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 sensor
This 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 methodsOne directly measures the intake air mass, and one makes corrections based on the air volume.
2. D-EFI (Manifold pressure controlctype)
This type measures the pressure in the intake manifold to detect the amount of the intake air using the intake air density.