This paper describes the experience gained during the successful development of a catalytic converter design for an in-line 4 cylinder application to meet the India 1998 cold start emissions standards. The vehicle application considered was an open loop carburetted system that met the 1997 hot start emission standards using a conventional Pt/Rh underbody mounted catalyst. The challenge was to meet the 1998 standards through catalyst changes and/or minor carburettor adjustments, thus providing the customer with the most cost-effective solution. The approach adopted was to use a mathematical computer simulation (MAESTRO™) developed by Delphi, that utilized engine out data obtained from emission testing of the vehicle to simulate proposed solutions. The biggest advantage of this approach was the ability to estimate the impact of system level changes on emissions performance thus enabling a quick optimization of the design variables. This allowed more time and resources for fabrication and validation testing of only the most likely solutions.