24-11-2012, 01:53 PM
Gasoline electronic Fuel Injection Systems
Gasoline electronic.ppt (Size: 1.69 MB / Downloads: 82)
Introduction
A modern gasoline injection system uses pressure from an electric fuel pump to spray fuel into the engine intake manifold. Like a carburetor, it must provide the engine with the correct air-fuel mixture for specific operating conditions. Unlike a carburetor, however, PRESSURE, not engine vacuum, is used to feed fuel into the engine. This makes the gasoline injection system very efficient
Improved atomization. Fuel is forced into the intake manifold under pressure that helps break fuel droplets into a fine mist.
Better fuel distribution. Equal flow of fuel vapors into each cylinder.
Smoother idle. Lean fuel mixture can be used without rough idle because of better fuel distribution and low-speed atomization.
System component :
Fuel tank
Electric fuel pump
Fuel filter
Electronic control unit
Common rail and Pressure sensor
Electronic Injectors
fuel line
Fuel tank
is safe container for flammable liquids and typically part of an engine system in which the fuel is stored and propelled (fuel pump) or released (pressurized gas) into an engine.
Typically, a fuel tank must allow or provide the following:
Safe (UL Approved) fuel storage, there is some concern that UL (Underwriters Laboratories) is not the final arbiter of safety.
Filling (the fuel tank must be filled in a secure way) No Sparks.
Storage of fuel (the system must contain a given quantity of fuel and must avoid leakage and limit evaporative emissions)
Electric fuel pump
An electric fuel pump is used on engines with fuel injection to pump fuel from the tank to the injectors. The pump must deliver the fuel under high pressure (typically 30 to 85 psi depending on the application) so the injectors can spray the fuel into the engine.
Electric fuel pumps are usually mounted inside the fuel tank,
Some vehicles may even have two fuel pumps (a transfer pump inside the tank, and a main fuel pump outside).
Electric fuel pumps come in a variety of designs. Some older applications use a positive displacement "roller cell" pump. This type uses rollers mounted on an offset disc that rotates inside a steel ring. Fuel is drawn into the spaces (cells) between the rollers and pushed along from the pump inlet to the outlet. This type of pump can generate very high pressure, and the flow rate tends to be constant. But the output comes in pulses, so a muffler is often mounted in the fuel line after the pump to dampen pressure pulses. A roller cell pump may also be mounted outside the fuel tank, and used with a second low pressure supply pump mounted inside the fuel tank.
Working of ECU
Control of fuel injection: ECU will determine the quantity of fuel to inject based on a number of parameters. If the throttle pedal is pressed further down, this will open the throttle body and allow more air to be pulled into the engine. The ECU will inject more fuel according to how much air is passing into the engine. If the engine has not warmed up yet, more fuel will be injected .
Control of ignition timing : A spark ignition engine requires a spark to initiate combustion in the combustion chamber. An ECU can adjust the exact timing of the spark (called ignition timing) to provide better power and economy.
fuel line
Fuel line hoses carry gasoline from the tank to the fuel pump, to the fuel filter, and to the fuel injection system. While much of the fuel lines are rigid tube, sections of it are made of rubber hose, which absorb engine and road vibrations.
There are two basic types of fuel hose: Fuel and oil hoses that meet the SAE 30R7 standard, and fuel injection hose that meets the requirements of SAE 30R9.