ENGINE-OFF NATURAL VACUUM TESTING FOR VARIABLE DISPLACEMENT ENGINE VEHICLES
First Claim
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1. A method, comprising:
- adjusting an evaporative emissions leak test parameter based on a ratio of cylinder run time of a deactivatable cylinder of an engine, to vehicle run time; and
indicating degradation based on the adjusted parameter.
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Abstract
A method, comprising: adjusting an evaporative emissions leak test parameter based on a ratio of cylinder run time of a deactivatable cylinder of an engine, to vehicle run time; and indicating degradation based on the adjusted parameter. The adjusted parameter may thus more accurately reflect the state of a vehicle configured to run with one or more cylinders deactivated. In this way, the evaporative emissions leak test may realize improved robustness and performance metrics, thus reducing warranty costs associated with poor test metrics.
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Citations
20 Claims
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1. A method, comprising:
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adjusting an evaporative emissions leak test parameter based on a ratio of cylinder run time of a deactivatable cylinder of an engine, to vehicle run time; and indicating degradation based on the adjusted parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A vehicle system, comprising:
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an engine comprising one or more selectively operable cylinders; a fuel system isolatable from atmosphere via one or more valves; and a controller configured with instructions stored in non-transitory memory, that when executed, cause the controller to; adjust one or more thresholds for an engine-off natural vacuum test based on a ratio of cylinder run time to total vehicle run time; following a vehicle-off event, isolate the fuel system from atmosphere; and indicate degradation of the fuel system based on the one or more adjusted thresholds. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. A method for a vehicle fuel system, comprising:
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adjusting a pressure rise threshold and a vacuum threshold for an engine-off natural vacuum test based on a ratio of cylinder run time to total vehicle run time; following a vehicle-off event, closing a canister vent valve responsive to the ratio of cylinder run time to total vehicle run time being greater than an initiation threshold; monitoring a fuel tank pressure for a first testing duration; responsive to a fuel tank pressure reaching the adjusted pressure rise threshold during the first testing duration, indicating that the vehicle fuel system is intact; responsive to a fuel tank pressure failing to reach the adjusted pressure rise threshold during the first testing duration, coupling the vehicle fuel system to atmosphere; responsive to the fuel tank pressure decreasing to atmospheric pressure, isolating the vehicle fuel system from atmosphere; monitor a fuel tank vacuum for a second testing duration; responsive to a fuel tank vacuum reaching the adjusted vacuum threshold during the second testing duration, indicate that the vehicle fuel system is intact; and indicating degradation of the vehicle fuel system responsive to the fuel tank vacuum failing to reach the adjusted vacuum threshold during the second testing duration.
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Specification