Electronic fuel injection (EFI)

Fuel Injection of Modern Vehicle

What is EFI?

This type of system uses computer-controlled fuel injectors to spray fuel into the engine’s intake ports rather than mechanically controlled injectors or a carburetor. Electronic fuel injection is considered to be superior to carburetion because it allows more precise fuel metering for easier starting, lower emissions, better fuel economy and performance.

Typical EFI components

q Fuel Pump

q     Injectors

q     Fuel Pressure Regulator

q     ECM - Engine Control Module; includes a digital computer and circuitry to communicate with sensors and control outputs.

q     Wiring Harness.

q     Various Sensors.

EFI comes in several varieties:

1.     Throttle Body Injection (TBI).

2.     Multi Port Fuel Injection (MFI).

3.     Gasoline direct Inje

Throttle Body Injection

Incorporated electrically controlled a single injector or pair of injectors mounted in a centrally located throttle body. The injector sprays gasoline into the air in the intake manifold where the gasoline mixes with air. This mixture then passes through the throttle valve and enters into the intake manifold

Port Fuel Injection

    In the port injection arrangement, the injector is placed on the side of the intake manifold near the intake port. The injector sprays gasoline into the air, inside the intake manifold. The gasoline mixes with the air in a reasonably uniform manner. This mixture of gasoline and air then passes through the intake valve and enters into the cylinder. Every cylinder is provided with an injector in its intake manifold.

Gasoline Direct Injection (GDI)

q Fuel is injected directly into the cylinder chamber.

q     Direct injection engines have two design:

v     High-swirl design, which have a deep bowl in the piston, a low no of holes in the injector and moderate injection prs.

 Low-swirl or quiescent engines are characterized by having a shallow bowl in the piston, a large no of holes in the injector and higher injection pr.

Merits of EFI System

Better atomization and vapourization will make the engine less knock prone.

e.       Formation of ice on the throttle plate is eliminated.

f.       Distribution of fuel being independent of vapourization, less volatile fuel can be used.

g.       Variation of air-fuel ratio is almost negligible even when the vehicle takes different positions like turning, moving on gradients, uneven roads etc.

h.       Position of the injection unit is not -so critical and thereby the height of the engine (and hood) can be less.

Demerits of EFI System

a        High maintenance cost,

b.       Difficulty in servicing, and

c.       Possibility of malfunction of some sensors.