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ALA On Multipoint Fuel Injection System

SHREE SADS VIDYAMANDAL INSTITUTE OF TECHNOLOGYGUIDED BY:Pro. Vandana Y Gajjar S.V.M.I.T.(Bharuch)

PREPAIRED BY:Patel Manthan_130450119106_MPFIPatel Mihir_130450119107_MPFI

Context Part A: Earlier Fuel Supply System and Fuel Requirements For Good Combustion.Part B: Multipoint Fuel Injection System.Note: This Power Point Presentation as base on GTU Syllabus.

PART:-A

Fuel Supply to Engine:In petrol engines, the air and fuel is mixed outside the engine and partly evaporated mixture is supplied to the engine.In S.I. engine suction created is sufficient to create air flow and fuel injected easily evaporates. While for C.I. engine separate injection system is used.The process of preparing air fuel mixture in S.I. engine outside cylinder is called carburetion with the help of carburetor.It is desirable to have complete vaporized mixture in cylinder for proper combustion.

The design of carburetor is difficult and complicated as the requirement by the engine for A/F ratio vary from 1/1 to 15/1 under different operating conditions.

Operating Difficulties For Carburetors:It has number of moving parts which may out and effects the performance.Ice formation and freezing may be take place and may be affect the combustion.In multi cylinder engine A/F mixture ratio may vary in each cylinder.Air and fuel has to pass from various path and devices like chock, ventury, inlet/outlet pipes, bends, throttle valve which may restrict the flow and decreases the volumetric efficiency.Backfiring may be take place in suction and exhaust manifold.

Air-fuel Mixture And Mixture Requirement:The desired A/F ratio is one that gives the maximum economy . But the engines used for transportation, the A/F ratio must change depending on whether maximum economy or maximum power is desired and also for different loads and speeds.There is limited range of A/F ratio which is 7/1 to 20/1 for S.I. engine.

PART:-B

Fuel Injection:Fuel injection is a system for introducing fuel into internal combustion engines, and into automotive engines, in particular. It is always indirect, petrol being injected into the inlet manifold or port rather than directly into combustion chamber. This ensures that fuel is well mixed with the air before it enters the chamber.On diesel engines, fuel injection is necessity, while for petrol engines it is alternative to the carburetor or gasoline direct injection.

The primary difference between carburetors and fuel injection is that fuel injection atomizes the fuel through a small nozzle under high pressure, while a carburetor relies on suction created by intake air, accelerated though a ventury tube to draw the fuel into airstream.Basically, there are two types of fuel injection system:

Objectives Of Fuel Injection:Power output, fuel efficiencyEmission performance Ability to accommodate alternative fuelsReliability and smooth operationInitial and maintenance costDiagnostic capabilityRange of environmental operationEngine tuning

Multipoint Fuel Injection System:The purpose of this system is to supply proper A/F mixture to each cylinder of the engine. These are classified as:

Port Injection System:The injector is fitted in the inlet manifold near the inlet valve. The uniform mixture formed enters into the cylinder.Every cylinder is provided with a separate injector in multi-cylinder engine as shown in fig below.

Multi-point Flue Injection (MPFI) near Port

Continuous Port Injection System:In this kind of system, the petrol is sucked from the tank by a pump and pressurized petrol at 3 bar is supplied through a distributor to the fuel injector to a particular cylinder. The relief valve shown in the fig maintains the pressure and allows the excess petrol to return to tank.The pump may be drive by engine or separate motor.In this system, the petrol is injected continuously into the inner port as shown in fig at a varied rate. The distribution may be made by having a separate metering pump for each cylinder, all are timed by the arrangement of a series of cams on one cam shaft.

Lucas Mechanical Petrol Injection System

Now-a-days electronically controlled fuel injection system are used as it functions rapidly and responds automatically to the change in manifold air pressure, engine speed, crankshaft angle and many other factors.This system access data from various sensing devices then adjust the A/F ratio for the best performance of the engine.This system has to contain a means of supplying extra fuel for cold starting , during warming and enriching the mixture during acceleration.

Throttle Injection System:The system is shown in the fig, where single injector is used like a single carburetor. The throttle valve controls the amount of air entering in the intake manifold.The injector is located above the throat of the body and injected fuel mixes with air. then the mixture passes into the intake manifold. The fuel injected is controlled as per the speed and load on the engine.The combustion chamber injection is just similar to CI-engines.Mitsubishi engineers Drs. Ando and Akira were successful to develop a gasoline direct injection(GDI) engine in 1996.

To understand arrangement of the system, the conventional carburetor system with two types of injection systems shown in fig.

Throttle Body Injection (Single Point)

The most widely used GDI injector is needle type, high pressure, swirl spray unit which delivers conical spray.It has finite no of holes to provide uniform fuel spray over conical circumference. This method of spray has two important advantages:Pressure energy is transformed into an axial momentum and partial into rotational which results in better atomization.It can provide various spray geometry.

Fuel Injectors:The fuel injectors are screwed into either the inlet manifold or the cylinder head and are angled so that the spray of fuel is fired towards inlet valve. The injectors are of two types, depending upon the injection system.The first system uses continuous injection where fuel is squirted into the inlet port all the time the engine is running. The injector simply act as spray nozzle to break up the fuel into a fine spray, it does not actually control the fuel flow.The other popular system is timed injection where the fuel is delivered in manifold to coincide with the induction stroke of the cylinder.

MECHANICAL INJECTORELECTRONIC INJECTOR

Electronic control of MPFI system:We know that fuel injection reduces emission of exhaust gases and develops maximum power with equal power generation by each cylinder. However, the mechanical system response is slow as well as it has few limitation because of system inertia.In present modern system, computer and solenoid operated fuel injectors are used to meter and inject right amount of fuel at right time into cylinder.The computer receives signals either in form of current or voltage from different sensors.

The system contains different sensors as given below:Inlet manifold pressure sensor: It is used to sense the pressure of the air in the intake manifold in order to adjust A/F ratio as per load on the engine.Air flow sensor: Measures volume of air flowing through intake manifold to adjust A/F ratioEngine speed sensor: Sense the speed of the engine to adjust A/F ratioThrottle position sensor: Monitors position of throttle valve to adjust A/F ratio for required speed and accelerationEngine temperature sensor: Senses the outlet temperature of cooling water so that ECU adjust the A/F ratio for mixing rich mixture

Knock sensor: Detects pitching noise so that the ignition timing can be retarded to avoid knockingExhaust gas sensor: Measures O2 percentage in exhaust gases and calculate A/F ratio for adjustment.

The MPFI electronic system on the basis of function, is divided into three main components as listed below:Electronic control unit (ECU)Fuel supply unitAir induction unit

Electronic Control Unit (ECU):This system is shown in figure. In this system, the sensor monitor the inlet air temperature, outlet cooling water temperature, the O2 in the exhaust manifold, the throttle position, air volume entering cylinder and engine speed send signals to ECU.

Fuel Supply Unit:The fuel from pump is supplied through cold start injector with the help of cold start switch which supplies rich A/F mixture to the air-intake chamber.The main injector operates only after getting signal from ECU once engine starts.

Air-induction UnitThe fig is self explanatory. The quantity of air supplied is controlled, in such a way that is necessary for complete combustion.

The MPFI electronic system is also classified as D-MPFI system: The main input signal are the intake manifold pressure, Engine speed and flow volume of air which are sent to ECU to control the A/F ratio. L-MPFI system: The main input signal are air flow rate and engine speed to regulate fuel quantity injected.

The both system mentioned above, sends the information of respective sensors to ECU and then ECU processes the information and sends commend to fuel injector to regulate fuel injected. Then the mixture formed enters into the engine.

D-MPFI SYSTEML-MPFI SYSTEM

Advantages of petrol injection system:Engine requires different A/F ratio at different operating condition like idling, part/full load, acceleration, etc. this system satisfy all condition and provides required A/F ratio at different condition results in best performance.There is no ventury as in carburetor so there is sooth flow of air, hence volumetric efficiency increases.Less problem of icing and vapor lock.Easy starting.In multi cylinder engine same A/F ratio will be supplied to all cylinders.

As required A/F ratio supplied at different conditions, exhaust emission will be lower and more power developed.Improved bsfc results in better mileage of an automobile.

Disadvantages of petrol injection system:High initial costMajor parts electronic so can be repair which increases the cost of maintenance.Skilled worker and special service equipments required for diagnosis and maintenance.System is more complicated which require more care and attention.

Applications:Here is the example of automobile company using MFI system.Ford first debuted their multi-port fuel injection on the 1983 1.6 liter Escorts and the 2.3-liter Mustang and Thunderbirds. Multi-port or MFI became Fords standard fuel-injection system on all V-6 and V-8 engines in 1986.

Comparison Between Carburetor And MPFI:Structural difference:Carburetor consists of an air inlet through air filter, after that there is chock valve and passing it air pass through a throat in which it mix with fuel and there is throttle valve after which mixture pass into engine.Construction of fuel injector consist of following things: O-ring, filter, Electric connector, Electric coil, Magnet, etc.Device category:Carburetor is a pure mechanical device where as fuel injector could be pure mechanical or electrical device but most of them are electrical now.

Diagnose of problem:The complete electronic nature of the electric fuel injector allows problems to be diagnosed simply by connecting the ECU to diagnostic device or a computer where as in carburetors a specific experience is required for maintenance and tuning because it has to be done manually.Fuel variation:Fuel injector allow the engine to perform with various fuels, and the operation from the drivers perspective is smooth and fast this property is completely absent in carburetor.

Efficiency and Emissions reducing:The fuel consumption can be optimized to suit the performance of the engine in the fuel injectors, which increasing the efficiency and reducing the emission where as in carburetor fuel consumption cannot be optimized because of its working phenomena.

Supplier of fuel injection system:There are many companies providing services of automotive parts to automobile manufactures. But here, is the one company having major distribution of automotive parts of Germany.Bosch is the multinational company founded on 15 nov., 1886. The founder of this company was Robert Bosch.Boschs core products:Automotive components: Brakes, controls, electronics ,fuel systems, generators, steering systemSome industrial products and building products

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