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Submitted By

 Vipin Kumar Gupta

 VIth Sem

Diploma (Mech)

12114M02058

Submitted To

Dr. Narendra Wadekar

H.O.D.(Mechanical) 

MULTI POINT FUEL

INJECTION

(MPFI)

Govt Polytechnic college katni

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INTRODUCTION

 Air and fuel are supplied to an I.C.Engine whereexothermic reactions take place inside the combustion

chamber and the heat energy is converted into useful

work.

 To produce energy inside the engine , air fuel mixture

is to be burnt in correct amount. For mixing the air and

fuel in correct range different devices are used.

 The preparation of a homogeneous mixture of air-fuel

vapour mixture requires atomisation of liquid fuel

droplets and mixing the finely divided fuel particles

with air. The atomisation is accomplished by spraying

the liquid fuel through a nozzle into a stream of air

which is moving with large velocity.

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CARBURETOR

 Petrol vehicles use device called carburetor for

supplying the air fuel mixture in correct ratio to

cylinders in all rpm ranges. due to construction of

the carburetor is relatively simple, it has been

used almost exclusively on gasoline engines inthe past.

 These days in place of the carburetor, the MPFI

(multi point fuel injection) system is used,

assuring proper air fuel ratio to the engine byelectrically injecting fuel in accordance with

various driving conditions.

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FUEL ATOMISATION

  During fuelling of a cylinder the fuel is pressurised

which causes the fuel to become a vapour,

allowing it to burn easily (compared to the fuel

being delivered to the cylinder in liquid form)

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FUEL INJECTION

 The primary difference between carburetors andfuel injection is that fuel injection atomizes the fuel

by forcibly pumping it through a small nozzle under

high pressure, while a carburetor relies

on suction created by intake air accelerated through

a Venturi tube to draw the fuel into the airstream.

 Modern fuel injection systems are designed

specifically for the type of fuel being used. Somesystems are designed for multiple grades of fuel

(using sensors to adapt the tuning for the fuel

currently used). Most fuel injection systems are for

gasoline or diesel applications.

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OBJECTIVES OF FUELINJECTION SYSTEM

  The injection system of the compression ignitionengine should fulfill the following objectivesconsistently and precisely:

1. Meter the appropriate quantity of fuel, asdemanded by the speed of, and the load on, theengine at the given time.

2. Distribute the metered fuel equally amongcylinders in a multi-cylinder engine.

3. Inject the fuel at the correct time (with respectto crank angle) in the cycle.

4. Inject the fuel at the correct rate (per unit timeor crank angle degree).

5. Begin and end injection sharply withoutdribblin.

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 There are two major divisions of Fuel Injection

systems:Solid Injection systems, which inject only the liquid fuel

through the injectors.

 Air Injection systems, which inject air along with the

liquid fuel

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VARIOUS INJECTION SYSTEM

MPFIsystem

Port injection

ThrottleBody injection

L-MPFI System

D-MPFISystem

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 THROTTLE BODY INJECTION SYSTEM

The throttle body injection (TBI) system uses one or twoinjector valves mounted in a throttle body assembly. The

injectors spray fuel into the top of the throttle body air horn.

The TBI fuel spray mixes with the air flowing through the

air horn. The mixture is then pulled into the engine by

intake manifold vacuum.

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Throttle Body Injection System

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L & D MPFI GASOLINE INJECTION

SYSTEM

  I-mpfi systemstands forIntelligent-

Multi Point Fuel Injection System, and

 D-mpfi systemstands forDirect-Multi Point

Fuel Injection System.

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D-MPFI GASOLINE INJECTION

SYSTEM

The D-MPFI system is the manifold fuel injection

system . In this type , the vacuum in the intake

manifold is first sensed .In addition the volume of

air is sensed by its density . As air enters into the

intake manifold ,the manifold pressure sensordetects the intake manifold vacuum and sends the

information to the ECU . The speed sensor also

sends the information about the rpm of the engine

to the ECU . The ECU in turn sends command tothe injector to regulate the amount of gasoline

supply for injection . When the injectors spray fuel

in the intake manifold the gasoline mixes with the

air and the mixture enters the cylinder.

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L & D MPFI GASOLINE INJECTION

SYSTEM

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INTRODUCTION

MPFI- a technology used in petrol engines

Uses a small computer to control the car’s engine

In MPFI engine one fuel –injector is installednear each cylinder ,that is why it is called multi

point fuel injection.

Before MPFI system, there was a technology

called “Carburetor” .

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The computer in the MPFI system decides what

amount of fuel to inject

System also learns from the drivers driving

habits

MPFI system makes engine fuel efficient .

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MAIN COMPONENTS OF MPFI SYSTEM

This system has four major components they are:

a) Air intake system

i. Throttle body

ii. Idle air control valve

b) Fuel delivery system

iii. Fuel pump

iv. Pressure regulator system

v. Injector

c) Electronic control system

vi. Engine Control Module (ECM)

vii. On-Board diagnostic system

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 AIR INTAKE SYSTEM

 The air (corresponding to the throttle valve

opening) is filtered by the air cleaner, passes

through the throttle body, and is distributed by

the intake manifold and finally drawn into each

combustion chamber. When the lAC valve isopened according to the signal from ECM, the air

bypasses the throttle valve through bypass

passage and is finally drawn into the intake

manifold.

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FUEL DELIVERY SYSTEM

 The fuel in the fuel tank is pumped up by the

fuel pump, filtered by fuel filter and fed under

pressure to each injector through the delivery

'pipe. As the fuel pressure applied to the injector

is always kept a certain amount higher than thepressure in the intake manifold by the fuel

pressure regulator, the fuel is injected into the

intake port of the cylinder head when the injector

opens according to the injection signal formECM. The fuel relieved by the fuel pressure

regulator return through the fuel return to the

fuel tank.

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INJECTORS

The opening of the injector is controlled by the vehicles ECU

The injector is supplied with the battery voltage via a relay,

the earth circuit is controlled by the ECU

When the circuit is completed by the ECU a solenoid

operates, the injector valve opens, fuel is then able to be

sprayed into the inlet manifold

The valve moves roughly 1.5-10 milliseconds. This is known

an injector duration or opening time

The ECU will make amendments to the duration depending

on engine temperature, loading air temperature and batteryvoltage

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THE ROLE OF THE INJECTORS

  The injector delivers a finely atomized spray of

fuel into the inlet port

  The injectors also vary the amount of fueldelivered to suit the engines conditions

 

The spray is obtained by passing fuel (that is

pressurised) through the nozzle of the injector

It is located in the inlet manifold near the cylinder

head intae port

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TYPES OF INJECTORS

1. Pintle Type Injector-Offers good

atomization of fuel.

  Prone to deposit build up on the Pintle

valve (deposits can reduce the amount offuel flow, and therefore the vehicle will

run leaner than recommended.

2.Hole type injector- Fuel is delivered

through holes drilled in a director plate at

the injector tip.

 Offers good fuel atomization and gives

better resistance to deposit build-up.

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The injector is placed on the

side of the intake manifold

near the intake port

Every cylinder is providedwith an injector in its intake

manifold .

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 ELECTRONIC CONTROL SYSTEM

 The electronic control system consist of various

sensors which detect the stateofengine and

driving conditions, ECM which controls various

devices according tothesignals from the sensors

and Various controlled devices. The systems are  Fuel injection control

system

 Idle speed control system

 Fuel pump control system,

 Ignition control system,

 Radiator fan control system,

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 ELECTRONIC CONTROL UNIT’S

CHIP

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WORKING

Injection nozzle atomizes fuel into very small

droplets.

 Achieved by providing loaded valve needle forcing

out fuel through small orifice.

Nozzle valve seats on conical seating due to

spring pressure on spindle.

Spring pressure is suitably adjusted by adjusting

screw to give correct opening pressure to fuel.

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Fuel enters to passage drilled in nozzle holder and

flows to an annular groove around needle seat.

The needle (nozzle) valve is then lifted against spring

pressure to allow high pressure fuel to flow into

combustion chamber.

Nozzle valve closes when fuel pressure becomes less

than spindle spring pressure.

Extra fuel going up to nozzle spindle is carried away

through leak-off pipe to fuel tank.

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FUNDAMENTALS OF FUEL

INJECTION

MPFI Systems can either be: Sequential Simultaneous Group

These techniques result in better ‘power

balance’ amongst the cylinders, higher

output from each one of them, along

with faster throttle response.

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TYPES OF MPFI SYSTEMS

Simultaneous injectors will operate all (or groups of

injectors) at the same time

Sequential will operate independently and open and

close at different times (determined by the ECU)Group used in cylinder pairs [in V-series engines]

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'Sequential' is the best from the above

considerations of power balance/output

“Sefi’’-Sequential Electronic Fuel Injection -

technically is the best of the above variants ofMPFI

The ‘on-board’ ECU primarily controls the

Ignition Timing and quantity of fuel to be

injected .

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 ADVANTAGES OF MPFI1. Improved fuel consumption

2. Better for the environment

3. Better performance.

4. Immediate response, in case of sudden acceleration / deceleration.

5.  No need to crank the engine twice or thrice in case of cold starting as

happens in the carburetor system.

6. More uniform A/F mixture will be supplied to each cylinder; hence the

difference in power developed in each cylinder is minimum. Vibration

from the engine equipped with this system is less, due to this the life of

engine components is improved.

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THANK-

 YOU