Powertrain Management: Description and Operation

GF07.10-P-1016MCC Camshaft Adjustment, Function








1 Camshaft adjuster
2 Supply line engine oil pressure
3 Oil line "advanced"
4 Oil line "retarded"
5 Return flow
Y49 Adjustable camshaft timing solenoid

General
Adjustment of the rotation angle of the intake camshaft alters the point in time of opening and closing of intake valves. This leads to improvement of the gas exchange and reduction of pollutants in the exhaust.
At low rpms adjustment in the direction "advanced" causes the intake valves to open earlier.
This has the effect:
- that return flow of the suctioned in fuel/air mixture is prevented
- there are less damaging exhaust gases
- a high torque as a result of improved cylinder charge

At high rpms adjustment in the direction "retarded" causes the intake valves to open later.
This has the effect:
- long continued flow of the suctioned in fuel/air mixture
- a high engine output die to an improved cylinder charge

Function
Adjustment of intake camshafts takes place map-controlled via the ME-SFI [ME] control unit (N3/10) which directly actuates the adjustable camshaft timing solenoid.
The adjustable camshaft timing solenoid integrated in the engine oil circuit is supplied via the oil pump with engine oil. The pressure generated by the oil pump is used to actuate the camshaft adjuster in the direction "advanced" (large valve overlap) or "retarded" (low valve overlap). To do this the adjustable camshaft timing solenoid is connected via the oil line "advanced" and the oil line "retarded" with the camshaft adjuster.
The oil lines are released or closed off by the adjustable camshaft timing solenoid according to requirements and the intake camshaft is adjusted in the direction "advanced" or "retarded".
The adjustment time is dependent on the engine oil pressure, the oil viscosity and the oil temperature.
The intake camshafts can be adjusted from "advanced" to "retarded" over a range of 50°.
Excess engine oil in the engine oil circuit is passed back via the return on the adjustable camshaft timing solenoid.