Fuel Atomizer or Injector

“Fuel injector is an electronically controlled mechanical device that is responsible for spraying (injecting) the right amount of fuel into the engine so that a suitable air/fuel mixture is created for optimal combustion.” 

Types of Fuel Injector

1. Single-point or throttle body injection

2. Port or multi-point fuel injection

3. Sequential fuel injection

4. Direct injection

1. Single-point or throttle body injection

The throttle body injection (TBI) system is one of the first types of injection systems ever used by vehicles. Before TBI, vehicles used a carburetor. TBIs work in a manner very similar to a carburetor. The fuel is still sucked into the cylinders because of the suction created by the engine. However, TBIs are controlled by an electronic computer within the vehicle. The computer provides more accuracy by determining the amount of fuel that should be deposited into the engine. This accuracy ensures less fuel is wasted and allows the vehicle to run more efficiently.

2. Port or multi-point fuel injection

Multi-port fuel injection (MPFI) systems operate just how their name implies: with multiple intake ports. MPFIs are mounted onto each intake port. These intake ports are located just on the outside of the engine’s cylinders. In MPFI, each cylinder receives its own direct spray of fuel. So in a six-cylinder engine, there would be six injection ports. All individual injectors spray at the same time. This can sometimes lead to issues when leftover fuel is left behind while waiting for the next intake period. The fuel may condense into a liquid form and then be rendered unusable by the engine. Although MPFI is more efficient than TBI, sequential fuel injection offers even better fuel efficiency.

3. Sequential fuel injection

Sequential fuel injection, also called sequential port fuel injection (SPFI) or timed injection, is a type of multiport injection. Though basic MPFI employs multiple injectors, they all spray their fuel at the same time or in groups. As a result, the fuel may “hang around” a port for as long as 150 milliseconds when the engine is idling.Sequential fuel injection triggers each injector nozzle independently. Timed like spark plugs, they spray the fuel immediately before or as their intake valve opens. It seems like a minor step, but efficiency and emissions improvements come in very small doses.

4. Direct injection

Direct injection systems differ from other fuel injection systems because they bypass the intake valves and deposit fuel straight into the cylinder’s combustion chamber.Direct injection has been used in diesel engines since 1920 and has been used in gasoline aircrafts since World War 2. However, performance vehicle manufacturers like Audi and BMW are beginning to use the direct injection system in their vehicles as well. Because the fuel is sprayed right into the engine, it offers high levels of power and efficiency, which is ideal for performance vehicles.

Construction of Fuel Injector

Its consists of nozzle valve fitted in the nozzle body. The nozzle valve is held on its seat by a spring body which exert a pressure through the spindle. A adjusting screw are use for adjusting the nozzle valve lift. Feeling pin are use for indicating whether valve is working properly or not. 

Working of Fuel Injector

The fuel under the pressure from the fuel pump enter the injector through a passages B & C & lift the nozzle valve. The fuel travels down nozzle N & injected into the engine cylinder in the form of fine spray. Then the pressure of the oil is falls, the nozzle valve occupied its seat under the spring force & fuel supply is cut off. 

Any leakage of fuel accumulated above the valve is led to the fuel tank through the passage A. The leakage occurs when the nozzle valve is worn out. A sudden drop in pressure occurs & delivery valve falls back & occupied its seat against the spring force. 

When the engine is stopped, the plunger is rotated, at this position the rectangular slot in the line with spill port & there is no possibility of pressure build up above the plunger as the upper part of the plunger always remain in the connection with spill port. Therefore there is no delivery of the fuel.

Advantages of Fuel Injector

1. No problem in starting.

2. Throttle response is very sharp compared to a carburetor.

3. Less maintenance required.

Disadvantages of Fuel Injector

1. Fuel injection depend on lot of sensors and hence a normal mechanic cannot deal issues related to it so skill worker required.

2. High initial cost.