the idle air flow rate set through the electronic throttle;
the moment of ignition with the advantage of maintaining smooth engine operation as the environmental parameters and loads applied vary.
The Engine Management Node controls and manages the injection so that the air/fuel ratio is always sufficiently close to the stoichiometric value in order to ensure optimum conversion efficiency for the catalyzer; in full power and high usage conditions the mixture is enriched to guarantee maximum performance.The main functions of the system are basically as follows:
self-learning;
system self-adjustment;
self-diagnosis;
CODE recognition;
cold starting check;
combustion - Lambda sensor check;
check on phase transformer and modular intake manifold
detonation control;
check on mixture enrichment during acceleration;
fuel cut-off during release of accelerator pedal;
fuel vapour recovery;
control of maximum rpm;
fuel supply - electric fuel pump control;
connection with climate control system;
recognition of cylinder position;
injection time adjustment;
ignition advance adjustment;
idle speed control;
control of engine cooling fan;
connection with automatic transmission control unit (where fitted);
connection with ABS control unit;
connection with instrument panel.
Fuel System fault diagnosis;
catalyzer fault diagnosis;
Lambda sensors fault diagnosis;
Misfire fault diagnosis;
OPERATION
Operating strategies
General remarks
Injection systemThe essential conditions that must always be satisfied in the preparation of the air/fuel mixture for the smooth operation of controlled ignition engines are, basically:
the "metering" (air/fuel ratio) should be kept as close as possible to the stoichiometric value to ensure the maximum conversion capacity of the catalytic converters (max. efficiency).
the "homogeneity" of the mixture comprising petrol diffused in the air as finely and evenly as possible.
The information that the Engine Management Node processes to ensure optimum metering is received by means of electrical signals sent by:
*- air flow meter and air temperature sensor, for the exact intake air quantity.
rpm sensor, which produces an alternating single phase signal whose frequency indicates the engine speed. This signal is used by the Engine Management Node for detecting misfire.
throttle potentiometer for recognizing the acceleration conditions required.
coolant temperature sensor located on the thermostat.
Lambda sensors for determining the oxygen content of the exhaust gases and, through the downstream sensor, for diagnosing the efficiency of the catalyzers.
Ignition system.The ignition system is the static advance, inductive discharge type (i.e. with no high tension distributor) with power modules inside the Engine Management Node.In this ignition system each coil supplies the spark plugs for the relevant cylinder.The advantages of this solution are:
less electrical overload;
guarantee of constant discharge at each spark plug.
There is a map stored in the Engine Management Node containing the entire series of optimum ignition advance values (for the cylinder in the explosion stroke) that the engine can adopt depending ont he engine speed and load requirements.The Engine Management Node makes corrections to the advance value mainly depending on:
engine coolant temperature.
intake air temperature.
detonation.
throttle valve position.
The information that the Engine Management Node processes to operate the coils is received by means of electrical signals sent by:
air flow meter with built in air temperature sensor, for the exact intake air quantity.
rpm sensor, which produces an alternating single phase signal whose frequency indicates the engine speed.
2 detonation sensors (at the rear of the cylinder block one between the 1st and 2nd cylinders, the other between the 4th and 5th) to recognize the cylinder where detonation is taking place and correct the ignition advance.
throttle position potentiometer to recognize minimum load, partial load and full gas conditions.
timing sensor.
Self-learning.
The Engine Management Node implements the self-learning logic in the following conditions:removing-refitting or replacing the Engine Management Node.removing-refitting or replacing the throttle casing.The values stored in the Engine Management Node memory are preserved when the battery is disconnected.
System self-adjustment.
The Engine Management Node is equipped with a self-adjustment function that is designed to recognize the changes that take place in the engine due to the processes of bedding in and ageing of both the components and the engine itself in time.These changes are memorized in the form of modifications to the basic map and are designed to adapt the operation of the system to the gradual alterations in the engine and the components compared with when they were new.This self-adjustment function also makes it possible to compensate for the inevitable differences in any replacement components (due to production tolerances).From the analysis of the exhaust gases, the Engine Management Node modifies the basic map in relation to the engine specifications when new.The self-adjustment parameters are not cancelled if the battery is disconnected.
Self-diagnosis
The Engine Management Node auto-diagnostic system checks that the system is working properly and signals any irregularities by means of an MIL warning light in the instrument panel with a standardized ideogram and colour laid down by European regulations. This warning lights signals both engine management faults and faults that are detected by the EOBD strategies.The MIL warning light operating logic is as follows:
with the ignition on, the warning light comes on and remains on until the engine has been started up. The Engine Management Node self-diagnostic system checks the signals coming from the sensors comparing them with the permitted limits:
Siganalling of faults during stating:
the failure of the warning light to go out when the engine has been started indicates that there is an error memorized in the Engine Management Node.
Signalling of faults during operation:
the warning light flashing indicates possible damage to the catalyzer through the presence of misfire.
the warning light coming on constantly indicates the presence of engine management or EOBD errors.
RECOVERY.From time to time the Engine Management Node defines the type of recovery according to the components that are faulty. The recovery parameters are managed by components that are not faulty.
Code recognition.
The moment the Body Computer receives the ignition ON signal, it converses with the Engine Management Node to allow starting. For vehicles equipped with Passive Entry see {DF55].
Cold starting check.
In cold starting conditions the following occurs:
a natural weakening of the mixture which results in poor evaporation (poor turbulence of the fuel particles at low temperatures).
reduced evaporation of the fuel.
condensation of the fuel on the internal walls of the intake manifold.
increased viscosity of the lubricant oil.
The Engine Management Node recognizes this condition and corrects the basic injection time:
coolant temperature.
intake air temperature.
battery voltage.
engine speed.
The ignition advance only depends on the number of revs and the temperature of the engine coolant.Whilst the engine is warming up, the Engine Management Node operates the motorized throttle to regulate the quantity of air required to ensure that the engine does not cut out.The rotation speed decreases proportionally as the engine temperature increases until the nominal value is reached when the engine has warmed up.
Combustion - Lambda sensor check.
In EOBD systems the Lambda sensors, which are all the same type, are located upstream of the catalyzer and downstream of the catalyzer. The upstream sensor carries out the mixture strength control known as 1st closed loop. The sensor downstream of the catalyzer is used for the fault diagnosis of the catalyzer and to modulate the 1st loop parameters. With this in mind, the adaptation of the second loop is designed to recover both production differences and the slight changes in the response of upstream sensors that may occur due to ageing and pollution. This control is known as the 2nd closed loop.
Check on phase transformer and modular intake manifold .
In order to ensure the optimum quantity of air drawn in by the engine, the Engine Management Node controls:
the intake timing in two angular positions.
the geometry of two different length intake manifolds.
The Engine Management Node sets the "open" stage at maximum speed:
cam advance = 18° engine
intake chamber long ducts.
In other engine operating conditions, the Engine Management Node selects the most suitable configuration for optimum performance, consumption and emissions.In the release stage, the chamber intake ducts are always short.
Knock control.
The Engine Management Node detects the presence of detonation (engine knock) by processing the signal from the relevant sensors.The Engine Management Node continuously compares the signals coming from the sensors with a threshold which is, in turn, continually updated to take into account background noise and engine ageing.The Engine Management Node is capable of detecting the presence of detonation (or the onset of detonation) in every cylinder and reducing the ignition advance for the cylinder concerned (in steps of 3° up to a maximum of 6°) until it disappears. Later on, the advance is gradually restored to the basic value (in steps of 0.8°).In acceleration conditions a higher threshold is used to take into account the increased engine noise under these circumstances.The detonation control logic is also equipped with a self-adaptation logic which memorizes the advance reductions that are continuously repeated in order to adapt the map to the different operating conditions that the engine finds itself in.
Check on enrichment during acceleration.
If, during an acceleration request, the variation in the air flow rate signal exceeds a predefined increase, the Engine Management Node increases the injection (time) to reach the number of revs required rapidly.Recovery:the Engine Management Node replaces the signal coming from the faulty air flow meter with the throttle potentiometer signal.
Fuel cut off during over-run (cut-off)
Whilst the accelerator pedal is released and beyond a preset engine rpm level, the Engine Management Node:
cuts off the supply to the injectors.
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