3356174 - INTRODUCTION - PETROL FUEL INJECTION SYSTEM

CONSTRUCTION SPECIFICATIONS

The control unit, when the engine is idling, controls the ignition time and the air flow rate, with the benefit of maintaining smooth engine operation even when environmental and applied load parameters change.The control unit controls and manages the injection so that the air/fuel ratio is always sufficiently close to the stoichiometric ratio to ensure maximum conversion efficiency for the catalyzers.

The system functions are essentially as follows:

  • self-adaptation;
  • diagnostics;
  • CODE recognition;
  • starting and post-starting;
  • operation when cold;
  • operation in full load conditions;
  • operation in acceleration;
  • operation in deceleration;
  • cut-off operation;
  • restriction of maximum rpm;
  • operation with engine idling;
  • knock control;
  • operation with phase transformer activated;
  • engine idle speed control;
  • control of fuel vapour recovery;
  • control of modular manifold;
  • radiator cooling fan check;
  • combustion control;
  • recovery;
  • Lambda sensor diagnostics
  • catalyzer fault diagnosis
  • misfire fault diagnosis
  • fuel system diagnostics

COMPOSITION OF THE SYSTEM

The diagram below illustrates the main system components.
1 , Fuel pump2, Inertia switch3, Speedometer4, Battery5, Ignition switch6, Injection system relays7, Air conditioner compressor8, Injection/ignition control unit9, Rev counter10, Diagnostic socket11, System failure warning light12, Throttle position sensor13, Motorized throttle body with built in air flow meter14, Engine idle adjustment actuator15, Modular manifold actuator control solenoid valve16, Phase transformer electromagnet17, Injectors18, Ignition coil19, Cam angle sensor20, Radiator fan21, RPM sensor22, Detonation sensor23, Engine coolant temperature sensor24, Fuel vapour recovery solenoid valve25, Lambda sensors upstream of the catalyzer26, Body computer (with Fiat CODE function)26, Lambda sensor downstream of the catalytic converter

OPERATION

INJECTION SYSTEM

The injection management strategies serve the purpose of providing the engine with the correct amount of fuel at the required moment on the basis of engine operating conditions.
The presence of the air flow meter makes it possible to measure the mass of air introduced directly, making the presence of the intake air temperature sensor superfluous.
The injection management strategies essentially involve computing the injection time, determining the injection stage in the engine cycle and the subsequent implementation of the stage by controlling the injectors.The "basic" injection time, depending on the specifications of the injector, corresponds to the quantity of fuel to be injected into each cylinder.Depending on the throttle opening, this quantity is, in turn, determined by dividing the amount of air introduced by each cylinder for the desired mixture strength in relation to the engine operating point.The final injection time is determined by means of a calculation algorithm whereby the base pulse constant is corrected by a series of coefficients that take into account the different engine operating conditions.
A, "Basic" injection timeB, Corrective coefficiencts (low engine temperature, high engine temperature, starting and post-starting, full throttle opening, deceleration, acceleration)C, Mixture strength controlD, Self-adaptationE, Cut-offF, Intermediate injection timeG, Extra-pulseH, Non phased injection management

IGNITION SYSTEM

The ignition management strategies are designed to ensure that the spark strikes with the desired advance depending on the engine operating conditions.The management of the ignition basically consists of determining the ignition advance and its implementation through the operation of the power transistor incorporated in each coil.The baseline advance value, calculated on the basis of the intake air flow rate and the engine speed, is then corrected on the basis of the various engine service conditions.The control unit determines the moment of the start of the conduction of the current in the coil primary winding.The angle of this moment naturally changes in relation to the combustion TDC of each cylinder: its advance is directly proportional to engine rpm because the time required to saturate the current in the coil primary winding is more or less constant:The conduction start moment is corrected on the basis of battery voltage.
1, System power supply relay2, Interface connector3, Single ignition coil (pencil-coil)

DIAGRAM SHOWING INFORMATION ENTERING/LEAVING THE CONTROL UNIT

The main information entering/leaving the control unit is illustrated in the diagram below.
1, Engine management control unit2, Battery3, Ignition switch4, System power supply relay5 , Fuel pump6, Climate control system7, Radiator fan relay8, Radiator fan9, Body Computer (with Fiat CODE function)10, Phase transformer electromagnet relay11, Phase transformer electromagnet12, Rev counter13, Lambda sensors upstream of the catalyzer14, Diagnostic socket15, Ignition coils16, Injectors17, Fuel vapour solenoid18, Modular manifold actuator control solenoid valve19, Lambda sensor downstream of the catalytic converter20, Coolant temperature sensor21, Speedometer22, Accelerator pedal potetiometer23, Detonation sensor24, Cam angle sensor25, Engine rpm sensor26, Motorized throttle body with built in air flow meter27, Electric fuel pump relay

SELF-ADAPTATION

The control unit is equipped with a self-adapation function which is designed to memorize any changes between the basic map and the corrections, imposed by the Lambda sensor, that could occur during operation.These changes (due to the ageing of the system and engine components) are memorized permanently allowing the adapation of the operation of the system to the gradual alterations in the engine and the components compared with when they were new.The strategy is disabled when the active charcoal filter scrubbing solenoid valve is open.If the control unit is replaced, the vehicle must be road tested to allow the engine to reach operating temperature and the control unit self-adaptation function to intervene (especially during idling stops).

DIAGNOSTICS

The system is fitted with a self-diagnostic function that checks for faults in the components listed below.

Actuators:

  • Injectors
  • Coils
  • Fuel vapour solenoid valve
  • Motorized throttle actuator
  • Fuel pump relay
  • Modular manifold solenoid valve
  • Phase transformer solenoid valve relay
  • Climate control compressor relay (if fitted)

Sensors:

  • Engine rpm sensor
  • Cam angle sensor
  • Air flow meter
  • Lambda sensors (upstream / downstream)
  • Coolant temperature sensor
  • Knock sensor
  • Throttle position sensor
Fault detection, if validated, leads to the fault being permanently saved and also exclusion of the sensor from the system until it is repaired.The control unit 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 light indicates engine management faults and also faults detected by EOBD diagnostic strategies.

The MIL warning light operating (mil) strategy is as follows:

  • with the ignition on, the warning light comes on and remains on until the engine has been started up. The control unit self-diagnostic system checks the signals coming from the sensors comparing them with the permitted limits.
  • the failure of the warning light to go out when the engine has been started indicates that there is an error memorized in the control unit.
  • the warning light comes on in flashing mode to indicate possible catalytic converter damage due to misfiring.
  • the warning light comes on in constant mode to indicate the presence of engine management or EOBD diagnostic errors.

RECOVERY

If the sensors/actuators are found to be faulty, the control unit replaces the missing data, if possible, by reconstructing it using software so that the engine will continue to operate.
Not all the engine management errors cause the warning light to come on.

The system can be tested using the diagnostic tester in three stages:

  • Display of a sereies of functional parameters (with the engine switched off or running)
  • Display of the errors and their deletion
  • Activation of several actuators (active diganosis).

OPERATING STRATEGIES

Code recognition

The moment the control unit receives the ignition ON signal it converses with the Body Computer (Fiat CODE function) and only gives the go ahead for starting if the correct code is received.The communication takes place via the dedicated two-way serial line that connects the two control units.

Starting and post-starting

Injection managementThe "basic" injection time is increased by a multiplcation coefficient for the entire time the engine is driven by the starter motor.When starting has taken place, the coefficient is gradually reduced until it disappears within a certain time; the lower the engine temperature, the longer this time.On starting, the control unit immediately recognizes the engine timeing. It is therefore capable of managing the phased injection from the first explosion.
k, Enrichment coefficientt, Timea, Engine temperature function decreaseON, Engine driven (crank)OFF, Engine started (run)Ignition managementDuring start-up, it is not possible to manage advance normally because the considerable fluctuations in rotation speed will not allow correct calculation of the advance.The advance is therefore managed by taking the tooth at 65° as a reference for the start of conduction and the tooth at 10° as a reference for the ignition advance.As a result the control unit implements a fixed advance of 10° throughout the time the engine is cranked by the starter motor.

Control of combustion

Adjustment of lambda valueAn effective means of reducgin the emission of harmful substances in the exhaust gases is the post-treatment of the exhaust gases in the three-way catalytic converter. This transforms the three harmful components of the exhaust gases CO, HC and NOx into H2O, CO2 and N2.The transformation of all three components can only be achieved if the mixture ratio is sufficiently close to the stoichiometric value.Instead of the mixture ratio the so-called "Lambda" factor is used indicating the ratio between the actual mixture and the stoichiometric ratio.If the "Lambda" is equal to 1 this means that the engine is receiving a stoichioemtric mixture. If the "Lambda" is more than 1 then the mixture is lean, if the "Lambda" is less than 1 then the mixture is rich.To produce the optimum operating conditions the control unit works with a closed loop criteria based on the Lambda sensor signal.When the sensor signal indicates a rich mixture the control unit decreases the injector supply, whilst it increases the supply when the signal indicates that the mixture is lean.The system is therefore made up of the engine (controlled element), the Lambda sensor (measuring element), the control unit (regulating element) and the injectors (actuators).Lambda system operationThe control unit modifies the injection time by means of a PID regulator (proportional, integrated, derived) allowing the Lambda sensor to produce a voltage signal that varies from 50 Mv (lean mixture) to 900 mV (rich mixture).Following the output signal from the Lambda sensor the control unit modifies the injection time, via the regulator, thereby allowing the engine to operate within the optimum Lambda factor for the conversion of the gases in the catalytic converter (objective).

Correction and self-adaptation function

There may be variations in the engine and in the injection system components in relation to the optimum conditions due to ageing or temporary malfunctions.The Lambda system is capable of correcting these variation using the corrective and self-adaptation functions.Following a Lambda sensor signal that is not optimum as a result of a malfunction, the control unit can correct the mixture strength by 21%.If a corrective factor persists, the control unit adapts its basic map to the new engine conditions. The self-adaptation, like the corrective factor, can reach a maximum of 21%.

The following are used in the vehicle exhaust system:

  • two Lambda sensors at the exhaust manifold outlet and before the pre-catalyzers controlling the closed loop combustion for the cylinder pairings 1-4 2-3.
  • a third Lambda sensor, positioned after
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