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EFI System

Fuel Injection System

Description Types of injection machine
Electronic Petrol Injection (EPI) or also called Eletronic Fuel Injection (EFI) is a fuel injection control technology developed at this time to replace the gasoline engine carburetor. Generally the system EPI / EFI divided into two types:
  • Based on the number injectornya.
  • Based injectornya placement.
  • Based on the number of EPI or EFI engine injector consists of:
  • Single Point Injection. (SPI)

Single Point Injection (SPI) or so-called Throttle Body Injection (TBI) or Central Fuel Injection System: which only use one for a few Cylinder Fuel Injector. Injector fitted before the suction channel is above the throttle valve. The principle works the injectors supplying fuel for the purpose some cylinders at once. Construction of single-point injection can be seen in the picture.



Multi Point Fuel Injection (MPI) is also called port fuel injection (PFI), put over the hole injector suction (intake port). Each cylinder has one injector. So, when it consisted of a 4-cylinder engine means that there are 4 injectors which supply the gasoline. Construction of multi-point fuel injection can be seen in the picture below.



MPI injection technology has advantages compared with SPI include:
1). The distribution of air-fuel mixture is uniform for each cylinder.
2). Response to changes in throttle position even faster.
3). More accurate in regulating the amount of fuel injected according to operating conditions.
Thus, the better the engine performance, reduced emissions and fuel consumption more efficient. Instead SPI system is simpler, because it tends to uneven distribution of air-fuel mixture is strongly influenced by the design of the suction channel.

Gasoline Direct Injection (GDI) which injectors are in the combustion chamber, so gasoline is sprayed directly into the combustion chamber without passing through the Intake Valve. The technology is still expensive, because the Fuel Injector Nozzle material must withstand the high temperatures in the combustion chamber.
To further clarify the position of the three types of injector placement position, can be seen in the image below.


Based injectornya placement.
Indirect Injection. That system spraying fuel into the intake manifold as used in the injection system of gasoline engine, gasoline is not sprayed directly into the combustion chamber


Direct Injection. That system spraying fuel directly into the combustion chamber. Injectornya located in the combustion chamber, so gasoline is sprayed directly into the combustion chamber without passing through the Intake Valve. The technology is still expensive, because the Fuel Injector Nozzle material must withstand the high temperatures in the combustion chamber. Construction direct injection can be seen in the picture


EPI / EFI Construction 
Basic construction
In general, the basic construction EPI / EFI divided into three systems, namely:

  • The system controls the intake air (Air Induction System)
  • The distribution of the fuel system (Fuel Delivery System)
  • Eletronic Control System (Eletronic Control System).

If seen from the above three control systems based on relationships with one another is a series of interrelated systems, each system has its own function. To further clarify each system with each component, will be explained further.



Intake air control system
Based on the engine intake air control system or EFI EPI can be classified into two types, namely:

Sistem D or D-Jetronic EFI (from the German "DRUCK" means pressure, the system that controls the amount of air entering the intake manifold is measured by the size of the vacuum. Computer input the amount of air that goes into the air intake chamber of sensor mounted in the intake manifold or the identification of the source of intake manifold vacuum. Input is used as basis injecting inputs from the engine speed. as the engine uses intake air sensor based on vacuum, the vacuum in the Intek changes that will transform the voltage delivered by the sensor to the Electronic Control Module (ECM). the ECM then sends a voltage of 5 volts as the input sensor.
D-Jetronik basic principles can be seen in the picture below.



Sensor input is at 5 volts, the voltage produced (sensor output) due to changes in vacuum varies between 0-5 volts.
L-EFI system or L-Jetronic (German for "AIR" which means the air, the system that controls the amount of air entering the intake manifold is measured by the amount of air flow velocity. Computer input the amount of air that goes into the air intake chamber of the sensor installed in the intake manifold or the identification of the source of air at the intake manifold outflows. Input is used as basis injecting inputs from the engine speed.
Figure shows the basic principle of L-Jetronic.



On machines that use the sensor in air by an air flow rate, the airspeed will swipe heat resistor will change the prisoners. Changes in the resistivity resistor will result in a change in voltage produced (sensor output). The sensor input voltage of 12 volts and an exit varies between 0-5 volts, which is used as the basis for calculating the amount of ECM incoming air.

Fuel distribution system
The fuel (petrol) is suppressed by a gas station works electrically controlled by the ECM, through the fuel filter (fuel filter) is applied to the operation of the injectors is controlled by the ECM. Fuel is sprayed when the valve on the injector open intermittently. Because the pressure in the pipe divider was made permanent by the presence of the fuel pressure regulator, then the amount of gasoline that dismprotkan depending on the length of the injector open.
Fuel distribution systems (fuel Delivery System) can be seen in picture



The length of time the fuel injection is generally divided into three systems:

  • Intermittently
  • What are governed by time
  • Continues


In the intermittent system, open and closing of the injectors do not see the intake valve working condition. At this injection system may be spraying fuel into the engine when the intake valve is open or closed. Intermittent injection system also called modulation injection system.
At timed injection system, the fuel really is aerosolized into the machine before or when the intake valve opens. Spraying gas in the system is always the intake valve working condition.
In the continuous system, the fuel is sprayed into the engine every time (continuously) for rotating machinery. Controlling the ratio of air-fuel mixture by adding or reducing the pressure on the injector. This way it will increase or decrease the fuel out of the injectors.

system control
In the development of the injection control system includes:

  • mechanical control system
  • The hydraulic-mechanical control system
  • The electronic control system.
  • Mechanical control systems. Control of mechanical injection does not require the ECM to control the injector opening.



Working principle:
The sensor will detect the license plate number of the intake air, if the air intake a little, then the movement of the sensor is also small, and if it increases the amount of air entering the motion sensor will move further and further so enlarged. Movement sensor plate is connected to a plunger that will determine the size of the fuel line to the injector.

Hydraulic-mechanical control systems. Injection system with a hydraulic-mechanical control using the mixture control unit (air intake sensor and fuel distributor unit) to operate the injectors. Inlet air flow sensor for this type of injection system uses electronic control.

Working principle:
Movement of the sensor plate is connected with the air intake which is placed at the center plunger gasoline distributors. When increasing the amount of air entering the sensor plate will be pushed up, this movement will push the plunger. The plunger movement will determine the extent of fuel to be supplied to the injector.



The electronic control system.
In the electronic control system using an engine control module (ECM) that serves as a central control system, gets input from the two main sensor is a sensor and the amount of air entering the engine rotation sensor that will be used to determine the basic injection volume. In addition to the above two sensors are other sensors that the ECM serves as input to correct for the amount of fuel injectors sprayed.



Correction system
Basic fuel injection engine EPI / EFI depends on two main sensor is a sensor air intake and engine rotation sensor. To enhance the magnitude of the injection time, it would require another sensor as a supporter for correcting sensor refinement ratio of air and fuel mixture (air fuel ratio) according to the working conditions of the engine. The amount of fuel (gasoline) is sprayed should be proportional to the amount of air enters the cylinder (AFR). The more air into the cylinder, the gas must be more to be sprayed. Sebalikya Similarly, the less air coming in, the volume of gas that is sprayed also the less.



For example, when the machine is turned on in a state still cold, the ECM requires inputs from ECT sensor (engine cooling temperature) to enrich the mixture so that the machine is turned on.

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