The operation of the phase regulator of the K4M engine

Camshaft Phaser of the K4M Engine — Design and Operation

To improve the filling of the cylinders with the fuel-air mixture in all operating modes, the 1.6 L engines are equipped with an intake camshaft phaser.

Shifting the closing moment of the intake valves optimises the filling of the cylinders with the fuel-air mixture depending on the crankshaft speed. As a result, torque at medium-load conditions and power at high crankshaft speed are increased.

Camshaft phaser mechanism
Fig. 1. Camshaft phaser mechanism

At high crankshaft speed, later closing of the intake valves ensures the intake of an additional portion of fuel-air mixture owing to the high velocity of the mixture flow. Conversely, at low speed the inertia of the mixture flow is small. Therefore, earlier closing of the exhaust valves is desirable in order to avoid insufficient filling of the cylinders and loss of torque due to the displacement of part of the fresh mixture. The higher the crankshaft speed, the later the intake valves should close.

Camshaft phaser solenoid valve
Fig. 2. Camshaft phaser solenoid valve

The amount of oil supplied to the phaser is determined by the solenoid valve mounted on the cylinder head (see Fig. 2). The valve is supplied with electrical power in the form of an alternating signal of the cyclic opening degree (amplitude 12 V and frequency 250 Hz). This allows oil to be supplied to the phaser mechanism and thus the phase shift angle to be changed.

Operation of the camshaft phaser
Fig. 3. Operation of the camshaft phaser: 1 — phaser rotor; 2 — phaser gear; 3 — intake camshaft; 4 — phaser electric valve

The camshaft phaser continuously changes the valve timing phases. The electronic control unit sends to the solenoid valve an alternating signal of the cyclic opening degree, whose value is proportional to the required phase shift. The phases continuously change from 0° to 43° in terms of crankshaft rotation angle.

At a crankshaft speed within 1500–4300 min-1 the ECU applies supply voltage to the solenoid valve. Above 4300 min-1 the solenoid valve supply is cut off. The phaser mechanism position then promotes cylinder filling at high crankshaft speed. In this position the locking plunger blocks the mechanism.

At a speed up to 1500 min-1 no supply voltage is applied to the solenoid valve. The mechanism is blocked by the plunger. From the moment supply is applied to the solenoid valve at a crankshaft speed above 1500 min-1, under the action of oil pressure the locking plunger retracts and releases the mechanism.

The solenoid valve of the camshaft phaser is controlled under the following conditions:

  • the crankshaft speed sensor is serviceable;
  • the camshaft position sensors are serviceable;
  • the injection system is serviceable;
  • after engine start;
  • the engine is not idling with the accelerator pedal depressed;
  • the threshold value of the injection profile, set taking into account load and crankshaft speed, has been reached;
  • the coolant temperature is within 10–120 °C;
  • the engine oil temperature is elevated.

Backup modes:

  • return of the phaser to its initial position;
  • zero phase shift.

Note. When the solenoid valve is blocked in the open position, the engine runs unsteadily at idle and the pressure in the intake pipe is increased. At the same time, noisier engine operation is noted.

Main faults of the camshaft phaser solenoid valve

  • open circuit;
  • short circuit to earth or to +12 V;
  • shift or mismatch of the programmed values;
  • incorrect determination of the phaser position;
  • control value outside the permissible limits.