Fuel Injection Systems

Introduction

• Car engines require the correct air and fuel mixture to run efficiently.
• Carburetors were used in older engines to mix air and fuel.
• Modern vehicles use fuel injection systems for better efficiency and performance.

Importance of Fuel Injection

• Fuel Injection System: Vital component delivering fuel to the combustion chamber.
• Provides the right amount of fuel at the right time for reliable operation.

Components of Fuel Injection System

• Fuel Rail: Connects fuel injectors to the fuel supply, located near the intake manifold.
• Fuel Pump: Delivers fuel from the tank to the injectors.
• Injector Body: Houses nozzle, electromagnetic coil, fuel filter, and fuel inlet. Made of metal, designed for high pressure and temperatures.
  • Fuel Inlet: Where fuel enters the injector.
  • Fuel Filter: Removes impurities before fuel is sprayed into the engine.

Injector Operation

• Electromagnetic Coil & Plunger: Pulls the plunger up, opening the pintle injector to spray fuel.
• Nozzle: Sprays a fine mist of fuel into the combustion chamber, controlled by an electrical signal from the ECU.
• Pressure Regulator: Maintains consistent fuel pressure by adjusting flow based on pressure levels.

Air-Fuel Ratio

• Ideal ratio for combustion in gasoline engines: 14.7:1 (Air:Fuel).
• Lean Mixture: More than 14.7:1.
• Rich Mixture: Less than 14.7:1.
• Monitored by sensors and controlled by the ECU for optimal combustion.

Comparison: Carburetor vs. Fuel Injection

• Carburetor: Simple, inexpensive, but less precise; phased out in the 1990s.
• Fuel Injection: Available for gasoline and diesel; more accurate, efficient, and meets emission standards.

Types of Fuel Injection Systems

1. Throttle Body Injection (TBI)

• Also known as single point injection; uses a single injector in the throttle body.
• Better than carburetors but less efficient at high RPMs.

2. Multi-Point Fuel Injection (MPFI)

• Fuel injected into the intake port, with each cylinder having its own injector.
• More precise than throttle body injection.

Types of MPFI:

• Sequential: Injects fuel in a specific order per cylinder, offering high precision.
• Batched: Injects fuel in groups of cylinders; simpler but less precise.
• Simultaneous: Injects fuel into all cylinders at once, reducing wastage.

3. Direct Injection

• Fuel injected directly into the combustion chamber, improving efficiency.
• Used in gasoline (GDI) and diesel engines.

Types of Direct Injection:

• Spray Guided: Injector located near the spark plug; optimal spray shape for mixing.
• Wall Guided: Fuel strikes chamber walls before mixing with air.
• Air Guided: Air guides fuel spray into the chamber, creating a vortex for mixing.

4. Dual Injection System

• Combines direct and port injection to optimize efficiency.
• Reduces carbon deposits, engine knock, and improves fuel delivery.

Conclusion

• Fuel injection systems enhance engine performance, fuel efficiency, and reduce emissions.
• Understanding these systems is essential for modern automotive technology.