Engine system and method for efficient emission control device purging
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Abstract
Various systems and methods are disclosed for carrying out combustion in a fuel-cut operation in some or all of the engine cylinders of a vehicle. Further, various subsystems are considered, such as fuel vapor purging, air-fuel ratio control, engine torque control, catalyst design, and exhaust system design.
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Citations
12 Claims
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1-7. -7. (canceled)
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8. A method for controlling an engine having at least a first and second group of cylinders, comprising:
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operating the engine in a first mode wherein the first cylinder group operates with air and substantially no injected fuel and the second cylinder group operates to combust air and injected fuel; and
transitioning the engine to operating in a second mode wherein both the first cylinder group and the second cylinder group operate to combust air and injected fuel, combustion in both said first and second cylinder group being lean of stoichiometry at a lean combustion limit with retarded ignition timing. - View Dependent Claims (9, 10, 11)
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12. A method for operating an engine with a first set of cylinders and a second set of cylinders, the method comprising:
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operating the first set of cylinders combusting a lean or stoichiometric air-fuel mixture and operating the second set of cylinders with substantially no injected fuel while inducting air; and
transitioning to combusting a lean air-fuel mixture in said second set of cylinders, wherein after said transition, said second set of cylinders is operated with said lean air-fuel mixture at a lean air-fuel ratio limit with retarded ignition timing while airflow and fuel injection are reduced.
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Specification