Operation in acceleration

Operation in acceleration

In this stage, the control unit increases as appropriate the quantity of fuel required by the engine (to obtain the maximum torque) in accordance with signals coming from the following components:

• throttle potentiometer;
• absolute pressure sensor;
• rpm and TDC sensor.

The "basic" injection time is multiplied by a coefficient in accordance with the temperature of the engine coolant, how quickly the throttle opens and the pressure increase in the inlet manifold.

If the sudden variation in injection time is calculated when the injector is already closed, the control unit re-opens the injector (extra pulse) to be able to compensate the strength as quickly as possible; subsequent injections are instead increased in accordance with the above-mentioned coefficients.

A. normal injection time
B. re-opening of injector (extra pulse)
C. injection time including enrichment
OFF. engine at stationary speed
ON. engine in transient

Over-rev protection

When the engine speed exceeds for over 10 seconds the value of 6700 rpm or instantaneously the "limit" value of 6900 rpm imposed by the manufacturer, the engine is in "critical" operating conditions.

When the electronic control unit recognizes that the above-mentioned speed has been exceeded, it inhibits the driving of the fuel injectors.

When the rpm returns to a non-critical value, driving of the injectors is resumed.

Electric fuel pump operation

The electric fuel pump is driven by the engine control unit via a relay.
The pump is stopped:

• if the engine falls below 50 rpm;
• after a certain period (about 5 seconds) with the ignition on without the engine being started (time-lagged enablement);
• if the inertial switch has intervened.

Fuel injector operation

The injectors are driven in a phased sequential manner. However, during starting, the injectors are first driven in parallel (full-group).

The injector phasing varies in accordance with the engine speed and intake air pressure in order to improve cylinder filling with advantages in terms of consumption, driveability and pollution.