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Assessment of Fuel Economy Technologies for Light-Duty Vehicles
coat cost based on April 2009 PGM prices. The emissions control system cost estimate differences then totaled $227.
For the V6 SUV case, the EEA estimate was $2,590, whereas that of the present study was $3,174. The EEA estimate for the engine was $1,715 versus $1,983 for the present study. Of the $268 difference, the majority is explained by the lack of a cabin heater in the EEA estimate and inclusion of the cabin heater for the present study at $99 (more costly than that of the midsize sedan I4 vehicle because of the larger cabin volume for the midsize SUV with the V6) and the air system (turbocharger and intercooler) for which EEA estimated $365 versus $485 for the present study. The remainder of the difference was due to emissions control. Again, one of the main differences was the use of an HP/LP EGR system for the present study as included in the Martec BOM but not in the EEA estimate ($86 difference). In addition, the present study included the use of a second DOC ($122) included in the Martec BOM that was worked out in collaboration with OEMs and suppliers.
Present Cost Estimates Compared to NHTSA Estimates
According to the NHTSA final ruling for 2011 (DOT/NHTSA, 2009), costs for CI engines and DCT6 transmissions were also derived from the Martec estimates. For the 2.0-L I4, the NHTSA number from Table 5.7 is $2,667, whereas the corresponding number from the present study is $2,393. Most of the difference between these estimates is due to the $292 reduction in aftertreatment system costs used in the present study and derived from using April 2009 PGM prices rather than the November 2007 prices reflected in the Martec numbers presumably used by the NHTSA. It is not known whether the NHTSA estimate includes the down sizing credit or not.
The NHTSA cost estimate of $5,600 retail price equivalent ($3,733 cost) from Tables IV-21, IV-22, and IV-23 (DOT/NHTSA, 2009) for the larger vehicle classes (e.g., large car versus sub compact, compact, and midsize car) is assumed to derive from the Martec cost estimate of $3,465 for V6 diesel ( Martec Group, Inc., 2008, p. 37). The corresponding value for the V6 CI engine from the present study was $3,174. A significant portion of the $559 difference between the NHTSA estimates and those of the present work is due to the inclusion in the Martec, and presumably also in the NHTSA, estimates of two-stage turbocharger systems that for the present study correspond to advanced-level engine technology, as described in the section “Engine Sizing Methodology.” As noted above, the costs from the present work that were used in Table 5.7 were those for the base-level technology configuration. The base level was assumed to use single-stage VGT turbo systems and the advanced level to use two-stage turbo systems. The cost estimate from the present work, which is included in Table 5.7, is for the base-level CI engine. Including the two-stage turbo system in the cost estimate from the present study would increase the estimate from $3,174 to $3,719, leaving a difference between the NHTSA estimate and the present estimate of about $14.
There are also other differences between the assumptions made in the present study and those of the Martec study. For the engine sizing methodology used herein, the baseline six-cylinder engine for the midsize vehicle class of about 4.2 L downsized by the assumed 83 percent is 3.5 L, whereas the Martec study assumes 3.0 L. According to the costing methodology used in the present study, the increase of displacement from 3.0 L to 3.5 L increases cost (entirely as a result of aftertreatment systems cost) from $921 to $964. Subtracting this difference from the engine cost estimate of $3,174 increases the cost differential between the NHTSA estimate and the present study from $14 to $57. As for the remaining difference, there is insufficient information in the NHTSA report to understand the sources of this difference, although it is less than 10 percent, which is well within the uncertainty of these cost estimates in general.
Advanced-Level CI Engine Cost Estimates
Cost estimates for the technologies necessary to raise base-level CI engines to advanced-level engines inherent in the gains described in Table 5.2 are listed in Table 5.8.
Advanced-Level Transmission Cost Estimates
There seems to be an emerging consensus that dual-clutch automatically shifted manual transmissions (DCTs) offer a very attractive combination of efficiency and driver satisfaction with acceptable cost. In the Ricardo, Inc., FSS studies for the EPA (EPA, 2008), CI engines were combined with DCT6 units for the simulations, as noted in earlier discussions of Table 5.1. For that reason, it was assumed for the present analysis that the CI replacements for SI engines would use DCTs. Transmission technologies are discussed in Chapter 7, which considers non-engine vehicle technologies. Cost estimates for advanced transmissions used for this committee’s work are also shown there and are summarized in Table 7.10.
Summary of Total SI to CI Power Train Replacement CostEstimates
The total estimated costs to replace 2007 model-year SI power trains with base-level and advanced-level CI power trains for the example midsize sedan and midsize SUV vehicles indicated in Tables 5.4 and 5.5 are summarized in Table 5.9.
Based on a combination of analysis and engineering judgment applied to information collected from many sources, the committee’s key findings are as follows regarding tech-