939005102 - INTRODUCTION - PETROL FUEL INJECTION SYSTEM
Introduction
The 3.2 V6 JTS engine features a fuel feed system with a high pressure pump for direct injection.An electronic control system supervises and governs all engine parameters to optimise performance and fuel consumption by means of a real-time response to different service conditions.The system is managed by a single control unit - a Bosch Motronic MED 7.6.2. with motorised throttle - which controls both the ignition and the sequential, phased injection.Depending on the signals received from numerous sensors, the control unit controls the injectors connected to it managing the following systems:- fuel supply;- ignition;- high pressure fuel pump control;- air supply;- accelerator pedal;- engine cooling;- exhaust with catalytic converters controlled by four Lambda sensors;- fuel vapour recirculation.The control unit for this JTS engine manages the operation of the high pressure fuel pump controlling the flow rate regulator and monitoring the pressure reached by means of a sensor located on the right bank rail.The throttle body is also controlled electronically by the control unit: the throttle opening is calculated in accordance with a specific logic inside the engine management control unit. In this way, in addition to there being no mechanical connection between the accelerator pedal and the throttle casing, the control unit is capable of managing the actual quantity of fuel required at any time the engineis operating controlling the pressure of the fuel and the starting point of the injection.The control unit also controls the four phase transformers to ensure optimum engine response in all operating conditions.The main system functions are essentially as follows:- self-learning;- system self-adaptation;- recognition of the Alfa Romeo CODE (immobilizer);- cold starting check control;- control of combustion - Lambda sensors;- detonation control;- control of enrichment during acceleration;- fuel cut-off when accelerator pedal is released;- 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 with ABS/VDC control unit;- fuel system diagnostics;- phase transformer management.Injection system diagram
1. Rpm and TDC sensor2. Left cylinder head exhaust camshaft timing sensor3. Left cylinder head inlet camshaft timing sensor4. Right cylinder head inlet camshaft timing sensor5. Right cylinder head exhaust camshaft timing sensor6. Throttle body7. Flow meter (with intke air temperature sensor)8. Fuel pressure sensor9. Oil level and temperature sensor10. Water temperature sensor11. Lambda sensor upstream of pre-catalyzer, right bank12. Lambda sensor upstream of pre-catalyzer, left bank13. Lambda sensor downstream of catalyzer, right bank14. Lambda sensor downstream of catalyzer, left bank15. Absolute pressure sensor16. Detonation sensor, left bank17. Detonation sensor, right bank18. Oil pressure sensor19. Injectors20. Coils21. Exhaust camshaft phase transformer solenoid, left cylinder head22. Inlet camshaft phase transformer solenoid, left cylinder head23. Inlet camshaft phase transformer solenoid, right cylinder head24. Exhaust camshaft phase transformer solenoid, right cylinder head25. Flow rate regulator26. Shut-off solenoid valve27. Fuel vapour solenoid valve28. Canister29. Low pressure pump in tankDiagram showing information entering/leaving the engine management control unit
1. Injectors2. Fuel pump3. Air conditioning compressor4. Engine cooling fan5. Cruise control system control (4 digital inputs)6. Lambda sensor downstream of the catalytic converter7. Air conditioning system gas pressure linear sensor8. Brake pedal switch9. Speedometer signal detected by CAN10. Lambda sensor upstream of the catalytic converter11. Coolant temperature sensor12. Timing sensors13. Detonation sensors14. Fuel pressure sensor15. Rpm sensor16. Accelerator pedal potentiometer17. Air flow meter with built in air temperature sensor18. Battery19. Clutch pedal switch20. Motorized throttle body21. CAN line22. Alfa CODE23. Diagnostic socket24. Fuel vapour recirculation solenoid valve25. Ignition coils26. Absolute pressure sensor27. Phase transformer control valves28. Injection warning light (MIL EOBD amber yellow)29. Oil pressure sensor30. Shut-off solenoid valve31. Hhigh pressure flow rate regulator
Bosch MED 7.6.2 control unit operating logics
Management of the phase transformers
The variable timing on the 3.2 JTS engine is the continuous regulation type and is applied to both the inlet camshafts and the exhaust camshafts.The overall adjustment range (inlet and exhaust) is 50 degrees and the controls between the inlet and exhaust sides are completely independent of one another.With the engine idling, both camshafts are in the "park" position; in this situation the exhaust camshafts are fully advanced and the inlet camshafts fully delayed and they remain like this during starting. This timing configuration guarantees the minimum crossover between the inlet and exhaust valves.The pins that lock the camshafts in the basic position ensure that they are in the correct position on starting and that there is no noise due to the uncontrolled rotation of the rotor in relation to the stator. To allow the movement of the phase transformer a certain operating pressure must be reached in order to release the pin locking the transformer in the basic position and allowing movement.Depending on the engine position, it is possible from the basic position to control the advance of the inlet camshafts and the delay of the exhaust camshafts within a maximum rotation range of 50 degrees for each shaft; what is of fundamental importance is that this system makes it possible to control all the intermediate positions for the shafts within the above mentioned range so that the best engine working conditions can be produced for all speed and load conditions.Timing diagram variation
A - Inlet shaft basic fitting position (completely delayed)B - Exhaust shaft basic fitting position (completely advanced)A'' - Maximum rotation in relation to inlet shaft positionB'' - Maximum rotation in relation to exhaust shaft positionThanks to the intervention of the phase transformers, the timing diagram can be altered as can be seen in the diagram above; in particular, the opening advance for the inlet valves can move inside the area defined by the line A and the line A'', whilst the closing delay for the exhaust valves can move inside the area definied by the line B and the line B''.The action of the phase transformers is therefore principally understood as controlling the opening advance of the inlet valves and the closing delay of the exhaust valves. Obviously the variation in the opening advance of the inlet valves also produces a variation in their closing point in the same way as the variation in the closing delay of the exhaust valves also produces a variation in the opening point.The maps used for the management of the timing diagram are a compromise between the opening advance and closing delay for both the inle and exhaust valves in terms of ensuring optimum consumption, performance and emissions.The control unit, depending on the information received concerning the following:- the engine temperature;- the engine speed;- the engine load;- the position of the accelerator pedal;- the Lambda sensor signals.manages the phase transformers independently, continuously controlling the four proportional control solenoid valves to ensure careful management of the timing for the best control of the emissions and the torque supplied by the engine.
Alfa code recognition
The moment the control unit receives the ignition ON signal it converses with the Body Computer, via the ALFA CODE function, to give the enablement for starting.
Self-learning
- installation of a new injection control unit,- installation of a new throttle body actuator,- removing-refitting or replcing the rpm/flywheel sensor for the recognition of misfire.The learning values for the throttle body are maintained with the battery disconnected.The learning values for the flywheel for recognizing misfire, on the other hand, are lost.
System self-adjustment
The control unit is equipped with a self-adjustment function that is designed to recognize the changes that take place in the engine due to the processes of bedding in and ageing of both the components and the engine itself in time.There are two adaptive functions depending on the two intervention plans: minimum and utilization.
Cold starting check
In cold starting conditions the mixture is naturally weakened causing low evaporation of the fuel at low temperatures and increased viscosity of the engine lubricant.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.During the start-up stage, the control unit sends an initial simultaneous injection command to all injectors (full-group injection). Once cylinder phase has been detected, normal phased sequential operation can begin.Whilst the engine is warming up, the control unit operates the throttle body to regulate the quantity of air required to ensure that the engine speed is sustained.The rotation speed is made to decrease with increasing temperature until the rated level is reached with the engine warm.
Control of combustion - lambda sensors
In EOBD systems the Lambda sensors are located upstream of the catalyzer system and downstream of the catalyzer.The upstream sensors control the mixture strength and are known as the upstream sensors closed loop. The sensors downstream of the catalytic converter are used to for converter diagnostics and to fine-tune 1st loop control parameters.The adaptation of the second loop is designed to recover both production losses and the slackening that occurs in the upstream sensors as a result of ageing and pollution.This control is known as the 2nd downstream sensors closed loop.
Detonation control
The control unit can delay ignition, selectively at the cylinder where it is required, depending on a combination of values received by the detonation and timing sensors and:- reduces the ignition advancesin steps of 3° up to a maximum of 12°;- updates the threshold value to take into account background noise and the 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 degrees until the recovery is complete.The control unit with a self-adaptive function:- stores advance reductions that are repeated continuously;- adjusts mapping to the various different engine service conditions.RECOVERYIf the detonation sensor is faulty, an ignition advance delay that varies according to the engine speed or temperature is implemented. Maximum ignition delay is always less than 6° engine.
Control of enrichment during acceleration
In cases of high acceleration demand, the control unit modifies injection time and throttle position.RECOVERYThe control unit replaces the signal coming from the faulty air flow meter with the signal for the potentiometer built-into the throttle casing actuator.
Fuel cut-off when the accelerator pedal is released
The control unit with:- detection of idling status;- rpm above a certain threshold;deactivates the fuel injection in the following cases:- engine speed below 1500 rpm;- engine temperature below 40 °C;Before reaching idling level, the rpm descent rate is assessed. If it is above a certain level, the fuel injection is partly reactivated according to a logic that involves the gentle accompaniment of the engine at idle speed.Once idling speed has been reached, normal functions are resumed.
Fuel vapour recovery
The fuel vapours, coming from the active charcoal filter (canister), are sent to the intake ducts to be burnt.This takes place by means of a solenoid valve operated by the control unit which alternates phases in which it is open (canister scavenging stage) with phases in which it is closed (carburation learning stage).During the opening phases, the solenoid valve opening duty-cycle is regulated by the control unit to eliminate the fuel vapours without altering the engine carburation.
Control of maximum rpm
According to the rpm level reached by the engine, the control unit:- beyond 7200 rpm removes the supply from the injectors (dynamic control of maximum speed)- after having checked the maximum speed with the dynamic control, carries out the maintenance by adjusting the position of the motorized throttle independently of the request coming from the accelerator pedal potentiometer (idle static control); this makes it possible to control the maximum speed keeping oscillations from the fuel cut off to a minimum.
Fuel pump control
The control unit:- supplies the electric fuel pump with the ignition ON (for 5 seconds)- supplies the pump with the ignition in the starting position and the engine speed above 25 rpm;- interrupts the supply to the pump with the ignition OFF or the engine speed below 25 rpm
Connection with climate control system
The compressor takes up power from the engine when the climate control system is activated.In idling conditions, the control unit adapts the air flow rate to the new power requirements with the advantage
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