24-07-2014, 10:39 AM
STUDY OF ELECTRONIC FUEL INJECTION SYSTEM
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ABSTRACT
A simple EFI can deliver as much power as a carburettor while dramatically reducing emission and fuel consumption. In Electronic Fuel Injection system ethanol is used as fuel then characteristic of ethanol sprays at port fuel injection .
The design of electronic fuel injection control automobile must take into account limitation imposed by the automotive environment and by mass production. The effect of diesel injection strategries on combustion, emission, fuel economy and the operation range with high efficiency and low emission fuelled with gasoline/diesel duel fuel on modified single- cylinder diesel engine. The experimental result showe that this combustion mode had the capability of achieving high efficiency. Working principle of Electronic Fuel Injection System with Engine control unit , which control all phenomenon of injection . fuel pressure regulator which maintained the pressure at the injectors. Excess pressure can overcome spring tension. Central port injector located in intake of manifold. With the help of light flashes with each electrical pulse injector circuit testing can be done. Injector cleaning used for periodic cleaning which remove varnish and other deposits
INTRODUCTION
The electronic fuel injection system (EFI) is simple, in theory. The design goal for an electronic fuel injection system is to deliver the correct air fuel ratio for varying load, the speed and temperature. Most modern EFI systems are incorporated in an ECU which also control the ignition system , and may control may other functions such as anti-lock brakes, traction control system , the transmission, etc, A fuel injection system itself consists of a source of pressurized fuel, fuel injectors and the electronic controller. The fuel system is composed of the fuel tank , a high pressure pump, and some method for regulating fuel pressure.
The injectors can be though of as electrically operated valves. The amount of fuel delivered to the engine is determine by size of the injectors, the amount of time that the injectors are open, and on the fuel pressure . The amount of time that injector is open is called the pulse width and is usually expressed in millisecond (one thousandths of second). Electronic Fuel Injection system are very precise, reliable and cost effective.
Working Principle Of Electronic Fuel Injection System
Figure (1) shows the components in a simplified electronic fuel injection system. Most fuel injection systems are electronically. The controller is the engine computer an electronic control module (ECM) or power train control module (PCM). It is also called the onboard computer because it is “on board” the vehicle. The various parts of engine and fuel system have sensors that send electric signals to ECM. Each sensor is device that receive and reacts to signal such as change in temperature, pressure, or voltage. Some sensors report the amount of air entering. Using this information, the ECM continuously calculates how much fuel to inject . It than opens the fuel injectors so the proper amount of fuel sprays out to produce the desire air fuel ratio
An electronic fuel injection system is a type of electronic control system. It includes sensors or input devices. A controller (ECM) an various actuators or output device that are operated by the ECM. Sensors that report to the ECM are 1)Engine speed,2)Throttle position, 3)Intake manifold vacuum 4)Engine coolant temperature 5)Amount and temperature of intake air, 6)Amount of oxygen in exhaust gas
Engine Control Unit
Modern engines are controlled by computers which are called ECU or EMS; Engine Control Unit or Engine Management System .Engine operation with computer. The ECU controls the functions of the engine and allows a precise management of the engine's operations using a variety of sensors.
This precision translates into better engine response and performance along with improved fuel consumption and pollution levels.
In addition, the engine management system enables control of the engine's temperature and moisture, which provides longer life as well as functional advantages.
Another advantage of the computerized engine is the ability to perform self "on board" diagnostic. The computer can detect problems which it saves as trouble codes that a professional can output with the scanning equipment. Engine management system scheme ECU also allows customizing and changing some of its operations to optimize functionality at any given moment and according to needs.
Modern Engine Control Units were introduced due to the technological ability to embed microprocessors that were fast enough to provide a real-time operation.
The first computers were used in Formula 1 racing cars, but it didn't take long until regular cars used them as well.
3Throttle Body Injection
Throttle body fuel injection is a type of fuel injection system where the fuel is injected into the throttle body. The throttle body fuel injection system, or TBI as referred to by GM or CFI by Ford, works using a single or pair of injectors. The throttle looks like a carburettor without the fuel bowl, the metering jets or the float.
This type of fuel injection system consists of only two major castings - the fuel body and the throttle body. The fuel body supplies the fuel while the throttle body has a valve that controls the flow of air. On the throttle, there are ports that gather signals to relay to the manifold absolute pressure sensor and to the emission control system..
The majority of modern cars employ fuel injection. It provides instant throttle response and improved fuel efficiency. Cars once utilized a carburetor, which were easy to clean and adjust; however, they dumped gasoline into the engine and sometimes had cold weather drivability issues. In the 1980s, throttle body fuel injection became widely used, but it was more or less an electronic carburetor. Cars today use individual fuel injectors for each cylinder, making fuel delivery far more precise with improved fuel economy. An onboard computer is able to adjust fuel delivery based on engine needs, which in turn reduces fuel consumption and lowers emissions. One of the easiest ways to get more MPG from your fuel injection is to modify driving habits. For instance, take off slowly from stops. Taking off quickly wastes gasoline.
[b]Multiple Port Injection[/b]
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 (or just MPI) 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. The intake is only slightly wet, and typical fuel pressure runs between 40-60 psi.
Many modern EFI systems utilize sequential MPFI
Figure(2.4): Multiple port Injection This type of fuel injection unit allows for very flexible intake manifold designs compared to the TBI systems. Another key advantage of the MPFI system is engine efficiency. By incorporating an injector above each intake valve air/fuel distribution from one cylinder to the next is very consistency
Central Port Injection System
From 1992 to 1996 General Motors implemented a system called Central Port Injection or Central Port Fuel Injection. The system uses tubes with poppet valves from a central injector to spray fuel at each intake port rather than the central throttle-body Fuel pressure is similar to a single-point injection system. CPFI (used from 1992 to 1995) is a batch-fire system, while CSFI (from 1996) is a sequential system. Central fuel injection has changed the way cars work. At one time, engines would receive their fuel mixture from the carburettor when the car would suck in air. The engine would then disperse the fuel throughout the engine which in turn would keep the engine running. With central fuel injection, the engine still sucks in the air but the distribution of the fuel, With fuel injection, the car does not rely on the suck of the engine. It has a more accurate
Conclusion
Manufacturing capability for fuel injection systems is well established in India, however, the capability to create technology lies undeveloped. Technology acquired in India is by purchase, through collaborations. Fuel injection system development and advances in diesel engines are strongly interlinked. Progress in one is possible only with progress in the other .Lack of competition has been a major constraint in evolving better engines/fuel injection equipment. Other reasons cited are small. size of the market, long lead times for development and high costs. repair a car. Modern fuel injection systems seem very complicated .However with little bit of knowledge and time spent analyzing, they are not as terrible as they look.Nearly all the components in an entire vehicle utilize the same principle.