Gasoline Particulate Filters (GPF), are universally acknowledged as a reliable and high cost effective emission control technology for particulate mass (PM) and particulate number (PN). Bare GPFs can be modified by coating with catalytic washcoat to provide emission reduction for THC, CO and NOx while back pressure (BP) and filtration efficiency (FE) might be influenced.
In this study, a four cylinder China 6B calibrated 1.6 L TGDI (turbo gasoline direct injection) vehicle was used to evaluate various catalyst combinations in the close-coupled and underfloor locations. In the close-couple 1 position (CC1), PGM loadings were varied on a 1 L TWC. Next in the close-coupled 2 position (CC2), coated and uncoated 1.4 L GPFs were evaluated. PGM loading was varied on the coated GPFs using 300/8 high porosity substrates. The uncoated GPFs used a 200/8 low porosity substrates. In the underfloor location, PGM loadings were varied on two 0.5 L TWC catalysts. All catalysts were aged using 4-mode aging to simulate 200,000 km of road aging. A total of eight catalyst combinations were evaluated using the WLTC cycle on the vehicle. Gaseous emissions were measure after each catalyst to determine the minimum PGM and catalyst volume that is necessary to meet our China 6B emission targets. In addition to gaseous emissions, particle number and GPF back pressures were measured. Results indicate that coated GPF significantly improves CO and NOx emission reduction and that coated GPF is necessary to achieve the CO emission targets of China 6B. It was also observed that coated GPFs operate at higher temperatures (+80°C) during the WLTC. This is primarily due to CO oxidation which will also enhance soot oxidation especially during deceleration fuel cut-offs. Not surprisingly, coated GPFs have higher back pressure especially during the high speed portions of the WLTC, however the impact on fuel consumption was not significant.