Abstract: An engine control unit and method of controlling the operation of a gas fuelled internal combustion engine of the kind having a gas injector for injecting gaseous fuel into each cylinder and an inlet manifold through which air flows into each cylinder of the engine, the inlet manifold having a manifold valve to control the flow of air into the inlet manifold. An improved control strategy employed by the engine control unit involves closed loop control of airflow through the inlet manifold of the engine. Manifold absolute pressure (MAP) (70) and manifold air temperature (MAT) (72) are employed to calculate air density (84) which is representative of the mass of air flowing through the inlet manifold (28). The detected air density (84) is compared to a desired air density (DAD) (86) and an air density correction (88) is calculated to adjust the manifold valve position (MVP) (90).

Abstract: A non-return valve for a pre-combustion chamber of a gas-fueled internal combustion engine. The valve includes a body having an inlet passage and an outlet passage in fluid communication with each other via an intermediate passage of reduced diameter. An annular valve seat is provided on the outlet side of the intermediate passage upon which the ball rests when the valve is in a first or closed position. The valve ball is arranged to move to a second position to open the valve to the flow of fluid through the valve. The outlet passage includes a cover member having plural apertures to allow the flow of gas through the outlet passage. The cover member serves to retain the valve ball within the outlet passage and of quenching the back flow of high temperature gases into the outlet passage. The internal diameter of the intermediate passage is selected to result in a predetermined flow rate through the valve to achieve the desired gas-to-air ratio in the pre-combustion chamber.

Abstract: An engine control unit for a gas fuelled internal combustion engine detects engine speed, throttle position, manifold absolute pressure, gas pressure, gas temperature, battery voltage, air temperature, engine phase and boost pressure control valve feed back position. The control unit calculates a percentage full load value for the engine based upon the detected engine speed and throttle position and utilizes the calculated percentage full load value to calculate the injector on time for each gas injector in a gas delivery system for the engine. Typically, the control unit employs the percentage full load value and the engine speed to calculate a required manifold absolute pressure value, and this calculated manifold absolute pressure value may then be employed together with the percentage full load value to calculate a percent allowable load value. The engine control unit employs the percentage allowable load value to calculate injector on time and spark advance for the engine.

Abstract: A gas delivery system for gas fuelled internal combustion engines, comprising a gas fuel delivery means for delivering a controlled amount of gaseous fuel to a region adjacent a source of ignition. The gas fuel delivery means comprises first and second delivery means for delivering gaseous fuel to a pre-combustion zone and a combustion zone respectively. Gas control means control the relative proportions of gaseous fuel delivered by the first and second delivery means respectively so that combustion in the combustion zone can be achieved with minimum gaseous fuel by initiating ignition of gaseous fuel in the pre-combustion zone. Thus, the fuel/air ratio within the combustion zone can be minimized (lean burn regime) without the onset of engine misfire.

Abstract: An apparatus and method for controlling the boost pressure of air delivered to a gas fuelled internal combustion engine from air compression means such as a turbocharger. An engine management system (EMS) controls a spark ignition system as well as a gas delivery system for controlling the delivery of gaseous fuel to a fuel inlet. Air is delivered to the engine through air inlet via air throttle means which is also under the control of the EMS. Boost pressure is controlled by an exhaust control valve which is operative to direct a proportion of the exhaust gases to turbocharger. The amount of compression of the air depends on the proportion of the exhaust gases diverted to the turbocharger, which is variable when the engine is operating on gaseous fuel under the control of EMS.