The ECU performs the following functions to determine the injection timing:
Conventional EFI-diesel
1. Determination of the target injection timing
2. Detection of the actual injection timing
3. Comparison of the target injection timing and the
actual injection timing
Common-rail EFI-diesel
4. Comparison of the target injection timing and the actual injection timing
Conventional EFI-diesel
1. Determination of the target injection timing
The target injection timing is determined by calculating the basic injection timing through the engine speed and the accelerator pedal opening angle, and by adding a correction value based on the water temperature, intake air pressure, and the intake air temperature.
Conventional EFI-diesel
1. Determination of the target injection timing
Conventional EFI-diesel
2. Detection of the actual injection timing
The detection of the actual injection timing is performed through a calculation based on the engine speed and crankshaft position signals. As with injection volume control, the variances that occur in injection timing control between pumps are corrected through the use of a correction resistor or a correction ROM.
REFERENCE
Injection Timing Detection
Conventional EFI-diesel
The cam plate and the rotor (which generates the NE signal of the engine speed sensor) rotate in unison. Therefore, the ECU is able to detect the timing when the plunger moves and an actual injection takes place by way of the position of the NE signal.
To address the phase discrepancy that occurs between the actual injection timing and the NE signal due to the individual variances of the pumps, a correction resister is used to correct and recognize it as the standard position. Compare the NE signal and the TDC signal of the crankshaft angle sensor and calculates the injection timinng in relation to the engine crankshaft angle as being the actual injection timing.
Conventional EFI-diesel
3. Comparison of the target injection timing and the actual injection timing
The ECU compares the target injection
timing and the actual injection
timing and sends timing advance and
timing retard signals to the timing
control valve so that the actual injection
timing and the target injection
timing match.