Detailed hydrocarbon speciation and particulate matter emissions during cold-start from turbocharged and naturally aspirated trucks

[Display omitted] •Detailed speciation of cold-start hydrocarbon emissions from turbo & NA GDI vehicles.•Order of magnitude reduction in total hydrocarbon emissions across three-way catalyst.•Hydrocarbon emissions spike at acceleration events dominated by paraffins and olefins.•Significant fraction of cold-start aldehydes comprised of C4 and larger species.•Size distribution of cold-start particles varied between turbo & NA vehicles. Cold-start emissions remain a barrier to vehicle emissions targets and the race to zero impact emissions. Current aftertreatment catalysts are highly efficient once active but struggle at lower temperatures encountered during a cold-start. Significant research can be found on controlling cold-start NOx emissions with fewer studies on the closely linked hydrocarbon (HC) and particulate matter (PM) emissions. This study provides a detailed characterization of HC and PM emissions during cold-start transients to facilitate the development of emissions control technologies for cold-start emissions reduction. To fill this knowledge gap, cumulative and time-resolved speciation of the HC composition and particulate particle size over the initial 250s of the FTP-75 drive cycle were investigated. Emissions from both a turbocharged (t-GDI) and a naturally aspirated (na-GDI) vehicle were compared to capture the range of emissions that cold-start trapping technologies might encounter across different engine architectures. While cumulative emissions were found to be similar, time-resolved measurements show HC composition and particle sizing varied during the cold-start.