Fiat 1996 Brava Service Manual page 262

Bravo-BravatiBkiev Engine
98 range Fuel system
10.
Starting
During starting the normal management of the advance is not possible on account of the considerable
fluctuations in the rotation speed which do not allow the dwell and the advance to be calculated cor­
rectly.
The control unit implements a fixed advance for the entire time the engine is driven by the starter motor.
Operation at high temperatures
This strategy is enabled when the intake air temperature exceeds a certain level.
The "basic" advance value is reduced according to this temperature.
Operation in cut off conditions
The injection advance is reduced on entry into cut-off: from the moment the supply of fuel is restored,
the advance gradually returns to the "basic" value.
Operation during take-off
This strategy is designed to reduce the advance when the vehicle moves off from a stationary position.
Operation with the engine idling
When the engine is idling, the management of
the advance is implemented independently of
the "basic" advance.
The advance value during idling is corrected in a
manner which is inversely proporational to the
variation in the speed in relation to the pre-set
speed which, in turn, depends on the tempera­
ture of the coolant.
In particular, the advance is increased if the
speed decreases and is decreased if the speed
increases, in order to ensure the stability of the
actual speed.
P4A12JJ01
Aoc: correction of the ignition advance during idling
+ A RPM: the speed during idling is higher than the nominal speed
- ARPM: the speed during idling is lower than the nominal speed
Control of the detonation
This strategy has the task of detecting the presence of the phenomenon of detonation, by processing the
signal coming from the relevant sensor. The strategy continuously compares the signal coming from the
sensor with a threshold, which is, in turn, constantly updated, to take into account background noise
and the ageing of the engine.
If the system recognizes the presence of detonation, the strategy reduces the ignition advance, in steps
of 3° up to a maximum of 9° until the phenomenon disappears. Later on, the advance is gradually re­
stored either until the basic value is reached or until the phenomenon occurs again.
The strategy also has a self-adjustment function which memorizes the reductions in the advance which
are continuously repeated to adapt the advance to the different conditions in which the engine finds it­
self (for example, the use of a low octane rating fuel). The strategy is capable of restoring the advance to
the map value if the conditions which caused the reduction no longer exist.
AOC'
- A R P M
i
>v +ARPM
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