Control Of The Idle Speed; Control Of The Maximum Speed Restriction; Control Of The Maximum Torque Restriction; Control Of Fuel Temperature - Fiat Bravo Service Manual

Engine
Fuel system
10.

Control of the idle speed

On the basis of the signals coming from the rpm sensor and the engine coolant temperature sensor, the
injection control unit controls the pressure regulator and varies the operating times for the injectors t o
keep the idle speed stable.
Under certain circumstances, in order to control the idle speed, the control unit also takes the battery
voltage into account.

Control of the maximum speed restriction

According to the engine speed, the injection control unit restricts the maximum speed through t w o
types of intervention:
- as the maximum speed is approached, it decreases the quantity of fuel injected, reducing the line pres-
sure;
- when 6000 rpm is exceeded, it inhibits the operation of the injectors.

Control of the maximum torque restriction

Depending on the engine speed, the injection control unit calculates the torque limit and maximum per-
missible fumes parameters based on pre-defined maps stored in the memory.
It then corrects the above parameters using engine coolant temperature and vehicle speed data and uses
the values obtained in this way for metering the quantity of fuel t o be injected involving the pressure
regulator and the injectors.

Control of fuel temperature

The injection control unit is constantly informed of the temperature of the fuel by the sensor on the re-
turn manifold.
If the temperature of the fuel exceeds a certain level (about 110 °C), the control unit reduces the line
pressure acting on the pressure regulator and leaving the injection times unaltered.
Control of engine coolant temperature
The injection control unit is constantly informed of the temperature of the engine coolant by the sensor
on the thermostat.
If the temperature of the engine coolant exceeds certain values, the control unit implements the f o l l o w -
ing strategies:
- it reduces the quantity of fuel injected acting on the pressure regulator and the injectors (power re-
duction);
- it operates the engine cooling radiator fan.
Control of heater plugs
The injection control unit controls the operation of the heater plugs control unit so that the temperature
in the combustion chambers is at a level w h i c h assists the self-ignition of the fuel and consequently fa-
cilitates starting.
In effect the injection control unit controls the operation of the heater plugs control unit for a certain
length of time both before starting (pre-heating) and after starting (post-heating) and also controls the
coming on of the warning light in the instrument panel.
The pre-heating and post-heating times plus the coming of the heater plugs warning light all vary ac-
cording to the temperature of the engine coolant.
4
Bravo-Brava
98 range
Print no. 506.670/16
ft™