23 April 2017

Electronic fuel injection system

In this article, we will check it out the electronic fuel injection system. There are different types of sensors uses in that system so we will check it out one by one.  

What is an electronic fuel injection system?

Nowadays modern gasoline injection systems use engine sensor, a computer and solenoid operated fuel injectors to meter and inject the right amount of fuel into the engine cylinders. These systems called electronic fuel injection system OR EFI. 
It can use electrical and electronic devices to monitor and control engine-operations.

An ECU full form is electronic control unit or the computer receives electrical signals in the form of current or voltage from various sensors then uses the stored data to operate the injectors, ignition system and other engine related devices. 
As a result, less unburned fuel leaves the engine as emissions, and the vehicle gives better performance. 

The different types of sensors used in electronic injection system are as follows :

  • Exhaust gas or oxygen sensor :
This type of sensor senses the amount of oxygen in the engine exhaust and calculates the air-fuel ratio. 
The output voltage of sensor changes in proportion to the air-fuel ratio.

  • Engine temperature sensor :
It senses the temperature of the engine coolant. By using this data the computer adjusts the mixture strength of rich side for cold starting.

  • Air inlet temperature sensor :
This type of sensor checks the temperature of the ambient air entering the engine for fine-tuning the mixture strength.

  • Airflow sensor :
This type of sensor monitors mass or volume of air flowing into the intake manifold for adjusting the quantity of fuel.

  • Throttle position sensor :
This type of sensor used for senses the movement of the throttle plate which helps to adjust the mixture flow for engine speed and acceleration. 

  • Manifold pressure sensor :
This type of sensor senses monitors vacuum in the engine intake manifold. So by using this mixture strength can be adjusted with changes in engine load.

  • Camshaft position sensor :
This type of sensor senses the rotation of engine camshaft or crankshaft for speed and timing of injection.

  • Knock sensor :
It is the microphone type sensor. 
It can detect ping or pre-ignition noise so that the ignition timing can be retarded.

Electronic fuel injection system working :

Fuel injection systems are comprised of a complex array of components that work together to supply fuel to the vehicle's engine and other controlled is done by ECU.

The fuel injector is an EFI is just a fuel valve. When it is not energized, spring pressure makes the injector to remain closed and no fuel will enter the engine till the computer sends the signal through the injector coil then fuel enter into the intake manifold.

The injector pulse width is an indication of the period for which each injector is energized and kept open. The computer decides and controls the injector pulse width based on the signals received from the different sensors.

Under full load conditions, the computer will sense a wide open throttle, high intake manifold pressure, and high inlet air flow. In this conditions the ECU will increase the injector pulse width to enrich the mixture which will enable the engine to produce high power.

Under low load conditions, the Electronic control unit will sens a narrow throttle and shorten the pulse width by which the injectors are kept in the closed position over a longer period of time so that the air-fuel mixture will become leaner and will result in better fuel economy.

For the cold weather conditions it has a cold start injector too. It serves the same purpose as the carburetor choke. This injector sprays fuel into the center of the engine intake manifold.