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Gaseous and particle emissions from a gasoline direct injection (GDI) and a port fuel injection (PFI) vehicle were measured at various ambient temperatures (22°C, -7°C, -18°C). These vehicles were driven over the U.S. Federal Test Procedure 75 (FTP-75) and US06 Supplemental Federal Test Procedure (US06) on Tier 2 certification gasoline (E0) and 10% by volume ethanol (E10). Emissions were analyzed to determine the impact of ambient temperature on exhaust emissions over different driving conditions. Measurements on the GDI vehicle with a gasoline particulate filter (GPF) installed were also made to evaluate the GPF particle filtration efficiency at cold ambient temperatures. The GDI vehicle was found to have better fuel economy than the PFI vehicle at all test conditions. Reduction in ambient temperature increased the fuel consumption for both vehicles, with a much larger impact on the cold-start FTP-75 drive cycle observed than for the hot-start US06 drive cycle.

Selective catalytic reduction (SCR) technology is being considered as the potential strategy for significant reduction of NOx emissions from diesel engines. Many challenges exist in the development of an On-Road SCR retrofit system in terms of system integration and optimization of control strategy in order to achieve highest NOx reduction given the diversity of duty cycles. The main considered challenges are: - The development of a generic control strategy that would work for a broad range of engines, - Development of a reliable and durable injection system that would be able to withstand the harsh environments on a heavy-duty vehicle, - Packaging of the system to be able to fit on a number of vehicles with different configurations, - Controlling ammonia slip and assurance of reducing agent (Urea) availability and quality. In this study a prototype SCR system was evaluated over engine and chassis dynamometer test cycles.