Assessment of different technical options in reducing particle emissions from gasoline direct injection vehicles

• We characterized the particle emissions of a “hybrid” port/direct injection gasoline.
• We assessed the performance of a gasoline particulate filter.
• We characterized the particle emissions of a flexi fuel direct injection gasoline.
• We investigated their emission performance under sub-zero ambient temperatures.
• We quantified the amount of sub-23 nm solid particles.

We assessed three different technical approaches targeting the control of particle number (PN) emissions from stoichiometric direct injection gasoline vehicles. The emission performance was evaluated under both the regulated New European driving cycle and the common artemis driving cycle, conducted at both 22 and −7 °C test cell temperatures. The most efficient measure was found to be the installation of a gasoline particulate filter which, with a filtration efficiency of more than 90%, effectively reduced the PN emission below the legislated diesel threshold of 6×1011 #/km, under all operating conditions examined. The use of 75–85% ethanol/gasoline blends on a flexi fuel vehicle resulted in large reductions in PN emissions, which spanned from approximately 20–35% under urban driving to an excess of 95% at motorway conditions. The emission performance of a Euro 4 vehicle utilizing a twin port/direct injection system verified the PN reduction potential offered by such strategies, exhibiting emissions in the 3-7×1011 #/km range over all hot-start tests. The fraction of nano-sized non-volatile particles that could not be detected with the legislated PN measurement procedure ranged between 10 and 35%, that is within the levels reported for late technology diesel vehicles (Mamakos et al., 2012b. Journal of Aerosol Science, 55:31–47). The study also provided evidence of volatile artefact interference downstream of the volatile particle remover when employing condensation particle counters with a cut-off size below the legislated 23 nm.