Suffusion is an internal erosion mechanism, which means the transport of fine particles within the soil due to hydraulic interflows. With the objective to characterize this mechanism and to study a scale effect presented in literature, a specific centrifuge bench is designed. Test specimens of mixture of sand and kaolinite are compacted in rigid walled cells. The specimen height is selected according to the applied gravity and the chosen effective stress. After saturation, specimens are subjected to centrifugal acceleration and to a vertical downward flow under a constant hydraulic head. The effect of the applied hydraulic gradient is examined and the study underlines that the increase of specimen height induces the decrease of critical hydraulic gradient and the increase of erosion rate. A new energy analysis of tests is developed, linking the expended power to the erosion rate. This method permits to avoid the effect of specimen height.