The 6-cylinder gasoline engine of BMW cars is designated M52. The head and cylinder block are made of aluminum alloy. Compared to cast iron, this metal has a higher thermal conductivity and a lower specific gravity. This reduces cooling costs and reduces fuel consumption. The cylinder head, which has four valves per cylinder, is equipped with a system for dynamically adjusting the position of the intake camshaft, called VANOS for short (veriable NockenwellenateuerungJ. Since 9/97, a dual VANOS system has been installed. In this case, both camshafts, depending on the speed of the crankshaft and the engine load, are rotated by the actuator relative to the corresponding chain sprockets so that optimal valve timing is ensured. The actuator operates on the basis of commands from the engine control unit. Model 525tds 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 displacement of 2.0, 2.5 and 3.0 liters (520d, 525d, 530d) the valves are controlled via roller rocker arms by two chain-driven camshafts located at the top. The second circuit is used to drive the high pressure fuel pump (injection pump) diesel engine or high pressure pump respectively. The high power of diesel engines is provided by supercharging with a turbocharger with a variable geometry of the turbine nozzle apparatus (VTG), charge air cooling, as well as direct fuel injection using the Common-Rail system.
Engine lubrication is provided by an oil pump, which in 6-cylinder gasoline engines is located in front 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 gearing 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 at the appropriate temperature is driven by the radiator fan through a viscous coupling. The pump is driven by a V-ribbed belt, which also drives the generator. It must be borne in mind that the coolant, regardless of the season, should be a mixture of soft water with antifreeze and anti-corrosion additives.
The preparation and ignition of the air-fuel mixture in gasoline engines is ensured by an electronic ignition and injection system, which guarantees long-term stable exhaust gas emissions. "Calm" the ignition system with separate ignition coils has no moving parts, so the system does not wear out during operation. In diesel engines, fuel metering is controlled by an electronic digital control system, called DDE for short (Digitale Diesel-Elektronik).