This course will begin with a brief overview of the history and drivers for engine mapping. It will then introduce the concept of Similarity, focusing on its application to internal combustion engines. It will then review how Similarity parameters are used in mapping for both emissions and diagnostics. The course will then review sensor selection, statistical data analysis and data screening. Next the course will describe typical test matrices both for emissions optimization/modeling and the development of diagnostics models. Finally, several case studies will be offered.