Fuel and lubricant impacts on GDI cold-start particulate matter

Melanie  Moses-DeBusk, NTRC – Oak Ridge National Laboratory

The automotive industry has embraced gasoline direct injection (GDI) technology as a mechanism to increase efficiency, with GDI vehicles now accounting for more than 50% of new U.S. sales.  However, along with the increased efficiency gains, GDI technology can increase particulate matter (PM) production, which previously had not been an issue for modern port fuel-injected gasoline vehicles. The U.S. EPA Tier 3 regulations, which began to phase in in 2017, set a limit for all light-duty vehicles of 3 mg/mile PM by 2020, with the potential to lower that to 1 mg/mile by 2025.  At the 1 mg/mile level, vehicles employing GDI technology will likely require some form of controls.  Most of the PM production on GDI-equipped vehicles occurs during the cold-start portion of the regulated FTP cycle, with ten times more PM typically being produced during the cold-start (Bag 1) than during the hot portion of the cycle (Bag 2 and 3).  Cold-start PM from GDI equipped engines contains a large fraction of organic carbon which is often attributed to lubricant entrainment in the PM; therefore, this study focuses on the impact that lubricant viscosity has on cold-start PM production and on the PM’s chemical properties. During 90s cold-start transient events on a GDI engine operating on E10 certification fuel, the mass of elemental carbon collected was not impacted by lubricant viscosity; however, the mass of the organic carbon was lower when a higher viscosity lubricant (20w-50) was used.  Cold-start transients for a series of oxygenated fuels were also investigated to examine the impact of fuel chemistry on PM formation and properties. The results of these GDI cold-start PM studies will be presented.