Analysis of High Mileage Gasoline Exhaust Particle Filters 2016-01-0941
The purpose of this work was to examine gasoline particle filters (GPFs) at high mileages. Soot levels for gasoline direct injection (GDI) engines are much lower than diesel engines; however, noncombustible material (ash) can cause increased backpressure, reduced power, and lower fuel economy. In this study, a post mortem was completed of two GPFs, one at 130,000 mi and the other at 150,000 mi, from two production 3.5L turbocharged GDI vehicles. The GPFs were ceramic wall-flow filters containing three-way catalytic washcoat and located downstream of conventional three-way catalysts. The oil consumption was measured to be approaching 23,000 mpqt for one vehicle and 30,000 mpqt for the other. The ash contained Ca, P, Zn, S, Fe, and catalytic washcoat. Approximately 50 wt% of the collected ash was non-lubricant derived. The filter capture efficiency of lubricant-derived ash was about 50% and the non-lubricant metal (mostly Fe) deposition rate was 0.9 to 1.2 g per 10,000 mi. Between 58 and 61 g of ash in total was collected, or 23 to 24 g/L. About 60-70% of the ash was on the filter walls and the rest was in the plug region. Average wall ash thicknesses were 12.4 μm. Plug ash density was 0.7 g/cm3. Wall ash density was over twice as high at 1.6 g/cm3 and reduced the filter wall permeability by about 75%. Although the exhaust gas backpressure did increase, there was no significant decrease in fuel economy as a result of the ash accumulation.