Abstract:

This analysis explores the impact of the shift towards GDI engines on real-world PM emissions from the U.S. light-duty fleet and the associated regulatory implications. The case study uses a database of tens of millions of measurements of in-use vehicle emissions previously compiled by The Real Urban Emissions (TRUE) Initiative. This report builds on a previous examination of carbon monoxide (CO), nitrogen monoxide (NO), and hydrocarbon (HC) emissions trends from LDVs by model year, adding an analysis of ultraviolet (UV) smoke measurements as an estimate of PM emissions. Data collected in 2019–2021 have been added to the database since the last analysis, allowing for an evaluation of more recent model year vehicles. In addition to real-world data, we also use U.S. EPA’s laboratory-based official certification test data to evaluate the PM emissions performance of GDI vehicles compared to PFI vehicles.