The objective of this effort was to develop an understanding of how different converter substrate cell structures impact tailpipe emissions and pressure drop from a total systems perspective. The cell structures studied were the following: The catalyst technologies utilized were a new technology palladium only catalyst in combination with a palladium/rhodium catalyst. A 4.0-liter, 1997 Jeep Cherokee with a modified calibration was chosen as the test platform for performing the FTP test.The experimental design focused on quantifying emissions performance as a function of converter volume for the different cell structures. The results from this study demonstrate that the 93 square cell/cm2 structure has superior performance versus the 62 square cell/cm2 structure and the 46 triangle cell/cm2 structure when the converter volumes were relatively small. However, as converter volume increases the emissions differences diminish. For this application the results also show that the higher cell density, lower mass substrates have a slight advantage in catalyst light-off. The emphasis of this study was a comparison of different cell structures, however, other factors such as thermal management, catalyst technology and air-fuel ratio control also contributed significantly to the relative performance of these systems.In conclusion, this study demonstrates the advantages of higher cell density structures to help meet future emissions challenges. In addition, this study also demonstrates that substrate support technology must be integrated with the catalyst technology, the converter packaging, and the engine management control to create a total system, which meets emissions and durability requirements.