Cars with gasoline direct-injected engines are helping automakers meet stricter government fuel economy standards, but they’re emitting five to 10 times more particulate matter than their port fuel-injected counterparts. This is the finding of researchers in Oak Ridge National Laboratory’s Fuels, Engines and Emissions Research Center. GDI engines inject fuel directly into the cylinder, increasing efficiency and compatibility with turbocharging, which allows drivers to have more power with smaller, lighter engines. “The tradeoff is higher particulate matter emissions,” said ORNL’s John Storey, who led the research team. Researchers also reported that particulate matter from GDI engines, expected to have more than 50 percent of the market share by 2017, is smaller and more varied in particle size than that of diesel particulate matter. The smaller particles contain more elemental carbon than diesel particulate matter and because of their size can penetrate deeper into the lungs, creating the potential for greater health risks. The ORNL team is examining approaches to mitigate particulate matter with fuels, combustion and emissions controls.