Abstract :
A multi-point
injection system, also called port injection, has an injector in the port (air-fuel
passage) going to each cylinder. Gasoline is sprayed into each intake port and
toward each intake valve. Thereby, the term multi-point (more than one location)
fuel injection is used.
Multipoint fuel injection (MFI)
locates an injector
immediately upstream of each inlet valve, which enables better control of
the air/fuel mixture to each cylinder.
Ever since
the World saw the first single cylinder petrol engine driven Car, a Carburetor became
synonymous with it. Later on with the advent of multi-cylinder Engines, so did the
Distributors. During the last Century, both evolved considerably till the ‘Euro-II’
like Pollution Norms got the better of them. For, the Carburetors worked on a fundamental
principle of ‘reaction’, which could easily get stifled for so many reasons. Whereas
man, as always, wanted to be literally in the Driver’s Seat, all the way along.
Thus, as the
cliché of necessity being the mother of invention goes, a System of controlled-feeding
of Fuel + Air + Ignition Spark to the ICE Cylinders in the early 80s evolved. A
system like that had to be based on its ‘needs of the moment’, such as the load
on it, engine rpm/road speed etc.
HOW MPFI WORKS?
The MPFI system
consists of one fuel injector placed near every
intake valve and directed towards it, in the fuel intake manifold.
Fuel is supplied to the injector through a common rail. The amount of air intake
is decided by the car driver by pressing the gas pedal, depending on the speed
requirement. The air mass flow sensor near throttle valve and the oxygen sensor
in the exhaust sends signal to
ECU. ECU determines
the air fuel ratio required ,hence the pulse width. Depending on the signal from
ECU the injectors inject fuel right into
the intake valve. The fuel sprayed at high pressure gts atomized into fine particles
and get mixed with air. The air fuel mixture is sucked ito the engine cylinder and
the combustion takes place.
FUNCTIONAL
DIVISIONS OF MPFI SYSTEM: The mpfi system can be functionally divided into the following
three main components :
1. Electronic control unit
2. Fuel system
3. Air induction system
The carburetor
were replaced by the single point injection in single cylinder engine. Th multicylinder
engines used distributors. But very shortly MPFI system replaced the distributors.
The modern day cars use MPFI engines ,which has electronic control in it. They
use the engine sensors, integrated chips to monitor the fuel injection time and
quantity The multipoint fuel injection are also used in the engines which use LP
gas as the fuel, with very less alterations in the gasoline run engine.
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