<div class="htmlview paragraph">The foundation for engine performance and emissions models is a phenomenological description of the combustion process. In this work, high speed movies and analysis of rapid compression machine experiments have been used to develop an understanding of the mechanisms that control combustion rates in the Texaco Controlled Combustion System. The rapid compression machine experiments are described and results have been interpreted to develop a description of the air motion, motion of the fuel spray and the combustion process in the Texaco engine.</div>