disadvantage was that dirt and dust could get into moving engine parts, causing excessive wear and possible malfunction of the engine. Frequent cleaning of the engine was required to keep it in normal working order. Some two-stroke diesel engines, such as the large slow-speed engines used in ships, have the crankcase as

84-399: A separate space from the cylinders, or as an open crank. The spaces between the crosshead piston and the crankshaft, may be largely open for maintenance access. Wet sump Within piston engines , a wet sump is part of a lubrication system whereby the crankcase sump is used as an integral oil reservoir. An alternative system is the dry sump , whereby oil is pumped from

105-405: A shallow sump into an external reservoir. Piston engines are lubricated by oil which is pumped into various bearings , and thereafter allowed to drain to the base of the engine under gravity. In most production automobiles and motorcycles , which use a wet sump system, the oil is collected in a 3 to 10 litres (0.66 to 2.20  imp gal ; 0.79 to 2.64  US gal ) capacity pan at

126-495: Is dependent on the engine design. A wet sump design can be problematic in a racing car, as the large g force pulled by drivers going around corners causes the oil in the pan to slosh, gravitating away from the oil pick-up, briefly starving the system of oil and damaging the engine. However, on a motorcycle this difficulty does not arise, as a bike leans into corners and the oil is not displaced sideways. Nevertheless, racing motorcycles usually benefit from dry sump lubrication, as

147-431: Is not used for the fuel/air mixture. Engine oil is recirculated around a four-stroke engine (rather than burning it as happens in a two-stroke engine) and much of this occurs within the crankcase. Oil is stored either at the bottom of the crankcase (in a wet sump engine) or in a separate reservoir (in a dry sump system). From here the oil is pressurized by an oil pump (and usually passes through an oil filter ) before it

168-423: Is squirted into the crankshaft and connecting rod bearings and onto the cylinder walls, and eventually drips off into the bottom of the crankcase. Even in a wet sump system, the crankshaft has minimal contact with the sump oil. Otherwise, the high-speed rotation of the crankshaft would cause the oil to froth, making it difficult for the oil pump to move the oil, which can starve the engine of lubrication. Oil from

189-441: Is the housing in a piston engine that surrounds the crankshaft . In most modern engines, the crankcase is integrated into the engine block . Two-stroke engines typically use a crankcase-compression design, resulting in the fuel/air mixture passing through the crankcase before entering the cylinder(s) . This design of the engine does not include an oil sump in the crankcase. Four-stroke engines typically have an oil sump at

210-443: Is the power piston, the lower side acts as a pump. Therefore an inlet valve is not required. Unlike other types of engines, there is no supply of oil to the crankcase, because it handles the fuel/air mixture. Instead, two-stroke oil is mixed with the fuel used by the engine and burned in the combustion chamber. Large two-stroke engines do not use crankcase compression, but instead a separate scavenge blower or supercharger to draw

231-404: Is uncovered and the compressed fuel/air mixture is pushed from the crankcase into the combustion chamber. Crankcase-compression designs are often used in small petrol (gasoline) engines for motorcycles, generator sets and garden equipment. This design has also been used in some small diesel engines, however it is less common. Both sides of the piston are used as working surfaces: the upper side

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252-419: The lubrication of the cylinder walls by means of a splashing action. Modern small engines, such as those used in lawnmowers, use a "slinger" (basically a paddle wheel) to perform the same function. Small two-stroke engines , such as in motorcycles and lawnmowers , have total loss lubrication. Such engines use crankcase compression to feed the fuel/air mixture through the crankcase. This precludes

273-422: The base of the engine, known as the sump or oil pan, where it is pumped back up to the bearings by the internal oil pump . A wet sump offers the advantage of a simple design, using a single pump and no external reservoir. Since the sump is internal, there is no need for hoses or tubes connecting the engine to an external sump which may leak. An internal oil pump is generally more difficult to replace, but that

294-436: The bottom of the crankcase and the majority of the engine's oil is held within the crankcase. The fuel/air mixture does not pass through the crankcase, though a small amount of exhaust gasses often enter as "blow-by" from the combustion chamber , particularly in engines with worn rings. The crankcase often forms the upper half of the main bearing journals (with the bearing caps forming the other half), although in some engines

315-411: The crankcase completely surrounds the main bearing journals. An open-crank engine has no crankcase. This design was used in early engines and remains in use in some large marine diesel engines. Many two-stroke engines use a crankcase-compression design, where a partial vacuum draws the fuel/air mixture into the engine as the piston moves upwards. Then as the piston travels downward, the inlet port

336-425: The crankcase, contamination of the oil and rust from condensation. To prevent this, modern engines use a crankcase ventilation system to expel the combustion gases from the crankcase. In most cases, the gases are passed through to the intake manifold. Early engines were of the "open-crank" style, that is, there was no enclosed crankcase. The crankshaft and associated parts were open to the environment. That made for

357-469: The engine. The consequence of this specific angle is free inertial forces of the first order. To compensate for this, the OM628 and OM629 use a balancer shaft located in the vee of the engine. To ensure even firing intervals the crankshaft uses split crank pins . The engine uses 97.0 mm cylinder spacing. The engine uses dual overhead camshafts on each bank (‘quad-cam’) with four valves per cylinder, operated by hydraulic tappets . Each cylinder bank uses

378-413: The fuel/air mixture into the compression chamber. Therefore the crankcases are similar to a four-stroke engine in that they are solely used for lubrication purposes. Most four-stroke engines use a crankcase that contains the engine's lubricating oil, as either a wet sump system or the less common dry sump system. Unlike a two-stroke (crankcase-compression) engine, the crankcase in a four-stroke engine

399-524: The shallow sump allows the engine to be mounted lower in the frame; and a remote oil tank can allow for improved lubricant cooling. On some dry sump motorcycles, such as the Yamaha TRX850 and the Yamaha TDM , the oil tank is integral to the engine, sitting atop the gearbox. Early stationary engines employed a small scoop on the extremity of the crankshaft or connecting rod to assist with

420-430: The sump may splash onto the crankshaft due to g-forces or bumpy roads, which is referred to as windage . Although the piston rings are intended to seal the combustion chamber from the crankcase, it is normal for some combustion gases to escape around the piston rings and enter the crankcase. This phenomenon is known as blow-by . If these gases accumulated within the crankcase, it would cause unwanted pressurisation of

441-402: The use of both wet sump and dry sump systems, as excess oil here would contaminate the mixture, leading to excess oil being burned in the engine and so excessive hydrocarbon emissions . These small engines run on specifically prepared fuel, a mixture of gasoline and two-stroke oil in a ratio recommended by the manufacturer. In some engines this mixture may also be independently pre-injected into

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