What is port fuel injection?

Short Answer:

Port Fuel Injection (PFI) is a system in which the fuel is injected into the intake port of each cylinder, just before the intake valve. This system ensures that the fuel mixes properly with air before entering the combustion chamber, resulting in better combustion efficiency and performance. Port fuel injection provides better control of the air-fuel ratio, smoother engine operation, and reduced emissions compared to carbureted systems.

In this system, each cylinder has a separate injector controlled electronically. It helps in improving fuel economy, providing quick throttle response, and reducing engine knocking. Port fuel injection is commonly used in modern petrol engines because of its simplicity and reliability.

Detailed Explanation :

Port Fuel Injection

Port Fuel Injection (PFI) is a modern fuel delivery system used in internal combustion engines, especially in petrol engines. In this method, fuel is injected into the intake port of each cylinder, located just before the intake valve. The injector sprays a fine mist of fuel that mixes with the air flowing into the combustion chamber. This pre-mixing of air and fuel ensures a homogeneous mixture and improves combustion quality.

In a typical PFI system, each cylinder has one injector that is electronically controlled. The timing and quantity of the injected fuel are managed by the Engine Control Unit (ECU) based on signals received from various sensors such as the throttle position sensor, oxygen sensor, crankshaft position sensor, and air-flow sensor. This electronic control helps achieve precise fuel metering and consistent performance under different driving conditions.

Working of Port Fuel Injection

When the engine is running, the ECU calculates the required amount of fuel according to engine load, speed, and air intake. The fuel pump sends fuel from the tank to the injectors at a controlled pressure. The injectors then spray the fuel into the intake port at the correct time. As the intake valve opens, the air-fuel mixture is drawn into the combustion chamber. Since the fuel has already mixed with air, combustion becomes more complete and efficient, resulting in better power output and lower emissions.

Port fuel injection works under two main modes:

  1. Sequential Injection: In this mode, each injector sprays fuel separately according to the firing order. The ECU controls the exact timing of each injector.
  2. Batch Injection: In this mode, all injectors in one group spray fuel at the same time. It is simpler but less efficient than sequential injection.

Sequential port injection is the most common type used in modern vehicles as it provides better fuel economy and throttle response.

Advantages of Port Fuel Injection

  1. Better Fuel Mixing: Fuel is injected near the intake valve, allowing proper vaporization and mixing with air before combustion.
  2. Improved Efficiency: More complete combustion leads to higher fuel efficiency and reduced fuel consumption.
  3. Lower Emissions: Controlled fuel delivery results in reduced carbon monoxide and hydrocarbon emissions.
  4. Smooth Operation: The engine runs smoothly with minimal vibration and knocking.
  5. Good Throttle Response: The system quickly adjusts the fuel supply according to the driver’s demand.
  6. Reliable Performance: Since each cylinder has its own injector, it ensures uniform fuel distribution and consistent power delivery.

Disadvantages of Port Fuel Injection

  1. Limited Fuel Atomization: Compared to direct injection systems, the fuel atomization is slightly less efficient.
  2. Possible Fuel Wastage: Some fuel may remain in the intake port, especially during cold starts.
  3. Complex Maintenance: The injectors and sensors need periodic cleaning and calibration.
  4. Not Suitable for High-Performance Engines: For engines needing very precise control, direct injection is preferred.

Applications

Port Fuel Injection systems are widely used in passenger cars, motorcycles, and small trucks. They are especially common in gasoline engines that require balance between performance, economy, and emission control. Examples include vehicles from manufacturers like Toyota, Honda, Hyundai, and Maruti Suzuki, which often use multi-point port fuel injection technology.

Comparison with Other Systems

Compared to carburetors, port fuel injection offers much better accuracy in fuel delivery. It eliminates problems like uneven mixture distribution and vapor lock. When compared with direct injection, it is less costly and easier to maintain, though slightly less efficient at higher performance levels.

Conclusion

Port Fuel Injection is a reliable and efficient fuel delivery system that provides precise fuel control, smooth performance, and reduced emissions. It is widely used because it offers a perfect balance of economy and performance for most modern petrol engines. Though newer technologies like direct fuel injection have emerged, PFI remains popular due to its simplicity, durability, and cost-effectiveness.