The operation of the injector can be divided into three stages:
· rest position
The coil (4) is de-energized and the shutter (6) is in the closed position and does not allow the introduction of fuel into cylinder Fc > Fa (Fc: due to the line pressure acting on control area 7 of the rod 1; Fa: due to the line pressure acting in supply volume (8).
· "start of injection"
The coil (4) is energized and causes the shutter (6) to be raised.
The control volume (9) fuel flows towards the return manifold (10) causing a decrease in pressure in the control area (7).
At the same time, the line pressure exerts a force Fa > Fc in the supply volume (8), via the supply duct (12), causing the raising of the pin (2) with the consequent introduction of fuel into the cylinders.
· "end of injection"
The coil (4) is de-energized and returns the shutter (6) to the closed position which recreates an equilibrium with forces which return the pin (2) to the closed position and consequently end the injection.
1, Pressure rod
2, Pin
3, Jet
4, Coil
5, Valve
6, Spherical shutter
7, Control area
8, Supply volume
9, Control volume
10, Fuel return - low pressure
11, Control duct
12, Supply duct
13, Electrical connection
14, Fuel inlet connector - high pressure
15, Spring
The supply manifold is fitted on the inlet side cylinder head.
With its volume of around 33 cc it dampens the fuel pressure oscillations due to:
· the operation of the pressure pump
· the opening of the injectors
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1, Auxiliary electric fuel pump
2, Heater plugs control unit
3, Speedometer
4, Rev counter
5, Heater plugs waring light
6, Injection warning light
7, E.G.R. modulating valve
8, Pressure regulator
9, Excess pressure sensor
10, Fuel temperature sensor
11, Fuel pressure sensor
12, Relay
13, Injection control unit
14, Injectors
15, Heater plugs
16, Rpm sensor
17, Water temperature sensor
18, Climate control connector
19, Diagnostic connector
20, Alfa Romeo CODE connector
21, Flow meter
22, Timing sensor
23, Accelerator pedal potentiometer
24, Clutch pedal switch
25, Brake pedal switch
26, Cruise control
The EDC-15C Common Rail is a high pressure electronic injection system for direct injection fast diesel engines.
The main features are:
· availability of high injection pressures (1350 bar)
· possibility of modulating these pressures between 150 bar and a maximum operating pressure of 1350 bar, irrespective of the engine rotation speed and load
· capacity of operating at high engine speeds (up to 6000 rpm)
· precision injection (advance and duration)
· reduction in consumption
· reduction in emissions.
The main functions of the system are basically as follows:
· control of the fuel temperature
· control of the engine coolant temperature
· control of the quantity of fuel injected
· control of the idle speed
· fuel cut-off during overrunning
· control of the cylinder balance during idling
· control of irregular operation
· control of exhaust fumes during acceleration
· control of exhaust gas recirculation (E.G.R.)
· control of maximum torque restriction
· control of maximum speed restriction
· control of the heater plugs
· control of engagement of climate control system (where fitted)
· control of auxiliary fuel pump
· control of the position of the cylinders
· control of the main injection advance and operation
· control of the closed loop injection pressure
· control of the electrical balance
· control of the supercharging pressure
· self-test
· connection to Alfa Romeo CODE (Immobilizer) control unit
The Common Rail systems makes it possible to carry out a pre-injection before T.D.C. with the advantage of reducing the derivative of the pressure in the combustion chamber, reducing the value of the combustion noise, typical of direct injection engines.
The control unit controls the quantity of fuel injected, regulating the line pressure and injection times.
The control unit processes the following information to control the quantity of fuel to inject:
· engine speed
· coolant temperature
· supercharging pressure
· air temperature
· intake air quantity
· battery voltage
· diesel pressure
· accelerator pedal position.
1, Electric fuel pump
2, Air conditioner compressor
3, Modulator for E.G.R. valve
5, Electric fans
6, Heater plugs control unit
7, Accelerator pedal potentiometer
8, Clutch/brake pedal switch
10, Fuel pressure sensor
11, Fuel temperature sensor
12, Cruise control
13, Coolant temperature sensor
14, Flow meter
15, Timing sensor
17, Speedometer
18, Battery
19, Alfa Romeo CODE
20, Diagnostic socket
21, Pressure regulator
22, Injectors
23, Heater plugs
24, Heater plugs warning light
25, Injection warning light
The control unit's self-test checks the signals coming from the sensors, comparing them with the permitted limits:
indication of starting faults
· warning light on for 4 secs indicates test stage
· warning light off after 4 secs indicates no faults in components that could affect the values established in emission control regulations
· warning light on after 4 secs indicates fault
fault indication during operation:
· warning light on indicates fault
· warning light off indicates no faults in components that could affect the values established in emission control regulations
recovery:
· the control unit defines as and when required the type of recovery depending on the faulty components
· the recovery parameters are managed by non-faulty components.
When the control unit receives the ignition "ON" signal, it dialogues with the Alfa Romeo CODE control unit to obtain starting enablement.
With the temperature of the fuel 110° C, measured by the sensor at the recirculation manifold, the control unit operates the pressure regulator in order to reduce the line pressure (it does not modify the injection times).
With the temperature of the engine coolant 105° C, the control unit:
· reduces the quantity of fuel injected (reduces the engine power)
· operates the cooling fans
· lights up the coolant overheating warning light
On the basis of the signals coming from the sensors and the values in the map, the control unit:
· operates the pressure regulator
· varies the injection time up to 3000 rpm
· varies the "main" injection time.
The control unit processes the signals coming from the various sensors (*) and regulates the quantity of fuel injected:
· varies the injector injection times.
Within certain limits the speed takes the battery voltage into account.
When the accelerator pedal is released the following logics are implemented:
· cuts off the supply to the fuel injectors
· partially reactivates the supply to the injectors before the idle speed is reached
· operates the fuel pressure regulator.
On the basis of the signals received from the sensors (*), the control unit controls the precision of the torque at idle speeds:
· varies the quantity of fuel injected in the individual injectors (injection time).
The control unit processes the signals received from the various sensors and determines the quantity of fuel to be injected via:
· the pressure regulator
· the opening time of the injectors.
When there is considerable acceleration, the control unit determines the optimum quantity of fuel to be injected, on the basis of the signals received from the flow meter and engine rpm sensor:
· varies the injector injection time.
On the basis of the engine load and signal coming from the accelerator pedal potentiometer, the control unit restricts the amount of air drawn in, implementing the partial intake of exhaust gases.
According to the number of revs, the control unit calculates the following from predefined maps:
· the torque limit
· the permissible fumes (limit).
It compares these minimum values and corrects them with other parameters:
· engine rpm
· vehicle speed
it controls the quantity of fuel to be injected (pressure regulator - injectors).
According to the number of revs, the control unit implements two intervention strategies:
· at 5000 rpm it cuts off the fuel, reducing the line pressure
· above 5400 rpm it deactivates the auxiliary pump and the injectors.
The control unit, during the following stages:
· starting
· post-starting
times the operation of the heater plugs control unit according to the engine temperature.
The control unit operates the air conditioning compressor:
· switching it on/off when the relevant switch is pressed
· switching it off momentarily (for around 6 secs) if there is substantial acceleration or a request for maximum power.
Irrespective of the engine speed, the control unit:
· supplies the auxiliary fuel pump with the ignition key in the ON position
· excludes the auxiliary pump supply if the engine is not started up within several seconds.
During each revolution of the engine, the control unit recognizes which cylinder is in the explosion stroke and operates the injection sequence at the appropriate cylinder.
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