Measurements of engine cylinder pressure have become routine at the General Motors Research Laboratories. EDPAC, an Engine Diagnostic Package, was designed and developed to process these data automatically from single-and multi-cylinder engines in order to provide engine performance and combustion information. EDPAC consists of several self-contained, independent software modules, each having a different analysis function. These include engine performance calculations, pressure-volume graphics, engine simulation for residual gas estimates, and heat release analysis. After each module is executed, computed results are stored automatically, providing input to subsequent software modules as well as providing a data base for future interrogation.Routine use of EDPAC to process pressure data results in reductions of costs, effort, and turn-around times. A data base containing performance, emissions, and combustion data is established automatically.