Understanding a multi-point fuel injection system

After the various articles published on this site on a fuel injection system in internal combustion engines, here we are on the multi-point injection types. The multi-point injection is a system or technique in which fuel is introduced into the cylinder of an internal combustion engine.

Today you’ll get to know the definition, functions, components, diagram, types, and working of a multipoint injection system. you’ll also get to know its advantages and disadvantages.

multi-point direct injection sytem

Read more: Understanding the fuel injection system in automobile engines


What is a multi-point injection system (MPFI)?

A multi-point injection which is abbreviated as MPFI is a system that injects fuel into the intake ports just upstream of each cylinder’s intake valve, rather than at a central point within an intake manifold.

Just as earlier mentioned, the MPFI is a system of injecting fuel into an internal combustion engine through multi ports situated on the intake valve of each cylinder. an exact quantity of fuel is delivering to each cylinder at the appropriate time.

Conventionally, petrol (or gasoline) engines are also called spark ignition (SI) engines. it uses a carburetor to mix air and fuel but it has poor response acceleration and deacceleration to the system. this carburetor also has a big problem with increased emissions. The purpose of these fuel injectors is to inject a precise quantity of fuel into the chamber.

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Functions of multi-point fuel injection

Below are the functions of a multi-point fuel injection system in gasoline engines:

  • Just as earlier mentioned, the primary function of MPFI is to inject a precise quantity of fuel into the combustion chamber.
  • These systems also produce better atomization and a swirl of fuel in the combustion chamber.
  • It reduces the difference in power in each cylinder.

Read more: Difference between fuel injection and carburetor

Components of a multi-point fuel injection

Below are the components of multi-point fuel injection in an automotive engine:

  • Fuel pressure regulator
  • Fuel injectors
  • Cylinders
  • Pressure spring
  • Control diaphragm

Multi-point fuel injection diagram:

diagram of a multi-point injection system

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Types of multi-point fuel injection system (MPFI)

There are three types of multi-point injection system which include:

  • Batched MPFI system
  • Simultaneous MPFI system
  • Sequential MPFI system

In a batched MPFI system, fuel is injected into a group or batches of the cylinders without bringing their intake stroke together.

In a simultaneous system, fuel is inserted into all cylinders at the same time. And finally,

In a sequential MPFI system, the injection is timed to overlap with the intake stroke of each cylinder.

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Working principle

Just as with other fuel injection methods in internal combustion engines, the working of a multi-point injection system is less complex and can be easily understood. In the system, multiple individual injectors are used to inject fuel into each cylinder through an intake port situated upstream of the cylinder’s intake value.

The fuel pressure regulator is connected to the fuel rail employing an inlet and outlet to direct the flow of the fuel. At the same time, the control diaphragm and pressure spring control the inlet valve opening and the amount of fuel that can return. The engine speed and load are change by the pressure in the intake manifold.

Watch the video to learn more about how a multi-point fuel injection system works:

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Advantages and disadvantages of a multi-point fuel injection (MPFI) system


Below are the advantages of a multi-point injection system on gasoline engines:

  • The system is reliable
  • It reduces the difference in power that each cylinder creates.
  • It increases the fuel efficiency of an engine
  • Better atomization of fuel
  • MPFI system have fewer emissions
  • Better utilization and distribution of fuel within an engine.
  • Better acceleration and deacceleration of engine
  • It improves the cold start properties of the engine
  • Vibrations in reduce in the engine
  • Improves durability and functionality of an engine

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Some other benefits include:

  • Easy engine tuning
  • Initial and maintenance cost
  • Smooth operations and drivability
  • Diagnostic capability
  • Ability to work with alternative fuels


Despite the various advantages of multi-point fuel injection, some limitations still occur. below are the disadvantages of multi-point fuel injection MPFI system in internal combustion engines:

  • Misfiring might occur sometimes
  • It requires regular inspection of fuel injectors
  • The system is expensive compared to conventional systems.
  • Repairing fuel injector can be tedious compared to carburetors
  • The system usually has a shorter life.
  • ECU failure could occur suddenly.
  • A hot engine might be difficult to start due to possible vapor lock in the steel fuel lines above the engine.

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In conclusion, a multi-point fuel injection system is also a method of injecting fuel into internal combustion engines. it’s abbreviated or often called an MPFI system. it offers good than bad, just as it’s mentioned in the advantages and disadvantages of the system. well, we’ve covered a lot on the multi-point injection system which includes, its definition, functions, components, types, and working.

I hope you enjoyed the reading, if so, kindly comment, share, and recommend this site to other technical students. Thanks!

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