Engine starting and warm-up fuel control method having low volatility fuel detection and compensation
First Claim
1. A method of operation for an internal combustion engine connected to drive one or more loads, said engine having an open-loop fuel control for maintaining an air/fuel ratio of said engine at a target value during engine starting and warm-up, comprising the steps of:
- measuring a speed of said engine during engine idling following starting;
detecting transitions of said loads that influence said speed;
detecting a high driveability index fuel if said measured speed falls to a calibrated percentage of a desired engine idle speed;
disabling said step of detecting a high driveability index fuel if said transitions are detected; and
temporarily enriching said air/fuel ratio relative to said target value when said high driveability index fuel is detected.
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Accused Products
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. When the presence of high DI fuel is detected, and the air/fuel ratio is temporarily enriched to alleviate the instability and to ensure acceptable driveability without unnecessarily increasing hydrocarbon emissions in the engine exhaust gases.
21 Citations
5 Claims
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1. A method of operation for an internal combustion engine connected to drive one or more loads, said engine having an open-loop fuel control for maintaining an air/fuel ratio of said engine at a target value during engine starting and warm-up, comprising the steps of:
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measuring a speed of said engine during engine idling following starting;
detecting transitions of said loads that influence said speed;
detecting a high driveability index fuel if said measured speed falls to a calibrated percentage of a desired engine idle speed;
disabling said step of detecting a high driveability index fuel if said transitions are detected; and
temporarily enriching said air/fuel ratio relative to said target value when said high driveability index fuel is detected. - View Dependent Claims (2, 3, 4, 5)
detecting commanded cycling of said compressor or commanded shifting of said transmission.
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3. The method of operation of claim 1, including the step of:
disabling said step of detecting said high driveability index fuel for a prescribed time interval following detection of said transitions.
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4. The method of operation of claim 1, including step of:
disabling said step of detecting said high driveablity index fuel unless a temperature of said engine is within a prescribed range and a run time of said engine is less than a calibrated run time.
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5. The method of operation of claim 1, wherein said step of temporarily enriching said air/fuel ratio includes the steps of:
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holding said air/fuel ratio at a first value determined as a function of said target value and a temperature of said engine;
controlling said air/fuel ratio according to a second value intermediate said first value and said target value; and
adjusting said air/fuel ratio to a closed-loop target value upon completion of said warm-up.
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Specification