199000947 - INTRODUCTION - PETROL FUEL INJECTION SYSTEM

SPECIFICATIONS

GENERAL SPECIFICATIONS

The Bosch Motronic ME7.6.3 system (with a micro-hybrid technology control unit) with a motorized throttle belongs to the category of ignition systems which have built-in phased-, sequential-type electronic injection.The fuel supply system is the returnless type.The control unit electronically manages the air flow rate at the rotation speed set by the electronic throttle, regulates the fuel injection so that the (air/fuel) ratio is always within optimum values, calculating the moment of ignition, in order to allow the smooth operation of the engine when the environmental parameters and loads applied vary.The system has a slider on-off device that allows one of the two inlet ducts inside the head to be closed to create turbulence in the combustion chamber. The control unit controls the opening/closing of the slider and receives feedback on its position by means of a special sensor. There is also a continuous variable timing system with oleodynamic activation.The ignition system is the static advance type with a single coil with three outlets. The power modules are housed inside the control unit.The self-adaptive engine management system can recognise the changes that take place in the engine. It compensates for them using the self-adaptive functions that correct the fuel mixture and air flow plans mapped in the control unit.There are two adaptive functions, in particular, for the fuel mixture plan, depending on whether the evaporation control solenoid valve is open or closed, plus an idle adaptation plan: the latter is capable of compensating effectively for any air seepage.The continuous self-adaptation of the fuel mixture plan makes it possible to ensure the correct amount of fuel in all temperature and altitude conditions.As a result of this, after every intervention it is necessary to drive the vehicle for at least 15 minutes in various operating conditions in order for any changes that have taken place in the system to be memorised in the control unit and to end the adaptation.

The main system functions are as follows:

  • injection time adjustment;
  • ignition advance adjustment;
  • cold starting check;
  • enrichment during acceleration check;
  • fuel cut-off during over-run;
  • idle speed management (also dependent on battery voltage);
  • restriction of the maximum engine speed;
  • combustion control with Lambda sensor;
  • petrol vapour recovery;
  • fan control;
  • climate control system engagement/disengagement;
  • self-diagnosis;
  • slider on-off control;
  • continuous variable valve timing control;
  • calculation of the vehicle speed;
  • automatic management of engine starting.

There is also a special function that manages the connection with the body computer via a two-way signal for the CAN line. This includes:

  • engine temperature for instrument panel (output);
  • battery voltage (output);
  • engine rpm (output) for instrument panel;
  • engine overheating warning light for instrument panel (output);
  • engine oil pressure warning light for panel (output);
  • vehicle speed (output) + mileometer (input/output);
  • Fiat code anti-theft device (input/output);
  • key status;
  • consumption signal (output) for trip computer.
  • fuel level signal (input)

Injection system

The essential conditions to be met by the air-fuel mixture for the efficient operation of engines with controlled ignition systems are mainly as follows:

  • the metering (air/fuel ratio) must be kept as close as possible to stoichiometric value to ensure that combustion is as fast as possible avoiding fuel wastage
  • the homogeneity of the mixture, consisting of petrol vapours distributed throughout the air as finely and uniformly as possible.
The injection/ignition system uses an indirect measuring system known as "SPEED DENSITY-LAMBDA".In other words, angular rotation speed, intake air density and control of mixture strength (feedback control).In practice, the system uses the ENGINE SPEED data (rpm) and the AIR DENSITY (pressure and temperature) the position of the slider and the position of the continuous phase transformer to measure the quantity of air drawn in by the engine.The quantity of air drawn in by each cylinder, for every engine cycle, also depends on the unit capacity and the volumetric efficiency as well as on the density of the intake air.The density of the air refers to the air drawn in by the engine and is calculated according to the absolute pressure and temperature, both measured in the intake manifold.Volumetric efficiency is the parameter that measures cylinder filling efficiency, measured on the basis of experiments conducted on the engine for the entire operating range and then stored in the electronic control unit memory.Having established the quantity of intake air, the system must provide the amount of fuel dictated by the desired mixture strength.The end of injection impulse or delivery timing is stored in a map in the control unit memory and varies according to the engine speed and the pressure in the intake manifold.In practice, it involves processing carried out by the electronic control unit to manage the timed, sequential opening of the four injectors, one per cylinder, for the length of time strictly necessary to make the air/petrol mixture as close as possible to the stoichiometric ratio.The fuel is injected directly into the manifold, near the inlet valves, at a pressure of around 3.5 bar.The speed (rpm) and the density of the air (pressure and temperature) are used for measuring the quantity of intake air which, when established, is used for metering the amount of fuel needed for 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 the engine operating conditions.It is vital for the air/fuel ratio to be close to the stoichiometric value for the correct and prolonged operation of the catalytic converter and for reducing pollutant emissions.

Ignition system

The ignition circuit is solid-state inductive discharge type, i.e. without an HT distributor, with power modules located inside the injection-ignition electronic control unit.The primary winding of each coil is connected to the power relay (thereby receiving battery voltage) and to the pins of the electronic control unit for earth connection.

After the starting stage, the electronic unit manages the basic advance taken from special maps in accordance with:

  • engine rpm
  • absolute pressure value (mmHg) measured in the intake manifold;
  • slider on-off position;
  • continuous variable valve timing control.
This advance setting is corrected according to the engine coolant temperature, intake air, detonation and throttle position.The spark plugs for the cylinders are connected directly to the coil secondary winding terminals (one per spark plug).

OPERATION

Diagram showing information entering/leaving the control unit

The information entering/leaving the control unit is illustrated in the diagram below.
1, Engine management control unit2, Battery3, Ignition switch4, Engine control system relay5, Electric fuel pump relay6, Fuel pump7, Radiator fan relay(s)8, Radiator fan9, Compressor engagement relay10, Compressor11, Ignition coils12, Spark plugs13, Injectors14, Canister scavenging solenoid valve15, Lambda sensor (pre-catalyser)16, Lambda sensor (post-catalyser)17, Coolant temperature sensor18, Detonation sensor19, Throttle control actuator and throttle position sensor20, Rpm and TDC sensor21, Injection timing sensor22, Air temperature/absolute pressure sensor23, Oil pressure switch24, Body computer:25, CODE control unit (via CAN)26, Diagnostic equipment connection (via CAN)27, Rev counter (via CAN)28, System failure lamp (via CAN)29, Speedometer (via CAN) and ABS control unit30, City button for power steering (via CAN)31, Slider on-off actuator32, Slider on-off position sensor33, Continuous phase transformer actuator34, Ambient pressure sensor

SELF-LEARNING

The control unit implements the self-learning logic under the following conditions:

  • removing-refitting or replacement of the injection control unit
  • removing-refitting or replacing the throttle casing
  • removing-refitting or replacing the continuous phase transformer
The values stored by the control unit are retained when the battery is disconnected.

SYSTEM SELF-ADJUSTMENT

The control unit 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 memorised 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 (owing to production tolerances).On the basis of exhaust gas analysis, the control unit modifies the basic map in relation to engine specifications when new.The self-adjustment parameters are not deleted if the battery is disconnected.

AUTODIAGNOSIS AND RECOVERY

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 standardised icon and colour, as 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 logic is as follows.The warning light comes on with the ignition on and remains on until the engine is started up; the control unit autodiagnostic system checks the signals coming from the sensors and compares them with the permitted data limits.

Fault indication during start up:

  • 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.

Fault indication during operation:

  • 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.
The control unit defines the recovery settings on each specific occasion according to which components are faulty.The recovery parameters are managed by non-faulty components.

SYSTEM CONTROLS AND MANAGEMENT

Fiat code recognition

The moment the control unit receives the MAR signal, it converses with the body computer to obtain the go-ahead for starting.The communication takes place via the two-way CAN line that connects the two control units.

Cold starting check

The following occurs in cold starting conditions:

  • a natural weakening of the mixture (which causes poor turbulence of the fuel particles at low temperatures)
  • reduced evaporation of the fuel
  • fuel condensation on inner walls of the intake manifold
  • higher lubrication oil viscosity.

The electronic control unit detects this condition and corrects the injection time on the basis of:

  • coolant temperature
  • intake air temperature
  • battery voltage
  • engine rpm.
The ignition advance is determined solely on the basis of rpm and coolant temperature.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 are all the same type and are located upstream of the catalytic conversion system and downstream of the converter.The pre-converter sensor controls 1st loop mixture strength (upstream sensor closed loop).The post-converter sensor is used for the fault diagnosis of the catalyser and for modulating the 1st loop control parameters.The second loop is therefore adaptive to make up for production discrepancies and slight drift that pre-catalyser sensor responses could experience due to ageing and contamination.This control is known as 2nd loop control (post-catalyser sensor closed loop).

Detonation control

The control unit detects the presence of detonation (engine knock) by processing the signal coming from the relevant sensor.The control unit continuously compares the signals coming from the sensor with a threshold which is, in turn, continually updated to take into account background noise and engine ageing.The control unit can therefore detect the presence of detonation (or the onset of detonation) in each individual cylinder and reduces the ignition advance in the cylinder involved (in steps of 3° up to a maximum of 6°) until the phenomenon 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 in order to take into account the increased noise of the engine under such circumstances.The detonation control logic also has a self-adjustment function which memorises the reductions in the advance that are continuously repeated in order to adapt the map to the different conditions that may affect the engine.

Enric

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