Introduction - PETROL INJECTION SYSTEM

1.6 TS

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 strategy

The 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 system

The 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-adaption

The 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-testing

The 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.

RECOVERY

From 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 code

When 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 sensors

In 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 angle positions (excluding 1.6 103 bhp versions)
• geometry of inlet ducts at two lengths (excluding 1.6 version)

At the maximum torque speed, the control unit sets the 'open' phase:

• cam advanced by 25° engine
• inlet box long ducts

At the maximum power speed, the control unit sets the 'closed' phase:

• cam in normal position
• inlet box short ducts.

At idle speed, the control unit sets the 'closed' phase:

• cam in normal position
• inlet box short ducts.

In the other engine operating conditions, the control unit selects the most suitable configuration to optimize performance - consumption - emissions.

During overrunning, the inlet ducts of the box are always 'short'.

The 1.6 T.Spark 120 bhp engine does not have a variable geometry manifold.

Knock control

The control unit detects the presence of knocking by processing the signal coming from the relevant sensor.

The control unit continuously compares the signals coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.

The control unit is therefore capable of detecting the presence of detonation (or the onset of detonation) in each individual cylinder and reduces the ignition advance for the cylinder concerned (in steps of 3 degrees up to a maximum of 6 degrees) until the phenomenon disappears. The advance is then gradually restored to the basic value (in steps of 0.8 degrees).

Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.

The knock control strategy also has a self-adaptation function, which memorizes the reductions in advance that may be repeated continuously, so as to adjust the mapping to the different conditions now affecting the engine.

Control of enrichment during acceleration

If during the acceleration demand, the variation in the air flow meter signal exceeds a predefined increment, the control unit increases the fuel injection time to compensate for the variation in the mixture ratio due to the increased pressure in the intake manifold (reduced fuel vaporation) so that the required rpm is reached rapidly.

RECOVERY

The control unit replaces the signal coming from the faulty air flow meter with the signal from the throttle valve potentiometer.

Fuel cut-off during over-run

During release of the accelerator pedal, and beyond a pre-established threshold, the control unit:

• cuts off the supply to the fuel injectors
• reactivates the supply to the fuel injectors at 1300-1500 rpm.

As there is no fuel supply, the rpm decreases more or less rapidly depending on the vehicle's driving conditions.

Before idle speed is reached, the trend of the fall in rpm is checked.

If it exceeds a certain value, the fuel supply is partially reactivated so that the engine can 'gently accompany' the drop towards idle speed.

The thresholds for reactivation of the fuel supply and for fuel cut-off vary depending on:

• engine coolant temperature
• vehicle speed
• engine rpm

Fuel vapour recovery

The (polluting) fuel vapours, collected in an activated-charcoal filter (canister), are sent to the inlet ducts to be burnt.

This takes place via a solenoid controlled by the control unit only when the engine's operating conditions so permit.

The control unit compensates for the additional quantity of fuel by reducing the delivery to the fuel injectors.

Control of the maximum rpm

Depending on the rpm reached by the engine, the control unit:

• over 6800 rpm cuts off the supply to the injectors (it is permitted to reach a maximum of 7200 rpm for a maximum of 3 secs).
• under 6800 rpm resumes driving of the fuel injectors.

Check on fuel-electric fuel pump supply

The control unit supplies the fuel pump:

• with the ignition key ON for 0.2 seconds
• with the ignition in the START position and the engine speed > 22.8 rpm

The control unit cuts off the supply to the fuel pump:

• with ignition in OFF position
• with engine speed < 22.8 rpm.

The returnless fuel supply system ensures a constant petrol pressure of 3.5 bar.

Connection to the climate control system

When the compressor is switched on and power is required, the control unit adjusts the air flow rate ensuring that optimum driveability is maintained.

The control unit momentarily interrupts the supply to the compressor:

• during starting
• by switching it off over 6200 rpm
• by switching it off if the engine temperature > 112° C.
• during pick-up with accelerator fully depressed.

Recognition of cylinder position

During each engine revolution, the control unit recognizes which cylinder is at the power stroke:

• it operates the injection and ignition sequence at the appropriate cylinder.

In the absence of the timing sensor signal, the control unit:

• deactivates the detonation sensor
• with the car moving, maintains phased injection
• when the engine is started, the engne management node controls the relevant coils individually. The coils then control both spark plugs on each cylinder individually.

Regulation of fuel injection times

The control unit calculates the injector opening times and controls them extremely quickly and precisely on the basis of:

• engine load (rpm and air flow)
• battery voltage
• engine coolant temperature;

Fuel injection is sequential and phased for each cylinder, and takes place at the optimum 'start-of-injection' point, while the 'end-of-injection' point remains fixed.

Adjustment of ignition advance values

Thanks to the mapping stored in its memory, the control unit can calculate the ignition advance in accordance with:

• engine load (idling, choke, full load depending on the rpm and air flow)
• intake air temperature
• engine coolant temperature

If necessary, ignition can be selectively delayed on any cylinder. This cylinder is identified through a combination of values recorded by the rpm and timing sensors.

Control of the idle speed

The control unit recognizes the idle condition by the accelerator pedal being in the 'released' position.

The control unit controls the position of the motorized throttle to control the idle speed according to the consumers switched on and the brake - clutch pedal signals.

Idling speed when warm is 840 ± 50 rpm.

Throttle opening management - city (selespeed version)

The control unit processes the signals coming from the:

• selespeed transmission control unit
• accelerator pedal potentiometer

for the management of the butterfly in the following modes:

• City for good handling and a comfortable ride.
• normal for sporty driving.

The system switches from City to Normal with:

• City key pressed and accelerator pedal fully released
• automatically after selecting a speed manually and releasing the accelerator pedal.

Activation of the function is indicated by a special LED on the control panel

Electric engine cooling fan check

The control unit controls the switching on of the electric fan in accordance with the coolant temperature:

• temperature for switching on 1st speed 95° C
• temperature for switching on 2nd speed 102° C

There is a further check (4 stage pressure switch signal) which engages the 1st or 2nd fan speed, according to the pressure of the refrigerant gas, with the air conditioning system switched on.

In the absence of the coolant temperature signal, the control unit activates the recovery function and switches on the fan 2nd speed until the error disappears.

Connection with the gearbox control unit (selespeed version)

Communcation between the engine control unit and the automatic transnmission control unit takes place via the CAN line available on both control units.

In the case of a gear shift (indicated by the transmission control unit), the injection control unit reduces drive torque by:

• a reduction in the ignition advances.
• reducing the throttle opening angle.

Recovery: if the CAN line is faulty, the injection control unit does not carry out the torque reduction requested by the transmission.

The transmission control unit implements a special recovery strategy.

Me7.3.1 injection/ignition control unit

The control unit is mounted in the engine bay over the throttle body and withstands high temperatures.

The control unit memory is the 'flash EPROM type, i.e. reprogrammable from the outside without intervening on the hardware.

The adoption of the Alfa Romeo CODE (immobiliser) does not allow control units to be exchanged between vehicles.

Replacement of the injection control unit, air capacity case or the throttle body integral with the D.V.E. means that the self-learning procedure has to be carried out.

PINS

A1 - Not connected

A2 - Not connected

A3 - Alfa Romeo CODE connection

A4 - Not connected

A5 - Not connected

A6 - Compressor engagement request

A7 - Power supply for accelerator pedal potentiometer

A8 - Signal for potentiometer - 1 accelerator pedal

A9 - Quadrinary - Fan 1st speed request

A10 - Cruise Control ON/OFF

A11 - Not connected

A12 - CAN-L line

A13 - Compressor relay control

A14 - Not connected

A15 - Direct supply

A16 - Supply controlled by ignition, via main relay

A17 - Not connected

A18 - Cruise Control warning light

A19 - T.MOT warning light

A20 - Preparation for Flash Programming

A21 - Not connected

A22 - Fuel level sensor

A23 - Not connected

A24 - Earth for potentiometer - 1 accelerator pedal

A25 - Earth for potentiometer - 2 accelerator pedal

A26 - Brake lights switch

A27 - Brake lights switch

A28 - SPORT function switch

A29 - CAN-H line

A30 - Fuel pump relay feed

A31 - Main relay activation

A32 - Supply controlled by ignition, via main relay

A33 - Not connected

A34 - Not connected

A35 - Rev counter signal

A36 - Not connected

A37 - Not connected

A38 - Not connected

A39 - Not connected

A40 - Signal for potentiometer - 2 accelerator pedal

A41 - Quadrinary - fan 2nd speed request

A42 - Cruise Control Resume

A43 - Cruise Control SET +

A44 - Speedometer sensor signal

A45 - CAN-H line

A46 - Injection warning light

A47 - Supply controlled by ignition

A48 - Supply controlled by ignition, via main relay

A49 - Not connected

A50 - Operation of fan 1st speed

A51 - Not connected

A52 - Fuel consumption signal

A53 - Diagnostic connection (K line)

A54 - Air temperature sensor signal

A55 - Not connected

A56 - Supply for accelerator pedal potentiometer

A57 - Air flow meter signal

A58 - Cruise Control SET -

A59 - Clutch pedal switch

A60 - Oil pressure switch

A61 - CAN-L line

A62 - Operation of fan 2nd speed

A63 - Air flow meter supply

A64 - Not connected

B1 - Throttle casing motor earth

B2 - Lambda sensor heating (pre-cat. left)

B3 - Operation of injector for cyl. 4

B4 - Variable geometry solenoid valve operation

B5 - Fuel vapour recovery solenoid control

B6 - Detonation sensor 2 reference earth

B7 - Lambda sensor earth (pre-cat. left)

B8 - Not connected

B9 - Not connected

B10 - Engine rpm sensor

B11 - Not connected

B12 - Not connected

B13 - Not connected

B14 - Cylinder 4 coil operation

B15 - Not connected

B16 - Cylinder 1 coil operation

B17 - Throttle casing motor supply

B18 - Not connected

B19 - Operation of injector for cyl. 1

B20 - Not connected

B21 - Not connected

B22 - Knock sensor 1

B23 - Lambda sensor signal (pre-cat. right)

B24 - Potentiometer - 1 throttle body

B25 - Engine coolant temperature

B26 - Sensors reference earth

B27 - Not connected

B28 - Lambda sensor signal (post-cat.)

B29 - Not connected

B30 - Cylinder 3 coil operation

B31 - Cylinder 2 coil operation

B32 - Not connected

B33 - Throttle casing motor earth

B34 - Lambda sensor heater (pre-cat. right)

B35 - Operation of injector for cyl. 3

B36 - Variable valve timing operation

B37 - Not connected

B38 - Not connected

B39 - Lambda sensor signal (pre-cat. left)

B40 - Potentiometer - 2 throttle body

B41 - Not connected

B42 - Timing sensor signal

B43 - Not connected

B44 - Not connected

B45 - Not connected

B46 - Not connected

B47 - Not connected

B48 - Not connected

B49 - Throttle casing motor supply

B50 - Lambda sensor heater (post-cat.)

B51 - Timing sensor power supply

B52 - Operation of injector for cyl. 2

B53 - Not connected

B54 - Knock sensor 1 reference earth

B55 - Lambda sensor earth (pre-cat. right)

B56 - Not connected

B57 - Not connected

B58 - Throttle casing potentiometers supply

B59 - Engine rpm sensor

B60 - Lambda sensor earth (post-cat.)

B61 - Not connected

B62 - Not connected

B63 - Not connected

B64 - Not connected

Injectors

The double-jet fuel injectors are installed on the distribution manifold.

A retainer secures the fuel injectors to the distribution manifold, and two O-rings ensure the seal.

The fuel injectors are responsible for delivering the necessary quantity of fuel to the engine.

They are 'all or nothing' devices, as they can remain in only two stable states, i.e. open or closed. They allow fuel to pass when they are open, while they block delivery when they are closed.

Engine coolant temperature sensor

It is fitted on the thermostatic cup and measures the temperature of the coolant by means of an NTC thermistor which has a negative resistance coefficient.

The sensor is produced using semiconductor technology, so if the temperature of the sensor increases as the temperature of the coolant increases, the resistance decreases.

As the variation in resistance is not linear, for the same temperature increment, it is higher for low temperatures than for high temperatures.

Knock sensor

The piezoelectric type detonation sensor is fitted on the cylinder block/crankcase and detects the intensity of the vibrations caused by the detonation in the combustion chambers.

The piezoelectric crystal forming the sensor detects the vibrations generated at a frequency of between 12 and 16 kHz, and transforms them into electrical signals sent to the fuel injection control unit.

Rpm sensor

It is fitted on the engine block, where it faces the phonic wheel located on the crankshaft.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the teeth of the phonic wheel (60-2 teeth).

The fuel injection control unit uses the rpm sensor to:

• determine the speed of rotation
• determine the angle of the crankshaft.

Operation

The passage from full to empty, due to the presence or absence of the tooth, causes a variation in the magnetic flow which is sufficient to generate an induced alternating voltage, resulting from the count of teeth located on a ring (or phonic wheel).

The frequency and range of the voltage sent to the electronic control unit provides it with the angular speed of the crankshaft.

1 - Brass bush

2 - Permanent magnet

3 - Plastic sensor casing

4 - Coil winding

5 - Polar core

6 - Ring gear or flywheel

7 - Coaxial two-wire cable or electrical connection

The distance (gap) for obtaining correct signals, between the end of the sensor and the flywheel, should be between 0.8 and 1.5 mm.

This gap is not adjustable, so if a value outside the tolerance range is measured, check the condition of the sensor and the phonic wheel.

1 - Maximum magnetic flow

2 - Minimum magnetic flow

3 - Induced alternating voltage trend

Timing sensor

Hall effect; it is mounted on the cylinder head and 'facing' the exhaust camshaft pulley.

The fuel injection control unit uses the timing sensor's signal to find out the TDC at the end of compression.

Accelerator pedal potentiometer

The accelerator pedal is fitted with two integrated potentiometers:

• one main one
• one safety one.

The injection control unit implements the following 'recovery' strategies

• if there is a fault with one of the two potentiometers, a throttle opening of up to 40° is allowed for a long period
• if both of the potentiometers fail completely, the throttle opening is excluded.

Operation

The sensor consists of a casing (1), fixed to the pedals by a flange, which contains a shaft (2), in an axial position, connected to the twin track potentiometer (3).

There is a coil spring on the shaft which guarantees the correct resistance to the pressure whilst a second spring ensures the return on release.

Operating range from 0° to 70°; mechanical stop at 88°.

Throttle body integral with d.v.e.

It is fitted on the inlet chamber and regulates the quantity of air drawn in by the engine.

According to the signal coming from the accelerator pedal potentiometer, the injection control unit controls the opening of the throttle by means of a direct current motor integrated in the throttle body integrated with D.V.L.

The throttle opening takes place between 0° and 80° therefore including the idle adjustment.

The throttle body integral with D.V.E. is equipped with two potentiometers integrated so that one controls the other and viceversa.

If both the potentiometers fail or there is no supply, the control unit reduces the engine torque according to the position of the accelerator pedal:

• fully depressed, it cuts off the supply to one or more pistons, until a maximum speed of 2500 rpm is reached.
• in intermediate positions, it cuts off the supply to one or more pistons, until a speed below 1200 rpm is reached.

If the throttle body integrated with D.V.E. or the injection control unit or the air chamber is replaced then the self-learning procedure must be carried out.

Air flow meter

The flow meter is located on the air inlet duct and is of the 'hot film' type.

The intake air temperature sensor is built into the flow meter.

The air flow meter cannot be dismantled.

1 - Covers

2 - Electronic card

3 - Sensor

4 - Support plate

5 - Support

6 - O-ring

7 - Temperature sensor

Operation

The operating principle is based on a heated diaphragm located in a measuring duct through which the intake air entering the engine flows.

The hot film diaphragm is kept at a constant temperature (about 120 ° C above the temperature of the incoming air) by the heating resistor.

The air mass passing through the measuring duct tends to draw heat from the diaphragm, so to keep the latter at a constant temperature, some current must flow through the resistor.

This current is measured by a suitable Wheatstone bridge.

The current is therefore proportional to the mass of flowing air.

The flow meter directly measures the air mass (not volume), thus eliminating problems of temperature, altitude, pressure, etc.

2.0 TS

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 strategy

The 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 system

The ignition is the inductive discharge type, (i.e. without a high tension distributor) 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.

OPERATING

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 logics

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-adaptation

The 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-diagnosis

The 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.

RECOVERY

From 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 code

When 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 probe

In 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:

• inlet timing at two angle positions
• geometry of inlet ducts over two lengths.

At the maximum torque speed, the control unit sets the 'open' phase:

• cam advanced by 25° engine
• inlet box long ducts

At the maximum power speed, the control unit sets the 'closed' phase:

• cam in normal position
• inlet box short ducts.

A idle speed, the control unit sets the 'closed' phase:

• cam in normal position
• inlet box short ducts.

In the other engine operating conditions, the control unit selects the most suitable configuration to optimize performance - consumption - emissions.

During overrunning, the inlet ducts of the box are always 'short'.

The 1.6 T.Spark 120 bhp engine does not have a variable geometry manifold.

Check on knocking

The control unit detects the presence of knocking by processing the signal coming from the relevant sensor.

The control unit continuously compares the signals coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.

The control unit is therefore capable of detecting the presence of detonation (or the onset of detonation) in each individual cylinder and reduces the ignition advance for the cylinder concerned (in steps of 3 degrees up to a maximum of 6 degrees) until the phenomenon disappears. The advance is then gradually restored to the basic value (in steps of 0.8 degrees).

Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.

The knock control strategy also has a self-adaptation function, which memorizes the reductions in advance that may be repeated continuously, so as to adjust the mapping to the different conditions now affecting the engine.

Check on enrichment during acceleration

If during the acceleration demand, the variation in the air flow meter signal exceeds a predefined increment, the control unit increases the fuel injection time to compensate for the variation in the mixture ratio due to the increased pressure in the intake manifold (reduced fuel vaporation) so that the required rpm is reached rapidly.

RECOVERY

The control unit replaces the signal coming from the faulty air flow meter with the signal from the throttle valve potentiometer.

Fuel cut-off during over-run

During release of the accelerator pedal, and beyond a pre-established threshold, the control unit:

• cuts off the supply to the fuel injectors
• reactivates the supply to the fuel injectors at 1300-1500 rpm.

As there is no fuel supply, the rpm decreases more or less rapidly depending on the vehicle's driving conditions.

Before idle speed is reached, the trend of the fall in rpm is checked.

If it exceeds a certain value, the fuel supply is partially reactivated so that the engine can 'gently accompany' the drop towards idle speed.

The thresholds for reactivation of the fuel supply and for fuel cut-off vary depending on:

• engine coolant temperature
• vehicle speed
• engine rpm

Fuel vapour recovery

The (polluting) fuel vapours, collected in an activated-charcoal filter (canister), are sent to the inlet ducts to be burnt.

This takes place via a solenoid controlled by the control unit only when the engine's operating conditions so permit.

The control unit compensates for the additional quantity of fuel by reducing the delivery to the fuel injectors.

Control of the maximum rpm

Depending on the rpm reached by the engine, the control unit:

• over 6800 rpm cuts off the supply to the injectors (it is permitted to reach a maximum of 7200 rpm for a maximum of 3 secs).
• under 6800 rpm resumes driving of the fuel injectors.

Check on fuel-electric fuel pump supply

The control unit supplies the electric pump:

• with the ignition key ON for 0.2 seconds
• with the ignition in the START position and the engine speed > 22.8 rpm

The control unit cuts off the supply to the electric pump:

• with ignition in OFF position
• with engine speed < 22.8 rpm.

The returnless fuel supply system ensures a constant petrol pressure of 3.5 bar.

Connection with climate control system

When the compressor is switched on and power is required, the control unit adjusts the air flow rate ensuring that optimum driveability is maintained.

The control unit momentarily interrupts the supply to the compressor:

• during starting
• by switching it off over 6200 rpm
• by switching it off if the engine temperature > 112° C.
• during pick-up with accelerator fully depressed.

Recognition of cylinder position

During each engine revolution, the control unit recognizes which cylinder is at the power stroke:

• it operates the injection and ignition sequence at the appropriate cylinder.

In the absence of the timing sensor signal, the control unit:

• deactivates the detonation sensor
• with the car moving, maintains phased injection
• with the engine started, the engine management node controls the relevant coils individually. The coils then control both spark plugs of each cylinder simultaneously.

Regulation of fuel injection times

The control unit calculates the injector opening times and controls them extremely quickly and precisely on the basis of:

• engine load (rpm and air flow)
• battery voltage
• engine coolant temperature;

Fuel injection is sequential and phased for each cylinder, and takes place at the optimum 'start-of-injection' point, while the 'end-of-injection' point remains fixed.

Adjustment of ignition advance values

Thanks to the mapping stored in its memory, the control unit can calculate the ignition advance in accordance with:

• engine load (idling, choke, full load depending on the rpm and air flow)
• intake air temperature
• engine coolant temperature.

The ignition can be selectively delayed at whichever cylinder requires it, by combining the values recorded by the rpm and timing sensors.

Control of the idle speed

The control unit recognizes the idle condition from the accelerator pedal being in the 'released' position.

The control unit controls the position of the motorized throttle to control the idle speed according to the consumers switched on and the brake - clutch pedal signals.

Idling speed when warm is 840 ± 50 rpm.

Throttle opening management - city (selespeed version)

The control unit processes the signals coming from the:

• selespeed transmission control unit
• accelerator pedal potentiometer

for the management of the butterfly in the following modes:

• City for good handling and a comfortable ride.
• normal for sporty driving.

The system switches from City to Normal with:

• City key pressed and accelerator pedal fully released
• automatically after selecting a speed manually and releasing the accelerator pedal.

Activation of the function is indicated by a special LED on the control panel.

Electric engine cooling fan check

The control unit controls the switching on of the electric fan in accordance with the coolant temperature:

• temperature for switching on 1st speed 95° C
• temperature for switching on 2nd speed 102° C

There is a further check (4 stage pressure switch signal) which engages the 1st or 2nd fan speed, according to the pressure of the refrigerant gas, with the air conditioning system switched on.

In the absence of the coolant temperature signal, the control unit activates the recovery function and switches on the fan 2nd speed until the error disappears.

Connection with the gearbox control unit (selespeed version)

Communcation between the engine control unit and the automatic transnmission control unit takes place via the CAN line available on both control units.

In the case of a gear shift (indicated by the transmission control unit), the injection control unit reduces drive torque by:

• a reduction in the ignition advances.
• reducing the throttle opening angle.

Recovery: if the CAN line is faulty, the injection control unit does not carry out the torque reduction requested by the transmission.

The transmission control unit implements a special recovery strategy.

Me7.3.1 injection/ignition control unit

The control unit is mounted in the engine bay over the throttle body and withstands high temperatures.

The control unit memory is the 'flash EPROM type, i.e. reprogrammable from the outside without intervening on the hardware.

The adoption of the Alfa Romeo CODE (immobiliser) does not allow control units to be exchanged between vehicles.

Replacement of the injection control unit, air capacity case or the throttle body integral with the D.V.E. means that the self-learning procedure has to be carried out.

PIN-OUT

A1 - Not connected

A2 - Not connected

A3 - Alfa Romeo CODE connection

A4 - Not connected

A5 - Not connected

A6 - Compressor engagement request

A7 - Power supply for accelerator pedal potentiometer

A8 - Signal for potentiometer - 1 accelerator pedal

A9 - Quadrinary - Fan 1st speed request

A10 - Cruise Control ON/OFF

A11 - Not connected

A12 - CAN-L line

A13 - Compressor relay control

A14 - Not connected

A15 - Direct supply

A16 - Supply controlled by ignition, via main relay

A17 - Not connected

A18 - Cruise Control warning light

A19 - T.MOT warning light

A20 - Preparation for Flash Programming

A21 - Not connected

A22 - Fuel level sensor

A23 - Not connected

A24 - Earth for potentiometer - 1 accelerator pedal

A25 - Earth for potentiometer - 2 accelerator pedal

A26 - Brake lights switch

A27 - Brake lights switch

A28 - SPORT function switch

A29 - CAN-H line

A30 - Fuel pump relay feed

A31 - Main relay activation

A32 - Supply controlled by ignition, via main relay

A33 - Not connected

A34 - Not connected

A35 - Rev counter signal

A36 - Not connected

A37 - Not connected

A38 - Not connected

A39 - Not connected

A40 - Signal for potentiometer - 2 accelerator pedal

A41 - Quadrinary - fan 2nd speed request

A42 - Cruise Control Resume

A43 - Cruise Control SET +

A44 - Speedometer sensor signal

A45 - CAN-H line

A46 - Injection warning light

A47 - Supply controlled by ignition

A48 - Supply controlled by ignition, via main relay

A49 - Not connected

A50 - Operation of fan 1st speed

A51 - Not connected

A52 - Fuel consumption signal

A53 - Diagnostic connection (K line)

A54 - Air temperature sensor signal

A55 - Not connected

A56 - Supply for accelerator pedal potentiometer

A57 - Air flow meter signal

A58 - Cruise Control SET -

A59 - Clutch pedal switch

A60 - Oil pressure switch

A61 - CAN-L line

A62 - Operation of fan 2nd speed

A63 - Air flow meter supply

A64 - Not connected

B1 - Throttle casing motor earth

B2 - Lambda sensor heating (pre-cat. left)

B3 - Operation of injector for cyl. 4

B4 - Variable geometry solenoid valve operation

B5 - Fuel vapour recovery solenoid control

B6 - Detonation sensor 2 reference earth

B7 - Lambda sensor earth (pre-cat. left)

B8 - Not connected

B9 - Not connected

B10 - Engine rpm sensor

B11 - Not connected

B12 - Not connected

B13 - Not connected

B14 - Cylinder 4 coil operation

B15 - Not connected

B16 - Cylinder 1 coil operation

B17 - Throttle casing motor supply

B18 - Not connected

B19 - Operation of injector for cyl. 1

B20 - Not connected

B21 - Not connected

B22 - Knock sensor 1

B23 - Lambda sensor signal (pre-cat. right)

B24 - Potentiometer - 1 throttle body

B25 - Engine coolant temperature

B26 - Sensors reference earth

B27 - Not connected

B28 - Lambda sensor signal (post-cat.)

B29 - Not connected

B30 - Cylinder 3 coil operation

B31 - Cylinder 2 coil operation

B32 - Not connected

B33 - Throttle casing motor earth

B34 - Lambda sensor heater (pre-cat. right)

B35 - Operation of injector for cyl. 3

B36 - Variable valve timing operation

B37 - Not connected

B38 - Not connected

B39 - Lambda sensor signal (pre-cat. left)

B40 - Potentiometer - 2 throttle body

B41 - Not connected

B42 - Timing sensor signal

B43 - Not connected

B44 - Not connected

B45 - Not connected

B46 - Not connected

B47 - Not connected

B48 - Not connected

B49 - Throttle casing motor supply

B50 - Lambda sensor heater (post-cat.)

B51 - Timing sensor power supply

B52 - Operation of injector for cyl. 2

B53 - Not connected

B54 - Knock sensor 1 reference earth

B55 - Lambda sensor earth (pre-cat. right)

B56 - Not connected

B57 - Not connected

B58 - Throttle casing potentiometers supply

B59 - Engine rpm sensor

B60 - Lambda sensor earth (post-cat.)

B61 - Not connected

B62 - Not connected

B63 - Not connected

B64 - Not connected

Injectors

The double-jet fuel injectors are installed on the distribution manifold.

A retainer secures the fuel injectors to the distribution manifold, and two O-rings ensure the seal.

The fuel injectors are responsible for delivering the necessary quantity of fuel to the engine.

They are 'all or nothing' devices, as they can remain in only two stable states, i.e. open or closed. They allow fuel to pass when they are open, while they block delivery when they are closed.

Enigine coolant temperature sensor

It is fitted on the thermostatic cup and measures the temperature of the coolant by means of an NTC thermistor which has a negative resistance coefficient.

The sensor is produced using semiconductor technology, so if the temperature of the sensor increases as the temperature of the coolant increases, the resistance decreases.

As the variation in resistance is not linear, for the same temperature increment, it is higher for low temperatures than for high temperatures.

Detonation sensor

The piezoelectric type detonation sensor is fitted on the cylinder block/crankcase and detects the intensity of the vibrations caused by the detonation in the combustion chambers.

The piezoelectric crystal forming the sensor detects the vibrations generated at a frequency of between 12 and 16 kHz, and transforms them into electrical signals sent to the fuel injection control unit.

Rpm sensor

It is fitted on the cylinder block/crankcase and 'faces' the flywheel on the crankshaft.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the teeth of the phonic wheel (60-2 teeth).

The fuel injection control unit uses the rpm sensor to:

• determine the speed of rotation
• determine the angle of the crankshaft.

Operation

The passage from full to empty, due to the presence or absence of the tooth, causes a variation in the magnetic flow which is sufficient to generate an induced alternating voltage, resulting from the count of teeth located on a ring (or phonic wheel).

The frequency and range of the voltage sent to the electronic control unit provides it with the angular speed of the crankshaft.

1 - Brass bush

2 - Permanent magnet

3 - Plastic sensor casing

4 - Coil winding

5 - Polar core

6 - Ring gear or flywheel

7 - Coaxial two-wire cable or electrical connection

The distance (gap) for obtaining correct signals, between the end of the sensor and the flywheel, should be between 0.8 and 1.5 mm.

This gap is not adjustable, so if a value outside the tolerance range is measured, check the condition of the sensor and the flywheel.

1 - Maximum magnetic flow

2 - Minimum magnetic flow

3 - Induced alternating voltage trend

Timing sensor

Hall effect; it is mounted on the cylinder head and 'facing' the exhaust camshaft pulley.

The fuel injection control unit uses the timing sensor's signal to find out the TDC at the end of compression.

Accelerator pedal potentiometer

The accelerator pedal is fitted with two integrated potentiometers:

• one main one
• one safety one.

The injection control unit implements the following 'recovery' strategies:

• if there is a fault with one of the two potentiometers, a throttle opening of up to 40° is allowed for a long period
• if both of the potentiometers fail completely, the throttle opening is excluded.

Operation

The sensor consists of a casing (1), fixed to the pedals by a flange, which contains a shaft (2), in an axial position, connected to the twin track potentiometer (3).

There is a coil spring on the shaft which guarantees the correct resistance to the pressure whilst a second spring ensures the return on release.

Operating range from 0° to 70°; mechanical stop at 88°.

Throttle body integral with d.v.e.

It is fitted on the inlet chamber and regulates the quantity of air drawn in by the engine.

According to the signal coming from the accelerator pedal potentiometer, the injection control unit controls the opening of the throttle by means of a direct current motor integrated in the throttle body integrated with D.V.L.

The throttle opening takes place between 0° and 80° therefore including the idle adjustment.

The throttle body integral with D.V.E. is equipped with two potentiometers integrated so that one controls the other and viceversa.

If both the potentiometers fail or there is no supply, depending on the position of the accelerator pedal, the control unit reduces the drive torque:

• fully depressed, it cuts off the supply to one or more pistons, until a maximum speed of 2500 rpm is reached
• in intermediate positions, it cuts off the supply to one or more pistons, until a speed below 1200 rpm is reached.

If the throttle body integrated with D.V.E. or the injection control unit or the air chamber is replaced then the self-learning procedure must be carried out.

Air flow meter

The flow meter is located on the air inlet duct and is of the 'hot film' type.

The intake air temperature sensor is built into the flow meter.

The air flow meter cannot be dismantled.

1 - Covers

2 - Electronic card

3 - Sensor

4 - Support plate

5 - Support

6 - O-ring

7 - Temperature sensor

Operation

The operating principle is based on a heated diaphragm located in a measuring duct through which the intake air entering the engine flows.

The hot film diaphragm is kept at a constant temperature (about 120 ° C above the temperature of the incoming air) by the heating resistor.

The air mass passing through the measuring duct tends to draw heat from the diaphragm, so to keep the latter at a constant temperature, some current must flow through the resistor.

This current is measured by a suitable Wheatstone bridge.

The current is therefore proportional to the mass of flowing air.

The flow meter directly measures the air mass (not volume), thus eliminating problems of temperature, altitude, pressure, etc.