As trochoidal-gear pump specifications become more demanding and design cycles shorter, the use of an innovative tool for modeling and simulation can be a cost effective and valuable guide to a more effective experimental work. The existing methodologies and software fail to thoroughly address the design by taking into account real effects to maximize efficiency and reduce flow fluctuation. Two new modules are added to the structured methodology of GeroLAB: minimum clearance module, teeth clearance related to leakage phenomenon, and relief groove effective port area module, modeling sharp rims with relief grooves in the porting plate which are related to flow performance. An analysis of the manufactured tolerance is conducted in four gear sets and results are compared and contrast. By using the bond graph model of a specific gerotor pump, flow performance is studied in nine cases with different relief grooves geometries and significant results are drawn. As a conclusion, these new modules aim to continue leading the designer to enhance the efficiency of a gerotor pump and the manufacturer to reduce costs by reducing time in experimental stage.