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Gasoline particulate filters (GPFs) are an important aftertreatment system that enables gasoline direct injection (GDI) engines to meet current emission standardsn note of GPFs may need to improonont accumulates on the GPF during engine operation. GPFs are often ‘pa during vehicle operation when the exhaust is sufficiently hot and it contains sufficient oxygen. This paper explores the effect that engine-out soot emissions and the frequency of GPF regeneration have on GPF filtration efficiency. Two GPF technologies were tested on two engine dynamometers as well as two production vehicles on a chassis dynamometer. The engines span a wide range of engine-out particle emissions (a range of almost one order of magnitude). The filtration efficiency of the GPFs were measured with a regulation-compliant particle number system (non-volatile particles > 23 nm), as well as with a particle counter with a lower cutoff of 2.5 nm, and with a differential mobility spectrometer.

With the growing awareness about the presence of fine/ultra fine particulates in the ambient air and their negative impact on climate and health, some regions of the world have started to look closer at the contribution of road traffic. Since Gasoline engines, in particular when injecting fuel directly into the combustion chamber, proved to emit relevant numbers of particulates, even hardly visible, the growing share of Gasoline DI engines and their small size of particulate emissions is a concern. To address the same, the EU has already set limits for the particulate number with EU6 from 2015 onwards. The US considers setting challenging limits by particulate mass. Since mass of ultra fine particulates is very low and difficult to measure, experts investigate if a measurement by number might better address the particular concern. The implementation of a coated Particulate Filter enables meeting not only basic demands during traditional emission test cycles.