Understanding of the mechanisms that a ect ow and pressure drop in porous ceramic diesel particulate lters is important in the design optimization of this class of diesel exhaust aftertreatment systems. Furthermore, determination of the parameters involved in the calculation of pressure drop as a function of collected soot mass is important for successful lter loading and regeneration modelling. This paper presents the results of an experimental analysis of pressure drop as a function of the geometric and operating parameters of cordierite and SiC diesel lters. Singlecell lters from cordierite and silicon carbide were prepared to single out any e ects from the complex ow processes that take place in a full-sized lter. The product of soot layer permeability and density was experimentally determined by employing a specially designed experimental apparatus. The calculation was supported by a simple computer calculation that is also presented in this paper. The distribution of soot loading inside the channels of a full-sized lter, in various loaded and partially regenerated conditions, was assessed by connecting the apparatus to discharge through selected channels of the lter. The results are shown to improve understanding of the e ects of partial regeneration and fuel additive residuals on lter back pressure and ow and soot loading distribution. Keywords: diesel particulate lters, pressure drop, ow maldistribution, diesel soot permeability, regeneration, fuel additives T 0 stagnation temperature ( K ) NOTATION u velocity (m/s) U mean ltration velocity (m/s) A area (m2) V vessel volume (m3) C D discharge coe cient w single-channel lter width (m) dm i mass discharged at the ith time step (kg/s) E substrate thickness (m) c speci c heat ratio c p /c v k permeability (m2) ¢P pressure drop across a single-channel lter L single-channel lter length (m) (Pa) m mass ( kg) (¢P) c calculated pressure drop across a single m v mass of air present in the vessel (kg) channel (Pa) m Ç real real mass owrate ( kg/s) m dynamic viscosity (Pa s) Ma Mach number r density (kg/m3) p T throat pressure ( Pa) (rk) p soot layer density times permeability product p Tc calculated pressure in the throat (Pa) (kg/m) p TG guessed pressure in the throat (Pa) p 0 vessel (identical to stagnation) pressure (Pa) R ideal gas constant [R air =287 kJ/(kg K )] Subscripts t time (s) atm atmospheric T temperature ( K ) c calculated ch channel f lter The MS was