Derivation of Turbocharged, Downsized Engine Direct Manufacturing Costs
The derivations of direct manufacturing costs for turbocharged, downsized engines, shown in Tables 8A.2a, b, and c (and Table S.2), are described below for an example of 2017 costs for an I4 engine. The derivation of costs for other engine types follows a similar process.
TABLE 8A.2 – WHITE ROWS (PRIMARY DOWNSIZING WITH THE SAME NUMBER OF CYLINDERS)
The turbocharged, downsized (TRBDS) engine costs for an I4 engine (downsized from a larger displacement I4 engine), shown on the white (primary) rows of Table 8A.2 are derived following NHTSA’s methodology shown in the TSD (EPA/NHTSA 2012) by considering the separate costs for turbocharging and downsizing, as follows:
- Starting with TRBDS1 (18 bar BMEP with 33 percent downsizing), Table 8A.2 shows a 2017 direct manufacturing cost for this engine of $288 (using the low most likely, or NHTSA, estimate). This cost is derived from the TSD as follows:
Turbocharging for 18 bar | $365 (TSD, Table 3-31) |
Downsizing I4-I4 | −$77 (TSD, Table 3-32) |
Net |
$288 (as shown in Table 8A.2) |
- The next step is TRBDS2 (24 bar BMEP, 50 percent downsizing), but the TSD only provides costs for this engine relative to the baseline engine as follows:
Turbocharging for 24 bar | $547 (TSD, Table 3-31) |
Downsizing I4-I4 | −$77 (TSD, Table 3-32) |
Net | $470 |
Incremental cost | $182 ($470 – $288) (as |
(TRBDS2-TRBDS1) | shown in Table 8A.2a) |
- The next step is CEGR1 (cooled EGR added to TRBDS2), which is a standalone cost from the TSD for adding the cooled EGR system.
Cooled EGR | $212 (TSD, Table 3-34) |
- The final step is CEGR2 (27 bar BMEP, 56 percent downsizing), but the TSD only provides costs (excluding the cost of cooled EGR system) relative to the baseline engine as follows:
Turbocharging for 27 bar | $911 (TSD, Table 3-31) |
Downsizing I4-I4 | −$77 (TSD, Table 3-32) |
Net | $834 |
Incremental cost | $364 ($834 – $470) (as |
(CEGR2-TRBDS2) | shown in Table 8A.2a) |
NHTSA subtracts the same cost of downsizing (−$77 credit, or cost save) in each downsizing step. Therefore, this results in applying the $77 credit for downsizing only once for the turbocharged, downsized engines. The downsizing credit does not depend on the amount of downsizing (TSD, Table 3-31), as long as the downsizing is from an I4 engine to a downsized I4 engine (such as a 2.5L I4engine to a 1.68L I4 engine).
This methodology is used for all of the white entries on Table 8A.2a, b, and c for turbocharged, downsized engines (and is consistent with the TSD, Table 3-33, although this table only shows total costs).
TABLE 8A.2 – BLUE ROWS (OPTIONAL DOWNSIZING WITH REDUCED NUMBER OF CYLINDERS)
The blue rows of Table 8A.2a, b, and c (and Table S.2) show costs for optional downsizing with a reduced number of cylinders, which is beyond the level of downsizing assumed by NHTSA in the white rows. NHTSA recognized that there are additional options for downsizing, which are
shown in Table 8.1. The additional downsizing options are complicated since they occur after other technologies have already been added to the engine prior to downsizing. For example, when an I4 engine is downsized to an I3 engine, it has already received four direct fuel injectors and a number other technologies listed in Table 8A.2. When downsizing to the I3 engine by eliminating one cylinder, credit is given for eliminating one of the direct fuel injectors and for a portion of the other technologies previously added.
An example of the derivation of the costs of applying optional downsizing from an I4 engine (TRBDS1) to an I3 engine (TRBDS2) is shown in Table 8.2. The process consists of first adding the costs of all of the new technologies added to the I4 engine as shown in the upper-left side of the table. Next, the incremental costs of downsizing and turbocharging for the next BMEP level are listed, followed by the costs of the new technologies applied to the I3 engine. Notice that the turbocharging cost of $182 shown in Table 8.2 is the same cost shown on the white row of Table 8A.2a for turbocharging to TRBDS2, as described above for the white rows. Taking the costs of the added technologies minus the costs of the portion of the deleted technologies yields −$92 net cost (save) for the new I3 engine at the next BMEP level (TRBDS2). This −$92 net cost (save) is labeled with an asterisk on the blue row labeled “I4 to I3” in Table S.2.
The −$92 net incremental cost for TRBDS2 relative to TRBDS1 was also applied to the example pathways in Chapter 8 following the guidelines contained in NHTSA’s decision trees and cost files for the decision trees. The −$92 (cost save) for 2017 shown in Table 8A.2a becomes −$89 for 2020 shown in Table 8A.2b and becomes −$82 for 2025 shown in Table 8A.2c (and Table S.2) by applying NHTSA’s learning factors.
Tables 8A.2a, b, and c (and Table S.2) show two costs for each of the optional downsizing entries because some of the previously added technologies, which are subsequently partially deleted with a reduction in number of cylinders, had low and high most likely cost estimates. The first of the two costs on the blue row were derived using the low most likely costs of the added and subsequently partially deleted technologies, and the second of the two costs were derived using the high most likely costs of the added and subsequently partly deleted technologies.
REFERENCE
EPA/NHTSA (Environmental Protection Agency/National Highway Traffic Safety Administration). 2012. Joint Technical Support Document, Final Rulemaking 2017-2025 Light-Duty Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards. EPA-420-R-12-901.