The introduction of the catalytic converter into the engine compartment has led to severe requirements for thermal insulation. The converter and the exhaust manifold constitute significant heat sources that increase the underhood air temperature and the direct radiation to surrounding components with limited heat tolerance.In the present study, various methods of converter thermal insulation are investigated, and recommendations for minimizing heat transfer are presented. The basic heat transfer mechanisms from the converter are first reviewed to provide a basis for understanding the most effective means of insulation. Ceramic fiber insulation with various thermal conductivities are evaluated at several different thicknesses. This type of internal insulation, which is often used for catalytic converters, is compared to heat shielding. It is found more effective.Experiment and/or simulation have been used to evaluate the various insulation methods. Simple one-dimensional heat transfer models have been used to support the experimental approach. These simple models have been found to be a very powerful tool for product design because they provide a means to quickly evaluate several competing scenarios.