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

•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.