For a three-way catalytic converter (TWCC), it is preferable to run simulation based on its light-off performance. Hence, the variation of temperature distribution can be clearly observed to estimate the maximum temperature achieved as a function of time. Due to experimental constraint, the objective was to compare the mass fraction values obtained from the experiment with simulation at steady state condition. At the end, the mass fraction values obtained from simulation are useful to optimize the converter geometries for maximum efficiency. For this purpose, GAMBIT and FLUENT, which came in one package, are used for both modelling and analysis.The model was outlined in x-y coordinate system featuring all necessary points including its inlet, cone and the body. These points are related to the actual dimensions of Fiat converter such as substrate length and diameter, as well as the inlet and outlet diameters. Since the converter is symmetry,only the upper half was modelled, however, in order to visualize the full-rendered converter, the lines are connected to