Injector Driving Time

The injector driving time at which the air/fuel ratio for the amount of intake air reaches the ideal air/fuel ratio is called basic driving time and is stored in the memory of ECU in advance.
During starting, the MAP value determined by the engine coolant temperature sensor signal is used as the basic driving time. During deceleration, the basic driving time is set as zero. Map value is a value set in advance and stored in the ROM inside the ECU.
The injector driving time is obtained by affecting corrections in on the following:
1. Oxygen Sensor Feedback Correction (Closed Loop Control Correction)-- During normal operation, with engine at normal operating temperatures, air/fuel ratio is corrected to the ideal mixture by using signals from the oxygen sensor. The three-way catalytic converter gives the best degree of purification at the ideal air/fuel ratio. Except at idle, a correction factor for oxygen sensor feedback operation has been stored in advance and during idle, this factor is applied for correction on the rich side to increase the air/fuel ratio over the ideal ratio, thus improving the idle stability. During idling, secondary air is supplied from the reed valve to reduce emissions (CO and HC).
2. Air/Fuel Ratio Map Correction (Open Loop Control Correction)-- During engine warm up and heavy load operation, correction to the optimum air/fuel ratio is made by the map values set by engine speed and amount of intake air.
3. Engine Coolant Temperature Correction-- To maintain operability during cold engine operation, correction is made as to allow a greater amount of fuel during lower engine coolant temperatures.
4. Intake Air Temperature Correction-- Change in air/fuel ratio due to the difference in intake air density caused by intake air temperature is corrected.
5. Atmospheric Pressure Correction-- Change in air/fuel ratio due to the difference in intake air density caused by change in atmospheric pressure is corrected.
6. Acceleration/Deceleration Correction-- To improve driveability during acceleration and deceleration, the amount of fuel is adjusted according with the change in throttle valve opening.
7. Dead Time Correction-- The injectors opened by the driving signal from the ECU have operational lag which changes according to the difference in battery voltage. Actual injector valve opening time becomes less than injector driving signal, failing to provide expected air/fuel ratio. Therefore, battery correction time corresponding to the battery voltage is added.