Cost and Fuel Economy Driven Aftertreatment Solutions -for Lean GDI- 2010-01-0363

New fuel economy standards intensify the power train development for more fuel efficient vehicles worldwide. Different approaches are utilized to improve the fuel efficiency of gasoline engines. Of all concepts, including downsizing plus turbocharging, stratified operation of spray-guided gasoline direct injection (GDI) engines show the greatest fuel savings benefit. A significant challenge for stratified GDI aftertreatment systems is to develop both catalysts and systems that can reduce the high amount and cost of precious metals currently needed to meet performance standards under low exhaust temperature operating conditions. Furthermore, tighter emission standards will exceedingly require high conversion rates for HC, CO and NOx. In this paper the most recently developed catalyst and systems for lean GDI aftertreatment will be compared with serial production EURO 5 systems against future legislated targets. One development focus is on improvement of three-way catalysts specifically for lean GDI applications needing advanced light-off behavior with regard to different gas atmospheres (lean, rich and λ==1).

An overview on the recent development improvements of NOx storage catalyst systems is given with regard to cost, performance and durability. New NOx storage catalyst systems show improved performance in the low temperature region which allows for enlarging the usable engine-map range of stratified gasoline injection to the lower speed/load points without additional heating measures used by calibrators to rapidly heat the exhaust catalysts. By further optimization of the aftertreatment system with regard to system integration (catalyst volume, precious metal distribution) a considerable reduction in precious metal is realized with improved over-all performance when compared to the current series applications. An outlook is given for the requirements of the aftertreatment for lean GDI in the US.