A computer simulation model was developed to predict the transient thermal responses of automotive exhaust systems. Heat transport due to convective flow, convection heat transfer between exhaust gas and pipe wall, conduction within pipes along the axial direction, and radiation to the ambient have been considered in the model. For dual wall pipes, conduction-convection through the air gap and radiation between the inner and outer pipes were included. This model can be used to study the effect of various parameters on converter inlet temperature. The predicted results were compared to measurements for temperature under transient and steady driving cycles.