Multi Port Fuel Injection (MPFI) is a fuel delivery strategy where each intake runner is equipped with an individual fuel injector. This configuration ensures that each cylinder receives fuel through its own dedicated intake path.

System Characteristics#

In an MPFI system, the number of injectors corresponds directly to the number of cylinders in the engine. For example, a standard four-cylinder Honda engine utilizes four injectors, each positioned to spray fuel directly into the intake port of its respective cylinder.

Note

MPFI is distinct from Throttle Body Injection (TBI), which typically utilizes one or two injectors located in a central throttle body assembly to feed all cylinders simultaneously.

Advantages of MPFI#

• Improved Fuel Atomization: By placing the injector closer to the intake valve, fuel has less distance to travel, reducing wall wetting and improving mixture homogeneity.
• Precise Fuel Metering: The Engine Control Unit (ECU) can manage fuel delivery for each cylinder more accurately, allowing for better air-fuel ratio control across varying engine loads and RPMs.
• Enhanced Throttle Response: The reduction in fuel travel time from the injector to the combustion chamber results in more immediate engine response to throttle inputs.