MPFIMPFI(Multi Point Fuel Injection)(Multi Point Fuel Injection)

IntroductionIntroduction

• In petrol vehicles carburetor is used for supplying air fuel mixture to the cylinder

• In response to the recent demand for cleaner exhaust emission improved drivability and mileage carburetor is not sufficient

• In place of the carburetor MPFI system is used in vehicles

• MPFI system is injects fuel into individual cylinders based on commands from engine control module

• The MPFI gives higher output, faster throttle response under varying driving conditions

FUNDAMENTALS OF FUEL FUNDAMENTALS OF FUEL INJECTIONINJECTION

• MPFI Systems can either be:

Sequential or Simultaneous or Group type

• These techniques result in better ‘power balance’ amongst the cylinders, higher output from each one of them, along with faster throttle response

• '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 of MPFI

• The ‘on-board’ ECU primarily controls the Ignition Timing and quantity of fuel to be injected

VARIOUS INJECTION SYSTEMVARIOUS INJECTION SYSTEM

MPFIsystem

Port injection

Throttle Body

injection

L-MPFI System

D-MPFI System

Components of MPFIComponents of MPFI• The system has four major components they are

1. Air intake system

2. Fuel delivery system

3. Electronic control system

4. Emission control system• Air intake system• It includes air filter, throttle body, intake

manifold, and finally drawn into the combustion chamber

Air intake systemAir intake system• Throttle body• It consist of throttle valve, T P sensor, which detect

the throttle valve opening• Idle air control valve which supplies bypass air

depending on the engine condition

• Fuel delivery system • It includes fuel pump, fuel filter and injector• Fuel pump• ECM controls its operation and centrifugal pump is

used to pump the fuel• The fuel pump also has a check valve to keep some

pressure in fuel feed line even when fuel pump is stopped

Pressure regulator systemPressure regulator system• It keep the fuel pressure applied to the

injector 2.9kg/cm^2

• Injector• Each cylinder have one injector• It inject the fuel into the inlet manifold according to

the signal from ECM

• Electronic control system• The electronic control system consist of various

sensors which detect the state of engine and driving conditions

•

Control systems are:Control systems are:• Fuel injection control system

• In which ECM controls the timing of fuel injection according to the signals from various sensors

• Injection time is calculated on the basis of engine speed

• Idle speed control system

• It keep the engine idle speed as specified at all times

Fuel pump control systemFuel pump control system• ECM controls the ON\OFF operation of the

fuel pump• Ignition control system• This system controls ignition timing• The ECM judges the engine conditions by

using signals from various sensors selects suitable ignition timing

• Controls of this system includes• Ignition timing at the engine start• Ignition timing after engine start

Radiator fan control systemRadiator fan control system• Radiator fan motor is turned ON and OFF by using

relays • Radiator fan motor turned ON at below 98degree

Celsius and OFF at below93degree Celsius

• Engine Control Module • It consist of micro computer, analogue\digital converter • It controls fuel injector, IAC valve, fuel pump relay

….etc•

WorkingWorking

Functional division of MPFIFunctional division of MPFI

MPFI ClassificationMPFI ClassificationDepending upon the working, there are further

two types

1. D-MPFI system

2. L-MPFI system

D-MPFI SystemD-MPFI System• In D-MPFI system (Manifold Fuel Injection

System), we measure the vacuum created in the intake manifold and air volume using its density.

• The block diagram of D-MPFI system shows the complete working of the system. Mainly we take the help of sensors and measure intake manifold vacuum using manifold pressure sensor and engine speed using speed sensor. After that both information's are sent to the ECU which further regulates the petrol supply.

D-MPFI Gasoline Inj. SystemD-MPFI Gasoline Inj. System

L-MPFI SystemL-MPFI System• In L-MPFI system (Port Fuel Injection System),

we measure engine speed and the amount of air actually entering in the engine. If we look at the block diagram of the L-MPFI system, air flow sensor measures actual amount of air and speed sensor measures the engine speed. Both information's are then sent to ECU which regulates the supply of petrol. -

L-MPFI Gasoline Inj. SystemL-MPFI Gasoline Inj. System

On-board diagnostic systemOn-board diagnostic system• ECM diagnosis troubles which may occur in the engine

when ignition switch is ON and the engine is running, it indicates trouble to the driver by flashing malfunction indication lamp

• And it stores the data about the trouble in ECM back up memory

• Emission control system• It includes evaporative canister

• Evaporative emission control system• This is used to prevent emission of fuel vapour

Sensors used in MPFISensors used in MPFI• Manifold absolute pressure sensor• This sensor senses pressure change in the intake

manifold• The signals from the MAP is used by the ECM to control

fuel injection pressure

• Throttle position sensor• This is connected to throttle valve shaft on the throttle

body and detects throttle valve opening

• Intake air temperature sensor• It located on the air cleaner outlet hose and constantly

measures the temperature of air entering to the intake manifold

• By sensing the temp. the ECM adjusts fuel injection quantity

Engine coolant temperature sensor Engine coolant temperature sensor • It is incorporated with coolant and measures the

coolant temperature

Oxygen sensor Oxygen sensor is installed on the exhaust manifold to

detect the concentration of oxygen in the exhaust gases

It is necessary to keep the air fuel ratio within a narrow range, and keep it in a stochiometric air fuel ratio

Vehicle speed speed sensor The vehicle speed sensor is located on the

transmission gear box or speedometer

Cam shaft position sensorCam shaft position sensor

• Using this signal ECM identifies cylinder whose piston is in the compression stroke

• Crank shaft position sensor• ECM uses this signal for knowing the engine

speed and cylinder identification

Advantages of MPFIAdvantages of MPFI

• 1) 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.

(2) No need to crank the engine twice or thrice in case of cold starting as happens in the carburetor system.

(3) Immediate response, in case of sudden acceleration / deceleration.

Advantages of MPFIAdvantages of MPFI

(4) 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.

(5) The mileage of the vehicle will be improved.

ConclusionConclusion• 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