2585388 - Introduction - PETROL INJECTION SYSTEM (BIPOWER)

The Marelli IAW 5NF system belongs to the category of systems integrated with:

inductive discharge digital electronic ignition
distributorless
sequential, phased electronic injection (1-3-4-2).

1, Fuel tank2, Electric fuel pump3, Multi-purpose valve4, Safety valve5, Fuel delivery pipe6, Injection-ignition ECU7, Battery8, Ignition switch9, Inertia switch10, Engine compartment junction unit11, Climate control system12, Fuel vapour cut-off valve13, Injection timing sensor14, Activated carbon filter15, Body Computer (tester connection and Fiat CODE signal)16, Absolute pressure and temperature sensor17, Rpm and TDC sensor18, Spark plugs19, Coolant temperature sensor20, Injectors21, Throttle and throttle position sensor actuator22, Accelerator pedal potentiometer23, Fuel supply manifold24, Air cleaner25, Ignition coils26, Lambda probe27, System failure warning light28, Rev counter29, Catalytic converter30, Lambda probe (post catalyzer)

During idling, the control unit checks:

the moment of ignition
the air flow with the benefit of maintaining correct operation of the engine when the environmental parameters and applied loads vary.

The control unit controls and manages fuel injection so that the stoichiometric ratio (air/fuel) is always at the optimum value.

The system''s functions are basically as follows:

system self-adaptation
self test
recognition of FIAT CODE
control of cold starting
control of combustion - Lambda sensors
control of detonation
control of mixture enrichment during acceleration
fuel cut-off during overrunning
fuel vapour recovery
limitation of the maximum rpm
fuel pump control
connection to the climate control system
recognition of cylinder position
adjustment of injection times
adjustment of ignition advance values
control and management of the idle speed
control of electric cooling fan.

Fuel injection system

The essential conditions that must always be met in the preparation of the air-fuel mixture for the correct operation of controlled-ignition engines are mainly:

the ''metering'' (air/fuel ratio) must constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the necessary rapidity of combustion, avoiding unnecessary fuel consumption
the ''homogeneity'' of the mixture, consisting of petrol vapours, diffused as finely and evenly as possible in the air.

The injection/ignition system uses an indirect measuring system known as the ''SPEED DENSITY LAMBDA'' type. in other words the angular rotation speed, density of the intake air and control of the mixture strength.In practice the system uses data on the ENGINE SPEED (rpm) and AIR DENSITY (pressure and temperature) to measure the quantity of air drawn in by the engine.The quantity of air drawn in by each cylinder, for each engine cycle depends not only on the density of the intake air, but also on the unit displacement and the volumetric efficiency.The density of the air refers to that of the air drawn in by the engine and calculated according to the absolute pressure and the temperature, both detected in the inlet manifold.Volumetric efficiency refers to the parameter relating to the coefficient for filling the cylinders measured on the basis of experimental tests carried out on the engine throughout the entire operating range and then stored in the electronic control unit memory.Having established the quantity of intake air, the system has to provide the quantity of fuel according to the desired mixture strength.The end of injection pulse or supply timing is contained in a map stored in the control unit memory and varies according to the engine speed and the pressure in the inlet manifold. In practice, it involves processing which the electronic control unit carries out to command the sequential, phased opening of the four injectors, one per cylinder, for the length of time strictly necessary to form the air/petrol mixture which is closest to the stoichiometric ratio.The fuel is injected directly into the manifold near the inlet valve at a pressure of around 3.5 bar.Whilst the speed (rpm) and the density of the air (pressure and temperature) are used to measure the quantity of intake air, which when established allows the quantity of fuel to be metered according to the desired mixture strength, the other sensors in the system (coolant temperature, butterfly valve position, battery voltage, etc.) allow the electronic control unit to correct the basic strategy for all engine operating conditions.It is vital for the air/fuel ratio to be around the stoichiometric value for the correct and prolonged operation of the catalytic silencer and for the reduction of pollutant emissions.

Ignition system

The ignition is of the inductive discharge type, breakerless with power modules located in the electronic injection/ignition control unit.The system has a coil for each cylinder connected directly to the spark plug.The primary winding for each coil is connected to the power relay (thereby receiving the battery voltage) and to the pins for the electronic control unit for connection to earth.

After the starting stage, the electronic unit manages the basic advance taken from a special map according to the:

engine rpm
absolute pressure value (mbar) measured in the inlet manifold.

This advance value is corrected according to the temperature of the engine coolant and the intake air.

Diagram of input/output info to/from control unit

The fuel level and engine oil presssure data reach the control unit via the CAN line.

1, Engine control unit2, Battery3, Ignition4, Engine control system relay5, Fuel pump relay6, Fuel pump7, Radiator fan relay/s8, Radiator fan9, Compressor activation relay10, Compressor11, Injectors12, Spark plugs13, Ignition coils14, Carbon filter flushing solenoid15, Lambda sensors (pre-catalyzer and post-catalyzer)16, Coolant temperature sensor17, Knock sensor18, Throttle and throttle position sensor actuator19, Engine rpm and TDC sensor20, Air pressure and absolute temperature sensor21, Engine oil pressure switch22, Body computer23, CODE control unit (body computer) (via CAN)24, Tester connection (via CAN line)25, Rev counter (via CAN line)26, System failure bulb (via CAN line)27, Speedometer (via CAN line)28, Injection timing sensor29, Accelerator pedal sensor30, Clutch pedal switch31, Coolant temperature sensor

System self-adaptation

The control unit has a self-adapation function which recognizes changes in the engine which occur as a result of bedding-in and ageing processes of both components and the engine itself.These changes are stored in the form of modifications to the basic mapping, and their purpose is to adapt the operation of the system to the gradual alterations in the engine and components compared with their characteristics when new.This self-adaptation function also makes it possible to even out inevitable differences (due to production tolerances) in any replaced components.From the exhaust gas analysis, the control unit changes the basic mapping in relation to the original characteristics of the new engine.The self-adaptation parameters are not cancelled if the battery is disconnected.

Self-diagnosis

The control unit''s self-test system checks the signals coming from the sensors, comparing them with the permitted limits:

indication of faults upon start-up:
warning light on for 4 s indicates test stage
warning light off after 4 secs indicates no faults in components that could affect the values established in emission control regulations
warning light on after 4 secs indicates fault
fault indication during operation
warning light on indicates fault
warning light off indicates no faults in components that could affect the values established in emission control regulations
recovery
the control unit defines as and when required the type of recovery depending on the faulty components
the recovery parameters are managed by non-faulty components.

Recognition of FIAT CODE

When the control unit receives the ignition ''ON'' signal, it dialogues with the Body Computer (Fiat CODE function) to obtain starting enablement.Communication takes place via the CAN line which connects the two control units.

RECOGNITION OF CYLINDER POSITION

The engine timing signal, together with the engine rpm and top dead centre (TDC) signal, allows the control unit to recognize the succession of cylinders to implement phased injection.This signal is generated by a Hall-effect sensor, positioned on the rocker cover near the phonic wheel formed on the camshaft pulley.

CONTROL OF COMBUSTION - LAMBDA SENSORS

In EOBD systems the Lambda sensors, which are all the same type but not interchangeable, are located one before (pre-) the catalyzer and one after (post-) the catalyzer.The pre-catalyzer sensor carries out the check on the mixture strength called 1st loop (closed loop of the pre-catalyzer sensor).The post catalyzer sensor is used for the catalyzer diagnosis and for finely modulating the 1st loop control parameters.With this in mind, the adjustment of the second loop is designed to recover both production differences and the slight deviations which the response from the pre-catalyzer sensor may show as a result of ageing and pollution.This check is called 2nd loop control (closed loop of post-catalyzer sensor).

EOBD (EUROPEAN ON BOARD DIAGNOSIS) SYSTEM

The implementation of the EOBD function is managed by the engine management control unit which manages the yellow warning light for the engine management system (EOBD) as described below.The warning light: is activated on request by the engine control unit for about 4 seconds (check) when the ignition key is turned to ''MAR''.The EOBD system carries out continuous diagnosis of the components related to the vehicle emissions system, signalling any deterioration of these components by the warning light in the panel coming on.

The aim of the system is:

keeping the efficiency of the system under control;
signalling an increase in emissions due to a vehicle malfunction;
signalling the need to replace deteriorated components.

Prompt repair of the problem which has caused the warning light to come on is vital in accordance with the legal requirements of the traffic regulations of the country in question.

Operation when cold

Under these circumstances there is a natural weakening of the mixture because of the poor turbulence of the fuel particles at low temperatures, reduced evaporation and condensation on the inner walls of the inlet manifold, all of which is exacerbated by the increased viscosity of the lubricant oil which, as is well known, increases the rolling torque of the engine mechanical components at low temperatures.The electronic control unit recognizes this condition on the basis of the coolant temperature signal, increasing the basic injection time.

Operation under full load

Operation in full load conditions is detected, by the control unit, through the values supplied by the butterfly position and absolute pressure sensors.In full load conditions, the basic injection time must be increased to obtain the maximum power supplied by the engine.

Operation during over-run

During this stage the engine has two strategies:

A negative, transitory strategy to keep the quantity of fuel supplied to the engine at the stoichiometric value (less pollution). This stage is recognized by the control unit when the butterfly position signal goes from a high voltage reading to a lower one.
A soft accompaniment strategy at the lower speed (dash-pot) to lessen the variation in the torque supplied (reduced engine braking).

Barometric correction

Atmospheric pressure varies according to the altitude creating a variation in the volumetric efficiency which requires correction of the basic mixture strength (injection time).The correction of the injection time depends on the variation in altitude and is automatically updated by the electronic control unit each time the engine is switched off and in certain butterfly position and rpm conditions. (for example at low speeds and with the butterfly wide open)

Operation during cut-off

The fuel cut-off strategy is implemented when the control unit recognizes the butterfly valve in the idle position and the engine speed is 1350 rpm (variable indicative value).The control unit only enables the cut-off when the engine temperature exceeds 0° C.The control unit with engine speed of 1270 rpm (variable indicative value) and butterfly valve in open position, re-enables the fuel supply to the engine.For very high speeds the cut-off is implemented even when the throttle is not completely closed, but when the pressure in the inlet manifold is particularly low (partial cut-off).

Operation during acceleration

During this stage, the control unit increases the quantity of fuel requested by the engine as appropriate (to achieve maximum torque) according to the following signals:

throttle position;
rpm and TDC signal

The ''basic'' injection time is multiplied by a coefficient which depends on the temperature of the engine coolant, the opening speed of the accelerator butterfly and the increase in pressure in the inlet manifold.If the sharp variation in the injection time is calculated when the injector is already closed, the control unit reopens the injector (extra pulse) in order to compensate the mixture strength extremely quickly; the subsequent injections are already increased on the basis of the coefficients mentioned previously.

Protection against excess rpm

When the engine rotation speed exceeds 6500 rpm for more than 10 seconds or reaches the ''limit'' of 6700 rpm set by the manufacturer for a moment, the engine is operating under ''critcal'' conditions.When the electronic control unit recognizes that the above speed has been exceeded, it prevents the operation of the injectors.When the rotation speed returns to a non critical value, the operation is resumed.

Fuel pump control

The electric fuel pump is controlled by the engine control unit by means of a relay.

The pump cuts out:

if the engine speed goes below about 50 rpm
after a certain period (about 5 seconds) with the ignition switch in the ON position without the engine being started up (timed go ahead)
if the inertia switch has operated.

Injector control

Check on knocking

The control unit detects the presence of knocking by processing the signal coming from the relevant sensor.The strategy continuously compares the signal coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.If the system recognizes the presence of detonation, the strategy reduces the ignition advance until the detonation disappears; the advance ia then gradually reset to the basic value, or until detonation arises again. In particular, advance increases are implemented gradually, whilst reductions are implemented immediately.Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.The strategy also features a self-adaptation function which temporarily memorizes the reductions in the advance that may be continuously repeated, in order to adjust the advance to the different engine operating conditions (for example, the use of a low octane rating fuel). The strategy is capable of restoring the advance to the threshold value memorized when the conditions which have caused the reduction no longer exist.

Management of radiator fan

Engine idle management

The control unit recognizes the idle condition from the accelerator pedal being in the ''released'' position. - According to the consumers switched on and the brake/clutch pedal signals, the control unit controls the position of the motorized butterfly.The idle speed when warm is 700 ± 50 rpm.

- Warming up stage

The engine speed is corrected, particularly on the basis of the engine coolant temperature.When the optimum temperature is reached, the idle management depends only on the signal coming from the rpm sensor; when external loads are switched on, the control unit controls the actuator to adjust the rpm to the new conditions and to manage the engine load while maintaining the idle speed.

Management of fuel vapour recirculation

This strategy controls the position of the vapour cut out solenoid valve in the following way:

during starting the solenoid remains closed, preventing the fuel vapours from enriching the mixture too much; this condition persists until the temperature of the coolant reaches 65° C;
with the engine up to to temperature, the electronic control unit sends the solenoid a square-wave signal (duty cycle) which modules its opening.

In this way the control unit controls the quantity of fuel vapours sent to the inlet, preventing considerable variations in the mixture strength.

In the condition listed below, the operation of the solenoid valve is inhibitied, maintaining the same in the closed position; this improves engine operation:

throttle valve in closed position
engine speed below 1500 rpm
inlet manifold pressure below the limit calculated by the control unit depending on the number of revs,

Climate control system management

The injection/ignition control unit is connected to the climate control system in that:

it receives the request to switch on the compressor and make the related interventions (additional air);
it gives the go ahead to switch on the compressor, when the conditions covered by the strategies have arisen;
it receives information relating to the climate control system pressure from the linear sensor and implements the appropriate interventions (radiator fan operation).

If the engine is idling, when the compressor turns on and power is required, the control unit drives the motorized throttle to increase the air flow.

The control unit disengages the compressor:

if the coolant temperature exceeds a certain threshold
if the engine rpm is below 700 rpm.

The control unit temporarily controls the disengagement of the compressor (for a few seconds):

during high power requests from the engine (strong acceleration)
during engine pickup:

Air temperature sensor

If the error is present during starting:

it assumes a value of 50 ° C
self-adjustment of the mixture strength is inhibited.

If the error is present in other conditions:

the last valid value is memorized and updated according to the engine temperature.

Knock sensor

If the sensor is faulty, the engine control unit implements more conservative ignition advance ''maps'' to safeguard the engine.

Pressure sensor

If the failure is present during starting, it uses a value of 1024 mbar.During operation the value used is calculated on the basis of parameters supplied by the throttle valve position sensor and the rpm sensor.Self-adjustment of the mixture strength is inhibited.

Vehicle speed sensor

The last vehicle speed value memorized is assumed.

Coolant temperature sensor

In the case of a fault, the control unit inhibits self-adjustment of the mixture strength and idle.It sets the last temperature value measured; if this does not correspond to the working temperature, the control unit increases it gradually in accordance to the time since the engine was started until the theoretical 80° C is reached.In addition when the ignition is switched on, the radiator cooling fan is switched on permanently at the second speed.

IAW 5NF injection/ignition control unit

The control unit is fitted in the engine compatment on the inlet manifold air chamber, and can withstand high temperatures.It is a digital type with a microprocessor, featuring a high calculation capacity, precision, reliability, versatility and low energy consumption and is maintenance-free.The task of the electronic control unit is to process the signals coming from the various sensors through the application of software algorithms and control the operation of the actuators (in particular the injectors, ignition coils and idle actuator) in order to ensure optimum engine operation.The adoption of the Fiat CODE does not allow control units to be exchanged between cars.

Pin-out

The diagram below shows the control unit pins.

(A) CONNECTOR FOR VEHICLE SIDE WIRING1 Not connected2 Accelerator pedal sensor supply3 Accelerator pedal sensor 2 supply/air conditioning pressure switch4 Not connected5 Not connected6 Fan 2 engagement request7 Minimum oil pressure signal8 Not connected9 Not connected10 Serial line K11 Not connected12 Key on and supply controlled by ignition (DBW)13 Not connected14 Fan 1 engagement request15 Accelerator pedal 2 sensor/air conditioning pressure switch earth16 Direct battery +12V17 Not connected18 Not connected19 Not connected20 Two-way CAN line (LOW)21 Not connected22 Not connected23 Not connected24 Not connected25 Not connected26 Air conditioning engagement request27 Not connected28 Not connected29 Key on and supply controlled by ignition (DBW)30 Not connected38 Not connected32 Not connected33 Not connected34 Not connected35 Not connected36 Two-way CAN line (LOW)37 Not connected38 Not connected39 Not connected40 Accelerator pedal potentiometer 2 signal41 Not connected42 Accelerator pedal potentiometer 1 signal43 Not connected44 Not connected45 Not connected46 Accelerator pedal sensor earth 147 Not connected48 Not connected49 Not connected50 Clutch pedal switch signal51 Two-way CAN line (HIGH)52 Two-way CAN line (HIGH)53 Not connected54 Not connected55 Fan low speed engagement56 Not connected57 Not connected58 Not connected59 Fan high speed engagement60 Not connected61 Not connected62 Fuel pump relay operation63 Not connected64 Air conditioning engagement(B) CONNECTOR FOR ENGINE SIDE WIRING1 Coil 4 operation2 Not connected3 Coil 3 operation4 Not connected5 Engine crankcase earth6 Engine crankcase earth7 Pressure and timing sensors earth8 Not connected9 Rpm / TDC sensor positive10 Not connected11 Not connected12 Not connected13 Pressure and timing sensors supply (+5V)14 Not connected15 DBW supply (motorized throttle ( (+5V)16 Not connected17 Coil 1 operation18 Not connected19 Coil 2 operation20 Not connected21 Eng

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The Marelli IAW 4AF.G1 system belongs to the category of systems integrated with:

inductive discharge digital electronic ignition
distributorless
sequential, phased electronic injection (1-3-4-2).

1, Safety and ventilation valve2, Fuel tank3, Electric fuel pump4, Idle speed actuator5, Battery6, Ignition switch7, Junction unit, engine compartment15, Body Computer (tester connection and Fiat CODE signal)9, Inertia switch10, Rev counter11, Injection system failure warning light12, Throttle valve position sensor18, Fuel supply manifold14, Injectors15, Air filter16, Spark plugs17, Ignition coils18, Engine coolant temperature gauge19, Air temperature and pressure sensor20, Rpm and T.D.C. sensor21, Detonation sensor22, Coolant temperature sensor23, Fuel vapour solenoid valve24, Active charcoal filter25, Air conditioner compressor26, Lambda probe (precatalyzer)27, Catalytic converter28, Injection-ignition control unit (petrol)29, Multi-function valve30, Engine coolant overheating warning light31, Lambda sensor (post-catalyzer)32, Injection timing sensor33, Methane engine management control unit34, Petrol pump deactivation relay

OPERATION

The system is configured to normally run on methane.

It is possible to switch from methane to petrol:

manually by using the mode selector (SEDIMO) located in the trinket compartment under the handbrake;
automatically through the engine management electronic control unit if the methane in the tank has run out (pressure in the cylinder below 11 bar) or in recovery conditions when methane operation is not advisable.

The engine is always started on petrol (to keep this fuel system working), with automatic changeover to methane after a few seconds (provided that the operating selector is set to methane).

The Magneti Marelli IAW 4AF.G1 essentially manages the following functions::

system self-adaptation
self test
recognition of FIAT CODE
control of cold starting
control of combustion - Lambda sensors
control of detonation
control of mixture enrichment during acceleration
fuel cut-off during overrunning
fuel vapour recovery
limitation of the maximum rpm
fuel supply check
connection to the climate control system
recognition of cylinder position
regulation of fuel injection times
adjustment of ignition advance values
control and management of the idle speed
control of electric cooling fan
diagnosis of ''Fuel System''
diagnosis of catalyzer
diagnosis of Lambda sensors
diagnosis of ''Misfire''
communication with the Metatron METAFUEL 6A0 control unit by means of a high speed CAN line that is used to exchange data, commands and other information.

The control unit controls and manages fuel injection so that the stoichiometric ratio (air/fuel) is always at the optimum value.

During idling, the control unit checks:

the moment of ignition
the air flow with the benefit of maintaining correct operation of the engine when the environmental parameters and applied loads vary.

INJECTION SYSTEM

There are basically two essential conditions that must always be met in the preparation of the air/fuel mixture for the smooth operation of controlled ignition engines, namely:

the ''metering'' (air/fuel ratio) must constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the necessary rapidity of combustion, avoiding unnecessary fuel consumption
the ''homogeneity'' of the mixture, consisting of petrol vapours, diffused as finely and evenly as possible in the air.

The injection/ignition system uses an indirect measuring system known as the ''SPEED DENSITY-LAMBDA'' type, in other words the angular rotation speed, the density of the intake air and the control of the mixture strength (feed-back).In practice the system uses data on the ENGINE SPEED (rpm) and AIR DENSITY (pressure and temperature) to measure the quantity of air drawn in by the engine.The quantity of air drawn in by each cylinder, for each engine cycle depends not only on the density of the intake air, but also on the unit displacement and the volumetric efficiency.The density of the air refers to that of the air drawn in by the engine and calculated according to the absolute pressure and the temperature, both detected in the inlet manifold by specific sensors.Volumetric efficiency refers to the parameter relating to the coefficient for filling the cylinders measured on the basis of experimental tests carried out on the engine throughout the entire operating range and then stored in the electronic control unit memory.Having established the quantity of intake air, the system has to provide the quantity of fuel according to the desired mixture strength.The end of injection pulse or supply timing is contained in a map stored in the control unit memory and varies according to the engine speed and the pressure in the inlet manifold. In practice, it involves processing which the electronic control unit carries out to command the sequential, phased opening of the four injectors, one per cylinder, for the length of time strictly necessary to form the air/petrol mixture which is closest to the stoichiometric ratio.The fuel is injected directly into the manifold near the inlet valve at a pressure of around 3.5 bar.Whilst the speed (rpm) and the density of the air (pressure and temperature) are used to measure the quantity of intake air, which when established allows the quantity of fuel to be metered according to the desired mixture strength, the other sensors in the system (coolant temperature, throttle valve position, battery voltage, etc.) allow the electronic control unit to correct the basic strategy for all engine operating conditions.It is vital for the air/fuel ratio to be around the stoichiometric value for the correct and prolonged operation of the catalytic silencer and for the reduction of pollutant emissions.The injection system operation and strategies are basically identical for both petrol and methane operation.

IGNITION SYSTEM

The ignition is of the inductive discharge type, breakerless with power modules located in the electronic injection/ignition control unit.The system has two high tension twin outlet coils joined in a single container and connected directly to the spark plugs.The primary winding for each coil is connected to the power relay (thereby receiving the battery voltage) and to the pins for the electronic control unit for connection to earth.

After the starting stage, the electronic unit manages the basic advance taken from a special map according to the:

engine rpm
absolute pressure value (mbar) measured in the inlet manifold.

This advance value is corrected according to the temperature of the engine coolant and the intake air.The spark plugs for cylinder 1-4 and 2-3 are connected directly (two at a time) by means of high tension leads to the terminals of the coil secondary winding and their connection is in series because the cylinder head joins them. This solution is also known as the ''lost spark'' becuse the energy accumulated by the coil is almost exclusively discharged at the electrodes for the spark plug of the cylinder under compression allowing the ignition of the mixture. The other spark is obviously not used, as no mixture is found in the cylinder to ignite, only exhaust gas.

DIAGRAM OF INPUT/OUTPUT INFORMATION TO/FROM THE CONTROL UNIT

Communication between the petrol engine control unit and the methane engine control unit takes place via the CAN line.

1, Engine control unit2 - Body computer3, CODE control unit (body computer) (via CAN network)4, Tester connection (via CAN network)5, Rev counter (via CAN network)6, Injection system failure warning light (via CAN network)7, Speedometer (via CAN network)8, Engine idle speed actuator9, Injectors10, Fuel vapour solenoid valve11, Spark plugs12, Ignition coils13, Compressor activation relay14, Air conditioner compressor15, Methane engine management control unit16, Coolant temperature sensor17, Intake air temperature and pressure sensor18, Butterfly valve position sensor19, Detonation sensor20, Rpm and TDC sensor21, Injection timing sensor22, Ignition switch23, Lambda sensor (pre-catalyzer)24, Lambda sensor (post-catalyzer)25, Fuel pump26, Radiator fan high and low speed relays27, Radiator fan

SELF-ADAPTATION OF THE SYSTEM

SELF-DIAGNOSIS

The control unit''s self-test system checks the signals coming from the sensors, comparing them with the permitted limits:

indication of faults upon start-up:
warning light on for 4 s indicates test stage
warning light off after 4 secs indicates no faults in components that could affect the values established in emission control regulations
warning light on after 4 secs indicates fault
fault indication during operation
warning light on indicates fault
warning light off indicates no faults in components that could affect the values established in emission control regulations
recovery
the control unit defines as and when required the type of recovery depending on the faulty components
the recovery parameters are managed by non-faulty components.

RECOGNITION OF FIAT CODE

STARTING AND POST-STARTING

During starting it is not possible to instantly recognize the engine timing and consequently it is not possible to implement the timed injection for the first injection for each cylinder.When the engine is first running an initial simultaneous (full-group) injection is carried out because the considerable fluctuations in the rotation speed do not allow the correct calculation of the injection stage; it is only later that the injection becomes phased.The ''basic'' injection time is increased by a multiplication coefficient for the entire time the engine is driven by the starter motor.After starting, the coefficient is gradually reduced until it disappears within a certain period; the lower the engine temperature, the longer this period.

COMBUSTION CONTROL - LAMBDA SENSORS

The Lambda sensors, which are all the same type but are not interchangeable, are located upstream and downstream of the catalyzer. The upstream sensors carry out the check on the mixture strength known as the 1st loop (upstream sensor closed loop). The sensor downstream of the catalyzer is used for the catalyzer diagnosis and for finely modulating the 1st loop control parameters. With this in mind, the adjustment of the second loop is designed to recover both production differences and those in the response of the upstream sensors which may occur as a result of ageing and pollution. This control is known as the 2nd loop (downstream sensor closed loop).

EOBD (EUROPEAN ON BOARD DIAGNOSIS) SYSTEM

The aim of the system is:

keeping the efficiency of the system under control;
signalling an increase in emissions due to a vehicle malfunction;
signalling the need to replace deteriorated components.

Prompt repair of the problem which has caused the warning light to come on is vital in accordance with the legal requirements of the traffic regulations of the country in question.

OPERATION WHEN COLD

OPERATION IN FULL LOAD CONDITIONS

OPERATION IN DECELERATION

During this stage the engine has two strategies:

A negative, transitory strategy to keep the quantity of fuel supplied to the engine at the stoichiometric value (less pollution). This stage is recognized by the control unit when the butterfly potentiometer signal goes from a high voltage reading to a lower one.
A soft accompaniment strategy at the lower speed (dash-pot) to lessen the variation in the torque supplied (reduced engine braking).

Barometric correction

Atmospheric pressure varies according to the altitude creating a variation in the volumetric efficiency which requires correction of the basic mixture strength (injection time).The correction of the injection time depends on the variation in altitude and is automatically updated by the electronic control unit each time the engine is switched off and in certain butterfly position and rpm conditions (typically at low speeds and with the butterfly wide open) (dynamic adjustment of barometric correction).

Operation during cut-off

The cut-off strategy is implemented when the control unit recognizes the throttle valve in the idle position (throttle potentiometer signal) and the engine speed exceeds 1350 rpm (variable indicative value). The control unit only enables the cut-off when the engine temperature exceeds 0° C.The recognition of the throttle valve in a non closed position or the engine speed below 1270 rpm (variable indicative value) re-enables the supply to the engine.For very high speeds the cut-off is implemented even when the throttle is not completely closed, but when the pressure in the inlet manifold is particularly low (partial cut-off).

OPERATION IN ACCELERATION CONDITIONS

During this stage, the control unit increases the quantity of fuel requested by the engine as appropriate (to achieve maximum torque) according to the signals coming from the following components:

throttle potentiometer;
rpm and T.D.C. sensor.

PROTECTION AGAINST EXCESS RPM

When the engine rotation speed exceeds 6500 rpm for more than 10 seconds or reaches the ''limit'' of 6700 rpm set by the manufacturer for a moment, the engine is operating under ''critical'' conditions.When the electronic control unit recognizes that the above speed has been exceeded, it prevents the operation of the injectors.When the rotation speed returns to a non critical value, the operation is resumed.

PETROL INJECTOR CONTROL

The operation of the injectors is the sequential, phased type. However, during starting the injectors are operated once in parallel (full-group).The timing of the injector operation varies according to the engine speed and pressure of the inlet air in order to improve the filling of the cylinders with advantages in terms of consumption, driveability and pollution.The injectors are electrically supplied via a fuse and specific relay contained in the engine compartment junction unit: the petrol management control unit closes the contact of the relay relating to the petrol injectors in accordance with the specific situations.To prevent errors during the changeover from petrol to methane, the engine management control unit simultaneously changes over the load of the petrol injectors to a resistance value in the control unit which simulates the resistance of the injectors; in this way there are no interruptions that could generate errors and result in the impossibility of changing over to methane.

CONTROL OF DETONATION

The control unit detects the presence of knocking by processing the signal coming from the relevant sensor. The strategy continuously compares the signal coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.If the system recognizes the presence of detonation, the strategy reduces the ignition advance until the phenomenon disappears. Later, the advance is gradually restored to the basic value or until the phenomenon occurs again. Later, the advance is gradually restored to the basic value or until the phenomenon occurs again.Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.The strategy also features a self-adaptation function which temporarily memorizes the reductions in the advance that may be continuously repeated, in order to adjust the advance to the different engine operating conditions (for example, the use of a low octane rating fuel). The strategy is capable of restoring the advance to the threshold value memorized when the conditions which have caused the reduction no longer exist.

MANAGEMENT OF RADIATOR FAN

The control unit directly controls the operation of the radiator fan according to the temperature of the engine coolant and the engagement of the climate control system.The fan is switched on when the temperature exceeds 97° C (1st speed) and 101° C (2nd speed). The switching off takes place with a hysteresis of 2° C below the engagement threshold.The high and low speed functions are managed by the intervention of specific relays located in the engine compartment junction unit and are operated by the control unit.

MANAGEMENT OF THE ENGINE IDLE

The general aim of this strategy is to keep the engine idling at around the value memorized (engine warm: 700 rpm); the position of the actuator depends on the following engine conditions:

Starting: when the key is inserted, the position of the actuator depends on the temperature of the engine coolant and the voltage of the battery (open-loop position).
Warming up: the engine speed is corrected, particularly on the basis of the engine coolant temperature. With the engine at operating temperature, the management of the idle depends on the signal coming from the rpm sensor; when external loads are switched on, the control unit manages the supported idle.
Deceleration stage: deceleration conditions outside of idling, the control unit controls the position of the engine idle speed actuator by means of a special flow rate curve (dash-pot curve), in other words it slows down the return of the shutter towards its seating, improving the engine braking effect.

RECOGNITION OF CYLINDER POSITION

The engine timing signal, together with the engine rpm and top dead centre (TDC) signal, allows the control unit to recognize the succession of cylinders to implement phased injection.This signal is generated by a Hall-effect sensor, positioned on the cylinder head near the phonic wheel on the inlet camshaft.

MANAGEMENT OF FUEL VAPOUR RECIRCULATION (PETROL)

This strategy controls the position of the vapour cut out solenoid valve in the following way:

during starting the solenoid remains closed, preventing the fuel vapours from enriching the mixture too much; this conditioner persists until the temperature of the coolant temperature reaches 65° C.
with the engine at operating temperature, the electronic control unit sends the solenoid valve a square wave signal (duty-cycle operation) and the opening is modulated.

In this way the control unit controls the quantity of fuel vapours sent to the inlet, preventing considerable variations in the mixture strength.

In the conditions listed below, the operation of the solenoid valve is inhibited, maintaining the same in the closed position; this improves engine operation:

throttle valve in closed position
engine speed below 1500 rpm
inlet manifold pressure below the limit calculated by the control unit depending on the number of revs.

MANAGEMENT OF THE CLIMATE CONTROL SYSTEM

The injection/ignition control unit is connected to the climate control system in that:

it receives the request to switch on the compressor and make the related interventions (additional air);
it gives the go ahead to switch on the compressor, when the conditions covered by the strategies have arisen;
it receives information on the state of the four-stage pressure switch and makes the appropriate interventions (radiator fan operation).

If the engine is idling, the control unit increases the flow rate of the air passing from the idle actuator before the compressor is switched on and, viceversa, it returns the actuator to the normal position after the compressor is switched off.

The control unit automatically controls the disengagement of the compressor:

at engine coolant temperatures above a certain level
if the engine rpm is below 700 rpm.

The control unit temporarily controls the disengagement of the compressor (for a few seconds):

during high power requests from the engine (strong acceleration)
during engine pickup.

RECOVERY

AIR TEMPERATURE SENSOR

If the error is present during starting:

it assumes a value of 50 ° C
self-adjustment of the mixture strength is inhibited.

If the error is present in other conditions:

the last valid value is memorized and updated according to the coolant temperature.

DETONATION SENSORIf the sensor is faulty, the engine control unit implements more conservative ignition advance ''maps'' to safeguard the engine.LAMBDA PROBESIn the case of a failure, the information transmitted is ignored and the system operates in open-loop.PRESSURE SENSORIf the failure is present during starting, it uses a value of 1024 mbar. During operation the value used is calculated on the basis of parameters supplied by the throttle valve position sensor and the rpm sensor. Mixture self-adaption is inhibited.BUTTERFLY VALVE POSITION SENSORIn the case of a fault, a value calculated from the absolute pressure sensor readings is set, and if this sensor is broken, a fixed value equal to a throttle opening of 50 degrees is set. The mixture strength and idle self-adjustment dash-pot strategies are suspended.VEHICLE SPEED SENSORThe control unit uses the last vehicle speed value memorized when there was no error.COOLANT TEMPERATURE SENSORIn the case of a failure the ECU inhibits the self-adjustment of the mixture strength and idle. It sets the last temperature value measured; if this does not correspond to the normal working value, the ECU increases it gradually according to the time since the engine was started up until it reaches 80 ° C. The radiator cooling fan is operated.ENGINE IDLE SPEED ACTUATORIn the event of a fault, the operation of the actuator is disabled and self-adjustment of the idle mixture strength is stopped.

IAW 4AF.G1 INJECTION/IGNITION CONTROL UNIT

The control unit is fitted under the front window bottom protection, and can withstand high temperatures.It is a digital type with a microprocessor, featuring a high calculation capacity, precision, reliability, versatility and low energy consumption and is maintenance-free.The task of the electronic control unit is to process the signals coming from the various sensors through the application of software algorithms and control the operation of the actuators (in particular the injectors, ignition coils and idle actuator) in order to ensure optimum engine operation and communicate with the METAFUEL 6A0 control unit via a high-speed CAN line to exchange data, commands and other information.The adoption of the Fiat CODE does not allow control units to be exchanged between cars.

IAW 4AF.G1 CONTROL UNIT PIN-OUT

The diagram below shows the control unit pins.

1, Earth for pre catalyzer Lambda sensor heater2, Earth for post catalyzer Lambda sensor heater3, Not connected4, Not connected5, Not connected6, CAN L7, Not connected8, Engine oil pressure signal (inlet)9, Pre converter Lambda sensor (negative)10, Not connected11, Not connected12, Post converter Lambda sensor (positive)13, Not connected14, Radiator fan high speed relay control (outlet)15, Pump relay enablement16, Not connected17, Not connected18, Not connected19, Not connected20, Pre catalyzer Lambda sensor (positive)21, Radiator fan high speed request signal22

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