mpfi system

MPFI SYSTEM

A

Research paper/Report

On

MPFI SYSTEM

For

The fulfillment of minor-2 examination assignment

By

The guidance of

Mr. Vivek Sharma

CAREER POINT UNIVERSITY, KOTA

SUBMITTED TO:-

Mr. VIVEK SHARMA

Asst. Prof. of ME Department


SUBMITTED BY:-

SUNIL KUMAR (K11255)

B.TECH (ME)

6th SEM.

MPFI SYSTEM

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

ABSTRACT


MPFI SYSTEM

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.


MPFI SYSTEM

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


MPFI SYSTEM

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


MPFI SYSTEM

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


MPFI SYSTEM

air/fuel mixture is supplied to the engine in each driving condition. The factors to determine

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.


MPFI SYSTEM

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


MPFI SYSTEM

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

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.


MPFI SYSTEM

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


MPFI SYSTEM

From various sensors.

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


MPFI SYSTEM

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.

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-


MPFI SYSTEM

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

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


MPFI SYSTEM

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

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


http://www.ijirset.com/

http://www.wikipedia.com/

mpfi system

Engineering