ESTIMATING VEHICLE FUEL REID VAPOR PRESSURE
First Claim
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1. A method for an engine, comprising:
- adjusting a leak test threshold for a fuel system leak test based on fuel volatility, the fuel volatility estimated during a vehicle-off condition after a refueling event while a fuel tank temperature is stable; and
indicating fuel system degradation based on the leak test.
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Abstract
Methods and systems are provided for estimating fuel volatility. During a vehicle-off condition following a refueling event, fuel volatility may be estimated. Based on estimated fuel volatility, fuel injection amount and leak test thresholds may be adjusted.
107 Citations
20 Claims
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1. A method for an engine, comprising:
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adjusting a leak test threshold for a fuel system leak test based on fuel volatility, the fuel volatility estimated during a vehicle-off condition after a refueling event while a fuel tank temperature is stable; and indicating fuel system degradation based on the leak test. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for an engine fuel system, comprising:
during a first vehicle-off condition following a refueling event, wherein a fuel tank temperature stays within a threshold range, isolating a fuel tank; and operating a fuel pump to estimate a fuel volatility. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. A hybrid vehicle system, comprising:
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an engine including an intake; an electric motor; a fuel system including a fuel tank, a fuel vapor canister, and a fuel pump, a first valve coupling the canister to the engine intake, a second valve coupling the canister to atmosphere; a pressure sensor coupled to the fuel tank; a temperature sensor coupled to the fuel tank; and a controller with computer readable instructions for; shifting to a sleep mode at a first vehicle-off event following a tank refueling event; waking up from the sleep mode upon elapse of a duration since the first vehicle-off event; monitoring a fuel tank pressure after the waking up; and if the fuel tank pressure stays within a threshold range during the monitoring, closing the first and second valves to seal the fuel tank; operating the fuel pump without operating the engine; estimating a fuel volatility based on a peak tank pressure; and adjusting a leak detection threshold based on the estimated fuel volatility. - View Dependent Claims (17, 18, 19, 20)
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Specification