VANOS Solenoid Valve, Exhaust
VANOS Solenoid Valve, Exhaust
VANOS solenoid valve, exhaust
The VANOS inlet and exhaust solenoid valves are positioned axially on the front of the cylinder head. The VANOS solenoid valves (with integrated non-return valve) distribute the engine oil pressure to the two VANOS units.
The variable camshaft timing control serves to enhance the torque in the lower and middle engine speed range. At the same time, the most favourable valve operation times for idle speed and maximum power output are adjusted.
Functional description
The variable camshaft timing control improves the torque in the lower and middle engine speed range. A greater valve overlap results in lower amounts of residual gas at idle speed. The exhaust-gas recirculation in the partial load range reduces the volume of nitrogen oxide. The following is also achieved:
- faster heating of the catalytic converters
- lower pollutant emissions after a cold start
- reduction in the fuel consumption
A VANOS solenoid valve activates the VANOS unit. The required positions of the intake and exhaust camshafts are calculated from the engine speed and the load signal (depending on the intake air temperature and coolant temperature). The DME control unit activates the VANOS unit accordingly. The intake camshaft can be variably regulated within its maximum adjustment range. When the correct camshaft position has been reached, the VANOS solenoid valve keeps the oil volume in the positioning cylinder in both vane cell chambers constant. This holds the intake camshaft in this position. To perform the adjustment, the variable camshaft timing control requires a feedback signal on the current position of the camshaft. A camshaft sensor on the intake side picks up the position of the camshaft. On engine start, the intake camshaft is in the end position ("late").
Structure and inner electrical connection
The VANOS solenoid valve, exhaust is connected by means of a 2-pin plug connection.
The VANOS solenoid valve, exhaust is a solenoid valve. The VANOS solenoid valve is supplied with voltage via terminal 15N. Activation by the engine control is pulse-width modulated.
Operation times diagram and setpoint values
Idle speed:
At idle speed, the camshafts are adjusted in such a way that there is a small valve overlap or none at all. The low residual gas content leads to stable combustion and thus to stable idling. The smallest valve overlap is achieved with great to the greatest possible intake spread and the greatest possible exhaust spread. The VANOS solenoid valves are de-energized here. This camshaft position is also assumed on stopping the engine.
Power output:
To achieve good power output at high engine speeds, the exhaust valves are opened late. This enables the expansion of combustion to move the piston for longer. The VANOS solenoid valve opens after TDC and closes late after BDC. This exploits the dynamic ram effects of the incoming air to increase performance.
Torque and power output:
To achieve high torque, a high volumetric efficiency must be achieved. Depending on the phase position of the intake pipe pressure peaks and valleys, the intake or exhaust valves must be opened or closed earlier or later. Depending on the intake pipe length, an engine without VANOS has precisely one engine speed with optimised cylinder charge. An engine with VANOS lies within a broad engine speed range with optimised cylinder charge. Reason: Both ejection of the fresh gases back into the intake pipe and a flow of residual gas back into the cylinder can be avoided.
Increasing torque with turbocharging
On the turbocharged engine, 'over-scavenging' - and thus significantly more torque - can be achieved at low engine speeds in the charged range with a positive scavenging divide by means of a large valve overlap. The effect: More air than is necessary for combustion flows through the engine. This means the compressor is not in the pump limit. Second effect: There is virtually no more residual gas in the cylinder.
Internal exhaust-gas recirculation with partial load
In contrast to the torque-optimised and power-optimised VANOS position, high exhaust-gas recirculation can also be forced with adjustment of the intake and exhaust camshaft. Decisive for the amount of internal exhaust-gas recirculation is: The size of the valve overlap as well as the pressure difference between the exhaust manifold and intake pipe. Internal exhaust-gas recirculation has the following characteristics:
- Fast response times compared to external exhaust-gas recirculation (with internal exhaust-gas recirculation, there is no residual gas in the intake plenum)
- Fast exhaust-gas heat recirculation into the cylinder (with a cold engine, the additional heat improves the mixture preparation and leads to lower hydrocarbon emissions)
- Reduction in the peak temperatures of the combustion and thus a reduction in the nitrogen oxide emission
Observe the following setpoint values for the VANOS solenoid valve:
Size Value
Voltage range 9 to 16 V
Duty cycle 1 to 99%
Frequency of the activation signal 200 to 250 Hz
Coil resistance Approx. 10.5 ohms
Operating pressure ≤ 10 bar
Temperature range -40 to 150 °C
Diagnosis instructions
Failure of the component
If the VANOS solenoid valve fails, the following behaviour is to be expected:
- Fault entry in the engine control unit
- Emergency operation
General notes
The VANOS solenoid valve now has 3 filter inserts that can be removed individually when soiled: Follow repair instruction.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.