Fuel Injection Systems in Modern Vehicles

Introduction

• Importance of air-fuel mixture in engine performance.
• Shift from carburetors to fuel injection systems.
• Fuel injection is essential for efficient and reliable engine operation.

Components of Fuel Injection System

• Fuel Rail:

  • Connects fuel injectors to fuel supply.
  • Located near the engine's intake manifold or cylinder head.

• Fuel Pump:

  • Delivers fuel from fuel tank to fuel injectors.

• Fuel Injector:

  • Injector body houses nozzle, electromagnetic coil, fuel filter, fuel inlet.
  • Made of metal (steel/aluminum) to withstand engine conditions.
  • Contains a fuel filter to remove impurities.

Injector Operation

• Electromagnetic coil pulls the plunger up, opening the pintle injector.
• Fuel is sprayed into the combustion chamber through the nozzle.
• Each spray is precisely timed and controlled by the ECU.

Pressure Regulator

• Ensures correct fuel pressure is maintained.
• Adjusts fuel flow based on pressure readings.

Air-Fuel Ratio

• Ideal ratio: 14.7:1 (Air:Fuel).
• Ratio influences combustion effectiveness.
• ECU adjusts air-fuel ratio using various sensors.

Comparison: Carburetors vs. Fuel Injection

• Carburetors:

  • Mix air and fuel before combustion.
  • Simpler, cheaper, but less precise.
  • Cannot adjust for varying conditions effectively.

• Fuel Injection:

  • Offers precision, efficiency, and better emissions control.
  • Suitable for both gasoline and diesel engines.
  • More complex but results in improved performance.

Types of Fuel Injection Systems

1. Throttle Body Injection (TBI):

   • Uses a single injector in the throttle body.
   • Limited precision and efficiency.

2. Multi-Point Fuel Injection (MPI):

   • Each cylinder has its own injector.

   • Provides better fuel metering and control.

   • Subtypes of MPI:

     • Sequential Injection:
       • Injects fuel in a specific order.
     • Batched Injection:
       • Groups injectors to supply fuel simultaneously.
     • Simultaneous Injection:
       • All injectors operate at the same time.

3. Direct Injection:

   • Injects fuel directly into the combustion chamber.
   • Offers better control over fuel-air mixture.
   • Used in both diesel and gasoline engines.
   • Types of Direct Injection:
     • Spray Guided:
       • Injector positioned near spark plug; fine spray pattern.
     • Wall Guided:
       • Fuel injected against chamber walls before mixing with air.
     • Air Guided:
       • Air guides the fuel to the chamber, creating a vortex.

4. Dual Injection System:

   • Combines both direct and port injection.
   • Addresses the drawbacks of both systems:
     • Reduces carbon deposits.
     • Minimizes engine knock.
     • Optimizes fuel efficiency.

Conclusion

• Fuel injection technology enhances engine performance, efficiency, and reduces emissions.
• Modern vehicles increasingly rely on sophisticated fuel injection systems for optimal operation.