Patent ID: 8763368

Claim:
A system for controlling a combustion engine, comprising: a natural gas fired or propane fired internal combustion engine configured to be maintained at a stationary site during operation; a catalyst reaction device mounted along an exhaust path of the engine, the catalyst reaction device be configured to reduce an amount of pollutants emitted from an exhaust outlet; a post-catalyst exhaust sensor arranged along the exhaust path after the catalyst reaction device and before the exhaust outlet; and an air-fuel ratio controller configured to control an air-fuel mixture input into the engine, the air-fuel ratio controller being communicatively connected to the post-catalyst exhaust sensor, wherein the air-fuel ratio controller automatically adjusts the air-fuel mixture input into the engine in response to a signal received from the post-catalyst exhaust sensor, wherein the air-fuel ratio controller automatically increases a fuel level in the air-fuel mixture in response to expiration of a preset lean timer that is triggered in response to the signal received from the post-catalyst exhaust sensor switching from a high signal to a low signal; a fuel valve communicatively connected to the air-fuel ratio controller, wherein the air-fuel ratio controller is configured to output a control signal to the fuel valve for controlling the air-fuel mixture input into the engine in response to the signal received from the post-catalyst exhaust sensor, wherein the post-catalyst exhaust sensor comprises an oxygen sensor, the system further comprising: a pre-catalyst exhaust sensor arranged along the exhaust path before the catalyst reaction device, the pre-catalyst exhaust sensor comprising another oxygen sensor; an inlet temperature sensor arranged along the exhaust path to detect a temperature of the exhaust path before the catalyst reaction device; and an outlet temperature sensor arranged along the exhaust path to detect a temperature of the exhaust path after the catalyst reaction device and before the exhaust outlet; wherein the post-catalyst exhaust sensor comprises a narrow-band oxygen sensor that is configured to output the signal to the air-fuel ratio controller indicative of a switching point when the natural gas fired or propane fired internal combustion engine is operating at approximately a stoichiometric level for the natural gas fired or propane fired internal combustion engine, wherein the air-fuel ratio controller comprises a user interface display device, wherein the air-fuel ratio controller adjusts the air-fuel mixture after a predetermined period of time that begins in response to detecting a change in the signal received from a post-catalyst exhaust sensor, wherein the user interface display device is configured to display a number of user-selectable options that implement a user's selection of the predetermined period of time.