Patent ID: 7128062

Claim:
A method for expanding the mid load range of a four-stroke gasoline direct-injection controlled auto-ignition (CAI) combustion engine having at least one cylinder with direct fuel injection and containing a piston reciprocably connected with a crank and defining a variable volume combustion chamber including an intake valve controlling communication with an air intake and an exhaust valve controlling communication with an exhaust outlet, the method comprising: employing a variable valve actuating system for variably actuating the intake and exhaust valves and operating the intake and exhaust valves with at least one of an exhaust re-compression valve strategy and an exhaust re-breathing valve strategy; providing a reservoir chamber in communication with said combustion chamber for temporary holding of residual burned gas; and operating the engine with CAI combustion during stable combustion in a mid-load operating range; whereby residual burned gas in the combustion chamber and the exhaust outlet enters into said reservoir chamber and then loses thermal energy while in the reservoir chamber before being drawn back into the combustion chamber, thereby extending the mid-load operating range of stable CAI combustion.