Combustion flame geometry calculation is a critical task in the design and analysis of combustion engine chamber. Combustion flame directly influences the fuel economy, engine performance and efficiency. Currently, many of the flame geometry calculation methods assume certain specific chamber and piston top shapes and make some approximations to them. Even further, most methods can not handle multiple spark plug set-ups. Consequently, most of the current flame geometry calculation methods do not give accurate results and have some built-in limitations. They are particularly poor for adapting to any kind of new chamber geometry and spark plug set-up design.This report presents a novel methodology which allows the accurate calculation of flame geometry regardless of the chamber geometry and the number of spark plugs. In this methodology, solid models are used to represent the components within the chamber and unique attributes (colors) are attached respectively to these components. Flame propagation, modeled as a chamber-contained expanding sphere centered at the spark-plug, is represented by a Constructive Solid Geometry tree. Due to the attribute migration during the boolean operations of the CSG, the proper surface and volume can be identified by searching the color. Therefore, flame surface areas and volume can be queried directly from the solid model regardless of the actual chamber shape and spark plug set-up.A system, called Flame Propagation Geometric Simulation (FPGS), based on this methodology has been implemented on top of Product Engineering Tool (PET) and Open I-DEAS using C++. The system demonstrates that the proposed methodology provides a generic and effective way for chamber flame geometry calculation. Moreover, this FPGS can be part of an integrated system to support the powertrain design process.