2585388 - Introduction - PETROL INJECTION SYSTEM (BIPOWER)
The Marelli IAW 59F system belongs to the category of systems integrated with:
- inductive discharge digital electronic ignition
- distributorless
- sequential, phased electronic injection (1-3-4-2).
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 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.
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.
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.
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.Whilst the engine is warming up, the electronic control unit also operates the stepping motor which determines the quantity of air needed to ensure that the engine does not cut out.
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 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. (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 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 ''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
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.
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
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 3° C below the engagement threshold.
Engine idle management
The general aim of this strategy is to keep the engine idling at around the value memorized (engine warm: 750 rpm); the position of the actuator depends on the following engine conditions:Starting stage
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 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.- Over-run
In 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 (fast idle).
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 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 on the state of the four-stage pressure switch and makes the appropriate interventions (radiator fan operation).
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.throttle valve position sensor
In 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 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.Engine idle speed actuator
In the event of a fault, the operation of the actuator is disabled and self-adjustment of the idle mixture strength is stopped.IAW 59F 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.
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