Sensors and actuators of the engine management system (VW Golf 4)

The throttle switch informs the control unit of the throttle position at idle speed. The control unit opens or closes the throttle valve via the servomotor and thus maintains a stable idle speed.

The coolant temperature and engine air temperature sensors change their resistance as the temperature changes, reporting the corresponding temperatures to the engine control unit.

The fuel vapor recovery system consists of an activated carbon filter and a magnetic valve. The activated carbon filter prevents harmful fuel vapors from penetrating from the fuel tank into the atmosphere, and the evaporating fuel is collected in a container with activated carbon. When the engine is running, the fuel vapors are fed back into the engine for afterburning under the control of the magnetic valve.

The oxygen sensor measures the oxygen content in the exhaust gas flow. The control unit uses its signal to maintain the content of harmful emissions in the exhaust gases at the lowest level. In vehicles with a catalytic converter, the composition of the exhaust gases is maintained at a level that ensures the best afterburning in the catalytic converter.

The knock sensor is used to detect the onset of detonation in the engine cylinders and, based on this information, the engine control unit reduces the ignition timing. If there are ignition faults, the control unit shuts off the fuel supply to the corresponding cylinder.

ENGINE 1.8-I-/ 125-PS

These engines use a variable-length air supply system, which changes the length of the air path entering the cylinders depending on the engine operating conditions. This is done using a pneumatically actuated rotary valve. At low engine speeds, the air enters via a longer path and, due to resonance, the engine is filled more completely, resulting in increased torque.



ENGINE 1,8-I/ 125 PS

For optimum engine operation at all speeds and increased torque, a valve timing shift system is used. The valve timing is determined by the position of the camshaft cams. The relative position of the camshafts is changed by a chain. The hydraulic shift mechanism changes the camshaft chain drive point depending on engine speed. As a result, the time interval between control of the intake and exhaust valves varies.