3239194 - Introduction - ENGINE

GLOSSARY

GLOSSARY

CONSTRUCTION FEATURES

6 cylinder engine in a 60° V formation, 3179 c.c., static advance ignition with a twin overhead camshaft for each cylinder head, hydraulic tappets, 4 valves per cylinder, Bosch Motronic ME2.1 integrated injection/ignition system.

View of engine compartment

. 1 - Engine coolant reservoir 2 - Air chamber 3 - Injection - ignition control unit 4 - Power steering fluid reservoir 5 - Throttle body integrated with D.V.L. 6 - Brake - clutch fluid reservoir 7 - Battery 8 - Fuel injectors 9 - Fuel manifold pipe

General characteristics

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

• fuel system;
• air supply system;
• engine cooling system;
• exhaust system;
• 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 idle rotation speed set by the electronic throttle.The control unit controls the moment of ignition with the advantage of keeping the engine running smoothly as the ambient parameters and loads applied vary.The control unit controls and manages fuel injection so that the stoichiometric ratio (air/fuel) is always at the optimum value.

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

• self-learning;
• sytem 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 with 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);
• control of the electric fans;
• connection with ABS/ASR control unit;
• connection with the automatic transmission control unit (where fitted);
• connection with the instrument panel;
• fuel system diagnosis;
• catalyzer diagnosis;
• detection of misfire;
• Lambda sensors diagnosis.

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 intake air;
• rpm sensor which produces an alternating, single-phase signal whose frequency indicates the engine rpm;
• accelerator pedal with throttle potentiometer, to recognize the driver conditions requested;
• – coolant temperature sensor on the thermostat;

- Lambda probes for determining the oxygen content in the exhaust gases.Ignition systemThe ignition is of the inductive discharge type, static advance type (i.e. without a high tension distributor) with power modules located in the fuel injection control unit.

The system has a single coil for each plug (MONOCOIL); 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;
• detonation.

The information the control unit processes in order to drive the single coils is received in the form of electrical signals emitted by:

• air flow meter and air temperature sensor, for the exact quantity of intake air;
• rpm sensor which produces an alternating, single-phase signal whose frequency indicates the engine rpm;
• detonation sensors (on the upper part of the cylinder block/crankcase between the two heads) to recognize the cylinder where detonation is occurring and correct the ignition advance;
• throttle potentiometer, to recognize the minimum, partial and full load conditions;
• timing sensor.

The control unit uses the rpm signal to recognize any misfire which could damage the catalyzers.

OPERATION

Diagram of input/output info to/from control unit 1 - Electric fuel pump 2 - Air conditioner compressor 3 - Electric fan 4 - Lambda sensors upstream of the catalytic preconverters 5 - Quadrinary 6 - Brake - clutch pedal switch 7 - Timing sensor 8 - Speedometer 9 - Lambda sensors downstream of the catalytic converters 10 - Coolant temperature sensor 11 - Detonation sensors 12 - Rpm sensor 13 - Accelerator pedal with integrated potentiometer 14 - Air flow meter with air temperature sensor 15 - Battery 16 - Throttle body integral with D.V.L.; 17 - CAN line ( for communication with ABS/ASR control units and automatic transmission) 18 - Alfa Romeo CODE 19 - Diagnostic socket 20 - Fuel vapour recirculation solenoid 21 - Ignition coils 22 - Engine Check warning light 23 - Rev counter 24 - Fuel injectors

System operating modes

Self-learning

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

• installation of new injection control unit,
• installation of a new throttle body actuator integratd with D.V.L.
• removing/refitting or replacement of rpm sensor/phonic wheel, for recognizing misfire.

The learnt values of the throttle body integrated with D.V.L. are preserved if the battery is disconnected.The learnt values of the phonic wheel for recognizing misfire are instead lost.System self-adaptationThe 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.There are two adaptation functions according to two intervention plans: minimum and usage.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 checks the signals coming from the sensors, comparing them with the permitted limits:

Indication of starting faults:

• the failure of the warning light to go out after 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 catalytic converter due to misfire.
• if the warning light comes on constantly, it indicates the presence of engine management errors or EOBD RECOVERY diagnosis 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 control unit receives the ignition 'ON' signal, it communicates with the Alfa Romeo CODE control unit to obtain starting enablement.Check on cold starting

In cold starting conditions there is a natural weakening of the mixture which causes 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.During starting, the control unit controls a first simultaneous injection for all the injectors (full-group injection) and, after recognizing the timing of the cylinders, it starts normal sequential phased operation.Whilst the engine is warming up, the control unit operates the butterfly casing integrated with D.V.L. to regulate the quantity of air required to ensure that the engine does not cut out.The rotation speed decreases as the engine temperature increases until the normal value is reached with the engine at operating temperature.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 sensors closed loop). The sensors downstream of the catalyzer are 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 sensors closed loop).Knock control

The control unit can delay the ignition selectively at the cylinder required, according to the combination of figures received from the detonation and timing sensors and:

• reduces the ignition advance in steps of 3° up to a maximum of 9°
• updates the level to take into account background noise and ageing of the engine.

During acceleration, the control unit uses a higher threshold for the increased engine noise.When the detonation disappears, the control unit increases the ignition advance in steps of 0.75° ??t?? ?t ?s ??µp?ete?? ?e???e?ed.

With the auto-adjustment function, the control unit:

• memorizes the various advance reductions, continuously repeated;
• adapts the map to the different engine conditions.

RECOVERYIn the case of fault with the timing sensor or the detonation sensor or the injection control unit, the ignition is delayed according to the engine temperature and speed. The maximum ignition delay is always below 9° engine.Control of the mixture enrichment during accelerationWhen there is a considerable acceleration request, the control unit modifies the injection time and the position of the butterfly.RECOVERYThe control unit replaces the signal coming from the faulty air flow meter with a signal from the potentiometer built into the throttle body actuator.Fuel cut-off with the accelerator pedal released

The control unit with:

• recognition of idle condition;
• engine speed above a certain threshold;

de-activates the fuel injection according to the:

• engine rpm;
• engine temperature;
• vehicle speed.

Before reaching the idle condition, the dynamics of the engine speed decrease are checked. If they exceed a certain value, the fuel supply is partly reactivated on the basis of a logic which makes provision for the 'gentle accompaniment' of the engine whilst idling.Having reached the idle condition, the normal functions are restored.Fuel vapour recoveryThe (polluting) fuel vapours, collected in an activated-charcoal filter (canister), are sent to the inlet ducts to be burnt.This is achieved by a solenoid controlled by the control unit which alternates phases when it is open (canister scrubbing phase) with phases when it is closed (carburation factors learning phase).During the open phases, the solenoid opening duty cycle is regulated by the

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