Near Zero Emission Internal Combustion Engines

Near zero emission levels from an internal combustion engine were achieved to meet California’s Partial Zero Emission Vehicle (PZEV) requirement beginning with the 2003 model year. Using a systems approach, the tailpipe emission requirements for the PZEV standard were cascaded to the base engine design, control system and catalyst system to achieve the engine-out emissions and catalyst efficiency requirements. Major emphasis was on low emission cold starting and rapid catalyst light-off. Overall catalyst efficiencies of over 99.9% for hydrocarbon emissions, 98.8% for carbon monoxide emissions and 99.5% for oxides of nitrogen emissions were achieved over 150K miles. In addition to achieving near zero levels for tailpipe emissions, on-board diagnostics were developed to detect malfunctions in the near zero emission control systems. Likewise, a near zero evaporative emission system was developed. Future PZEV developments are described as more vehicles will be required to meet the PZEV requirements in the future.