Impact of gasoline composition on particulate matter emissions from a direct-injection gasoline engine: Applicability of the particulate matter index

The new fuel property “particulate matter (PM) index” suggested by Aikawa et al. in their previous report, which reflects particulate matter emission potential of gasoline, has been shown to have a significant correlation with PM in port fuel injection engine. However, the particulate matter index applicability to direct-injection gasoline engines has not been well verified. The purpose of this study is to confirm the particulate matter index applicability to direct-injection gasoline engines. Results verified good correlation between particulate matter index and particulate matter emissions of a direct-injection gasoline engine, just as with the port fuel injection engine. The verification of particulate number emissions of the direct-injection gasoline engine on the US FTP-75 cycle indicated a high correlation with the particulate matter index. In particular, a significantly high correlation (R² = 0.9644) was observed in the FTP-75 cold-start phase (Phase 1) in which the fuel influences are considered most evident. The filter PM (PM mass) was simultaneously measured, and its correlation with PM index was verified. The correlation with PM mass was slightly lower than with particulate number, but it also had a good correlation with PM index. This indicated that the PM index will apply well to DI gasoline engines.