312000294 - INTRODUCTION - PETROL FUEL INJECTION SYSTEM
SPECIFICATIONS
GENERAL SPECIFICATIONS
The Bosch Motronic ME7.9.10 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 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;
- 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.
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;
OPERATION
Diagram showing information entering/leaving the control unit
The information entering/leaving the control unit is illustrated in the diagram below.
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
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.
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.
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-catalyser sensor is used for the fault diagnosis of the catalyser and for modulating the 1st loop control parameters.The second loop is therefore adaptive, in order 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.Enrichment during acceleration check
During this stage, the control unit increases the amount of fuel supplied to the engine (to produce the maximum torque), according to the signals coming from the following components:
- accelerator pedal potentiometer and throttle position.
- rpm and TDC sensor
Fuel supply - electric f
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