Operation In Acceleration; Over-Rev Protection; Electric Fuel Pump Operation; Fuel Injector Operation - Fiat Bravo Service Manual

Engine
Fuel system
10.

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 w i t h 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; subse-
quent injections are instead increased in accordance with the above-mentioned coefficients.

Over-rev protection

When the engine speed exceeds for over 10 seconds the value of 6700 rpm or instantaneously the " l i m -
it" 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 i n -
hibits 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) w i t h 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 w i t h the engine speed and intake air pressure in order t o i m -
prove cylinder filling with advantages in terms of consumption, driveability and pollution.
8
Bravo-Brava <0i 16v
A. normal injection time
B. re-opening
(extra pulse)
C. injection time including
enrichment
OFF. engine
speed
ON. engine in transient
P4A081J01
'98 range
of injector
at stationary
Publication no. 506.670/14