125000282 - INTRODUCTION - PETROL FUEL INJECTION SYSTEM

BOSCH M7.3.1 EOBD injection system

VIEW OF ASSEMBLY
1 - Fuel pump2 - Relays3 - Lambda sensors downstream of the catalytic converter4 - Lambda sensors upstream of the pre-catalyzer5 - Speedometer6 - Rev counter7 - Injection warning light8 - Injection/ignition control unit9 - Fuel vapour recirculation solenoid10 - Throttle body built into DVE11 - Climate control system connector12 - Tester connector13 - Alfa Romeo CODE connector14 - Air flow meter with air temperature sensor15 - Coolant temperature sensor16 - Dual brake pedal switch17 - Clutch pedal switch18 - Accelerator pedal potetiometer19 - RPM sensor20 - Knock sensor22 - Ignition coil23 - Timing sensor24 - Phase transformer25 - Injectors26 - Modular intake manifold solenoid

Construction specifications

Engine with 4 cylinders in line, dual ignition, 16 valves, twin overhead camshaft, electro-hydrauilc phase transformer, motorized throttle casing, with Bosch Motronic ME7.3.1EOBD electronic integrated injection/ignition system.

General specifications

The unit is a system made up of the engine and all circuits required for its operation:

  • fuel feed circuit
  • air intake circuit
  • engine cooling system
  • exhaust system with two pre-catalyzers connected to the exhaust manifold and a main catalyzer located under the body.
  • fuel vapour recirculation system.
The operation of these systems is optimised by an electronic control system governed by a control unit.

Operation of the injection/ignition system

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

  • ignition
  • phased sequential electronic injection.
The control unit controls the air flow rate at the idling speed set by the electronic throttle.The control unit controls the ignition time, with the benefit of maintaining smooth engine operation even when environmental and applied load parameters change.The control unit controls and manages the injection so that the air/fuel ratio is always close to the stoichiometric ratio to ensure maximum conversion efficiency for the catalyzers.

The main system functions are essentially as follows:

  • self-learning;
  • system self-adaptation;
  • self-diagnosis;
  • recognition of the Alfa Romeo CODE (immobilizer);
  • cold starting check control;
  • combustion - Lambda sensor control;
  • knock control;
  • control of enrichment during acceleration;
  • Fuel cut-off during over-run;
  • fuel vapour recovery;
  • control of maximum rpm;
  • fuel pump control;
  • connection with climate control system;
  • cylinder position recognition;
  • control of optimum injection time for each cylinder;
  • adjustment of ignition advance;
  • idle speed management (also dependent on battery voltage);
  • fan control;
  • connection to ABS control unit;
  • connection with the control panel;
  • torque management;
  • fuel system diagnostics;
  • catalytic converter diagnostics;
  • misfire diagnosis; detection of failed combustion
  • Lambda sensor diagnostics.
Torque control strategyThe drive-by-wire control systems are vital in satisfying the legal requirements such as fuel consumption and emissions as well as for improving the driveability of vehicles with petrol engines (starting, heating, transition response, safe driving, immobilizer, etc.).The torque for the most common petrol engines is mainly affected by the throttle valve which controls the mass of air drawn in by the engine (depending on the position of the accelerator pedal) and therefore also cylinder filling.In addition to this there are other parameters that affect the variation of the engine torque: the angle of ignition, the air/fuel (Lambda) ratio, the deactivation of the injection for several cylinders, similar to the increase in pressure in supercharged engines with turbochargers.Examples of other elements that affect torque are: the EGR, the adjustment of the camshaft and the switching of the intake manifold.Injection system

The essential conditions to be met by the air-fuel mixture for 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 levels to assure maximum catalytic converter conversion capacity (max. efficiency).
  • homogeneity of the mixture, consisting of petrol distributed throughout the air as finely and uniformly as possible.

Information that the control unit processes to control optimum metering is received by electrical signals emitted by:

  • air flow meter and air temperature sensor, for the exact quantity of air taken in
  • rpm sensor that generates an alternating single-phase signal whose frequency is an indicator of engine rpm. The control unit uses this signal to detect MISFIRE.
  • throttle potentiometer, to detect the required acceleration conditions
  • coolant temperature sensor on the thermostat
  • Lambda sensors to determine the oxygen content of the exhaust gases and, via the downstream sensor, to diagnose the efficiency of the catalyzers.
Ignition systemThe ignition system is static, inductive discharge type (i.e. without a HT distributor) with power modules located inside the injection control unit.The ignition system is arranged so that each coil supplies the spark plugs of the associated cylinder.

The advantages of this solution are:

  • lower electrical overload;
  • guaranteed constant discharge on each spark plug.
The control unit contains a memory map with a set of optimum ignition advance values (for the cylinder in combustion phase) that the engine can adopt according to the required speed and engine load.

The control unit corrects the advance value mainly on the basis of:

  • engine coolant temperature
  • intake air temperature
  • detonation
  • throttle valve position.

Information that the control unit processes to control the coils is received by electrical signals emitted by:

  • air flow meter and air temperature sensor, for the exact quantity of air taken in
  • rpm sensor that generates an alternating single-phase signal whose frequency is an indicator of engine rpm
  • detonation sensor (on the rear part of the crankcase between cylinders 2 and 3) to recognise the cylinder with knock and thus correct the ignition advance.
  • throttle position potentiometer to recognise minimum, partial and full load conditions.
  • timing sensor.

OPERATION

Diagram showing information entering/leaving the control unit
1 - Fuel pump2 - Air conditioning compressor3 - Fan4 - Lambda sensors downstream of the catalytic converter5 - Quadrinary6 - Brake pedal switch7 - Timing sensor8 - Speedometer9 - Lambda sensors upstream of the pre-catalyzers10 - Coolant temperature sensor11 - Knock sensor12 - RPM sensor13 - Accelerator pedal potetiometer14 - Air flow meter with air temperature sensor15 - Battery16 - Clutch pedal switch17 - Throttle body built into DVE18 - CAN line (for communication with ABS/ASR control units)19- Alfa Romeo CODE20 - Diagnotic socket21 - Fuel vapour recirculation solenoid22 - Ignition coil23 - Injection warning light24 - Modular intake manifold solenoid25 - Rev counter26 - Phase transformer27 - Injectors

Operating strategies

Self-learning

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

  • removing-refitting or replacement of the injection control unit
  • removal-refitting or replacement of the throttle body built into the DVE.
  • removal-refitting or replacement of the rpm sensor/phonic wheel for detection of misfiring.
The values stored by the control unit are maintained when the battery is disconnected.
System self-adjustmentThe 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 memorized 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 (due to production tolerances).The control unit modifies the basic map in relation to engine specifications when new on the basis of an exhaust gas analysis.The self-adjustment parameters are not deleted if the battery is disconnected.
Self-diagnosisThe 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 standardized ideogram and colour 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 (mil) strategy is as follows:

  • with the ignition on, the warning light comes on and remains on until the engine has been started up. The control unit self-diagnostic system checks the signals coming from the sensors comparing them with the permitted 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.
RECOVERYFrom time to time the control unit defines the type of recovery according to the components that are faulty.The recovery parameters are managed by components that are not faulty.
Recognition of the alfa romeo codeThe moment the NCM control unit receives the ignition ON signal it converses with the Body Computer Node (Alfa Romeo CODE) to obtain the go ahead for starting.This communication takes place via the dedicated two-way diagnostic serial line which connects the two control units.
Cold starting check

The following occurs in cold starting conditions:

  • a natural weakening of the mixture (low evaporation of the fuel at low temperatures)
  • 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.Whilst the engine is warming up, the control unit operates the idle speed actuator to regulate the quantity of air required to ensure that the engine does not cut out.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 checkIn EOBD systems, the Lambda sensors are all the same type and located upstream of the catalytic conversion system and downstream of the converter. The upstream sensors monitor concentration and are known as the 1st loop (closed loop of upstream sensor). The sensor downstream of the catalyzer is used for the fault diagnosis of the catalyzer and for modulating the 1st loop control parameters. The second loop is therefore adaptive to make up for production discrepancies and slight drift that upstream sensor responses could experience due to ageing and contamination. This control is known as 2nd loop control (downstream sensor closed loop).
Check on phase transformer and modular intake manifold

In order to ensure the optimum quantity of air introduced by the engine, the control unit controls:

  • the intake timing in two angular positions
  • the geometry of the intake manifolds in two lengths

The control unit sets the "open" stage at the maximum torque speed:

  • cam advance of 25° engine
  • intake chamber long ducts.

The control unit sets the "closed" stage at the maximum power speed:

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