This short course focuses on using a set of normalized engine parameters to determine engine emissions performance under a wide variety of operating conditions. The modeling techniques presented have been successfully used to determine the air requirements for many different engine models and to explain the differences in performance observed within engine families. This short course considers in detail the effects of scavenging and trapping on engine emissions. This short course will introduce a series of mathematical equations that are solved to determine the air manifold conditions that are necessary to achieve a specific emissions level from an engine. A Sample model will be created for the Cooper GMW series of engines that not only can be used to predict emissions, but also demonstrates the effects of trapping and scavenging on emissions. Considered in the example are the GMWA, GMWC and GMWH (C models converted to pure turbocharged) engines. Differences in emissions performance based on the scavenging configuration are fully explored. The authors intend to teach the methods that have been developed and then illustrate how these methods are used when modeling for emissions. The purpose of the course is to document ad demonstrate the science that underlies the art of creating emissions based air specifications.