Abstract: An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. When the engine idle speed error magnitude is less than a calibrated threshold, usage of high DI fuel is detected by identifying a surge signal based on the engine speed error fluctuation in a predetermined frequency range attributable to combustion instability due to the presence of high DI fuel in a cold engine. When the average amplitude of the surge signal exceeds a calibrated surge threshold, the presence of high DI fuel is detected. Additionally, the method is disabled for a prescribed period following commanded load transitions associated with the air conditioning system and the automatic transmission.

Abstract: An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. The usage of high DI fuel is detected during an engine idle period following starting by monitoring the engine speed to identify an engine speed excursion more than a calibrated percentage below the desired idle speed. The detection method is enabled under specified environmental conditions, provided the engine run time is greater than a specified time and the engine temperature is within a specified range. Additionally, the method is disabled for a prescribed period following commanded load transitions associated with the air conditioning system and the automatic transmission.

Abstract: An improved engine fuel control detects combustion instability due to the use of high driveability index (DI) fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. The usage of high DI fuel is detected during engine cranking by measuring the time required for the engine speed to increase from a lower reference speed to an upper reference speed, provided the engine run time is less than a calibrated value. A timer is started when the lower reference speed is achieved, and the timer value is compared to a crank time threshold determined as a function of the initial engine coolant temperature. If the timer value exceeds the crank time threshold before the engine speed reaches the upper reference speed, the presence of high DI fuel is indicated, and the air/fuel ratio is temporarily enriched.

Abstract: An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. When the engine idle speed error magnitude is less than a calibrated threshold, usage of high DI fuel is detected by identifying a surge signal based on the engine speed error fluctuation in a predetermined frequency range attributable to combustion instability due to the presence of high DI fuel in a cold engine. The speed error fluctuation content in the predetermined frequency range is identified with a Butterworth bandpass filter, and the bandpass filter output is low pass filtered to identify an average amplitude of the surge signal. When the engine speed error magnitude exceeds the calibrated threshold, the inputs of bandpass and low pass filters are set to zero.

Abstract: An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. The usage of high DI fuel is detected during engine cranking by measuring the time required for the engine speed to increase from a lower reference speed to an upper reference speed, provided the engine run time is less than a calibrated value. A timer is started when the lower reference speed is achieved, and the timer value is compared to a crank time threshold determined as a function of the initial engine coolant temperature.

Abstract: An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. The usage of high DI fuel is detected during an engine idle period following starting by monitoring the engine speed to identify an engine speed excursion more than a calibrated percentage below the desired idle speed. The detection method is enabled under specified environmental conditions, provided the engine run time is greater than a specified time and the engine temperature is within a specified range. Additionally, the method is disabled for a prescribed period following commanded load transitions associated with the air conditioning system and the automatic transmission.