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To qualify for an exemption from the tampering prohibition, vehicles/engines that have been converted to operate on a different fuel must meet emission standards and related requirements as described in this section. The modified vehicle/engine must meet the requirements that applied for the OEM vehicle/engine, or the most stringent OEM vehicle/engine standards in any allowable grouping. Fleet average standards do not apply unless clean alternative fuel conversions are specifically listed as subject to the standards.
(a) If the vehicle/engine was certified with a Family Emission Limit for NOX, NOX+HC, NOX+NMOG, or particulate matter, as noted on the vehicle/engine emission control information label, the modified vehicle/engine may not exceed this Family Emission Limit.
(b) Compliance with greenhouse gas emission standards is demonstrated as follows:
(1) Subject to the following exceptions and special provisions, compliance with light-duty vehicle greenhouse gas emission standards is demonstrated by complying with the N2O and CH4 standards and provisions set forth in 40 CFR 86.1818-12(f)(1) and the in-use CO2 exhaust emission standard set forth in 40 CFR 86.1818-12(d) as determined by the OEM for the subconfiguration that is identical to the fuel conversion emission data vehicle (EDV):
(i) If the OEM complied with the light-duty greenhouse gas standards using the fleet averaging option for N2O and CH4, as allowed under 40 CFR 86.1818-12(f)(2), the calculations of the carbon-related exhaust emissions require the input of grams/mile values for N2O and CH4, and you are not required to demonstrate compliance with the standalone CH4 and N2O standards.
(ii) If the OEM complied with alternate standards for N2O and/or CH4, as allowed under 40 CFR 86.1818-12(f)(3), you may demonstrate compliance with the same alternate standards.
(iii) If the OEM complied with the nitrous oxide (N2O) and methane (CH4) standards and provisions set forth in 40 CFR 86.1818-12(f)(1) or (3), and the fuel conversion CO2 measured value is lower than the in-use CO2 exhaust emission standard, you also have the option to convert the difference between the in-use CO2 exhaust emission standard and the fuel conversion CO2 measured value into GHG equivalents of CH4 and/or N2O, using 298 g CO2 to represent 1 g N2O and 25 g CO2 to represent 1 g CH4. You may then subtract the applicable converted values from the fuel conversion measured values of CH4 and/or N2O to demonstrate compliance with the CH4 and/or N2O standards.
(iv) Optionally, compliance with greenhouse gas emission requirements may be demonstrated by comparing emissions from the vehicle prior to the fuel conversion to the emissions after the fuel conversion. This comparison must be based on FTP test results from the emission data vehicle (EDV) representing the pre-conversion test group. The sum of CO2, CH4, and N2O shall be calculated for pre- and post-conversion FTP test results, where CH4 and N2O are weighted by their global warming potentials of 25 and 298, respectively. The post-conversion sum of these emissions must be lower than the pre-conversion conversion greenhouse gas emission results. CO2 emissions are calculated as specified in 40 CFR 600.113-12. If statements of compliance are applicable and accepted in lieu of measuring N2O, as permitted by EPA regulation, the comparison of the greenhouse gas results also need not measure or include N2O in the before and after emission comparisons.
(2) Compliance with heavy-duty engine greenhouse gas emission standards is demonstrated by complying with the CO2, N2O, and CH4 standards (or FELs, as applicable) and provisions set forth in 40 CFR 1036.108 for the engine family that is represented by the fuel conversion emission data engine (EDE). The following additional provisions apply:
(i) If the fuel conversion CO2 measured value is lower than the CO2 standard (or FEL, as applicable), you have the option to convert the difference between the CO2 standard (or FEL, as applicable) and the fuel conversion CO2 measured value into GHG equivalents of CH4 and/or N2O, using 298 g/hp-hr CO2 to represent 1 g/hp-hr N2O. Similarly, you may use 34 g/hp-hr CO2 to represent 1 g/hp-hr CH4 for model year 2021 and later engines, and you may use 25 g/hp-hr CO2 to represent 1 g/hp-hr CH4 for earlier engines. You may then subtract the applicable converted values from the fuel conversion measured values of CH4 and/or N2O to demonstrate compliance with the CH4 and/or N2O standards (or FEL, as applicable).
(ii) Small volume conversion manufacturers may demonstrate compliance with N2O standards based on an engineering analysis.
(iii) For conversions of engines installed in vocational vehicles subject to Phase 2 standards under 40 CFR 1037.105 or in tractors subject to Phase 2 standards under 40 CFR 1037.106, conversion manufacturers may omit a demonstration related to the vehicle-based standards, as long as they have a reasonable technical basis for believing that the modified vehicle continues to meet those standards.
(3) Subject to the following exceptions and special provisions, compliance with greenhouse gas emission standards for medium-duty vehicles and heavy-duty vehicles subject to 40 CFR 86.1819-14 is demonstrated by complying with the N 2 O and CH 4 standards and provisions set forth in 40 CFR 86.1819-14 and the in-use CO 2 exhaust emission standard set forth in 40 CFR 86.1819-14(b) as determined by the OEM for the subconfiguration that is identical to the fuel conversion emission data vehicle (EDV):
(i) If the OEM complied with alternate standards for N2O and/or CH4, as allowed under 40 CFR 86.1819-14(c) you may demonstrate compliance with the same alternate standards.
(ii) If you are unable to meet either the N2O or CH4 standards and your fuel conversion CO2 measured value is lower than the in-use CO2 exhaust emission standard, you may also convert the difference between the in-use CO2 exhaust emission standard and the fuel conversion CO2 measured value into GHG equivalents of CH4 and/or N2O, using 298 g CO2 to represent 1 g N2O. Similarly, you may use 34 g CO2 to represent 1 g CH4.for model year 2021 and later vehicles, and you may use 25 g CO2 to represent 1 g CH4 for earlier vehicles. You may then subtract the applicable converted values from the fuel conversion measured values of CH4 and/or N2O to demonstrate compliance with the CH4 and/or N2O standards.
(iii) You may alternatively comply with the greenhouse gas emission requirements by comparing emissions from the vehicle before and after the fuel conversion. This comparison must be based on FTP test results from the emission data vehicle (EDV) representing the pre-conversion test group. The sum of CO2, CH4, and N2O shall be calculated for pre- and post-conversion FTP test results, where CH4 and N2O are weighted by their global warming potentials as described in paragraph (b)(3)(ii) of this section. The post-conversion sum of these emissions must be lower than the pre-conversion greenhouse gas emission result. Calculate CO2 emissions as specified in 40 CFR 600.113. If we waive N2O measurement requirements based on a statement of compliance, disregard N2O for all measurements and calculations under this paragraph (b)(3)(iii).
(c) Conversion systems for engines that would have qualified for chassis certification at the time of OEM certification may use those procedures, even if the OEM did not. Conversion manufacturers choosing this option must designate test groups using the appropriate criteria as described in this subpart and meet all vehicle chassis certification requirements set forth in 40 CFR part 86, subpart S.
[81 FR 73971, Oct. 25, 2016; 89 FR 28149, Apr. 18, 2024]