Fuel vapour recovery

Fuel vapour recovery

The (pollutant in terms of the regulations) fuel vapours are sent to an active charcoal filter and from there towards the engine where they are burnt; this takes places by means of a solenoid valve which is operated by the control unit only when the engine is in a load condition which allows the correct combustion without the operation of the engine being "disturbed": in effect, the control unit compensates for this quantity of petrol entering with a reduction of the supply to the injectors.

Checking detonation

The function has the task of detecting the presence of the phenomenon of detonation (engine knocking) by processing the signal coming from the relevant sensors. The control unit constantly compares the signals coming from the sensors with a threshold value which, in turn, is continuously updated, to take into account background noise and the ageing of the engine.

The control unit is therefore capable of detecting detonation (or the early stages of detonation) and makes provisions to reduce the ignition advance (from 3° up to maximum of 9.7°), until the phenomenon disappears. Afterwards the advance is gradually restored until the basic value is reached.

In acceleration conditions, a higher threshold is used, to take into account the greater noise produced by the engine in these circumstances. The detonation control strategy is also equipped with a self-adjustment function which ensures the memorizing of the advance reductions which should be constantly repeated to adapt to the different conditions in which the engine finds itself.

Checking phase transformer

The control unit controls the solenoid valve which controls the phase transformer depending on the engine load conditions. When the temperature of the coolant exceeds 40 °C and when the engine speed is higher than the idle speed and lower than 4,800 rpm with the butterfly angle greater than about 8°, the control unit sends a signal to the solenoid valve which is activated and allows the transformer to decrease the timing diagram for the inlet stage by 18° (torque operation).

When the engine is idling or the speed exceeds 4,800 rpm, the control unit deactivates the solenoid valve and the transformer restores the inlet timing to the previous basic values.

Obviously the control of the phase transformer operates with a hystis field, i.e. the activating level for the solenoid valve is always higher than the deactivating level; this is designed to prevent balance conditions and a consequent too rapid succession passing from one timing diagram to another with obvious operating problems.

Connection with the climate control system

When the climate control is switched on the compressor absorbs power from the engine which, when idling, tends to cut out. To prevent this problem the control unit adjusts the air flow rate to the new power requirements, controlled by the appropriate actuator (this adjustment also takes place during usage conditions to maintain optimum "driveability"). Another function of the system is that of momentarily interrupting the supply to the compressor in the case of high power requirements by the engine (strong acceleration).

System self-adjustment

The control unit is equipped with a self-adjustment function which has the task of recognizing the changes which take place in the engine due to the settling processes which take place over a period of time and the ageing of both the components and the engine itself.

These changes are stored in the memory in the form of modifications to the basic map and have the task of adpating the operation of the system to the gradual alterations to the engine and the components in relation to the characteristics when new.