The 6-cylinder petrol engine of BMW cars has the designation M52. The cylinder head and cylinder block are made of aluminum alloy. Compared to cast iron, this metal has higher thermal conductivity and lower specific gravity. Due to this, cooling costs are reduced and fuel consumption is lower. The cylinder head, which has four valves per cylinder, is equipped with a dynamic adjustment system for the position of the intake camshaft, called VANOS for short (veriable Nockenwellenateuerung). Since 9/97, a double VANOS system has been installed. In this case, both camshafts are turned by the actuator relative to the corresponding chain sprockets depending on the crankshaft speed and engine load so that optimum valve timing is ensured. The actuator operates on the basis of commands from the engine control unit. The 525tds model is equipped with a 6-cylinder M51 turbocharged diesel engine with a displacement of 2.5 liters. The engine block is made of cast iron, and the cylinder head is made of light alloy.
In diesel engines with a working volume of 2.0, 2.5 and 3.0 l (520d, 525d, 530d) the valves are controlled via rocker arms with rollers by two overhead camshafts with a chain drive. The second chain is used to drive the high-pressure fuel pump (HPFP) of the diesel engine or, respectively, the high-pressure pump. The high power of diesel engines is achieved by boosting with a turbocharger with variable geometry of the turbine nozzle apparatus (VTG), cooling the charge air, and direct fuel injection using the Common Rail system.
The engine is lubricated by an oil pump, which in 6-cylinder petrol engines is located in the front part of the oil pan and is driven by a chain from the crankshaft. In diesel engines, the oil pump is located on the timing cover at the end of the crankshaft and has a toothed engagement with it. The oil taken from the oil pan is supplied through channels and pipelines to the bearings of the crankshaft and camshaft, as well as to the working surfaces of the cylinders.
The coolant pump is located at the front of the cylinder block. The pump shaft is driven by the radiator fan via a viscous coupling at the appropriate temperature. The pump is driven by a poly V-belt, which also drives the generator. It is important to keep in mind that the coolant, regardless of the season, should be a mixture of soft water with antifreeze and anticorrosive additives.
The preparation and ignition of the fuel-air mixture in petrol engines is ensured by an electronic ignition and injection system, which guarantees stable exhaust emission values over a long period of time. The "quiet" ignition system with separate ignition coils has no moving parts, which means that the system does not wear out during operation. In diesel engines, the fuel metering is regulated by an electronic digital control system, called DDE for short (Digitale Diesel-Elektronik).
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