AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Climate Impact of Gasoline Direct Injection (GDI) Vehicles
GEORGES SALIBA, Rawad Saleh, Yunliang Zhao, Albert A. Presto, Andrew Lambe, Bruce Frodin, Satya Sardar, Hector Maldonado, Andrew May, Allen Robinson, Carnegie Mellon University
Abstract Number: 236 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Gasoline direct injection (GDI) vehicles are being increasingly introduced because of their improved efficiency relative to traditional port fuel injection (PFI) vehicles. A concern is that GDI vehicles can have higher EC emissions than PFI vehicles. In this study we investigated the climate implications of switching from PFI to GDI engines using the global warming potential as a metric. Forty chassis dynamometer tests using the cold-start unified cycle were conducted at the California Air Resource Board’s Haagen Smit Laboratory. Gas (CO2, CO, NOx, THC, NMHC, and TOG) and particle phase (EC, OC, and PM) emission factors from 15 GDI vehicles were measured and compared to emissions from 10 PFI vehicles. GDI vehicles had lower CO2 emission rates (170 g/mi reduction) and higher EC emission rates (3.7 mg/mi increase) compared to PFI vehicles. We estimated that replacing a PFI fleet by a GDI fleet will produce a net global cooling two years after emission, because reduced CO2 emissions (due to higher efficiency) more than offset the additional warming from increased EC emissions. To further investigate the climate implications of GDI vehicles, we characterized (using two photo-acoustic extinctiometers) the presence of brown carbon in fresh and photo-chemically aged (inside a potential aerosol mass reactor) tailpipe emissions. Fresh vehicle emissions exhibited an angstrom exponent of 1.40 (with 95% CI of [1.18, 1.62]) potentially suggesting that fresh tailpipe emissions contain brown carbon. Aging tailpipe emissions slightly increased the angstrom exponent from 1.40 to 1.47 (with 95% CI of [1.28, 1.66]) indicating that oxidation of primary vapors emitted during vehicle combustion contribute negligibly to brown carbon formation.