The ECU performs the following three functions to determine the injection volume:
1. Calculation of basic injection volume
2. Calculation of maximum injection volume
3. Comparison of basic injection volume and maximum injection volume
1. Calculation of basic injection volume
The calculation of the basic injection volume is made based on the signals of the engine speed and the amount of pedal effort applied to the accelerator pedal.
2. Calculation of maximum injection
volume
The calculation of the maximum injection volume is made based on the signals from the engine speed sensor (NE sensor), water temperature sensor, intake air temperature sensor, fuel temperature sensor, and turbo pressure. In the common-rail type, the signals from the fuel pressure sensor are also used.
Injection Volume Correction
Intake air pressure correction
The injection volume is corrected in accordance with the intake air pressure (volume).
Intake air temperature correction
The density of the intake air (air volume) varies in accordande with the temperature of the intake air. (Low intake air temperature →Injection volume increase correction)
Fuel temperature correction
High fuel temperature →Injection volume increase correction
Cold engine correction
Low water temperature →Injection volume increase correction
Fuel pressure correction
In a common-rail type diesel, the changes in the fuel pressure in the common- rail are detected based on the signals from the fuel pressure sensor. If the fuel pressure is lower than the target pressure, the length of time the injector nozzles remain open is extended.
Calculation of maximum injection volume
The ECU compares the calculated basic injection volume and the maximum injection volume and determines the smaller one to be the injection volume. Accelerator 60 % constant speed driving Accelerator 100 % sudden acceleration
3. Comparison of basic injection volume and maximum injection volume
The difference in the actual injection volume in the conventional EFI-diesel created by the mechanical variances that occur from pump to pump are corrected.
REFERENCE
About the correction ROM :
Authorized workshops such as pump service shops use special tools to measure the pumps to replace the correction ROMs or to make corrective adjustments.
Other types of corrections:
In addition to the injection volume that has been determined here, fuel temperature correction is also made on some vehicle models. If the fuel temperature is high, the actual injection volume is lower (due to the low density) than the instructed value. Therefore, the instructed value must be increased.