The relationship between fuel penalty and precious metal loading in coupled LNTSCR systems for NOx reduction at low temperatures is determined. Simulations of adiabatic, aerobic NOx reduction determine the impact of catalyst architecture, precious metal loading, cycle time, catalyst length and the support material. These revealed that (a) high NOx conversion can be achieved for a given precious metal loading at low temperatures (510 K) with about 0.3% fuel penalty, (b) shortened cycle time and increased pulse duty reduce the overall NOx slip from the coupled catalyst and lead to significant improvement in the NOx conversion, (c) alternate arrangement of the LNT/SCR catalysts increases the NOx conversion, (d) a monotonic decreasing PGM loading in LNT leads to higher NOx conversion compared to uniform loading, (e) for a fixed catalyst volume, there is an optimal aspect ratio that maximizes the nonisothermal effect, and (f) metal based monolith supports improve NOx conversion. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 3421-3431, 2013