Recent vehicle durability experience with low emission concept hardware systems is described. The low-emission concept systems discussed include: thermal reactor only, a combined thermal reactor and HC/CO monolithic catalyst system, and a system combining low thermal inertia exhaust manifolds with dual-bed (NOx and HC/CO) catalytic converters.
Problems shown to influence either emission performance or vehicle function during both atypical and normal vehicle operation include: the melting of monolithic structures used to support both the NOx and the HC/CO catalytic promoters, the deleterious effect of the sulfur content of gasoline on the performance of pelleted NOx catalysts, and the loss of emission control with malfunctioning engine components.
Vehicle fuel economy and performance losses with these types of systems is documented.
Current redesign efforts on these low emission concept vehicle systems in an attempt to overcome the durability problems are described. Such redesign efforts include possible alterations in fuel volatility characteristics of the gasoline.