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#TechTalk: Multi-Point Injection

Posted November 25, 2021

2021 Hyundai Sonata SMARTSTREAM G2.5 petrol 2.5 MPi engine view finished in black. Photographed by AIMHO'S REBELLION 8490s at One Riverside, Kumbang Pasang (Gadong), Brunei.

This is the first in a content series we call #TechTalk where we make sense of all the automotive terms and jargon to give you a sense of what you’re driving.

First in line—MPI or Multi-Point Injection. Found on most modern cars, MPI is a type of fuel injection system or a system that introduces fuel to an internal combustion engine.  

Fuel injection systems are modern versions of the carburetor, which is a mechanical device used to mix fuel and air at a single point in the throttle body. Still in use on smaller engines like lawn mowers and some motorcycles, carburetors are not fully capable of controlling an accurate air-to-fuel ratio, which is ideally at 14.7:1. Thereby, carburetors could not meet the growing demand for better fuel efficiency and emission control.

Single versus Multipoint Injection Systems
a) Single Point, and b) Port or Multi-Point Fuel Injection Systems. Source: https://electricalfundablog.com


As opposed to carburetors, fuel injection systems can, under normal conditions, inject the right air-fuel mixture to the engine (the injection point depends on the type of fuel injection system).

A multi-point injection system injects fuel at each cylinder right outside the intake valves, allowing greater control over how much fuel the engine burns—compared to a single-point injection system where fuel is injected at the intake manifold (much like a carburetor).

MPI uses a separate injector nozzle for each cylinder to supply the correct quantity of fuel rather than relying on air pressure to do the job. Therefore, an MPI fuel system offers better fuel efficiency and engine response with reduced carbon emission.