FUEL SYSTEM

ELECTRONIC FUEL INJECTION ( EFI )
Description
The EFI system uses various sensors to detect the engine condition and vehicle running condition. And the engine ECU calculates at the optimum fuel injection volume, and causes the injectors to inject the fuel.The figure shows the basic EFI configuration.
Engine ECU
This calculates the optimum fuel injection duration based on the signals from the sensors.
Air flow meter or manifold pressure sensor
This detects the intake air mass or manifold pressure.
Crankshaft position sensor
This detects the crank angle and engine speed.
Camshaft position sensor
This detects the standard crank angle and the camshaft timing.
Water temperature sensor
This detects the coolant temperature.Throttle position sensorThis detects the throttle valve opening angle.
Oxygen sensor
This detects the oxygen concentration in the exhaust gas.

Types of EFI
There are two types of EFI system classified by the amount of the intake air detection method.
1.L-EFI (Air-flow control type)
This type uses an air flow meter to detect the amount of the air flowing in the intake manifold.There are two types of detection methods: One directly measures the intake air mass, and one makes corrections based on the air volume.
2.D-EFI (Manifold pressure control type)
This type measures the pressure in the intake manifold to detect the amount of the intake air using the intake air density.
Air Flow Meter
The L type of EFI is Used Air Flow Meter to measures the intake air mass, and one makes correction based on the air volume.The air flow meter is one of the most important sensors because it is used in L-type EFI to detect the intake air mass or volume.Signal of the intake air mass or volume is used to calculate the basic injection duration and basic ignition advance angle.The air flow meter is largely classified into two types, mass air flow meters that detect the intake air mass, and volume air flow meters,intake air mass, and volume air flow meters, respective types include the following.Mass air flow meter:Hot-wire typeVolume air flow meter:Vane type and optical Karman vortex type
Currently, most models use the hot-wire type of air flow meter because it has superior measurement accuracy, lighter weight, and better durability.