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Gasoline particulate filter (GPF) is considered a suitable solution to meet the increasingly stringent particle number (PN) regulations for both gasoline direct injection (GDI) and multi-port fuel injection (MPI) engines. Generally, GDI engines emit more particulate matter (PM) and PN. In recent years, GDI engines have gained significant market penetration in the automobile industry owing to better fuel economy and drivability. In this study, an accelerated ash loading method was tested by doping lubricating oil into the fuel for a GDI engine. Emission tests were performed at different ash loads with different driving cycles and GPF combinations. The results showed that the GPF could significantly reduce particle emissions to meet the China 6 regulation. With further ash loading, the filtration efficiency increased above 99% and the effects on fuel consumption and backpressure were found to be limited, even with an ash loading of up to 50 g/l.

New emissions regulations of light-duty vehicles (China 6) will be implemented in China from July 1, 2020. This standard includes two stages, China 6a and China 6(b), in which the PM limits of 4.5 mg/km and 3.0 mg/km are introduced respectively; the PN limit is set to be 6×1011 #/km for both stages. The WLTC testing cycle will be implemented in China 6 regulation as well. In this study a light-duty vehicle satisfying China 6(b) emission standards was developed by improving the engine raw emissions, optimizing the calibration and adding a coated GPF to the after-treatment system. The impacts of ash content and consumption of engine oil and the fast ash accumulation to vehicle emissions and backpressure were analyzed through dynamometer testing. The vehicle after-treatment system was then designed and developed to meet China 6(b) emission standards. The characteristics of soot accumulated through mimicking routine driving under cold environments were tested.