Patent attributes
An engine system and method of its operation are described. The method includes: operating the combustion chamber in a four stroke cycle by repeatedly opening a first exhaust valve of the combustion chamber once every four piston strokes while holding closed a second exhaust valve of the combustion chamber; after operating the combustion chamber in the four stroke cycle, operating the combustion chamber in a two stroke cycle by repeatedly opening the first exhaust valve once every four piston strokes and repeatedly opening the second exhaust valve once every four piston strokes during a different exhaust stroke than the first exhaust valve; and after operating the combustion chamber in the two stroke cycle, operating the combustion chamber in the four stroke cycle by repeatedly opening the second exhaust valve of the combustion chamber once every four piston strokes while holding closed the first exhaust valve of the combustion chamber.
