System connections to earth

The aim of this function is to wash the canister sufficiently without disturbing the operation of the engine (for example increase in harmful emissions, driving defects as the result of rapid variations in the mixture strength, decrease in the idle speed on account of an increase in the supplementary air flow rate or mixture strength etc.).

The control unit establishes the solenoid valve opening time taking the following parameters into account:

• the injection time cannot go below a minimum time;
• the quantity of air during idling should be compatible with the control of the engine revs.
• in open-loop conditions the quantity of fuel supplied via the canister cannot be managed with certainty so it should therefore be limited;
• the start of the scavenging should be slow and gradual.

The vapour inlet function (canister scavenging) communicates with other functions in the following way:

• it receives the average mixture strength to "learn" the hydrocarbons contained in the canister;
• it receives information from the fuel control that the injection time implemented is the minimum possible;
• it indicates the equivalents steps to the idle speed actuator to compensate for the quantity of vapours drawn in by the canister;
• it indicates the quantity of vapours supplied via the canister to the fuel control.

System connections to earth

The wiring for the injection/ignition system is connected to an earth point on the engine. The earth for the electronic control unit electronic circuits and the earths for the various system components are connected at this point. The electronic control unit, in turn, is connected to earth through the fixing bolts.

Corrosion at these earth points and poor connections to earth for the cables could cause operating defects.

Self-adjustment of the system

The control unit is equipped with a self-adjusting function which has the task of recognizing thechanges which take place in the engine due to bedding in over a period oftime and ageing of both the components and the engine itself.

These changes are memorized in the form of modifications tothe basic map and are designed to adapt the operation of the system to the gradual alterations to the engine and components compared with when they are new.

The self-adjustment parameters "learnt" by the control unit are used in all operating conditions because they correspond to derivations from the engine or the system.

Updating, on the other hand, can only take place if a series of conditions exists: authorization of the calibrated strategies, engine at operating temperature, operating conditions established for a certain length of time, derivation from average value of mixture strength correction ...

Once the update conditions for a self-adjustment parameter have occurred, the difference between the average actual value for the mixture strength coefficient and the theoretical value (i.e. the centre band value in the case of a stoichiometric target figure) is evaluted.

A significant difference means that the open-loop calibration is not centered and therefore the self-adjustment parameter for the updating area identified should be increased or decreased by a step proportional to the dispersion.

The parameters "learnt" by the control unit should satisfy the continuity function: after a "gain or offset" update the difference between the self-adjustment paramters in 2 adjacent rpm bands should not be too great. If necessary, the adjacent parameter should also be updated.