MPFI

1. MPFI SYSTEM
CAREER POINT UNIVERSITY, KOTA Page 1
A
Research paper/Report
On
MPFI SYSTEM
For
The fulfillment of minor-2 examination assignment
By
The guidance of
Mr. Vivek Sharma
SUBMITTED TO:-
Mr. VIVEK SHARMA
Asst. Prof. of ME Department
CAREER POINT UNIVERSITY, KOTA
SUBMITTED BY:-
SUNIL KUMAR (K11255)
B.TECH (ME)
6th SEM.

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CAREER POINT UNIVERSITY, KOTA Page 2
CONTENTS
Sr. No. TOPIC NAME Page No.
Abstract 3
1. Introduction 3
2. Working & principle 4
3. Special features & characteristics 4
4. Emission control system 9
5. Sensors used in MPFI System 11
6. Advantages & Disadvantages 12
7. Results 13
8. Future scope 13
9. Conclusion 14
10. References 14

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ABSTRACT
MPFI means Multi Point Fuel Injection system .Multiport fuel injection injects fuel into
the intake ports just upstream of each cylinder's intake valve, rather than at a central point
within an intake manifold. MPFI systems can be sequential, in which injection is timed to
coincide with each cylinder's intake stroke; batched, in which fuel is injected to the cylinders
in groups, without precise synchronization to any particular cylinder's intake stroke; or
simultaneous, in which fuel is injected at the same time to all the cylinders. In this system
each cylinder has number of injectors to supply or spray fuel in the cylinders as compared to
one injector located centrally to supply or spray fuel in case of single point injection system.
MPFI system injects fuel into individual cylinders, based on commands from the ‘on board
engine management system computer’ – popularly known as the Engine Control Unit/ECU.
These techniques result not only in better ‘power balance’ amongst the cylinders but also in
higher output from each one of them, along with faster throttle response. The electronic fuel
injection system supplies the combustion chambers with air/fuel mixture of optimized ratio
under widely varying driving conditions.
1. INTRODUCTION -
Air–fuel ratio (AFR) is the mass ratio of air to fuel present in an internal combustion engine.
It is highly desirable to vary the air-fuel ratio according to the load on the engine for better
fuel efficiency and mileage. But supplying the correct air-fuel ratio for a given speed is a big
challenge. Petrol vehicles uses 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 in the past. However in
response to recent demands for cleaner exhaust emission, more economical fuel
consumption, improved drivability, etc., the carburetor now must be equipped with various
compensating devices, making it more complex system. So In place of the carburetor,
therefore, the MPFI (multi point fuel injection) system is used, assuring proper air fuel ratio
to the engine by electrically injecting fuel in accordance with various driving conditions.

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2. WORKING & PRINCIPLE-
Fig. of mpfi system
Fuel injectors are nozzles that inject a spray of fuel into the intake air. Multipoint Port Fuel
Injector engine having one or more injectors are mounted by the intake valve of each
cylinder. They spray fuel into the region directly behind the intake valve, sometimes directly
On to the back of the valve face. The injectors are usually timed to spray the fuel into the
quasi stationary air just before the intake valve opens.
Because injection starts before the intake valve is open, there is a momentary pause in the air
flow, and the air velocity does not promote the needed mixing and evaporation enhancement.
When the valve then opens, the fuel vapor and liquid droplets are carried into the cylinder by
the on rush of air, often with the injector continuing to spray any backflow of hot residual
exhaust gas that occurs when the intake valve opens also enhances the evaporation of fuel
droplets.
3. SPECIAL FEATURES-
MAIN COMPONENTS OF MPFI SYSTEM:-
This system has four major components. They are:-
 AIR INTAKE SYSTEM
 FUEL DELIVERY SYSTEM
 ELECTRONIC CONTROL SYSTEM
3.1. 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

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each combustion chamber. When the lAC valve is opened according to the signal from ECM,
the air bypasses the1hrottle valve through bypass passage and is finally drawn into the intake
manifold.
a. Throttle Body -
The throttle body consists of the main bore, air bypass passage and the following parts.
Throttle valve, which is interlocked with the accelerator pedal and controls the amount of the
intake air. TP sensor which detects the throttle valve opening and sends a signal to ECM. lAC
valve, which supplies the bypass, air depending on Engine condition.
b. Idle Air Control Valve -
The lAC valve controls opening of the bypass air passage. The air bypasses the throttle valve
through bypass passage and is finally drawn into the intake manifold. Opening and closing of
the valve itself is determined by operation of the magnet, which is connected to it. The
magnet operates according to electric current from ECM.
3.2. 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 the pressure 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 form ECM. The fuel relieved by the fuel
pressure regulator return through the fuel return to the fuel tank.
A. Fuel Pump-
The electrical fuel pump located on the fuel tank consists of armature, magnet, impeller,
brush, check valve etc. The ECM controls its operation. When the power is supplied to the
fuel pump, the motor in the pump runs and so does the impeller. This causes a pressure
difference to occur between both sides of the impeller, as there are many grooves around it.
Then the fuel is drawn through the inlet port, and with its pressure increases, It is discharged
through the outlet port, the fuel pump also has a check valve to keep some pressure in the fuel
feed line even when the fuel pump is stopped.
B. Pressure Regulator System-
The fuel pressure regulator is diaphragm operated relief valve consisting of diaphragm,
spring and valve. It keeps the fuel pressure applied to the injector 2.9Kglcm^2 higher than
intake manifold at all times, The pressure applied to the upper chamber of the fuel pressure

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regulator intake manifold pressure and that to the lower chamber is fuel pressure. When the
fuel pressure rises more than 2,9Kg/cm2 higher than the intake manifold pressure, the fuel
pushes the valve in the regulator open and excess fuel return to the fuel tank through return
line.
C. Injector-
Each cylinder has one injector, which is installed between the intake manifold delivery pipes.
It is an electromagnetic type injection nozzle, which injects fuel into the intake port of the
cylinder head according to the signal from ECM. When the solenoid coil of the injector is
energised by ECM, it becomes an Electro magnet and attracts the plunger. At the same time,
the ball valve which is incorporated with the plunger opens and the injector which is under
the fuel pressure injects fuel. As the lift stroke of the ball valve of the injector is set constant,
the amount of fuel injected at one time is determined by the length of the time during which
the solenoid is energized.
3.3. ELECTRONIC CONTROL SYSTEM -
The electronic control system consist of various sensors which detect the state of engine and
driving conditions, ECM which controls various devices according to the signals 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
 Fuel Injection Control System-
The electronic fuel injection system supplies the combustion chambers with air/fuel mixture
of optimized ratio under widely varying driving conditions. It uses the sequential multi-port
fuel injection system, which injects fuel into each intake port of the cylinder head. In this
system ECM controls the time and timing of the fuel injection from the fuel injector into the
cylinder head intake port according to the signals from the various sensors so that suitable
air/fuel mixture is supplied to the engine in each driving condition. The factors to determine

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the injection time are the basic injection time which is calculated on the basis of the engine
speed and the intake manifold pressure and various compensation which are determined
according to the signals from various sensors that detect the state of the engine and driving
conditions.
 Idle Speed Control System -
This system controls the bypass airflow by means of ECM & lAC valve for the following
purposes. To keep the engine idle speed as specified at all times. The engine idle speed can
vary due to load applied to engine, to improve starting performance of the engine to
compensate air fuel mixture ratio when -decelerating, to improve drivability while engine is
warmed up. lAC valve operates according to duty signal sent from ECM. ECM detects the
engine condition by using the signals from various signals and switches and controls the
bypass airflow by changing lAC valve opening. When the vehicle is at a stop, the throttle
valve is at the idle position and the engine is running, the engine speed is kept at a specified
idle speed.
 Fuel Pump Control System -
ECM controls ON/OFF operation of the fuel pump by turning it ON, the fuel pump relay
under any of the conditions. For two seconds after ignition switch ON. While cranking engine
(while engine start signal is inputted to ECM). While crankshaft position sensor or camshaft -
position sensor signal is inputted to ECM.
 Ignition Control System -
This system controls electronically the time of electric current flow to ignition primary coil as
well as ignition timing. ECM judges the engine and vehicle conditions by using signals from
various sensors, selects the most suitable electric current flow time and ignition timing for
that engine and vehicle conditions from among those prestored in its memory and sends an
ignition signal to the igniter in ignition coil assembly. Controls of this system include three
different types as follows. Ignition timing control at engine start, ignition timing control after
engine start, electric current flow time control.

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 Radiator Fan Control System -
This system controls operation (ON/OFF) of the radiator fan motor. Radiator fan motor is
turned ON and OFF by its relay when ECM controls. Radiator fan motor turned ON at below
98°C and OFF at below 93°C.
a. Engine Control Module (ECM) -
ECM is installed to the underside of the instrument panel at the passenger's seat side. ECM is
a precision unit consisting of microcomputer, analogue/digital converter input/output unit etc.
It is an essential part of the electronic control system for its functions include not only such a
major function as to control fuel injector, lAC valve, fuel pump relay, etc. But also on-board
diagnostic system (self-diagnosis function) and fail-safe function.
b. On-Board Diagnostic System –
ECM diagnosis troubles which may occur in the area including the following parts when the
ignition switch is ON and the engine is running, and indicates the result by turning on or
flashing malfunction indicator lamp (CHECK ENGINE LIGHT).
1. Oxygen sensor
2. Engine coolant temp sensor
3. TP sensor
4. IATsensor
5. MAP sensor
6. CMP sensor
7. VS sensor
8. CKP sensor
9. CPU of ECM
ECM and malfunction indicator lamp (MIL) operate as follows Malfunction indicator lamp
lights when the ignition switch is turned ON but engine at stop with the diagnosis switch
terminal ungrounded regardless of the condition of electronic fuel injection system. This is
only to check the malfunction indicator lamp bulb and its circuit. If the above areas of
electronic fuel injection system; is free from any trouble after the engine start while engine is
running. Malfunction indicator lamp turns OFF. When ECM detects a trouble which has
occurred in the above areas, it makes malfunction indicator lamp turn ON while the engine is
running to warn the driver of such occurrence of trouble and at the same time is stores the

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trouble area in ECM back-up memory. The memory is kept as it is even if the trouble was
only temporary and disappeared immediately and it is not erased unless the power to ECM is
shut off for specified time 60 sec. or longer. ECM also indicates trouble area in memory by
means of flashing of malfunction indicator lamp at the time of inspection.
 Fail- Safe Function –
Even when a trouble has occurred in such area of electronic fuel injection system that
includes the following parts and a failure signal is sent to ECM. Control over the injector,
idle air control valve and others are maintained on the basis of the standard signals and/or
CPU. This function is called failsafe function. Thus with this function a certain level of
engine performance is available even when some failure occurs in such area and disability in
running is avoided.
4. EMISSION CONTROL SYSTEM -
The need to control the emissions from automobiles gave rise to the computerization of the
automobile. Hydrocarbons, carbon monoxide and oxides of nitrogen are created during the
combustion process and are emitted into the atmosphere from the tail pipe. There are also
hydrocarbons emitted as a result of vaporization of gasoline and from the crankcase of the
automobile. Manufacturers’ are adding of pollution control devices and the creation of a self
adjusting engine. 1981 saw the first of these self adjusting engines. They were called
feedback fuel control systems.
 Emission control in Petrol engine passenger cars -
A petrol engine without emission control produces large emissions of nitrogen oxides and
unburnt hydrocarbons. The technology that manufacturers have used to meet stiffer emission
requirements is the three-way catalytic converter and new technology such as MPFI, it
maintain proper air fuel mixture at stoichiometric ratio by the use of sensors in the engine,
thereby ensuring proper combustion of the air fuel mixture due to this it reduces the
emissions from the vehicles.

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4.1 CATALYTIC CONVERTER -
Automotive emissions are controlled in three ways; one is to promote more complete
combustion so that there is less by products. The second is to reintroduce excessive
hydrocarbons back into the engine for combustion and the third is to provide an additional
area for oxidation or combustion to occur. This additional area is called a catalytic converter.
The catalytic converter looks like a muffler. It is located in the exhaust system ahead of the
muffler. Inside the converter are pellets or a honeycomb made of platinum or palladium. The
platinum or palladium is used as a catalyst (A Catalyst is a substance used to speed up a
chemical process). As hydrocarbons or carbon monoxide in the exhaust are passed over the
Catalyst, it is chemically oxidized or converted to carbon dioxide and water. As the converter
works to clean the exhaust, it develops heat. The dirtier the exhaust, the harder the converter
works and the more heat that is developed. In some cases the converter can be seen to glow
from excessive heat. If the converter works this hard to clean a dirty exhaust it will destroy
itself. Also leaded fuel will put a coating on the platinum or palladium and render the
converter ineffective.
Catalytic oxidizers are used in most cars around the world. Because catalytic oxidizers cannot
operate in the presence of lead, their introduction caused leaded gasoline to be phased out.
Ideally the byproducts of an automobile engine are only carbon dioxide, water, and some
nitrogen. This is similar to the chemical output of animals. But in practice, the combustion
process in an engine is never 100% efficient, leaving behind hot, yet unburned hydrocarbons.
Oxidizer fitted to a car’s tailpipe rapidly oxidizes a large percentage of the remaining unburnt
Hydrocarbons, resulting in cleaner emissions. However, the speed at which catalytic
oxidizers must operate to catch unburnt hydrocarbons before they fly out the tailpipe puts
limits on how efficient the oxidation process can be.
4.2 EVAPORATIVE EMISSION CONTROL SYSTEM -
The evaporative emission control system is used to prevent emission of fuel vapour. The
vapour generated in the fuel tank while driving or the Engine at a stop passes through a tank
pressure control valve and enters the EVAP canister was the charcoal absorbs the stores the
fuel vapour. The EVAP canister purge valve is controlled by ECM according to signals
From various sensors.

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5. SENSORS USED IN MPFI:-
5.1 Manifold Absolute Pressure (MAP) Sensor-
This sensor senses pressure change in the intake manifold and converts it into voltage
Change. It consists of a semi-conductor type pressure converting element, which converts a
pressure change into an electrical change and, an electronic circuit which amplifies and
corrects the electric change. The ECM sends a 5-volt reference voltage to the pressure sensor.
As the manifold pressure changes, the electrical resistance of the sensor also changes By
monitoring the sensor output voltage ,ECM knows the manifold pressure, ECM uses the
voltage signal from the pressure sensor as one of the signals to control fuel injector.
5.2 Throttle Position Sensor -
The throttle position sensor is connected to the throttle valve shaft on the throttle body, and
detects throttle valve opening, the throttle opening is detected by the potentiometer. A 5-volt
reference Voltage is applied to the sensor from ECM and as Brush moves over the print
resistance according to the throttle valve opening, the output voltage varies accordingly. By
monitoring sensor output voltage, ECM detects the throttle valve opening. ECM uses the
signal from TP sensor as one of the signals to control various devices.
5. 3 Intake Air Temperature Sensor-
Located on the air cleaner outlet hose, this sensor constantly measures the temperature of the
air entering there and converts a change in the air temperature into that in resistance through
its thermostat. That is, as is temperature lowers, resistance increases and as it rises, resistance
decreases. As air density of the intake air varies with Variation in temperature, ECM, by
monitoring the resistance, adjusts the amount of fuel injection according to the air
temperature.
5.4 Engine Coolant Temperature Sensor-
Incorporated with coolant temperature. Gauge and installed to thermostat case, this sensor
measures the temperature of the engine coolant and converts its change into that in resistance
through the thermistor like the air temperature sensor, by monitoring the resistance of the
coolant temperature sensor, ECM detects the engine coolant temperature and that affects
most systems under the control of ECM.

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5.5 Oxygen Sensor-
The oxygen sensor is installed on the exhaust manifold to detect the concentration of oxygen
in the exhaust gases. in order of engines equipped with the three- way catalytic converter to
achieve their best exhaust emission purification performance, it is necessary for the air-fuel
ratio to be kept within a narrow range near the theoretical air-fuel ratio. The oxygen sensor
senses whether the air-fuel ratio is richer on leaner than the theoretical air-fuel ratio, The
oxygen sensor is located in the exhaust manifold and consists of an element made of
zirconium dioxide (ZrO2, a kind of ceramic material) This element is coated on both inside
and outside with a thin layer of platinum. Atmospheric air is introduced into the inside of the
sensor, and outside of the sensor is exposed to the exhaust gases.
If the Oxygen concentration on the inside surface of the zirconium element differs greatly
from that on the outside surface at high temperatures, the zirconium element generate a
voltage when the air-fuel mixture is lean there is lot of oxygen in the exhaust gas, so there is a
little difference between oxygen concentration inside and outside the sensor element. Thus
the voltage generated by the zirconium element is low if the air-fuel mixture is rich; the
oxygen in the exhaust has almost disappears. This creates a large difference in the oxygen
concentrations inside and outside the sensor and voltage generated by the zirconium element
is large. The ECM uses this signal to increase or reduce the injection volume to keep the air-
fuel ratio at an even value near the stoichiometric air-fuel ratio.
5.6 Vehicle Speed Sensor-
The vehicle speed sensor, located on the transmission gearbox or speedometer, Generates a
signal in proportion to the vehicle speed. Receiving this signal, the speedometer uses it for
operation of its indicator and also converts it into to the ON/OFF signal by doubling the
cycle. This signal is sent to ECM where it is used as one of the signals to control various
devices.
5.7 Camshaft Position Sensor-
The sensor is mounted on the sensor case (distributor less ignition case) on tile camshaft let
side for distributor less ignition vehicle and other vehicles on the distributor. The signal rotor
is press-fitted onto the camshaft (distributor less ignition vehicle) and other vehicles on the
distributor shaft. As the sensor has a built-in hall element and a waveform forming circuit, it

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converts changes in the magnetic flux caused by rotation of the signal rotor into electric pulse
signals, Using this signal and the signal from the CKP sensor (if equipped), ECM identifies
the cylinder whose piston is in the compression stroke.
5.8 Crank Shaft Position Sensor-
The sensor consists of magnet and coil. It is mounted on oil pan with specified air gap
between the sensor core end and crankshaft timing belt pulley tooth. As the crankshaft turns,
AC voltage is generated in the sensor. ECM uses this signal as: Engine speed, Cylinder
identification.
6. ADVANTAGES OF MPFI SYSTEM-
 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.
 No need to crank the engine twice or thrice in case of cold starting as happens in the
carburetor system.
 Immediate response, in case of sudden acceleration / deceleration.
 Since the engine is controlled by ECM* (Engine Control Module), more accurate
amount of A/F mixture will be supplied and as a result complete combustion will take
place. This leads to effective utilization of fuel supplied and hence low emission level.
 The mileage of the vehicle will be improved.
7. RESUTS –
In this system the fuel is injected into the intake port of each cylinder just before the inlet
valve. It requires one or more injectors per cylinder. The advantages of this system are
improved power and torque through improved volumetric efficiency and more uniform fuel
distribution to each cylinder and rapid response to the changes in the throttle position and
hence an appreciable fuel economy.
8. FURURE SCOPE-
The performance of MPFI engines is always better than the Carburetor SI engine. MPFI SI
engine as well as Carburetor SI engines and reduced the exhaust emissions. Performance

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parameters for MPFI SI engine are better and recommended for the automobile vehicles. It
can be best right solution to oil crisis. The MPFI engine performed satisfactorily on Ethanol
& without any hardware modification. Ethanol reduces the environmental impacts of
transportation, reduce the dependence on crude oil imports and offer business possibilities to
agricultural enterprises for periods of excess agricultural production.
9. CONCLUSION -
Almost all vehicles in India are changing to the mpfi because of law emissions, improved
mileage and drivability since the engine is controlled by micro computer more accurate
amount of a/f mixture will be supplied and as a result complete combustion will take place.
This leads to effective utilization of fuel supplied and hence low emission level. It reduces
wastage of fuel by the use of sensors and other control systems.
10. REFERENCES-
 I.C.Engine- V. Ganeshan
 www.wikipedia.com
 www.ijser.org
 www.ijirset.com
 www.ijfeat.org
 www.ijera.com
 www.howstuffworks .com
 www.indiacar.com