Gasoline direct injection (GDI) is a variant of fuel injection petrol engines.

 

The gasoline is highly pressurised, and injected via a com-mon rail fuel line directly into the combustion chamber of each cylinder, as opposed to conventional multi-point fuel injection that happens in the intake tract, or cylinder port.

With the GASITALY F5 GDI conversion system, including compo-nents with the most advance technology and developed in the the sector, we give the opportunity to run this last technology engines also with gas.

 

 

 

 

 

Quick information:

  • A minimum petrol consumption is always present in gas mode, the amount of the petrol used depends by the engine features and therefore could be variable on different vehicles.
  • The petrol injectors emulation is the most delicated part of the application.
  • Dedicated istructions are necessary for every king of engine to connect properly wires and sensors.
  • Gas nozzle positioning on the manifolds must be done in right position and with the proper direction of the injected gas flow

GASITALY F5 DIRECT INJECTION - TSI/FSI/GDI ENGINES


WHAT IS IT THE GASOLINE DIRECT INJECTION?

Gasoline direct injection (GDI) is a variant of fuel injection petrol engines. The gasoline is highly pressurised, and injected via a common rail fuel line directly into the combustion chamber of each cylinder, as opposed to conventional multi-point fuel injection that happens in the intake tract, or cylinder port.

Direct injection allows precise control over the quantity of fuel and the time in the cycle it is introduced into the cylinder. Thus, for maximum power, it is possible to inject a full quantity of fuel in the induction stroke, while for low load, maximum economy (lean-burn) operation it is possible to inject a smaller quantity of fuel during the compression stroke.

The major advantages of a GDI engine are increased fuel efficiency and high power output. In addition, the cooling effect of the injected fuel and the more evenly dispersed mixtures allow for more aggressive ignition timing curves. Emissions levels can also be more accurately controlled.

The fuel supply system uses a high pressure pump to store fuel (boost of 50÷120 bar) in the fuel rail that feeds the injectors. The fuel rail is made sufficiently large that pressure fluctuations within it are minimised as each injector opens. The pressure of the fuel in the injector supply rail is controlled by an electronicallycontrolled bypass valve that is varied in flow by being pulse-width modulated by the Electronic Control Unit (ECU). A fuel pressure sensor is used to monitor fuel rail pressure.

Injector: Compared with a conventional
port fuel injection system, the fuel
injectors must be capable of working
with huge fuel pressures and also injecting
large amounts of fuel in very short periods.

The reason for the much reduced time
in which the injection can be completed is
due to the fact that all the injection must
sometimes occur within just a portion of
the induction stroke.
The fuel requirements at idle can drop
the opening time to just 0.4 milliseconds.

The Main Differences With The Traditional Multi-Point Fuel Injection, And What You Must Know About The Conversion To Gas:

  • Petrol injectors are located into the combustion chamber.
  • High and variable pressure into the petrol injection common rail.
  • Fuel Stratified Injection (FSI).
  • Variable Geometry of the intake manifolds.
  • Petrol injectors work with high pressure and high temperature:
    Partial injection of petrol is necessary in gas mode in some engine conditions (high load, high rpm) to preserve the integrity of the petrol injectors. There is a petrol consumption in gas mode that can not be eliminated.
  • Petrol injectors are driven in current-mode (high voltage, high current with current feedback and fine diagnostic controls):
    The Hardware of gas ECU for direct injection is quite different from the standard one.Every petrol injector type needs dedicated configuration of gas ECU in order to emulate properly the petrol injectors (sophisticated cut injector
    electronic stage).
  • Peak and hold management of the injector is made with high voltage and switching signal on positive pole. Positive signals are common for two injectors (2 pairs: 1-4, 2-3):
    Is not possible to use the signal on the positive of the injector, the KOEO signal has to be taken elsewhere (i.e ignition coil), dedicated instructions are necessary.
  • Fuel pressure is continuously controlled by a pressure regulator and monitored by the petrol ECU by reading a pressure sensor.
  • In gas mode petrol injectors are inhibited, there is no flow of petrol in the rail and petrol ECU reads unattended pressure values:
    Gas ECU can emulate pressure sensor signal, in order to keep petrol pressure in the expected range and prevent sensor fault detection by petrol ECU (MIL ON). To obtain a correct emulation, the pressure sensor signal must be properly
    connected to gas ECU and the OBD communication with the petrol ECU is required.
  • Stratified injection mode is used in some vehicle to reduce the emission adding fuel during the compression stroke.
  • Is not possible to intruduce the gas-air mixture in the compression phase and this implies the impossibility to run on gas in the fuel stratified injetion condition:
    Some localized conditions, where FSI strategy take place, can be individuated and in that conditions the gas system must run in “petrol mode”. There is a petrol consumption in gas mode that can not be eliminated.
    However, in some applications a specific emulation procedure can be used to avoid petrol addition running on gas by inhibition of the FSI strategy.
  • Many direct injection engines have variable intake manifolds: geometry of the intake pipes can be modified while the engine is running by acting on special throttle located inside the manifolds. Air flow is optimized depending on engine condition, giving more power and torque, and improving fuel efficiency.
  • Turbocharger and compressors are very frequent on direct injection engines to improve engine performance:
    Gas nozzle positioning on the manifolds is critical. Dedicated instructions are needed to make the holes on the manifolds in the right position, and to give the proper direction of the injected gas flow.
    In some cases special pipes and nozzles are required in order to optimize gas injection throught the manifolds. Special pipes are put into the intake ducts and connected to proper nozzles to the gas injectors.
    The length of the pipes between gas injectors and intake manifold, as the size of gas injector nozzles are fitted depending on specific engine features.

Conclusion:

  • A minimum petrol consumption is always present in gas mode, the amount of the petrol used depends by the engine features and therefore could be variable on different vehicles.
  • The petrol injectors emulation is the most delicated part of the application.
  • Dedicated istructions are necessary for every king of engine to connect properly wires and sensors.
  • Gas nozzle positioning on the manifolds must be done in right position and with the proper direction of the injected gas flow.