Engine Lubrication: Description and Operation
Oil Supply
Oil supply
The engine has a map-controlled oil pump. Oil is supplied according to requirements which means that only the amount of engine oil actually used is supplied. The volume-flow-controlled oil pump reduces fuel consumption by up to 1%. This oil pump builds up oil pressure which initially routes oil through an oil duct to the oil filter. from where it is supplied to the crankshaft bearings and connecting rod bearings via an oil duct. An additional main oil duct fills the vertical line to the cylinder head. An oil duct in the cylinder head leads to the VANOS solenoid valves, chain tensioner, hydraulic valve clearance compensating elements and vacuum pump.
Brief component description
Descriptions of the following components of the oil supply are provided:
Engine-oil pressure sensor
The engine oil-pressure sensor employs a capacitative measurement process to monitor the absolute pressure. The absolute pressure required for a more precise oil-pressure control. Within the engine oil-pressure sensor is a ceramic plate containing gold platelets. The oil pressure from the oil passage changes the distance between the platelets to vary the capacitance. The electronic processing circuit measures the capacitance. Once processed, the data are transmitted to the DME as an input signal.
The engine oil-pressure sensor is connected with a 3-pin plug connector. The engine-management control unit supplies the unit with 5 volts and earth. The measurement range is 0.5 to 4.6 volts, which corresponds to oil pressures of 0.5 bar (50 kPa) to 10.5 bar (1050 kPa).
The engine-oil pressure sensor is screwed into the combined oil filter and oil-to-water heat exchanger.
Map-controlled oil pump with oil pressure control valve
The engine features a map-controlled oil pump. This pump only delivers exactly as much oil as each operating range of the engine requires. The oil pump is an external gear pump. The oil pump is driven by a chain from the crankshaft.
The oil pressure control valve is integrated into the oil pump.
The oil pressure control valve is a solenoid valve (3/2-way valve). The Digital Motor Electronics (DME) controls the oil pressure control valve via a pulse-width modulated signal. This allows more precise activation of the oil pump than activation via volumetric flow.
Engine ventilation heating
The engine ventilation heating is located at the inlet to the clean air pipe. The engine ventilation heating is optional equipment (SA842 cold-climate version).
The DME control unit activates the engine ventilation heating at terminal 87 (terminal 15 on) via the engine ventilation heating relay thus supplying the engine ventilation heating with terminal 30. The engine ventilation heating relay is located in the power distribution box in the engine compartment.
Switch-on conditions:
- Terminal 15 on
- Ambient temperature less than 2 °C
- Less than 360 seconds have elapsed following engine start (time increases depending on engine oil temperature, coolant temperature and driving speed)
When the engine is cold, the engine ventilation heating prevents ice formation from freezing condensation within the engine ventilation. If freezing occurs in the engine ventilation system, the pressure in the crankcase may increase. This may cause engine oil to be burnt or pushed past gaskets out of the engine. The oil loss can lead to total destruction of the engine.
NOTICE: US version of engine ventilation heating.
The US version features a purge air line for ventilation of the crankcase. The engine ventilation heating systems are controlled directly by the engine control (not via relay). Observe the wiring diagram in the diagnosis.
System functions
The following system functions are described:
US version of crankcase ventilation N18
The crankcase ventilation in the US version is monitored electrically. via an electrical bridge at the plug connection for the purge air line. This monitors whether the purge air line is correctly connected. Observe the wiring diagrams in the diagnosis.
Map-controlled oil-pressure control
The oil volume delivered continues to be regulated via the oil pressure according to requirements.
although the map-controlled oil-pressure control is controlled by the DME. using the following input variables:
- Engine speed
- Engine temperature
- Load
The DME activates the oil pressure control valve via a pulse-width modulated signal. The oil pressure control valve then sets a corresponding oil pressure which is used to charge the oil pump control piston.
The map-controlled oil pump allows the oil pump to be controlled even more precisely which contributes towards a reduction in consumption and CO2 emissions.
The oil pressure required is reduced across the engine speed range. The required output of the oil pump is less compared to volumetric flow control.
Notes for Service department
General notes
NOTICE: Failure of oil-pressure control system.
When the map-controlled oil-pressure control drops out, the oil supply is volumetric flow-controlled instead (emergency operation). Fuel consumption may increase as a result, depending on the motorization.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.