Repair manual

Oil Circulation System
21
Change-Over Point to High Pressure
Setting
The system changes over to the high pressure setting at
an engine speed of approximately 3500 rpm. Oil Pressure
Regulating Valve N428 is de-energized for this.
This simultaneously causes the switchable pressure port
and the port to the pressureless chamber in the oil pan to
close.
Since the surface of the control piston is no longer
effective, the force of the regulating spring is now
predominant.
The control piston moves far enough to open the port to
the front piston face of the cam lobe unit.
The oil pressure acting upon the front piston face and the
compression spring push the cam lobe unit back again,
so that both pump gears are again almost in parallel with
one another and the pump is operating at its maximum
delivery rate. The cam lobe unit remains in this position
until an oil pressure of approximately 47 psi (3.3 bar) is
reached.
Note
The self-regulating oil pump always
operates in the high pressure setting
during the first 620 mi (1000 km). This
allows for the higher thermal load on
components during the break-in period.
Cam Lobe Unit is
Displaced Back
Pumped
Oil
Control Piston
is Displaced
Regulating
Spring
Oil Passage to
Front Piston
Face is Opened
Switchable
Pressure
Port (now
pressureless)
Oil Pressure
Regulation
Valve N428
Engine
Speed [rpm]
Relative Oil
Pressure [bar]