Ammonia Selective Catalytic Reduction (SCR) is a key emission control component utilized in diesel engine applications for NOx reduction. There are several types of SCR catalyst currently in the market: Cu-Zeolite, Fe-Zeolite and Vanadia. Diesel vehicle and engine manufacturers down select their production SCR catalyst primarily based on vehicle exhaust gas temperature operation, ammonia dosing strategy, fuel quality, packaging envelope and cost.For Vanadia SCR, the operating temperature is normally controlled below 550oC to avoid vanadium sublimation. In emerging markets, the Vanadia SCR is typically installed alone or downstream of the DOC with low exhaust gas temperature exposure. Vanadia SCR is also utilized in some European applications with passive DPF soot regeneration. However, further improvement of Vanadia SCR NOx conversion at low exhaust gas temperatures will be required to meet future emission regulations (i.e.: HDD Phase 2 GHG). A High-Porosity Substrate with increased Vanadia catalyst loading is a viable solution to achieve higher conversion efficiency targets at low exhaust temperatures (< 300oC).Previously, a study about High-Porosity Substrates with high Cu-Zeolite catalyst loadings demonstrated higher NOx conversion, as well as a potential for 50% reduction in SCR substrate volume when compared to the baseline, conventional substrates and catalyst loadings. In addition, the study found High Cell Density enhanced NOx conversion over a wide exhaust temperature range .In this study, High-Porosity Substrate of various design configurations with a high Vanadia catalyst loading were initially evaluated on a gas reactor, from which several candidates were down selected for further evaluation on an engine bench test. These results are presented in this paper.