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Development of a heavy-duty natural gas engine to improve its lean operating characteristics is detailed in this paper. Testing to determine the lean misfire limit is described, as well as investigations into the cause of lean misfire in this engine. Details of engine modifications to improve the lean misfire limit are also included. The development process resulted in a significant improvement in the lean performance of the engine (i.e., an extended lean misfire limit, better combustion stability, and lower hydrocarbon emissions).

Advancements in natural gas engine control technology can result in natural gas engines which are more efficient, powerful, responsive, and durable than those currently available. The vast majority of hardware required to make these advancements exists or can be modified for application on natural gas engines. Given this, an investigation to develop and incorporate advanced natural gas engine control technology was completed. Advanced control techniques for equivalence ratio control, knock detection and control, misfire detection and control, and turbocharger transient surge supression are detailed in this paper. Control strategies were developed and applied to a heavy-duty on-highway natural gas engine using a personal computer-based prototyping control system. The engine control system advancements resulted in a natural gas engine with increased efficiency, power density, and response, along with reduced emissions over the current state-of-the-art in natural gas engines.