High fuel efficiency has become an extremely desirable trait for internal combustion engines. This motivation has driven extensive research on methods to improve fuel efficiency on engines of various sizes. Many of these methods involve changes to the properties of the combustion process. One way to induce these property changes is through varying the phasing of combustion. Combustion phasing can be defined as the time in the engine cycle, specifically the compression and expansion strokes, where combustion occurs. A change in combustion phasing causes a change in combustion duration. The duration of combustion impacts how the energy and work potential of the energy (availability) from the fuel are utilized. Analysis techniques based on the first and second law of thermodynamics have been developed to determine the energy and availability distributions. These distributions are utilized to visualize and quantify any improvements made to engine efficiency as combustion phasing is altered. The test engine utilized is a spark ignition (SI) engine meaning that the combustion phasing variations are completed by varying the ignition timing. In light of the test platform being a two-cylinder, industrial-use engine, this thesis focuses on determining the impact of combustion phasing on energy and availability distributions in an air-cooled, rich running utility engine subject to tight manufacturing cost constraints --Abstract, page iii