commodity cost basis used, thus allowing modification of those costs in the present work to reflect recent decreases in commodity pricing for PGMs.

Incremental CI diesel engine cost estimates developed in the present study for replacing 2007 model-year SI gasoline engines with equivalent performance CI diesels are summarized in Tables 5.4, 5.5, and 5.6. Appendix G contains the same information for full-size body-on-frame pickup trucks.

Since the exhaust emissions systems are a significant fraction of the cost for CI diesel power trains, the brief entries in Tables 5.4 and 5.5 are described in more detail in Table 5.6. Note that the entries in Tables 5.4 and 5.5 reflect choices made for NO_x aftertreatment technologies. For the midsize sedan, it was assumed that the 70 percent aged conversion efficiency currently achievable with NSC-based systems would be sufficient for emissions compliance through the year 2020. Using the spreadsheet from which the cost estimates shown in Table 5.6 were obtained, it was also determined that for a 2.0-L CI engine for a midsize sedan, the NSC system is a lower cost approach ($688) than is a urea-SCR-based system ($837). As a result, Table 5.6 contains no cost estimates for the SCR-urea system for the midsize sedan. This choice could be changed depending on success in meeting LEV III requirements with NSC-based systems and changes in PGM commodity prices. However, for the heavier SUV, SCR-urea with its capability for 85 to 93 percent conversion efficiency will be required for emissions compliance. As a result, there are no entries in Table 5.6 for NCS NO_x aftertreatment for the SUV since it is assumed that SCR technology will be used.

Commodity prices were quite volatile between 2004 and 2008 (Martec Group, Inc., 2008), making product planning for CI diesel vehicles quite challenging. To illustrate the impact of PGM (platinum group metals consisting of platinum, palladium, and rhodium) commodity price volatility, Table 5.6 includes estimates for the precious metal wash coats used in the catalysts in separate rows labeled PGM loading. In addition, two columns are shown for each of the two reference vehicles. Columns two and four correspond to the PGM prices in November 2007 used in the Martec study (Martec Group, Inc., 2008). The estimates in columns three and five illustrate emissions systems costs based on PGM prices from April 2009 computed in the present study. These latter costs were used for the aftertreatment system cost estimates in Tables 5.4 and 5.5 because they are considered more representative of the post 2009 period. Obviously, this price situation must be monitored, since it is unlikely to remain at April 2009 levels until 2020. For the sedan with an advanced-level downsized 1.6-L engine, emissions system cost between November 2007 and April 2009 dropped 30 percent. Note that the catalyst volumes for the cost computation for the downsized 1.6-L engine were not reduced from the 2.0-L sizes since the 1.6-L engine must produce the same power