2892433 - INTRODUCTION - CNG FUEL SYSTEM (BIPOWER)

The system for running on two types of fuel comprises the Magneti Marelli IAW 4EF.G1 system for petrol operation and the Metatron METAFUEL 5D0.2B0 system for operating on methane. The two systems are connected via a high speed CAN line.

The Magneti Marelli IAW 4EF.G1 system belongs the category of systems integrated with:

  • inductive discharge, digital, electronic ignition
  • static advance
  • sequential, phased type electronic injection (1-3-4-2).

The Metatron METAFUEL 5D0.2B0 belongs the category of systems integrated with:

  • sequential, phased type electronic injection (1-3-4-2).
The METAFUEL system is clear for the basic system for all components and the operation of the basic system is not affected in all operating conditions.The two control units share some of the system elements. This sharing is transparent to the basic system.

The list of components shared by the two systems, connected in parallel, is as follows:

  • intake manifold pressure sensor;
  • throttle position sensor;
  • engine rpm sensor;
  • engine timing sensor;
  • Lambda sensor upstream of the catalytic converter.

The list of additional components for the methane system is as follows:

  • methane pressure sensor on the high pressure line;
  • methane pressure and temperature sensor on the manifold;
  • methane injectors with activation relay;
  • methane cut out solenoid valves with activation relay.
1, Methane engine management control unit2, Injection system relay3, Battery4, Ignition switch5, Petrol or methane operating mode selector 6, Petrol operation green warning light (Power Mode)7, Methane level gauge8, Diagnostic tester connection9, Methane solenoid valve relay (on canisters and on pressure reduction unit)10, Solenoid valves on canisters11, Methane canisters12, Inertia switch13, Petrol pump14, Petrol pump cut out relay15, Lambda sensor upstream of the catalyzer16, Solenoid valve on pressure reduction unit17, Methane pressure sensor18, Methane pressure reduction unit19, Air pressure and temperature sensor20, Engine timing sensor21, RPM and TDC sensor22, Methane manifold and injectors23, Injector relay24, Petrol engine management control unit25, Throttle valve position sensor26, Methane pressure and temperature sensor on the manifold

OPERATION

The system is configured to normally run on methane.

Methane/petrol switching can take place:

  • as a result of a manual command by the user through activating the switching button in the passenger compartment;
  • automatically when ordered by the methane engine management control unit if the methane in the tank has run out (pressure in the canister less than 14 bar) or in the recovery condition when methane operation is not advisable.
In the first case, methane operation is only restored when the button is deactivated; in the second case, it takes place when the conditions that brought it about no longer exist (on subsequent starting). The engine is started up on petrol with an automatic shift to methane after a few seconds designed to keep the injectors and the petrol pump working efficiently. There must therefore always be petrol in the tank. For this reason, there are two fuel level gauges. Starting up on methane is only possible in recovery.The operating mode is signalled by means of the PETROL operation warning light (POWER MODE) located in the instrument panel. Irrespective of the position of the switching button, if this indicator is off it means unequivocable methane operation and if it is on it means petrol operation.There is a CAN communication line between the two electronic units through which data, commands and other information required for the correct management of the two control units is exchanged.

The functions managed by the METATRON 5DO.2B0 control unit are, basically, as follows:

  • Petrol operation
  • Methane operation
  • Engine Signal Management
  • Ignition management
  • Injection management
  • Idle speed management
  • System self-adjustment
  • Start-up
  • Operation during acceleration and deceleration
  • Cut-off operation
  • Operation in full load conditions
  • Protection beyond revs
  • Barometric correction
  • Fuel vapour recovery
  • Control of combustion gases - Pre-catalyzer Lambda sensor
  • EOBD emission control
  • Air conditioning compressor connection
  • Fuel level signalling
  • Switching between two operating modes (petrol and methane)
  • Connection with electronic key (Fiat CODE)
  • System self-diagnosis
  • Petrol pump operation
  • Methane cut out solenoid valve operation.

DIAGRAM SHOWING INFORMATION ENTERING/LEAVING THE CONTROL UNIT

The communcation between the petrol engine management control unit and the methane engine management control unit takes place via the CAN line.
1, Methane engine management control unit2, Battery3, Ignition switch4, Injection system relay5, Solenoid valve relay on canisters and on pressure reduction unit6, Canister solenoid valves7, Methane pressure reduction unit solenoid valve8, Methane pressure sensor9, Lambda sensor upstream of the catalyzer10, Diagnostic tester connection11, Methane level gauge12, Methane injectors13, Methane injector relay14, Petrol or methane operating mode selector 15, Petrol pump16, Petrol pump cut out relay17, Throttle valve position sensor18, Petrol engine management control unit19, Air pressure and temperature sensor20, RPM and TDC sensor21, Engine timing sensor22, Methane pressure and temperature sensor on the manifold

PETROL OPERATION

In this operating mode there are no functional variations in relation to the basic system.The basic electronic unit does not alter its behaviour and the system management strategies are the same as for the basic version.The specific elements for the methane system do not interfere in any way with the basic system.

METHANE OPERATION

The engine runs on methane except during the starting stage (obviously with the selector positioned at GAS Mode before starting). The petrol pump is not supplied when changing to methane operation.The METAFUEL electronic unit only manages the phased, sequential type methane injection. All the other engine management functions, including the ignition advance, are left to the basic unit. Injection takes place directly through the operation of the specific methane system injectors. The ignition advance is adjusted by sending the basic electronic unit the advance variation to be added to the one for petrol operation. This communication takes place via the CAN line between the two control units.The commands for the petrol injectors, the fault diagnosis and the petrol self-learning strategy are also disabled via the CAN. The other basic electronic unit functions are carried out normally and all the input signals remain unchanged. All the commands are implemented as usual (stepper, ignition, etc.).The METAFUEL electronic unit processes the information coming from the basic system sensors and the additional ones in order to recognize the system operating conditions and produce suitable commands for the methane injectors. The management strategies use typical curves and control parameters stored in the METAFUEL electronic unit memory. The calibration figures are defined on the basis of performance, consumption, emission and driveability aims.The specific management strategies for the methane system are basically as follows:

ENGINE SIGNAL MANAGEMENT

The METAFUEL electronic unit recognizes the engine timing and determines the injection timing angle. This recognition takes place by processing the signals coming from the timing sensor and from the rpm and TDC sensor. These two signals make up the engine signals.The synchronization of the signals and signal wave shapes are the same as those for the basic electronic unit.

IGNITION MANAGEMENT

The coil charging time and the moment of ignition in relation to TDC are always determined and managed by the basic electronic unit which receives the variation in the advance to be implemented from the METAFUL via the CAN.The METAFUEL electronic unit memory contains a map of the advance shift values according to the engine speed and load conditions. The calculation of the advance correction involves selecting a basic value and correcting in according to the coolant temperature.

INJECTION MANAGEMENT

The aim of the fuel management is to supply the correct amount of fuel required by each cylinder to satisfy the objectives of performance, consumption and engine emissions. The METAFUEL unit also manages the starting stage.The injection is the sequential, phased type.The METAFUEL control unit uses an indirect type engine load measurement system (speed-density). This method is used to calculate the quantity of fuel to inject into each cylinder for each engine cycle.The methane is supplied by modulating the injector opening time. The injector inlet pressure is regulated by the pressure reduction unit.The METAFUEL unit injection strategies make it possible to supply the correct amount of methane to the engine in all operating conditions (acceleration, deceleration, altitude, cold weather).

IDLE SPEED MANAGEMENT

The management of the idle speed (stepper management) is carried out by the basic electronic unit; the METAFUEL unit alters the idle speed with a suitable offset transmitted via the CAN in order to prevent the engine from stalling in certain operating conditions (e.g. power assisted steering) due to the control of the fuel only by the METAFUEL unit.

SYSTEM SELF-ADJUSTMENT

The self-adjustment strategies allow the adjustment of the injection to the changes in the system due to production dispersions and ageing of the engine.

STARTING

The engine is always started up on petrol. Starting up on methane is only permitted in recovery.

OPERATION IN ACCELERATION AND DECELERATION CONDITIONS

These operating conditions are identified by means of the throttle and manifold pressure signals.During these two stages the METAFUEL unit adjusts the fuel injection as quickly as possible in order to maximize acceleration torque and ensure optimum driveability during deceleration.

CUT-OFF OPERATION

The fuel cut off strategy is implemented when the throttle is closed at high engine speeds. This strategy is only enabled above a certain coolant temperature level. The METAFUEL electronic unit manages the inlet and outlet from this stage in order to reduce emissions during these engine operating conditions.

OPERATION IN FULL LOAD CONDITIONS

Full load operating conditions are not managed because when running on gas the engine operates under stoichiometric conditions in all operating conditions.

PROTECTION BEYOND REVS

The METAFUEL electronic unit manages the protection of the engine outside of revs. This protection involves cancelling the injection times when a given speed is exceeded. Normal injection is resumed when the speed returns to below the critical value.

BAROMETRIC CORRECTION

There is a strategy in the METAFUEL control unit that recognizes the altitude and implements a barometric correction of the mixture strength.

FUEL VAPOUR RECOVERY

When running on methane the management of the petrol canister purge is carried out by the METAFUEL unit by sending the command to the basic unit via the CAN line.As far as the methane fuel supply system is concerned, it is sealed. The fuel is present in a gaseous form in every point of the circuit from the canister to the injectors. The pressure of the methane in the section between the canister and the pressure reduction unit never exceeds the maximum pressurizing pressure in any operating conditions. Methane vapour recovery systems are therefore not needed.

CONTROL OF COMBUSTION GASES - LAMBDA SENSOR

The METAFUEL electronic unit uses the signal for the Lambda sensor upstream of the catalyzer to control the metering of the air/methane mixture in order to ensure maximum catalyzer conversion efficiency.

EMISSION CONTROL

The METAFUEL electronic unit uses the signal from the methane perssure and temperature sensor on the manifold to correct the injection times, thereby controlling the exhaust emissions which are within the regulations for EURO3 - EOBD.

AIR CONDITIONING COMPRESSOR CONNECTION

The METAFUEL electronic unit is not connected to the air conditioning system.The switching on and off of the compressor in certain operating conditions to improve the performance of the engine is managed by the basic electronic unit through the same modes and operating conditions as for the basic system.

FUEL LEVEL SIGNALLING

The METAFUEL electronic unit measures the pressure value inside the tank. The tank filling level is determined on the basis of this information; this information is then sent from the METAFUEL control unit to the special gauge located in the instrument panel.

SWITCHING BETWEEN THE TWO OPERATING MODES (PETROL AND GAS)

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