Fiat 1998 Marea Weekend, Service Manual

Page: 276 / 846

Engine
Fuel system
16v
Marea- Marea Weekend ft
99 update
10.
MANAGEMENT OF THE INJECTION
The injection management strategies are designed to provide the engine with the correct amount of fuel at
the desired time according to the engine operating conditions.
NOTE The presence of the flow meter allows the intake air mass to be measured directly making the pres-
ence of the intake air temperature sensor superfluous.
The management of the injection basically consists of calculating the injection time, determining and then
implementing the injection timing via the operation of the injector.
The "basic" injection time depends on the specifications of the injector and corresponds to the quantity of
fuel to be injected into each cylinder. The latter is, in turn, determined by multiplying the quantity of air
drawn in by each cylinder (calculated according to the quantity of intake air and the engine rotation
speed) by the desired mixture strength for the engine operating point.
The final injection time is determined by means of a calculation algorhythm in which the "basic" time is
corrected by a series of coefficients which take into account the different engine operating conditions
which are highlighted by the various sensors in the system.
A: "basic" injection time
B: correction coefficients:
low engine temperature
high engine temperature
starting and post-starting
butterfly fully open
deceleration
acceleration
C: feed-back mixture control
D: self-adjustment
E: cut-off
F: intermediate injection time
G: extra-pulse
H: non phased injection manage-
ment
6
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