Patent ID: 7143727

Claim:
A method for operating an internal combustion engine having at least a first and second cylinder, comprising: during at least one operating condition, operating the first cylinder to receive directly injected fuel, mix said fuel with fresh air inducted past an intake valve of the first cylinder, combust said mixture, and exhaust at least a portion of said mixture past an exhaust valve of the first cylinder; and concurrent with said operation of the first cylinder, operating the second cylinder to hold an intake valve of the second cylinder closed for at least a cycle of said second cylinder, receive directly injected fuel, and then exhaust at least a portion of said fuel past an exhaust valve of the second cylinder to generate unburned reductants in an exhaust of the engine wherein said exhaust valve of the second cylinder is temporarily opened to exhaust at least said portion of directly injected fuel to the exhaust, and a closing timing of said exhaust valve from said temporarily opened position relative to crank angle is varied with an operating parameter while said intake valve of the second cylinder is held closed.