Fuel flow in an EFI system is primarily regulated by
time, specifically
the duration of injector opening. However, there are other factors that play a role:
1. Injector Open Time: This is the key factor controlling fuel flow. The
ECU (Electronic Control Unit) determines the desired amount of fuel based on various engine parameters (RPM, air intake, etc.). It then sends a signal to the injector, telling it how long to open and release fuel. The longer the injector stays open, the more fuel flows through.
2. Injector Size: While not the main control method, the size of the injector nozzle also influences flow. Larger nozzles allow more fuel to pass through in a given time, while smaller ones deliver less. However,
injectors are typically pre-calibrated and chosen to match the engine's needs, and their size isn't directly adjusted to regulate fuel flow.
3. Fuel Pressure: Although not the primary control method, fuel pressure can indirectly affect flow. In some systems, a
pressure regulator maintains a constant pressure in the fuel rail, ensuring consistent delivery. However, in
common rail systems, the pressure can vary dynamically based on engine demands. This can slightly impact flow but is not the main control method.
Additional Factors:
- Temperature sensors: Engine and air temperature affect air density, influencing the required fuel. The ECU adjusts injector open time based on these readings.
- Oxygen sensors: These sensors monitor exhaust oxygen levels, indicating the air-fuel ratio. The ECU adjusts injector open time to maintain the optimal ratio for efficient combustion and emissions control.
In summary, the primary control for fuel flow in an EFI system is the injector open time, determined by the ECU based on various engine parameters and feedback from sensors. While injector size and fuel pressure play supporting roles, they are not directly manipulated to regulate flow.