This paper describes the application of the discrete transfer model of thermal radiation in the engine CFD code KIVA for the simulation of diesel combustion and heat transfer. The comprehensive modelling of flows and heat transfer in engines requires accurate evaluation of transient temperature and radiation properties of the gaseous combustion products. A submodel for autoignition chemistry and a soot formation and oxidation model have been incorporated in the general computational fluid dynamics procedure, and Hottel's mixed grey and clear gas concept has been used to evaluate emissivities. Results of calculations are presented for engine aerodynamics, cylinder pressure and temperature, soot concentration, and radiative heat fluxes. Radiative heat fluxes have been compared with data, in similar experimental engines. Comparisons between the predictions and data show encouraging agreement. Inclusion of the submodels for autoignition and soot formation and combustion seem to have greatly enhanced radiation predictions. It is concluded that present prediction techniques can be useful in providing information in engine flows under a variety of engine operating conditions.