Fiat 1998 Marea Weekend, Руководство по обслуживанию

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Marea-Marea Weekend®
16v
Engine
1998 range
Fuel system
10.
The management strategies control ignition advance and fuel supply as effectively as possible to ensure
mixture concentration is constantly corrected as engine load and environmental conditions change.
System operating strategies are essentially as follows:
-injection management;
-ignition management;
-Fiat CODE immobiliser function management;
-radiator fan management
-engine idle control;
-fuel vapour recirculation management;
-test management
-heating/ventilation system management
INJECTION MANAGEMENT
The ignition management strategies are designed to provide the engine with the correct amount of fuel
at the right moment in accordance with engine service conditions.
The injection-ignition system uses an indirect measurement system known as «SPEED DENSITY -
LAMBDA», i.e. angular speed of rotation, intake air density, retro-active concentration check.
In practice this system uses ENGINE SPEED (revs per minute) and AIR DENSITY (pressure and temper-
ature) to measure the amount of air taken in by the engine.
The amount of air taken in by each cylinder upon each engine stroke depends on intake air density and
also on standard displacement and volumetric efficiency.
Air density is taken to be the density of air taken in by the engine and calculated as a function of absolute
pressure and temperature - both measured in the inlet manifold.
Volumetric efficiency is a parameter relating to the cylinder filling coefficient. It is calculated on the basis
of experimental tests carried out on the engine throughout its service range and then memorized in the
Once the amount of air taken in has been established, the system must provide sufficient fuel to make up
the required fuel mixture concentration.
The injection trigger pulse or time at which fuel delivery begins is mapped in a control unit and alters ac-
cording to engine speed and intake manifold pressure. In practice, the the ECU performs calculations in
order to control sequential, phased opening of the four injectors, one per cylinder for the length of time
strictly necessary to form an air-fuel mixture as close as possible to a stoichiometric ratio.
Fuel is injected directly into the manifold close to the intake valves at a differential pressure of some 3
bar.
Speed (no. of revolutions per minute) and air density (pressure and temperature) are used to measure
intake air quantity, which is used in turn to calculate the amount of fuel needed to achieve the required
mixture proportions. The other sensors in the system (coolant temperature, throttle valve position, bat-
tery voltage, etc.) allow the ECU to correct the baseline strategy for each specific engine service condi-
tion.
In order to keep the catalytic converter working efficiently and reduce polluting emissions, it is essential
to ensure the air-fuel ratio is maintained at near stoichiometric levels.
ECU.
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