This quarterly report discusses the results from a testing phase of the project that evaluates emission control technologies applied to a two-stroke cycle natural gas-fueled engine. In this phase, a one cylinder Ajax DP-115 (a 13.25 in bore x 16 in stroke, 360 rpm engine) is used to assess a sequential analysis and evaluation of a series of engine upgrades. As with most of the engines used in the natural gas industry, the Ajax engine is a mature engine with widespread usage throughout gas gathering industry. The end point is an assessment of these technologies that assigns a cost per unit reduction in NO{sub x} emissions. This report describes potential emission reduction technologies followed by a battery of tests that demonstrate synergies between some of the more promising technologies. While the end-goal is a closed loop control, low cost NO{sub x} retrofit package, additional work remains. The battery of tests include pre-combustion chambers, in-cylinder sensors, the means to adjust the air-to-fuel ratio, and modification of the air filter housing. During several phases of the tests, the ignition timing also was varied to determine the optimal point for ignition timing. The results from these tests suggest that an optimum exists where …