This paper reports a study of turbulence generation after a monolith honeycomb. Large eddy simulation is used to analyze the turbulence generated when steady, turbulent, or pulsating flow leaves a monolith channel. Substrates with different cell densities, wall thicknesses, and channel cross-sectional shapes are investigated. The results show that the magnitude of the turbulence generated depends on the wall thickness and monolith void fraction, though not much on the cell density. For pulsating flow, different frequency of the pulsations produced only slightly different results, however, the amplitude of the pulsations is proportional to the magnitude of the turbulence generated. The outflow of the channels can act as a jet and trigger turbulence along a distance from 10 to 30 channel diameters, significantly affecting the total pressure drop and the inlet conditions for elements in series downstream, such as particulate filters or other substrates.