3026087 - Introduction - PETROL INJECTION SYSTEM

BOSCH M7.3.1 EOBD injection system

VIEW OF ASSEMBLY
1 - Electric fuel pump 2 - Relays 3 - Lambda sensors downstream of catalyzer 4- Lambda sensors upstream of pre-catalyzer 5 - Speedometer 6 - Rev counter 7 - Injection warning light 8 - Injection/ignition control unit 9 - Fuel vapour recirculation solenoid valve 10 - Throttle body integral with D.V.E. 11 - Climate control connector 12 - Diagnostic connector 13 - Alfa Romeo CODE connector 14 - Air flow meter with air temperature sensor 15 - Coolant temperature sensor 16 - City (Selespeed version only) 17 - Brake pedal dual switch 18 - Clutch pedal switch 19 - Accelerator pedal potentiometer 20 - Rpm sensor 21 - Knock sensor 22 - Ignition coils 23 - Timing sensor 24 - Variable valve timing 25 - Injectors 26 - Modular intake manifold solenoid valve (excluding 1.6 version)

Construction features

Engine with 4 cylinders in line, twin spark ignition, 16 valves, twin overhead camshaft, electro-hydraulic variable valve timing (excluding 1.6 105 bhp version), counter-rotating balancer shafts (2.0 version), motorised throttle body, equipped with Bosch Motronic ME7.3.1 EOBD integrated electronic injection/ignition.

General characteristics

The unit comprises the engine and all the systems required for its operation:

  • fuel supply system
  • air supply system
  • engine cooling system
  • exhaust system with two pre-catalyzers, connected to the exhaust manifold, and one main catalyzer, positioned under the bodyshell.
  • fuel vapour recirculation system.
The operation of these systems is optimized by an electronic control system governed by a control unit. An understanding of the operating logic of the control unit gives an overall picture of the entire GROUP 10 system.

Operation of the injection/ignition system

The Bosch Motronic ME7.3.1 system with a motorized butterfly belongs to the category of integrated systems with:

  • ignition
  • sequential and phased electronic injection.
The control unit controls the air flow rate at the rotation speed set through the electronic throttle.The control unit controls the moment of ignition in order to keep the engine running smoothly as the ambient parameters and loads applied vary.The control unit controls and manages the injection so that the air/fuel ratio is always close to the stoichiometric value to maximize the conversion efficiency of the catalyzers.

The main operating principles of the system are basically as follows:

  • self-learning;
  • system self-adaptation;
  • autodiagnosis;
  • recognition of the Alfa Romeo CODE (Immobilizer);
  • control of cold starting;
  • control of combustion - Lambda sensors;
  • control of knock;
  • control of mixture enrichment during acceleration;
  • fuel cut-off with the accelerator pedal released;
  • fuel vapour recovery;
  • control of the maximum rpm;
  • control of the fuel pump;
  • connection to the climate control system
  • recognition of cylinder position;
  • control of the optimum injection time for each cylinder;
  • adjustment of ignition advance values;
  • management of the idle speed (also according to the battery voltage);
  • management of throttle opening laws (City mode - Selespeed version only);
  • control of the electric fans;
  • connection with ABS control unit;
  • connection with the gearbox control unit (Selespeed version only);
  • connection with the instrument panel;
  • torque management;
  • fuel system diagnosis;
  • catalyzer diagnosis;
  • misfire diagnosis; misfire detection
  • Lambda sensors diagnosis.
Torque control strategyThe drive by wire systems represent vital tools in satisfying legal requirements such as emissions and fuel consumption in addition to improvements in the driveability of vehicles with petrol engines (starting, heating, transition response, driving safety, immobilizer, etc.).The torque for most common petrol engines is mainly affected by the throttle valve which controls the mass of air drawn in by the engine (according to the position of the accelerator pedal) and therefore also the refilling of the cylinder.In addition to this there are also other parameters which affect the variation of the engine torque: the ignition angle, the air/fuel ratio (Lambda), the deactivation of the injection in certain cylinders, likewise the control of the increase in pressure in engines with turbochargers.Examples of other elements which affect torque are: the EGR, the adjustment of the camshaft and the switching of the intake manifold.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) should constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the maximum conversion capacity for the catalytic converter (max. efficiency).
  • the 'homogeneity' of the mixture, consisting of petrol, diffused as finely and evenly as possible in the air.

The information processed by the control unit for controlling optimum metering is received in the form of electrical signals emitted by:

  • air flow meter and air temperature sensor, for the exact quantity of air drawn in
  • rpm sensor which produces an alternating, single-phase signal whose frequency indicates the engine rpm. This signal is used by the control unit to detect misfire
  • throttle potentiometer, to recognize the acceleration conditions requested
  • coolant temperature sensor located on the thermostat
  • Lambda sensors to determine the oxygen content of the exhaust gases and, through the downstream sensor, to diagnose the efficiency of the catalyzers.
Ignition systemThe ignition is of the inductive discharge type, distributorless, with power modules located in the fuel injection control unit.In the ignition system each coil supplies the spark plugs for the appropriate cylinder.

The advantages of this solution are:

  • less electrical overload;
  • guarantee of constant discharge at each spark plug.
Stored in the control unit, there is a map containing the entire set of optimum ignition advance values (for the cylinder at the power stroke) that the engine can adopt in relation to the rpm and required engine load.

The control unit corrects the advance values mainly in accordance with:

  • engine coolant temperature
  • intake air temperature
  • knock
  • throttle valve position

The information which the control unit processes to operate the ignition coils is received by means of electrical signals emitted by the:

  • air flow meter and air temperature sensor, for the exact quantity of air drawn in
  • rpm sensor, which generates an alternating single-phase signal whose frequency indicates the engine rpm
  • knock sensor (on the rear of the engine block between the 2nd and 3rd cylinders) which recognizes which cylinder is knocking and corrects its ignition advance
  • throttle position potentiometer, to recognize minimum, partial opening and full load conditions
  • timing sensor.

OPERATION

Diagram of input/output info to/from control unit
1 - Electric fuel pump 2 - Air conditioner compressor 3 - Electric fan 4 - Lambda sensor downstream of catalyzer 5 - City (Selespeed version only) 6 - Quadrinary 7 - Brake pedal switch 8 - Timing sensor 9 - Speedometer 10 - Lambda sensors upstream of pre-catalyzers 11 - Coolant temperature sensor 12 - Knock sensor 13 - Rpm sensor 14 - Accelerator pedal potentiometer 15 - Air flow meter with air temperature sensor 16 - Battery 17 - Clutch pedal switch 18 - Throttle body integrated with D.V.E. 19 - CAN line (for communication with ABS/ASR and automatic transmission control units Selespeed version only) 20 - Alfa Romeo CODE 21- Diagnostic socket 22 - Fuel vapour recirculation solenoid valve 23 - Ignition coils 24 - Injection warning light 25, Modular intake manifold solenoid valve (2.0 only) 26 - Rev counter 27 - Variable valve timing 28 - Injectors

Operating strategies

Self-learning

The control unit implements the self-learning mode in the following conditions:

  • removing-refitting or replacement of the injection control unit
  • removing-refitting or replacement of the throttle body integrated with D.V.E.
  • removing-refitting or replacement of the rpm sensor/flywheel, for recognizing misfire.
The values memorized by the control unit are preserved if the battery is disconnected.
System self-adaptionThe control unit has a self-adaption 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-testingThe control unit autodiagnostic system controls the correct operation of the system and signals any faults by means of an (MIL) warning light in the instrument panel which has a standardized European colour and ideogram. This warning light signals both engine management faults and problems detected by the EOBD strategies.

The (MIL) warning light operating logic is as follows:

  • with the ignition key in the ON position, the warning light comes on and remains on until the engine has been started up. The control unit's self-test system checks the signals coming from the sensors, comparing them with the permitted limits:

Signalling of faults during engine starting:

  • the failure of the warning light to go out once the engine has been started up means that there is an error memorized in the control unit.

Fault indication during operation

  • the warning light flashing indicates possible damage to the catalyzer due to misfire.
  • the warning light on constantly indicates the presence of engine management errors or EOBD errors.
RECOVERYFrom time to time, the control unit defines the type of recovery according to the components which are faulty.The recovery parameters are managed by those components which are not faulty.
Recognition of the alfa romeo codeWhen the NCM control unit receives the ignition 'ON' signal, it communicates with the Body Computer (Alfa Romeo CODE function) to obtain starting enablement.Communication takes place via the dedicated bidirectional serial diagnostic line which connects the two control units.
Control of cold starting

The following occurs during cold starting:

  • a natural weakening of the mixture because of the poor evaporation of the fuel at low temperatures
  • condensation of the fuel on the inner walls of the inlet manifold
  • increased viscosity of the lubricant oil.

The electronic control unit recognizes this condition and corrects the fuel injection time in accordance with:

  • coolant temperature
  • intake air temperature
  • battery voltage
  • engine rpm.
The ignition advance depends solely on the engine rpm and the coolant temperature.Whilst the engine is warming up, the electronic control unit operates the idle speed actuator, which determines the quantity of air required to guarantee that the engine speed is sustained.The rpm is made to decrease in proportion to the increase in temperature of the engine until the optimum value with the engine up to temperature is obtained.
Check on combustion - lambda sensorsIn EOBD systems the Lambda sensors, which are all the same type, are located upstream of the catalyzer 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).
Check on variable valve timing and modular inlet manifold

To optimize the quantity of air drawn in by the engine, the control unit checks:

  • intake timing at two angl
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