Oil Supply
Oil Supply
Oil supply
The oil supply in line with requirements only delivers the amount of engine oil that is actually needed. The volume-flow- regulated oil pump lowers fuel consumption by up to 1 %.
Brief description of components
The following components are described for the oil supply:
Oil-pressure switch
The oil-pressure switch monitors the lubricating system. The oil-pressure indicator light lights up if the oil pressure does not exceed a defined value. This value is approx. 0.2 to 0.5 bar.
The oil-pressure switch is connected to the DME across a signal cable. If the switch is not operated, there is a voltage of 12 Volts on this cable; if the switch is operated, there is a voltage of 0 Volts. The data interchange is digital.
Volume-flow-regulated oil pump
The engine has a volume-flow-regulated oil pump. This pump supplied exactly the amount of oil required by each operating range. The oil pump is an external gear pump. The oil pump is driven by a chain from the crankshaft.
This oil pump is derived from the gear oil pump. On this pump, the non-driven gear (oil pump gear) can be shifted axially, which varies the delivery volume. The operation of the oil pump means that only the amount of oil required is delivered. This requirement-based control means that an average of up to 160 Watts less drive power is required than for a conventional oil pump. At approx. 6000 rpm, up to 1.25 kW of drive power is saved; the average fuel consumption is lowered by approximately 1 %.
System functions
The following system functions are described:
Pressure circulation lubrication
The N12 engine is equipped with pressure circulation lubrication. The oil drawn in by the oil pump via an intake pipe from the oil pan flows through the full-flow oil filter. The oil then enters the main oil gallery, which usually runs in the engine block parallel to the crankshaft.
Branch ducts lead to the main bearings of the crankshaft. The crank and conrod journals are supplied with oil by the main bearings, as the crankshaft has corresponding bore holes. Part of the oil is branched off the main oil gallery and fed to the cylinder head at the corresponding lubrication points.
Engine ventilation heating
The N12 engine has engine ventilation heating. The engine ventilation heating is at the entry to the fresh air pipe. Engine ventilation heating is an optional extra (optional extra 842 cold country version).
At constant speed and temperatures below -25 °C as well as in the case of extreme short-distance driving, the intake line could freeze.
The engine ventilation heating is implemented by means of a PTC heating element that sets the temperature to approx. 80 °C. The engine ventilation heating is activated via the engine ventilation heating relay. This relay is supplied with vehicle voltage by terminal 87. The relay is activated by the DME with earth.
The engine ventilation heating relay is in the distribution box in the engine compartment.
At terminal 87 (terminal 15 On), the DME control unit activates the engine ventilation heating via the engine ventilation heating relay. This supplies the engine ventilation heating with terminal 30. The engine ventilation heating relay is in the distribution box in the engine compartment.
Switch-on conditions:
- Terminal 15 ON
- Ambient temperature less than 2 °C
- Time after engine start less than 360 seconds (time is extended depending on engine oil temperature, coolant temperature as well as driving speed)
Notes for Service department
General information
NOTE: Engine ventilation heating depends on the fitted options.
Optional extra 842 cold country version is compulsory in various cold countries (series standard in USA and Canada).
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