Single point fuel injection system: Definition, Working, Diagram [with Pdf]

What is single point fuel injection system?

Single point fuel injection system is the type of fuel injection system that uses a single fuel injector for mixing of the fuel. It has only one injector that injects the fuel before entering into the intake manifold.

In this system, the fuel is mixed with fuel before the throttle valve. The single-point fuel injection system is also known as throttle body injection.

Single point fuel injection system diagram:

Single point fuel injection system

Single point fuel injection system working:

In a single-point fuel injection system, the fuel injector is arranged before the throttle body.

The amount of fuel to be injected is decided by the engine control unit. The engine control unit takes the input from different sensors and decides the amount of fuel to be supplied for the injection.

The fuel injector sprays the fuel for mixing with the flow of air and this air-fuel mixture enters the intake manifold.

The intake manifold further distributes the mixture to all cylinders.

Advantages and disadvantages of single-point fuel injection system:

Advantages of single point fuel injection system:-

  1. Simple construction.
  2. Accurate fuel supply (in comparison with carburetor).
  3. Easy maintenance.
  4. It uses only a single injector.
  5. Reliable operation.

Disadvantages of single-point fuel injection system:-

  1. Ununiform fuel supply to all cylinders.
  2. Less efficient.
  3. It wets the intake manifold by forming a layer of fuel on the intake manifold.
  4. Lower fuel economy.

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2 thoughts on “Single point fuel injection system: Definition, Working, Diagram [with Pdf]”

  1. Why is the injector shown before the throttle valve? Surely, it’s better to have a single point injector squirt into the manifold? As drawn, when the throttle valve is (partially) closed the fuel is just sprayed at it?

    Reply
    • If the single point fuel injector injects fuel directly into the intake manifold, then the fuel will not properly mix with the air. As a result, the single point fuel injector will supply rich air-fuel mixture to the closest cylinder and lean mixture to the farthest cylinder.

      To prevent this, the single point fuel injector injects fuel before the throttle valve, giving it enough time to prepare a homogeneous mixture.

      Reply

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