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Automobile Engineering Lab Lab Experiments

Study of Oil Filter, Fuel Filter, Fuel Injection System, Carburetor, MPFI

Working of Simple Carburetor

If you compare MPFI with single-point fuel injection, single-point fuel injection has only one centrally located fuel injector which supplies fuel to all cylinders, but in a multi point fuel injection system, each cylinder has a separate fuel injector that supplies fuel from the fuel tank to the cylinders. If you have to know that the idea behind an engine is to burn gasoline to create pressure, and then to turn the pressure into motion. A remarkably tiny amount of gasoline is needed during each combustion cycle. Something on the order of 10 milligrams of gasoline per combustion stroke is all it takes!

The goal of a carburetor is to mix just the right amount of gasoline with air so that the engine runs properly. If there is not enough fuel mixed with the air, the engine "runs lean" and either will not run or potentially damages the engine. If there is too much fuel mixed with the air, the engine "runs rich" and either will not run (it floods), runs very smoky, runs poorly (bogs down, stalls easily), or at the very least wastes fuel. The carb is in charge of getting the mixture just right.

Working of Simple Carburetor

MPFI-Multi Point Fuel Injection System


Despite the rapid development in carburetors which are cheap and efficient, the automobile industry prefers to use a gasoline injection system in spark ignition (S I Engines). Then, there must be some advantages of the gasoline injection system over the carburetor system which we are going to see it at the end of this article. There are different types of gasoline injection systems in S I Engines, and one of them is a Multi-Point Fuel Injection System (MPFI). In this article, we are going to learn about components, use and working of multi point fuel injection system.

Components in Multi Point Fuel Injection System (MPFI):

There are different components used in the MPFI system as follows:

  • A mechanical solenoid injector
  • The electronic control unit (ECU) - It controls ignition timing and quality of the fuel.
  • Electronic sensors to monitors different output such as exhaust gas temperature, coolant temperature, speed, and throttle position.
  • Air filters to remove solid particles from the atmospheric air.
simple carburetor
mifi system diagram

Working of Multi Point Fuel Injection or MPFI System:

  1. In the MPFI system, using the fuel pump which is driven by the electric motor is used to spray fuel into the engine intake manifold.
  2. This technique helps to provide an accurate air-fuel ratio at all operating conditions.
  3. The suction pressure of the engine is used to spray the fuel into the cylinders ( In carburetors, the vacuum is used to provide the fuel).
  4. As shown in the figure, you can see that a single injector is placed on the intake port of the different cylinders.
  5. Using the electrical fuel pump, fuel from the fuel tank supplies to each fuel injector equally.
  6. The process of fuel injection occurs simultaneously in each injector once in every rotation.

Classification of MPFI system:

MPFI system is classified into systems as follows:

  • D-MPFI System: D-MPFI is a manifold fuel injection system.
  • 2. L-MPFI System:L-MPFI is a port fuel injection system.

Advantages of MPFI system:

  1. The power generated by the engine is more than the carburetion system.
  2. Due to the accurate mixture of air-fuel supplied to each cylinder, the difference between power generated at each cylinder is negligible.
  3. Engine vibrations from MPFI equipped engines are very less, hence the life of MPFI system equipped engines is high.
  4. This system is very responsive in case of sudden acceleration or deceleration.
  5. Lower fuel consumption leads to better mileage.
  6. The volumetric efficiency of MPFI is high.

Disadvantages of MPFI system:

  1. The system is complex hence costly.
  2. It requires more space.