Design features of the engine 1.6 duratec ti-vct car Ford Focus 2

The main design difference between the 1.6 Duratec Ti-VCT engine and the 1.4 and 1.6 Duratec engines is the presence of a variable valve timing system (VCT).

Elements of the valve timing control system :

1 - actuator (under the upper front cover of the timing drive - not visible in the photo);
2 - cover;
3 - solenoid valve;
4 - camshaft position sensor

The variable valve timing system provides independent control of the position of the intake and exhaust camshafts.
The VCT system allows you to set the optimal timing of the gas distribution mechanism for each moment of engine operation in order to increase its power and dynamic characteristics, as well as to reduce exhaust toxicity. The system is controlled by an electronic engine control unit (ECU). The main elements of the VCT system include control solenoid valves, actuators and camshaft position sensors.
The two solenoid valves of the system (one for each camshaft) are installed in a special cover located between the upper front timing cover and the cylinder head cover. The cover of the VCT system is at the same time a common front cover for the bearings of both camshafts and a holder for the shaft seals.
The timing belt drives the actuators of the system, which transmit rotation to the camshafts using hydromechanical coupling. At the other ends of the camshafts, sensor drive disks are fixed that monitor the positions of the shafts. The camshaft position sensors themselves are fixed in the cylinder head cover.

Solenoid valves of the system
From the oil line of the cylinder head, engine oil through the channels made in the VCT cover is supplied to the solenoid valves of the valve timing system and then to the actuators of the system.
At the ECU commands, the spool device of each solenoid valve controls the supply of oil under pressure to the working cavity of the actuator or the draining of oil from it. As a result of hydromechanical action, the individual elements of the actuator are mutually moved and the camshaft rotates to the required angle, changing the valve timing. The spool arrangement of the solenoid valves of the system is very sensitive to engine oil contamination. Therefore, in addition to the conventional oil filter, another filter is integrated in the channel of the cylinder head that supplies oil to the valves. This filter cannot be replaced, and if it becomes clogged, oil continues to be supplied uninterruptedly to the system elements through the bypass section of the line.

Source: http://wiki.zr.ru/74-1_%D0%A0%D0%B5%D0%BC%D0%BE%D0%BD%D1%82_Ford_Focus_II.