The Impact of Gasoline Direct Injection System Design on PM Emissions

Gasoline Direct Injection engines can have significantly higher particulate mass (PM) and particulate number (PN) emissions relative to equivalent displacement Port Fuel Injected engines. Both the EPA and California Air Resources Board have adopted new stringent standards to be phased in over the next 10 years. The California regulations continue to tighten to a 1 mg/mi PM limit that is phased-in beginning with model year 2025 with full compliance by model year 2028. This study examines the different fuel injection system technology improvements that will be used to attain the standards to as well as their relative costs, market penetration potential, emission reduction and fuel economy impacts.

The identification of alternative approaches and the analysis of their impacts was performed in two tasks. The first task was a comprehensive literature review and the findings of the review are presented. In the second task, information on topics not fully informed by the literature review was obtained from interviews with experts at auto-manufacturers and fuel system suppliers. The information from the interviews was integrated with the findings from the literature review to develop a comprehensive understanding of vehicle PM emissions and the pathways that manufacturers could follow to comply with the 1 mg/mi standard.