primary intended service class to the standards of this paragraph (e),
it is not allowed to opt out of these standards. Engines certified to
these standards are not eligible for early credits under paragraph (a)
of this section.

----------------------------------------------------------------------------------------------------------------
             Tractors                      LHD Engines               MHD Engines               HHD Engines
----------------------------------------------------------------------------------------------------------------
Model Years 2013-2015.............  NA......................  512 g/hp-hr.............  485 g/hp-hr.
Model Years 2016 and later \1\....  NA......................  487 g/hp-hr.............  460 g/hp-hr.
----------------------------------------------------------------------------------------------------------------
Vocational........................         LHD Engines               MHD Engines               HHD Engines
----------------------------------------------------------------------------------------------------------------
Model Years 2013-2015.............  618 g/hp-hr.............  618 g/hp-hr.............  577 g/hp-hr.
Model Years 2016 through 2020 \a\.  576 g/hp-hr.............  576 g/hp-hr.............  555 g/hp-hr.
----------------------------------------------------------------------------------------------------------------
\1\ Note: these alternate standards for 2016 and later are the same as the otherwise applicable standards for
  2017 through 2020.

    (f) Separate OBD families. This paragraph (f) applies where you
separately certify engines for the purpose of applying OBD requirements
(for engines used in vehicles under 14,000 pounds GVWR) from non-OBD
engines that could be certified as a single engine family. You may
treat the two engine families as a single engine family in certain
respects for the purpose of this part, as follows:
    (1) This paragraph (f) applies only where the two families are
identical in all respects except for the engine ratings offered and the
inclusion of OBD.
    (2) For purposes of this part and 40 CFR part 86, the two families
remain two separate families except for the following:
    (i) Specify the testable configurations of the non-OBD engine
family as the testable configurations for the OBD family.
    (ii) Submit the same CO2, N2O, and
CH4 emission data for both engine families.
    (g) Assigned deterioration factors. You may use assigned
deterioration factors (DFs) without performing your own durability
emission tests or engineering analysis as follows:
    (1) You may use an assigned additive DF of 0.0 g/hp-hr for
CO2 emissions from engines that do not use advanced or off-
cycle technologies. If we determine it to be consistent with good
engineering judgment, we may allow you to use an assigned additive DF
of 0.0 g/hp-hr for CO2 emissions from your engines with
advanced or off-cycle technologies.
    (2) You may use an assigned additive DF of 0.020 g/hp-hr for
N2O emissions from any engine through model year 2020, and
0.010 g/hp-hr for later model years.
    (3) You may use an assigned additive DF of 0.020 g/hp-hr for
CH4 emissions from any engine.
    (h) Advanced-technology credits. If you generate credits from model
year 2020 and earlier engines certified for advanced technology, you
may multiply these credits by 1.5, except that you may not apply this
multiplier and the early-credit multiplier of paragraph (a) of this
section.
    (i) CO2 credits for low N2O emissions. If you certify your model
year 2014, 2015, or 2016 engines to an N2O FEL less than
0.04 g/hp-hr (provided you measure N2O emissions from your
emission-data engines), you may generate additional CO2
credits under this paragraph (i). Calculate the additional
CO2 credits from the following equation instead of the
equation in Sec.  1036.705:

CO2 Credits (Mg) = (0.04-FELN2O) [middot] (CF)
[middot] (Volume) [middot] (UL) [middot] (10-6) [middot]
(298)

    (j) Alternate standards under 40 CFR part 86. This paragraph (j)
describes alternate emission standards for loose engines certified
under 40 CFR 86.1819-14(k)(8). The standards of Sec.  1036.108 do not
apply for these engines. The standards in this paragraph (j) apply for
emissions measured with the engine installed in a complete vehicle
consistent with the provisions of 40 CFR 86.1819-14(k)(8)(vi). The only
requirements of this part that apply to these engines are those in this
paragraph (j), Sec. Sec.  1036.115 through 1036.135, 1036.535, and
1036.540.
    (k) [Reserved]
    (l) Credit adjustment for spark-ignition engines and light heavy-
duty compression-ignition engines. For emission credits generated from
model year 2020 and earlier engines subject to spark-ignition standards
and light heavy-duty compression-ignition engines, multiply any banked
credits that you carry forward to demonstrate compliance with model
year 2021 and later standards by 1.36.
    (m) Infrequent regeneration. For model year 2020 and earlier, you
may invalidate any test interval with respect to CO2
measurements if an infrequent regeneration event occurs during the test
interval. Note that Sec.  1036.530 specifies how to apply infrequent
regeneration adjustment factors for later model years.
    (n) Supplying fuel maps. Engine manufacturers not yet subject to
standards under Sec.  1036.108 in model year 2021 must supply vehicle
manufacturers with fuel maps (or powertrain test results) as described
in Sec.  1036.130 for those engines.
    (o) Engines used in glider vehicles. For purposes of recertifying a
used engine for installation in a glider vehicle, we may allow you to
include in an existing certified engine family those engines you modify
(or otherwise demonstrate) to be identical to engines already covered
by the certificate. We would base such an approval on our review of any
appropriate documentation. These engines must have emission control
information labels that accurately describe their status.
    (p) Transition to Phase 2 CO2 standards. If you certify
all your model year 2020 engines within an averaging set to the model
year 2021 FTP and SET standards and requirements, you may apply the
provisions of this paragraph (p) for enhanced generation and use of
emission credits. These provisions apply separately for medium heavy-
duty engines and heavy heavy-duty engines.
    (1) GHG emission credits you generate with model year 2018 through
2024 engines may be used through model year 2030, instead of being
limited to a five-year credit life as specified in Sec.  1036.740(d).
    (2) You may certify your model year 2024 through 2026 engines to
the following alternative standards:

----------------------------------------------------------------------------------------------------------------
                                               Medium  heavy-   Heavy  heavy-
                 Model years                       duty--           duty--       Medium  heavy-   Heavy  heavy-
                                                 vocational       vocational     duty-- tractor   duty--tractor
----------------------------------------------------------------------------------------------------------------
2024-2026...................................             538              506              467              442
----------------------------------------------------------------------------------------------------------------

Subpart C--Certifying Engine Families

Sec.  1036.205  What must I include in my application?

    Submit an application for certification as described in 40 CFR
86.007-21, with the following additional information:
    (a) Describe the engine family's specifications and other basic
parameters of the engine's design and emission controls with respect to
compliance with the requirements of this part. Describe in detail all
system components for controlling greenhouse gas emissions, including
all auxiliary emission control devices (AECDs) and all fuel-system
components you will install on any production or test engine. Identify
the part number of each component you describe. For this paragraph (a),
treat as separate AECDs any devices that modulate or activate
differently from each other.
    (b) Describe any test equipment and procedures that you used if you
performed any tests that did not also involve measurement of criteria
pollutants. Describe any special or alternate test procedures you used
(see 40 CFR 1065.10(c)).
    (c) Include the emission-related installation instructions you will
provide if someone else installs your engines in their vehicles (see
Sec.  1036.130).
    (d) Describe the label information specified in Sec.  1036.135. We
may require you to include a copy of the label.
    (e) Identify the CO2 FCLs with which you are certifying
engines in the engine family; also identify any FELs that apply for
CH4 and N2O. The actual U.S.-directed production
volume of configurations that have CO2 emission rates at or
below the FCL and CH4 and N2O emission rates at
or below the applicable standards or FELs must be at least one percent
of your actual (not projected) U.S.-directed production volume for the
engine family. Identify configurations within the family that have
emission rates at or below the FCL and meet the one percent
requirement. For example, if your U.S.-directed production volume for
the engine family is 10,583 and the U.S.-directed production volume for
the tested rating is 75 engines, then you can comply with this
provision by setting your FCL so that one more rating with a U.S.-
directed production volume of at least 31 engines meets the FCL. Where
applicable, also identify other testable configurations required under
Sec.  1036.230(b)(2).
    (f) Identify the engine family's deterioration factors and describe
how you developed them (see Sec.  1036.241). Present any test data you
used for this.
    (g) Present emission data to show that you meet emission standards,
as follows:
    (1) Present exhaust emission data for CO2,
CH4, and N2O on an emission-data engine to show
that your engines meet the applicable emission standards we specify in
Sec.  1036.108. Show emission figures before and after applying
deterioration factors for each engine. In addition to the composite
results, show individual measurements for cold-start testing and hot-
start testing over the transient test cycle. For each of these tests,
also include the corresponding exhaust emission data for criteria
emissions. Note that Sec.  1036.235 allows you to submit an application
in certain cases without new emission data.
    (2) [Reserved]
    (h) State whether your certification is limited for certain
engines. For example, if you certify heavy heavy-duty engines to the
CO2 standards using only transient testing, the engines may
be installed only in vocational vehicles.
    (i) Unconditionally certify that all the engines in the engine
family comply with the requirements of this part, other referenced
parts of the CFR, and the Clean Air Act. Note that Sec.  1036.235
specifies which engines to test to show that engines in the entire
family comply with the requirements of this part.
    (j) Include the information required by other subparts of this
part. For example, include the information required by Sec.  1036.725
if you participate in the ABT program.
    (k) Include the warranty statement and maintenance instructions if
we request them.
    (l) Include other applicable information, such as information
specified in this part or 40 CFR part 1068 related to requests for
exemptions.
    (m) For imported engines or equipment, identify the following:
    (1) Describe your normal practice for importing engines. For
example, this may include identifying the names and addresses of any
agents you have authorized to import your engines. Engines imported by
nonauthorized agents are not covered by your certificate.
    (2) The location of a test facility in the United States where you
can test your engines if we select them for testing under a selective
enforcement audit, as specified in 40 CFR part 1068, subpart E.
    (n) Include information needed to certify vehicles to GHG standards
under 40 CFR part 1037 as described in Sec.  1036.510.

Sec.  1036.210  Preliminary approval before certification.

    If you send us information before you finish the application, we
may review it and make any appropriate determinations, especially for
questions related to engine family definitions, auxiliary emission
control devices, adjustable parameters, deterioration factors, testing
for service accumulation, and maintenance. Decisions made under this
section are considered to be preliminary approval, subject to final
review and approval. We will generally not reverse a decision where we
have given you preliminary approval, unless we find new information
supporting a different decision. If you request preliminary approval
related to the upcoming model year or the model year after that, we
will make best-efforts to make the appropriate determinations as soon
as practicable. We will generally not provide preliminary approval
related to a future model year more than two years ahead of time.

Sec.  1036.225  Amending my application for certification.

    Before we issue you a certificate of conformity, you may amend your
application to include new or modified engine configurations, subject
to the provisions of this section. After we have issued your
certificate of conformity, you may send us an amended application
requesting that we include new or modified engine configurations within
the scope of the certificate, subject to the provisions of this
section. You must also amend your application if any changes occur with
respect to any information that is included or should be included in
your application.
    (a) You must amend your application before you take any of the
following actions:
    (1) Add an engine configuration to an engine family. In this case,
the engine

configuration added must be consistent with other engine configurations
in the engine family with respect to the criteria listed in Sec.
1036.230.
    (2) Change an engine configuration already included in an engine
family in a way that may affect emissions, or change any of the
components you described in your application for certification. This
includes production and design changes that may affect emissions any
time during the engine's lifetime.
    (3) Modify an FEL and FCL for an engine family as described in
paragraph (f) of this section.
    (b) To amend your application for certification, send the relevant
information to the Designated Compliance Officer.
    (1) Describe in detail the addition or change in the engine model
or configuration you intend to make.
    (2) Include engineering evaluations or data showing that the
amended engine family complies with all applicable requirements. You
may do this by showing that the original emission-data engine is still
appropriate for showing that the amended family complies with all
applicable requirements.
    (3) If the original emission-data engine for the engine family is
not appropriate to show compliance for the new or modified engine
configuration, include new test data showing that the new or modified
engine configuration meets the requirements of this part.
    (4) Include any other information needed to make your application
correct and complete.
    (c) We may ask for more test data or engineering evaluations. You
must give us these within 30 days after we request them.
    (d) For engine families already covered by a certificate of
conformity, we will determine whether the existing certificate of
conformity covers your newly added or modified engine. You may ask for
a hearing if we deny your request (see Sec.  1036.820).
    (e) For engine families already covered by a certificate of
conformity, you may start producing the new or modified engine
configuration any time after you send us your amended application and
before we make a decision under paragraph (d) of this section. However,
if we determine that the affected engines do not meet applicable
requirements, we will notify you to cease production of the engines and
may require you to recall the engines at no expense to the owner.
Choosing to produce engines under this paragraph (e) is deemed to be
consent to recall all engines that we determine do not meet applicable
emission standards or other requirements and to remedy the
nonconformity at no expense to the owner. If you do not provide
information required under paragraph (c) of this section within 30 days
after we request it, you must stop producing the new or modified
engines.
    (f) You may ask us to approve a change to your FEL in certain cases
after the start of production, but before the end of the model year. If
you change an FEL for CO2, your FCL for CO2 is
automatically set to your new FEL divided by 1.03. The changed FEL may
not apply to engines you have already introduced into U.S. commerce,
except as described in this paragraph (f). You may ask us to approve a
change to your FEL in the following cases:
    (1) You may ask to raise your FEL for your engine family at any
time. In your request, you must show that you will still be able to
meet the emission standards as specified in subparts B and H of this
part. Use the appropriate FELs/FCLs with corresponding production
volumes to calculate emission credits for the model year, as described
in subpart H of this part.
    (2) You may ask to lower the FEL for your engine family only if you
have test data from production engines showing that emissions are below
the proposed lower FEL (or below the proposed FCL for CO2).
The lower FEL/FCL applies only to engines you produce after we approve
the new FEL/FCL. Use the appropriate FELs/FCLs with corresponding
production volumes to calculate emission credits for the model year, as
described in subpart H of this part.
    (g) You may produce engines as described in your amended
application for certification and consider those engines to be in a
certified configuration if we approve a new or modified engine
configuration during the model year under paragraph (d) of this
section. Similarly, you may modify in-use engines as described in your
amended application for certification and consider those engines to be
in a certified configuration if we approve a new or modified engine
configuration at any time under paragraph (d) of this section.
Modifying a new or in-use engine to be in a certified configuration
does not violate the tampering prohibition of 40 CFR 1068.101(b)(1), as
long as this does not involve changing to a certified configuration
with a higher family emission limit.

Sec.  1036.230  Selecting engine families.

    See 40 CFR 86.001-24 for instructions on how to divide your product
line into families of engines that are expected to have similar
emission characteristics throughout the useful life. You must certify
your engines to the standards of Sec.  1036.108 using the same engine
families you use for criteria pollutants under 40 CFR part 86. The
following provisions also apply:
    (a) Engines certified as hybrid engines may not be included in an
engine family with engines with conventional powertrains. Note that
this does not prevent you from including engines in a conventional
family if they are used in hybrid vehicles, as long as you certify them
conventionally.
    (b) If you certify engines in the family for use as both vocational
and tractor engines, you must split your family into two separate
subfamilies. Indicate in the application for certification that the
engine family is to be split.
    (1) Calculate emission credits relative to the vocational engine
standard for the number of engines sold into vocational applications
and relative to the tractor engine standard for the number of engines
sold into non-vocational tractor applications. You may assign the
numbers and configurations of engines within the respective subfamilies
at any time before submitting the end-of-year report required by Sec.
1036.730. If the family participates in averaging, banking, or trading,
you must identify the type of vehicle in which each engine is
installed; we may alternatively allow you to use statistical methods to
determine this for a fraction of your engines. Keep records to document
this determination.
    (2) If you restrict use of the test configuration for your split
family to only tractors, or only vocational vehicles, you must identify
a second testable configuration for the other type of vehicle (or an
unrestricted configuration). Identify this configuration in your
application for certification. The FCL for the engine family applies
for this configuration as well as the primary test configuration.
    (c) If you certify in separate engine families engines that could
have been certified in vocational and tractor engine subfamilies in the
same engine family, count the two families as one family for purposes
of determining your obligations with respect to the OBD requirements
and in-use testing requirements of 40 CFR part 86. Indicate in the
applications for certification that the two engine families are covered
by this paragraph (c).
    (d) Engine configurations within an engine family must use
equivalent greenhouse gas emission controls. Unless we approve it, you
may not produce nontested configurations without the same emission
control hardware included on the tested

configuration. We will only approve it if you demonstrate that the
exclusion of the hardware does not increase greenhouse gas emissions.
    (e) If you certify both engine fuel maps and powertrain fuel maps
for an engine family, you may split the engine family into two separate
subfamilies. Indicate this in your application for certification, and
identify whether one or both of these sets of fuel maps applies for
each group of engines. If you do not split your family, all engines
within the family must conform to the engine fuel maps, including any
engines for with the powertrain maps also apply.

Sec.  1036.235  Testing requirements for certification.

    This section describes the emission testing you must perform to
show compliance with the greenhouse gas emission standards in Sec.
1036.108.
    (a) Select a single emission-data engine from each engine family as
specified in 40 CFR part 86. The standards of this part apply only with
respect to emissions measured from this tested configuration and other
configurations identified in Sec.  1036.205(e). Note that
configurations identified in Sec.  1036.205(e) are considered to be
``tested configurations''. Whether or not you actually tested them for
certification. However, you must apply the same (or equivalent)
emission controls to all other engine configurations in the engine
family. In other contexts, the tested configuration is sometimes
referred to as the ``parent configuration'', although the terms are not
synonymous.
    (b) Test your emission-data engines using the procedures and
equipment specified in subpart F of this part. In the case of dual-fuel
and flexible-fuel engines, measure emissions when operating with each
type of fuel for which you intend to certify the engine. (Note:
measurement of criteria emissions from flexible-fuel engines generally
involves operation with the fuel mixture that best represents in-use
operation, or with the fuel mixture with the highest emissions.)
Measure CO2, CH4, and N2O emissions
using the specified duty cycle(s), including cold-start and hot-start
testing as specified in 40 CFR part 86, subpart N. The following
provisions apply regarding test cycles for demonstrating compliance
with tractor and vocational standards:
    (1) If you are certifying the engine for use in tractors, you must
measure CO2 emissions using the applicable ramped-modal
cycle specified in Sec.  1036.505, and measure CH4, and
N2O emissions using the specified transient cycle.
    (2) If you are certifying the engine for use in vocational
applications, you must measure CO2, CH4, and
N2O emissions using the specified transient duty cycle,
including cold-start and hot-start testing as specified in 40 CFR part
86, subpart N.
    (3) You may certify your engine family for both tractor and
vocational use by submitting CO2 emission data from both
ramped-modal and transient cycle testing and specifying FCLs for both.
    (4) Some of your engines certified for use in tractors may also be
used in vocational vehicles, and some of your engines certified for use
in vocational may be used in tractors. However, you may not knowingly
circumvent the intent of this part (to reduce in-use emissions of
CO2) by certifying engines designed for tractors or
vocational vehicles (and rarely used in the other application) to the
wrong cycle. For example, we would generally not allow you to certify
all your engines to the ramped-modal cycle without certifying any to
the transient cycle.
    (c) We may perform confirmatory testing by measuring emissions from
any of your emission-data engines. If your certification includes
powertrain testing as specified in 40 CFR 1036.630, this paragraph (c)
also applies for the powertrain test results.
    (1) We may decide to do the testing at your plant or any other
facility. If we do this, you must deliver the engine to a test facility
we designate. The engine you provide must include appropriate
manifolds, aftertreatment devices, electronic control units, and other
emission-related components not normally attached directly to the
engine block. If we do the testing at your plant, you must schedule it
as soon as possible and make available the instruments, personnel, and
equipment we need.
    (2) If we measure emissions on your engine, the results of that
testing become the official emission results for the engine as
specified in this paragraph (c). Unless we later invalidate these data,
we may decide not to consider your data in determining if your engine
family meets applicable requirements.
    (3) Before we test one of your engines, we may set its adjustable
parameters to any point within the physically adjustable ranges.
    (4) Before we test one of your engines, we may calibrate it within
normal production tolerances for anything we do not consider an
adjustable parameter. For example, this would apply for an engine
parameter that is subject to production variability because it is
adjustable during production, but is not considered an adjustable
parameter (as defined in Sec.  1036.801) because it is permanently
sealed. For parameters that relate to a level of performance that is
itself subject to a specified range (such as maximum power output), we
will generally perform any calibration under this paragraph (c)(4) in a
way that keeps performance within the specified range.
    (5) We may use our emission test results for steady-state, idle,
cycle-average and powertrain fuel maps, as long as we perform at least
three valid tests. We will use mean values for each point to specify
our fuel maps and may use the resulting fuel maps as the official
emission results. We may also consider how the different fuel maps
affect GEM emission results as part of our decision. We will not
replace individual points from your fuel map, but we may make separate
determinations for steady-state, idle, cycle-average and powertrain
fuel maps.
    (6) If you supply cycle-average engine fuel maps for the highway
cruise cycles instead of generating a steady-state fuel map for these
cycles, we may perform a confirmatory test of your engine fuel maps for
the highway cruise cycles by either of the following methods:
    (i) Directly measuring the highway cruise cycle-average fuel maps.
    (ii) Measuring a steady-state fuel map as described in paragraph
(c)(5) of this section and using it in GEM to create our own cycle-
average engine fuel maps for the highway cruise cycles.
    (d) You may ask to use carryover emission data from a previous
model year instead of doing new tests, but only if all the following
are true:
    (1) The engine family from the previous model year differs from the
current engine family only with respect to model year, items identified
in Sec.  1036.225(a), or other characteristics unrelated to emissions.
We may waive this criterion for differences we determine not to be
relevant.
    (2) The emission-data engine from the previous model year remains
the appropriate emission-data engine under paragraph (b) of this
section.
    (3) The data show that the emission-data engine would meet all the
requirements that apply to the engine family covered by the application
for certification.
    (e) We may require you to test a second engine of the same
configuration in addition to the engine tested under paragraph (a) of
this section.
    (f) If you use an alternate test procedure under 40 CFR 1065.10 and
later testing shows that such testing does not produce results that are
equivalent to the procedures specified

in subpart F of this part, we may reject data you generated using the
alternate procedure.

Sec.  1036.241  Demonstrating compliance with greenhouse gas emission
standards.

    (a) For purposes of certification, your engine family is considered
in compliance with the emission standards in Sec.  1036.108 if all
emission-data engines representing the tested configuration of that
engine family have test results showing official emission results and
deteriorated emission levels at or below the standards. Note that your
FCLs are considered to be the applicable emission standards with which
you must comply for certification.
    (b) Your engine family is deemed not to comply if any emission-data
engine representing the tested configuration of that engine family has
test results showing an official emission result or a deteriorated
emission level for any pollutant that is above an applicable emission
standard (generally the FCL). Note that you may increase your FCL if
any certification test results exceed your initial FCL.
    (c) Apply deterioration factors to the measured emission levels for
each pollutant to show compliance with the applicable emission
standards. Your deterioration factors must take into account any
available data from in-use testing with similar engines. Apply
deterioration factors as follows:
    (1) Additive deterioration factor for greenhouse gas emissions.
Except as specified in paragraphs (c)(2) and (3) of this section, use
an additive deterioration factor for exhaust emissions. An additive
deterioration factor is the difference between the highest exhaust
emissions (typically at the end of the useful life) and exhaust
emissions at the low-hour test point. In these cases, adjust the
official emission results for each tested engine at the selected test
point by adding the factor to the measured emissions. If the factor is
less than zero, use zero. Additive deterioration factors must be
specified to one more decimal place than the applicable standard.
    (2) Multiplicative deterioration factor for greenhouse gas
emissions. Use a multiplicative deterioration factor for a pollutant if
good engineering judgment calls for the deterioration factor for that
pollutant to be the ratio of the highest exhaust emissions (typically
at the end of the useful life) to exhaust emissions at the low-hour
test point. Adjust the official emission results for each tested engine
at the selected test point by multiplying the measured emissions by the
deterioration factor. If the factor is less than one, use one. A
multiplicative deterioration factor may not be appropriate in cases
where testing variability is significantly greater than engine-to-
engine variability. Multiplicative deterioration factors must be
specified to one more significant figure than the applicable standard.
    (3) Sawtooth and other nonlinear deterioration patterns. The
deterioration factors described in paragraphs (c)(1) and (2) of this
section assume that the highest useful life emissions occur either at
the end of useful life or at the low-hour test point. The provisions of
this paragraph (c)(3) apply where good engineering judgment indicates
that the highest useful life emissions will occur between these two
points. For example, emissions may increase with service accumulation
until a certain maintenance step is performed, then return to the low-
hour emission levels and begin increasing again. Such a pattern may
occur with battery-based electric hybrid engines. Base deterioration
factors for engines with such emission patterns on the difference
between (or ratio of) the point at which the highest emissions occur
and the low-hour test point. Note that this applies for maintenance-
related deterioration only where we allow such critical emission-
related maintenance.
    (4) [Reserved]
    (5) Dual-fuel and flexible-fuel engines. In the case of dual-fuel
and flexible-fuel engines, apply deterioration factors separately for
each fuel type by measuring emissions with each fuel type at each test
point. You may accumulate service hours on a single emission-data
engine using the type of fuel or the fuel mixture expected to have the
highest combustion and exhaust temperatures; you may ask us to approve
a different fuel mixture if you demonstrate that a different criterion
is more appropriate.
    (d) Calculate emission data using measurements to at least one more
decimal place than the applicable standard. Apply the deterioration
factor to the official emission result, as described in paragraph (c)
of this section, then round the adjusted figure to the same number of
decimal places as the emission standard. Compare the rounded emission
levels to the emission standard for each emission-data engine.
    (e) If you identify more than one configuration in Sec.
1036.205(e), we may test (or require you to test) any of the identified
configurations. We may also require you to provide an engineering
analysis that demonstrates that untested configurations listed in Sec.
1036.205(e) comply with their FCL.

Sec.  1036.250  Reporting and recordkeeping for certification.

    (a) Within 90 days after the end of the model year, send the
Designated Compliance Officer a report including the total U.S.-
directed production volume of engines you produced in each engine
family during the model year (based on information available at the
time of the report). Report the production by serial number and engine
configuration. Small manufacturers may omit this requirement. You may
combine this report with reports required under subpart H of this part.
    (b) Organize and maintain the following records:
    (1) A copy of all applications and any summary information you send
us.
    (2) Any of the information we specify in Sec.  1036.205 that you
were not required to include in your application.
    (c) Keep routine data from emission tests required by this part
(such as test cell temperatures and relative humidity readings) for one
year after we issue the associated certificate of conformity. Keep all
other information specified in this section for eight years after we
issue your certificate.
    (d) Store these records in any format and on any media, as long as
you can promptly send us organized, written records in English if we
ask for them. You must keep these records readily available. We may
review them at any time.

Sec.  1036.255  What decisions may EPA make regarding my certificate of
conformity?

    (a) If we determine your application is complete and shows that the
engine family meets all the requirements of this part and the Act, we
will issue a certificate of conformity for your engine family for that
model year. We may make the approval subject to additional conditions.
    (b) We may deny your application for certification if we determine
that your engine family fails to comply with emission standards or
other requirements of this part or the Clean Air Act. We will base our
decision on all available information. If we deny your application, we
will explain why in writing.
    (c) In addition, we may deny your application or suspend or revoke
your certificate if you do any of the following:
    (1) Refuse to comply with any testing or reporting requirements.
    (2) Submit false or incomplete information (paragraph (e) of this
section applies if this is fraudulent). This includes doing anything
after submission of your application to

render any of the submitted information false or incomplete.
    (3) Render inaccurate any test data.
    (4) Deny us from completing authorized activities (see 40 CFR
1068.20). This includes a failure to provide reasonable assistance.
    (5) Produce engines for importation into the United States at a
location where local law prohibits us from carrying out authorized
activities.
    (6) Fail to supply requested information or amend your application
to include all engines being produced.
    (7) Take any action that otherwise circumvents the intent of the
Act or this part, with respect to your engine family.
    (d) We may void the certificate of conformity for an engine family
if you fail to keep records, send reports, or give us information as
required under this part or the Act. Note that these are also
violations of 40 CFR 1068.101(a)(2).
    (e) We may void your certificate if we find that you intentionally
submitted false or incomplete information. This includes rendering
submitted information false or incomplete after submission.
    (f) If we deny your application or suspend, revoke, or void your
certificate, you may ask for a hearing (see Sec.  1036.820).

Subpart D--Testing Production Engines

Sec.  1036.301  Measurements related to GEM inputs in a selective
enforcement audit.

    (a) Selective enforcement audits apply for engines as specified in
40 CFR part 1068, subpart E. This section describes how this applies
uniquely in certain circumstances.
    (b) Selective enforcement audit provisions apply with respect to
your fuel maps as follows:
    (1) A selective enforcement audit for an engine with respect to
fuel maps would consist of performing measurements with production
engines to determine fuel-consumption rates as declared for GEM
simulations, and running GEM for the vehicle configurations specified
in paragraph (b)(2) of this section based on those measured values. The
engine is considered passing for a given configuration if the new
modeled emission result for each applicable duty cycle is at or below
the modeled emission result corresponding to the declared GEM inputs.
The engine is considered failing for a given configuration if the new
modeled emission result for any applicable duty cycle is above the
modeled emission result corresponding to the declared GEM inputs.
    (2) Evaluate cycle-average fuel maps by running GEM based on
simulated vehicle configurations representing the interpolated center
of every group of four test points that define a boundary of cycle work
and average engine speed divided by average vehicle speed. These
simulated vehicle configurations are defined from the four surrounding
points based on averaging values for vehicle mass, drag area (if
applicable), tire rolling resistance, tire size, and axle ratio. The
regulatory subcategory is defined by the regulatory subcategory of the
vehicle configuration with the greatest mass from those four test
points. Figure 1 of this section illustrates a determination of vehicle
configurations for engines used in tractors and Vocational HDV using a
fixed tire size (see Sec.  1036.540(c)(3)(iii)). The vehicle
configuration from the upper-left quadrant is defined by values for
Tests 1, 2, 4, and 5 from Table 3 of Sec.  1036.540. Calculate vehicle
mass as the average of the values from the four tests. Determine the
weight reduction needed for GEM to simulate this calculated vehicle
mass by comparing the average vehicle mass to the default vehicle mass
for the vehicle subcategory from the four points that has the greatest
mass, with the understanding that two-thirds of weight reduction for
tractors is applied to vehicle weight and one-third is understood to
represent increased payload. This is expressed mathematically as
Mavg = Msubcategory - \2/3\ [middot]
Mreduction, which can be solved for Mreduction.
For vocational vehicles, half of weight reduction is applied to vehicle
weight and half is understood to represent increased payload. Use the
following values for default vehicle masses by vehicle subcategory:

 Table 1 of Sec.   1036.301--Default Vehicle Mass by Vehicle Subcategory
------------------------------------------------------------------------
                                                              Default
                   Vehicle subcategory                     vehicle mass
                                                               (kg)
------------------------------------------------------------------------
Vocational Light HDV....................................           7,257
Vocational Medium HDV...................................          11,408
Class 7 Mid-Roof Day Cab................................          20,910
Class 8 Mid-Roof Day Cab................................          29,529
Class 8 High-Roof Sleeper Cab...........................          31,978
Heavy-Haul Tractor......................................          53,750
------------------------------------------------------------------------

    (3) This paragraph (b)(3) provides an example to illustrate how to
determine GEM input values for the four vehicle configurations
identified in paragraph (b)(2) of this section. If axle ratio is 2.5
for Tests 1 and 2, and 3.5 for Tests 4 and 5, the average value is 3.0.
A tire size of 500 revolutions per mile would apply for all four tests,
so the average tire size would be that same value. Similarly,
Crr is 6.9 kg/tonne since that value applies for all four
points. The calculated average value of CdA is 6.9 m\2\. The
calculated average vehicle mass is 28,746.5 kg. Weight reduction is
4,847 kg or 10,686 pounds (\3/2\ [middot] (31,978 - 28,746.5)).
    (4) Because your cycle-average map may have more or fewer test
points, you may have more than or fewer than the number of audit points
shown in Figure 1 of this section. If the audit includes fuel-map
testing in conjunction with engine testing relative to exhaust emission
standards, the fuel-map simulations for the whole set of vehicles and
duty cycles counts as a single test result for purposes of evaluating
whether the engine family meets the pass-fail criteria under 40 CFR
1068.420. If the audit includes only fuel-map testing, determine
emission results from at least three different engine configurations
simulated with each applicable vehicle configuration identified in
Sec.  1036.540; the fuel-map simulation for each vehicle configuration
counts as a separate test for the engine.

[GRAPHIC] [TIFF OMITTED] TR25OC16.048

    (c) If your certification includes powertrain testing as specified
in 40 CFR 1036.630, these selective enforcement audit provisions apply
with respect to powertrain test results as specified in 40 CFR part
1037, subpart D, and 40 CFR 1037.550. We may allow manufacturers to
instead perform the engine-based testing to simulate the powertrain
test as specified in 40 CFR 1037.551.
    (d) We may suspend or revoke certificates for any appropriate
configurations within one or more engine families based on the outcome
of a selective enforcement audit.

Subpart E--In-Use Testing

Sec.  1036.401  In-use testing.

    We may perform in-use testing of any engine family subject to the
standards of this part, consistent with the Clean Air Act and the
provisions of Sec.  1036.235. Note that this provision does not affect
your obligation to test your in-use engines as described in 40 CFR part
86, subpart T.

Subpart F--Test Procedures

Sec.  1036.501  How do I run a valid emission test?

    (a) Use the equipment and procedures specified in this subpart and
40 CFR 86.1305 to determine whether engines meet the emission standards
in Sec.  1036.108.
    (b) You may use special or alternate procedures to the extent we
allow them under 40 CFR 1065.10.
    (c) This subpart is addressed to you as a manufacturer, but it
applies equally to anyone who does testing for you, and to us when we
perform testing to determine if your engines meet emission standards.
    (d) For engines that use aftertreatment technology with infrequent
regeneration events, apply infrequent regeneration adjustment factors
as described in Sec.  1036.530.
    (e) Test hybrid engines as described in Sec.  1036.525 and 40 CFR
part 1065.
    (f) Determine engine fuel maps as described in Sec.  1036.510(b).
    (g) The following additional provisions apply for testing to
demonstrate compliance with the emission standards in Sec.  1036.108
for model year 2021 and later engines:
    (1) If your engine is intended for installation in a vehicle
equipped with stop-start technology, you may use good engineering
judgment to turn the engine off during the idle portions of the duty
cycle to represent in-use operation, consistent with good engineering
judgment.
    (2) Use one of the following methods to measure CO2
emissions:
    (i) Use the ramped-modal cycle specified in Sec.  1036.505 using
either continuous or batch sampling.
    (ii) Measure CO2 emissions over the ramped-modal cycle
specified in 40 CFR 86.1362 using continuous sampling. Integrate the
test results by mode to establish separate emission rates for each mode
(including the transition following each mode, as applicable). Apply
the weighting factors specified in 40 CFR 86.1362 to calculate a
composite emission result.
    (3) Measure or calculate emissions of criteria pollutants
corresponding to your measurements to demonstrate compliance with
CO2 standards. These test results are not subject to the
duty-cycle standards of 40 CFR part 86, subart A.

Sec.  1036.505  Ramped-modal testing procedures.

    (a) Starting in model year 2021, you must measure CO2
emissions using the ramped-modal cycle in 40 CFR 86.1362 as described
in Sec.  1036.501, or using the ramped-modal cycle in this section.
    (b) Measure emissions using the ramped-modal duty cycle shown in
the following table to determine whether engines meet the steady-state
compression-ignition standards specified in subpart B of this part:

                               Table 1 of Sec.   1036.505--Ramped-Modal Duty Cycle
----------------------------------------------------------------------------------------------------------------
                                           Time in mode
                RMC mode                     (seconds)       Engine speed \1\ \2\      Torque (percent) \2\ \3\
----------------------------------------------------------------------------------------------------------------
1a Steady-state.........................             124  Warm Idle.................  0.
1b Transition...........................              20  Linear Transition.........  Linear Transition.
2a Steady-state.........................             196  A.........................  100.
2b Transition...........................              20  Linear Transition.........  Linear Transition.
3a Steady-state.........................             220  B.........................  50.
3b Transition...........................              20  B.........................  Linear Transition.
4a Steady-state.........................             220  B.........................  75.
4b Transition...........................              20  Linear Transition.........  Linear Transition.
5a Steady-state.........................             268  A.........................  50.
5b Transition...........................              20  A.........................  Linear Transition.
6a Steady-state.........................             268  A.........................  75.
6b Transition...........................              20  A.........................  Linear Transition.
7a Steady-state.........................             268  A.........................  25.
7b Transition...........................              20  Linear Transition.........  Linear Transition.
8a Steady-state.........................             196  B.........................  100.
8b Transition...........................              20  B.........................  Linear Transition.
9a Steady-state.........................             196  B.........................  25.
9b Transition...........................              20  Linear Transition.........  Linear Transition.
10a Steady-state........................              28  C.........................  100.
10b Transition..........................              20  C.........................  Linear Transition.
11a Steady-state........................               4  C.........................  25.
11b Transition..........................              20  C.........................  Linear Transition.
12a Steady-state........................               4  C.........................  75.
12b Transition..........................              20  C.........................  Linear Transition.
13a Steady-state........................               4  C.........................  50.
13b Transition..........................              20  Linear Transition.........  Linear Transition.
14 Steady-state.........................             144  Warm Idle.................  0.
----------------------------------------------------------------------------------------------------------------
\1\ Speed terms are defined in 40 CFR part 1065.
\2\ Advance from one mode to the next within a 20 second transition phase. During the transition phase, command
  a linear progression from the speed or torque setting of the current mode to the speed or torque setting of
  the next mode.
\3\ The percent torque is relative to maximum torque at the commanded engine speed.

Sec.  1036.510  Engine data and information for vehicle certification.

    You must give vehicle manufacturers information as follows so they
can certify model year 2021 and later vehicles:
    (a) Identify engine make, model, fuel type, engine family name,
calibration identification, and engine displacement. Also identify
which standards the engines meet.
    (b) This paragraph (b) describes three different methods to
generate engine fuel maps. Manufacturers may generally rely on any of
the three mapping methods. However, manufacturers must generate fuel
maps using either cycle-average or powertrain testing as described in
paragraphs (b)(2) and (3) of this section for hybrid engines and hybrid
vehicles. Also, vehicle manufacturers must use the powertrain method
for any vehicle with a transmission that is not automatic, automated
manual, manual, or dual-clutch.
    (1) Combined steady-state and cycle-average. Determine steady-state
engine fuel maps and fuel consumption at idle as described in Sec.
1036.535, and determine cycle-average engine fuel maps as described in
Sec.  1036.540, excluding cycle-average fuel maps for highway cruise
cycles.
    (2) Cycle-average. Determine fuel consumption at idle as described
in Sec.  1036.535, and determine cycle-average engine fuel maps as
described in Sec.  1036.540, including cycle-average engine fuel maps
for highway cruise cycles. In this case, you do not need to determine
steady-state engine fuel maps under Sec.  1036.535. Fuel mapping for
highway cruise cycles using cycle-average testing is an alternate
method, which means that we may do confirmatory testing based on
steady-state fuel mapping for highway cruise cycles even if you do not;
however, we will use the steady-state fuel maps to create cycle-average
fuel maps. In Sec.  1036.540 we define the vehicle configurations for
testing; we may add more vehicle configurations to better represent
your engine's operation for the range of vehicles in which your engines
will be installed (see 40 1065.10(c)(1)).
    (3) Powertrain. Generate a powertrain fuel map as described in 40
CFR 1037.550. In this case, you do not need to perform fuel mapping
under Sec.  1036.535 or Sec.  1036.540.
    (d) Provide the following information if you generate engine fuel
maps using either paragraph (b)(1) or (2) of this section:
    (1) Full-load torque curve for installed engines, and the full-load
torque curve of the engine with the highest fueling rate that shares
the same engine hardware, including the turbocharger, as described in
40 CFR 1065.510. You may use 40 CFR 1065.510(b)(5)(i) for engines
subject to spark-ignition standards. Measure the torque curve for
hybrid engines as described in 40 CFR 1065.510(g) with the hybrid
system active.
    (2) Motoring torque map as described in 40 CFR 1065.510(c)(2) and
(4) for conventional and hybrid engines, respectively.
    (3) Declared engine idle speed. For vehicles with manual
transmissions, this is the engine speed with the transmission in
neutral. For all other vehicles, this is the engine's idle speed when
the transmission is in drive.

Sec.  1036.525  Hybrid engines.

    (a) If your engine system includes features that recover and store
energy during engine motoring operation, test the engine as described
in paragraph (d) of this section. For purposes of this section,
features that recover energy between the engine and transmission are
considered related to engine motoring.
    (b) If you produce a hybrid engine designed with power take-off
capability and sell the engine coupled with a

transmission, you may calculate a reduction in CO2 emissions
resulting from the power take-off operation as described in 40 CFR
1037.540. Quantify the CO2 reduction for your engines using
the vehicle-based procedures, consistent with good engineering
judgment.
    (c) For engines that include electric hybrid systems, test the
engine with the hybrid electric motor, the rechargeable energy storage
system (RESS), and the power electronics between the hybrid electric
motor and the RESS. You may ask us to modify the provisions of this
section for testing engines with other kinds of hybrid systems.
    (d) Measure emissions using the same procedures that apply for
testing non-hybrid engines under this part, except as specified in this
part and 40 CFR part 1065. For ramped-modal testing, deactivate the
hybrid features unless we specify otherwise. The following provisions
apply for testing hybrid engines:
    (1) Engine mapping. Map the engine as specified in 40 CFR 1065.510.
This requires separate torque maps for the engine with and without the
hybrid features active. For transient testing, denormalize the duty
cycle using the map generated with the hybrid feature active. For
steady-state testing, denormalize the duty cycle using the map
generated without the hybrid feature.
    (2) Engine shutdown during testing. If you will configure
production engines to shut down automatically during idle operation,
you may let the engine shut down during the idle portions of the duty
cycle.
    (3) Work calculation. Calculate positive and negative work done
over the cycle according to 40 CFR 1065.650(d), except that you must
set power to zero to calculate negative work done for any period over
the cycle where the engine produces net positive power or where the
negative power is solely from the engine and not the hybrid system.
    (4) Limits on braking energy. Calculate brake energy fraction,
xb, as follows:
    (i) Calculate xb as the integrated negative work over
the cycle divided by the integrated positive work over the cycle
according to Eq. 1036.525-1. Calculate the brake energy limit for the
engine, xbl, according to Eq. 1036.525-2. If xb
is less than or equal to xbl, use the integrated positive
work for your emission calculations. If xb is greater than
xbl use Eq. 1036.525-3 to calculate an adjusted value for
cycle work, Wcycle, and use Wcycle as the work
value for calculating emission results. You may set an instantaneous
brake target that will prevent xb from being larger than
xbl to avoid the need to subtract extra brake work from
positive work.
[GRAPHIC] [TIFF OMITTED] TR25OC16.049

Where:

Wneg = the negative work over the cycle.
Wpos = the positive work over the cycle.
[GRAPHIC] [TIFF OMITTED] TR25OC16.050

Where:

Pmax = the maximum power of the engine with the hybrid
system engaged.
[GRAPHIC] [TIFF OMITTED] TR25OC16.051

Where:

Wcycle = cycle work when xb is greater than
xbl.

    Example:
Wneg = 4.69 kW-hr
Wpos = 14.67 kW-hr
Pmax = 223 kW
[GRAPHIC] [TIFF OMITTED] TR25OC16.052

xbl = 4.158.10-4[middot].223 + 0.2247 = 0.317
kW
since xb > xbl;;
Wcycle = 14.67 - ([bond]4.59[bond] - 0.317[middot]14.67)
= 14.63 kW-hr

    (ii) Convert from g/kW-hr to g/hp-hr as the final step in
calculating emission results.
    (5) State of charge. Correct for the net energy change of the
energy storage device as described in 40 CFR 1066.501.

Sec.  1036.530  Calculating greenhouse gas emission rates.

    This section describes how to calculate official emission results
for CO2, CH4, and N2O.
    (a) Calculate brake-specific emission rates for each applicable
duty cycle as specified in 40 CFR 1065.650. Apply infrequent
regeneration adjustment factors to your cycle-average results as
described in 40 CFR 86.004-28 for CO2 starting in model year
2021. You may optionally apply infrequent regeneration adjustment
factors for CH4 and N2O.
    (b) Adjust CO2 emission rates calculated under paragraph
(a) of this section for measured test fuel properties as specified in
this paragraph (b). This adjustment is intended to make official
emission results independent of differences in test fuels within a fuel
type. Use good engineering judgment to develop and apply testing
protocols to minimize the impact of variations in test fuels.
    (1) Determine mass-specific net energy content,
Emfuelmeas, also known as lower heating value, in MJ/kg,
expressed to at least three decimal places, as follows:
    (i) For liquid fuels, determine Emfuelmeas according to
ASTM D4809 (incorporated by reference in Sec.  1036.810).
    (ii) For gaseous fuels, determine Emfuelmeas using good
engineering judgment.
    (2) Determine your test fuel's carbon mass fraction, wC,
as described in 40 CFR 1065.655(d), expressed to at least three decimal
places; however, you must measure fuel properties rather than using the
default values specified in Table 1 of 40 CFR 1065.655. Have the sample
analyzed by three different labs and use the arithmetic mean of the
results as your test fuel's wC.
    (3) If, over a period of time, you receive multiple fuel deliveries
from a single stock batch of test fuel, you may use constant values for
mass-specific energy content and carbon mass fraction, consistent with
good engineering judgment. To use this provision, you must demonstrate
that every subsequent delivery comes from the same stock batch and that
the fuel has not been contaminated.
    (4) Correct measured CO2 emission rates as follows:
    [GRAPHIC] [TIFF OMITTED] TR25OC16.053

Where:

eCO2 = the calculated CO2 emission result.
Emfuelmeas = the mass-specific net energy content of the
test fuel as determined in paragraph (b)(1) of this section. Note
that dividing this value by wCmeas (as is done in this
equation) equates to a carbon-specific net energy content having the
same units as EmfuelCref.
EmfuelCref = the reference value of carbon-mass-specific
net energy content for the appropriate fuel type, as determined in
Table 1 of this section.
wCmeas = carbon mass fraction of the test fuel (or
mixture of test fuels) as determined in paragraph (b)(2) of this
section.

    Example:
eCO2 = 630.0 g/hp[middot]hr
Emfuelmeas = 42.528 MJ/kg
EmfuelCref = 49.3112 MJ/kgC
wCmeas = 0.870

[GRAPHIC] [TIFF OMITTED] TR25OC16.054

eCO2cor = 624.5 g/hp[middot]hr

          Table 1 of Sec.   1036.530--Reference fuel properties
------------------------------------------------------------------------
                                       Reference fuel
                                        carbon-mass-     Reference fuel
                                        specific net       carbon mass
            Fuel type\1\               energy content,   fraction, wCref
                                      EmfuelCref,  (MJ/        \2\
                                          kgC) \2\
------------------------------------------------------------------------
Diesel fuel.........................           49.3112             0.874
Gasoline............................           50.4742             0.846
Natural Gas.........................           66.2910             0.750
LPG.................................           56.5218             0.820
Dimethyl Ether......................           55.3886             0.521
High-level ethanol-gasoline blends..           50.3211             0.576
------------------------------------------------------------------------
\1\ For fuels that are not listed, you must ask us to approve reference
  fuel properties.
\2\ For multi-fuel streams, such as natural gas with diesel fuel pilot
  injection, use good engineering judgment to determine blended values
  for EmfuelCref and wCref using the values in this table.

    (c) Your official emission result for each pollutant equals your
calculated brake-specific emission rate multiplied by all applicable
adjustment factors, other than the deterioration factor.

Sec.  1036.535  Determining steady-state engine fuel maps and fuel
consumption at idle.

    This section describes how to determine an engine's steady-state
fuel map and fuel consumption at idle for model year 2021 and later
vehicles. Vehicle manufacturers may need these values to demonstrate
compliance with emission standards under 40 CFR part 1037 as described
in Sec.  1036.510.
    (a) General test provisions. Perform fuel mapping using the
procedure described in paragraph (b) of this section to establish
measured fuel-consumption rates at a range of engine speed and load
settings. Measure fuel consumption at idle using the procedure
described in paragraph (c) of this section. If you perform cycle-
average mapping for highway cruise cycles as described in Sec.
1037.540, omit mapping under paragraph (b) of the section and instead
perform mapping as described in paragraph (c) and (d) of this section.
Use these measured fuel-consumption values to declare fuel-consumption
rates for certification as described in paragraph (e) of this section.
    (1) Map the engine as described in Sec.  1036.510(a)(2) and (3),
and perform emission measurements as described in 40 CFR 1065.501 and
1065.530 for discrete-mode steady-state testing. This section uses
engine parameters and variables that are consistent with 40 CFR part
1065.
    (2) Measure NOX emissions for each specified sampling
period in g/s. You may perform these measurements using a
NOX emission-measurement system that meets the requirements
of 40 CFR part 1065, subpart J. Include these measured NOX
values any time you report to us your fuel consumption values from
testing under this section. If a system malfunction prevents you from
measuring NOX emissions during a test under this section but
the test otherwise gives valid results, you may consider this a valid
test and omit the NOX emission measurements; however, we may
require you to repeat the test if we determine that you inappropriately
voided the test with respect to NOX emission measurement.
    (b) Steady-state fuel mapping. Determine fuel-consumption rates for
each engine configuration over a series of steady-state engine
operating points as described in this paragraph (b). You may use shared
data across an engine platform to the extent that the fuel-consumption
rates remain valid. For example, if you test a high-output
configuration and create a different configuration that uses the same
fueling strategy but limits the engine operation to be a subset of that
from the high-output configuration, you may use the fuel-consumption
rates for the reduced number of mapped points for the low-output
configuration, as long as the narrower map includes at least 70 points.
Perform fuel mapping as follows:
    (1) Select ten speed points that include warm idle speed,
fnidle, the highest speed above maximum power at which 70%
of maximum power occurs, nhi, and eight equally spaced
points between fnidle and nhi. Control speed to
within 1% of nhi (see 40 CFR 1065.610(c)).
    (2) Select ten torque values, including T = 0, maximum mapped
torque, Tmax mapped, and eight equally spaced points between
T = 0 and Tmax mapped. Replace any torque setpoints that are
above the mapped torque at a given speed, Tmax, minus 5
percent of Tmax mapped. with one test point at
Tmax. Control engine torque to within 5% of
Tmax mapped.
    (3) You may need to adjust dynamometer settings any time the engine
is operating on the low-speed or high-speed governor to maintain stable
engine operation. You may change the dynamometer's speed setpoint as
needed to avoid activating the engine's governor. You may alternatively
set the dynamometer mode to torque-control, in which case speed can
fall outside of 1% of nhi.
    (4) Precondition the engine as described in 40 CFR 1065.510(b)(2).
    (5) Within 60 seconds after concluding the preconditioning
procedure, operate the engine at nhi and Tmax.
    (6) After the engine operates at the set speed and torque for 60
seconds, start recording measurements using one of the following
methods:
    (i) Carbon mass balance. Record speed and torque and measure
emissions and other inputs needed to run the chemical balance in 40 CFR
1065.655(c) for (29 to 31) seconds; determine the corresponding mean
values for the sampling period. We will use carbon mass balance.
    (ii) Direct measurement of fuel flow. Record speed and torque and
measure fuel consumption with a fuel flow meter for (29 to 31) seconds;
determine the corresponding mean values for the sampling period.
    (7) After completing the sampling period described in paragraph
(b)(6) of this section, linearly ramp the engine over 15 seconds to the
next lowest torque value while holding speed constant. Perform the
measurements described at the new torque setting and

repeat this sequence for all remaining torque values down to T = 0.
    (8) Continue testing to complete fuel mapping as follows:
    (i) At T = 0, linearly ramp the engine over 15 seconds to operate
at the next lowest speed value and increase torque to Tmax.
Perform measurements for all the torque values at the selected speed as
described in paragraphs (b)(6) and (7) of this section. Repeat this
sequence for all remaining speed values down to fnidle to
complete the fuel-mapping procedure. You may interrupt the mapping
sequence to calibrate emission-measurement instrumentation only during
stabilization at Tmax for a given speed. If you use batch
sampling to measure background emissions, you may sample periodically
into the bag over the course of multiple test intervals defined by the
period between calibrations of emission-measurement instrumentation.
The background sample must be applied to correct emissions sampled over
the test interval(s) between calibrations.
    (ii) If an infrequent regeneration event occurs during fuel
mapping, invalidate all the measurements made at that engine speed.
Allow the regeneration event to finish, then restart engine
stabilization at Tmax at the same engine speed and continue
with measurements from that point in the fuel-mapping sequence.
    (9) If you determine fuel-consumption rates using emission
measurements from the raw or diluted exhaust, calculate the mean fuel
mass flow rate, mifuel, for each point in the fuel map using
the following equation:
[GRAPHIC] [TIFF OMITTED] TR25OC16.055

Where:

mifuel = mean fuel mass flow rate for a given fuel map
setpoint, expressed to at least the nearest 0.001 g/s.
MC = molar mass of carbon.
wCmeas = carbon mass fraction of fuel (or mixture of test
fuels) as determined in 40 CFR 1065.655(d), except that you may not
use the default properties in Table 1 of 40 CFR 1065.655 to
determine [alpha], [beta], and wC for liquid fuels.
niexh= the mean raw exhaust molar flow rate from which
you measured emissions according to 40 CFR 1065.655.
xCcombdry= the mean concentration of carbon from fuel and
any injected fluids in the exhaust per mole of dry exhaust as
determined in 40 CFR 1065.655(c).
xH2Oexhdry= the mean concentration of H2O in
exhaust per mole of dry exhaust as determined in 40 CFR 1065.655(c).
miCO2DEF= the mean CO2 mass emission rate
resulting from diesel exhaust fluid decomposition as determined in
paragraph (b)(10) of this section. If your engine does not use
diesel exhaust fluid, or if you choose not to perform this
correction, set miCO2DEF equal to 0.
MCO2 = molar mass of carbon dioxide.

    Example:
MC = 12.0107 g/mol
wCmeas = 0.869
niexh= 25.534 mol/s
xCcombdry= 0.002805 mol/mol
xH2Oexhdry= 0.0353 mol/mol
miCO2DEF= 0.0726 g/s
MCO2 = 44.0095 g/mol
[GRAPHIC] [TIFF OMITTED] TR25OC16.056

    (10) If you determine fuel-consumption rates using emission
measurements with engines that utilize diesel exhaust fluid for
NOX control, correct for the mean CO2 mass
emissions resulting from diesel exhaust fluid decomposition at each
fuel map setpoint using the following equation:
[GRAPHIC] [TIFF OMITTED] TR25OC16.057

Where:

miDEF= the mean mass flow rate of injected urea solution
diesel exhaust fluid for a given sampling period, determined
directly from the engine control module, or measured separately,
consistent with good engineering judgment.
MCO2 = molar mass of carbon dioxide.
wCH4N2O = mass fraction of urea in diesel exhaust fluid
aqueous solution. Note that the subscript ``CH4N2O'' refers to urea
as a pure compound and the subscript ``DEF'' refers to the aqueous
32.5% urea diesel exhaust fluid as a solution of urea in water with
a nominal urea concentration of 32.5%.
MCH4N2O = molar mass of urea.

    Example:
miDEF= 0. 304 g/s
MCO2 = 44.0095 g/mol
wCH4N2O = 32.5% = 0.325
MCH4N2O = 60.05526 g/mol
[GRAPHIC] [TIFF OMITTED] TR25OC16.058

    (11) Correct the measured or calculated mean fuel mass flow rate,
mifuel at each engine operating condition to a mass-specific
net energy content of a reference fuel using the following equation:
[GRAPHIC] [TIFF OMITTED] TR25OC16.059

Where:

Emfuelmeas = the mass-specific net energy content of the
test fuel as determined in Sec.  1036.530(b)(1).
EmfuelCref = the reference value of carbon-mass-specific
net energy content for the appropriate fuel. Use the values shown in
Table 1 of Sec.  1036.530 for the designated fuel types, or values
we approve for other fuel types.
wCref = the reference value of carbon mass fraction for
the test fuel as shown in Table 1 of Sec.  1036.530 for the
designated fuels. For other fuels, use the reference carbon mass
fraction of diesel fuel for engines subject to compression-ignition
standards, and use the reference carbon mass fraction of gasoline
for engines subject to spark-ignition standards.

    Example:
mifuel= 0.933 g/s
Emfuelmeas = 42.7984 MJ/kgC
EmfuelCref = 49.3112 MJ/kgC
wCref = 0.874
[GRAPHIC] [TIFF OMITTED] TR25OC16.060

    (c) Fuel consumption at idle. Determine values for fuel-consumption
rate at idle for each engine configuration as described in this
paragraph (c). You may use shared data across engine configurations,
consistent with good engineering judgment. Perform measurements as
follows:
    (1) Precondition the engine as described in 40 CFR 1065.510(b)(2).
    (2) Within 60 seconds after concluding the preconditioning
procedure, operate the engine at its minimum declared warm idle speed,
fnidlemin, as described in 40 CFR 1065.510(b)(3), set zero
torque, and start the sampling period. Continue sampling for (595 to
605) seconds. Perform measurements using carbon mass balance. Record
speed and torque and measure emissions and other inputs as described in
40 CFR 1065.655(c); determine the corresponding mean values for the
sampling period. Calculate the mean fuel mass flow rate,
mifuel, during the sampling period as described in paragraph
(b)(9) of this section.
    Manufacturers may instead measure fuel consumption with a fuel flow
meter and determine the corresponding mean values for the sampling
period.
    (3) Repeat the steps in paragraphs (c)(1) and (2) of this section
with the engine set to operate at a torque setting of 100 N[middot]m.
    (4) Repeat the steps in paragraphs (c)(1) through (3) of this
section with the engine operated at its declared maximum warm idle
speed, fnidlemax.
    (5) If an infrequent regeneration event occurs during this
procedure, invalidate any measurements made at that idle condition.
Allow the regeneration event to finish, then repeat the measurement and
continue with the test sequence.
    (6) Correct the measured or calculated mean fuel mass flow rate,
mifuel at each of the four idle settings to account for
mass-specific net energy content as described in paragraph (b)(11) of
this section.
    (d) Steady-state fuel maps used for cycle-average fuel mapping of
the cruise cycles. Use the appropriate default steady-state engine fuel
map as specified in Appendix I to this part to generate cycle-average
fuel maps under Sec.  1036.540, as amended based on the measurements
specified in this paragraph (d). Measure fuel consumption at idle at
the four specified engine operating conditions. For any values from the
default map that lie within the boundaries of the engine speed and
torque values represented by these idle-operating points, use the
measured values instead of the default values. You may use shared data
across engine configurations, consistent with good engineering
judgment. Determine values for fuel-consumption rate at idle for each
engine configuration as follows:
    (1) Determine idle torque, Tidle, at the engine's
maximum warm idle speed using the following equation:
[GRAPHIC] [TIFF OMITTED] TR25OC16.061

Where:

Tfnstall = the maximum engine torque at
fnstall.
fnidle[speed] = the applicable engine idle speed as
described in this paragraph (d).
fnstall = the stall speed of the torque converter; use
fntest or 2250 rpm, whichever is lower.
    Pacc = accessory power for the vehicle class; use
1500 W for Vocational Light HDV, 2500 W for Vocational Medium HDV,
and 3500 W for Tractors and Vocational Heavy HDV.

    Example:
Tfnstall = 1870 N[middot]m
fntest = 1740.8 r/min = 182.30 rad/s
fnstall = 1740.8 r/min = 182.30 rad/s
fnidlemax = 700 r/min = 73.30 rad/s
Pacc = 1500 W

[GRAPHIC] [TIFF OMITTED] TR25OC16.062

    (2) Precondition the engine as described in 40 CFR 1065.510(b)(2).
    (3) Within 60 seconds after concluding the preconditioning
procedure, operate the engine at its maximum declared warm idle speed,
fnidlemax, as described in 40 CFR 1065.510(b)(3), set torque
to the value determined in paragraph (d)(1) of this section, after the
engine operates at the set speed and torque for 60 seconds, start the
sampling period. Continue sampling for (29 to 31) seconds. Perform
measurements using carbon mass balance. Record speed and torque and
measure emissions and other inputs as described in 40 CFR 1065.655(c);
determine the corresponding mean values for the sampling period.
Calculate the mean fuel mass flow rate, mifuel, during the
sampling period as described in paragraph (b)(9) of this section.
Manufacturers may instead measure fuel consumption with a fuel flow
meter and determine the corresponding mean values for the sampling
period.
    (4) Repeat the steps in paragraphs (d)(2) and (3) of this section
with the engine set to operate at zero torque.
    (5) Repeat the steps in paragraphs (d)(1) through (4) of this
section with the engine operated at its declared minimum warm idle
speed, fnidlemin.
    (6) If an infrequent regeneration event occurs during this
procedure, invalidate any measurements made at that idle condition.
Allow the regeneration event to finish, then repeat the measurement and
continue with the test sequence.
    (7) Correct the measured or calculated mean fuel mass flow rate,
mifuel at each of the four idle settings to account for
mass-specific net energy content as described in paragraph (b)(11) of
this section.
    (e) Measured vs. declared fuel-consumption rates. Select fuel-
consumption rates in g/s to characterize the engine's fuel maps. These
declared values may not be lower than any corresponding measured values
determined in paragraphs (b) through (d) of this section. You may
select any value that is at or above the corresponding measured value.
These declared fuel-consumption rates, which serve as emission
standards under Sec.  1036.108, are the values that vehicle
manufacturers will use for certification under 40 CFR part 1037. Note
that production engines are subject to GEM cycle-weighted limits as
described in Sec.  1036.301.

Sec.  1036.540  Determining cycle-average engine fuel maps.

    (a) Overview. This section describes how to determine an engine's
cycle-average fuel maps for model year 2021 and later vehicles with
transient cycles. This may also apply for highway cruise cycles as
described in Sec.  1036.510. Vehicle manufacturers may need one or both
of these to demonstrate compliance with emission standards under 40 CFR
part 1037. Generating cycle-average engine fuel maps consists of the
following steps:
    (1) Determine the engine's torque maps as described in Sec.
1036.510(a).
    (2) Determine the engine's steady-state fuel map and fuel
consumption at idle as described in Sec.  1036.535.
    (3) Simulate several different vehicle configurations using GEM
(see 40 CFR 1037.520) to create new engine duty cycles, as described in
paragraph (c) of this section. The transient vehicle duty cycles for
this simulation are in 40 CFR part 1037, Appendix I; the highway cruise
cycles with grade are in 40 CFR part 1037, Appendix IV. Note that GEM
simulation relies on vehicle service classes as described in 40 CFR
1037.140.
    (4) Test the engines using the new duty cycles to determine fuel
consumption, cycle work, and average vehicle speed as described in
paragraph (d) of this section and establish GEM inputs for those
parameters for further vehicle simulations as described in paragraph
(e) of this section.
    (b) General test provisions. The following provisions apply for
testing under this section:
    (1) To perform fuel mapping under this section for hybrid engines,
make sure the engine and its hybrid features are appropriately
configured to represent the hybrid features in your testing.
    (2) Measure NOX emissions for each specified sampling
period in grams. You may perform these measurements using a
NOX emission-measurement system that meets the requirements
of 40 CFR part 1065, subpart J. Include these measured NOX
values any time you report to us your fuel consumption values from
testing under this section. If a system malfunction prevents you from
measuring NOX emissions during a test under this section but
the test otherwise gives valid results, you may consider this a valid
test and omit the NOX emission measurements; however, we may
require you to repeat the test if we determine that you inappropriately
voided the test with respect to NOX emission measurement.
    (3) This section uses engine parameters and variables that are
consistent with 40 CFR part 1065.
    (c) Create engine cycles. Use GEM to simulate several different
vehicle configurations to create transient and highway cruise engine
cycles corresponding to each vehicle configuration, as follows:
    (1) Set up GEM to simulate vehicle operation based on your engine's
torque maps, steady-state fuel maps, and fuel consumption at idle as
described in paragraph (a)(1) and (2) of this section.
    (2) Set up GEM with transmission gear ratios for different vehicle
service classes and vehicle duty cycles as described in Table 1 of this
section. These values are based on automatic or automated manual
transmissions, but they apply for all transmission types.

                          Table 1 of Sec.   1036.540--Assigned Transmission Gear Ratios
----------------------------------------------------------------------------------------------------------------
                                                                                Tractors and
                                                           Light HDV and       Tractors and        heavy HDV,
                      Gear number                            medium HDV         heavy HDV,       highway cruise
                                                                             transient cycle         cycle
----------------------------------------------------------------------------------------------------------------
1......................................................               3.10               3.51               12.8
2......................................................               1.81               1.91               9.25
3......................................................               1.41               1.43               6.76
4......................................................               1.00               1.00               4.90
5......................................................               0.71               0.74               3.58
6......................................................               0.61               0.64               2.61

7......................................................  .................  .................               1.89
8......................................................  .................  .................               1.38
9......................................................  .................  .................               1.00
10.....................................................  .................  .................               0.73
----------------------------------------------------------------------------------------------------------------

    (3) Run GEM for each simulated vehicle configuration as follows:
    [GRAPHIC] [TIFF OMITTED] TR25OC16.063

    [GRAPHIC] [TIFF OMITTED] TR25OC16.064

Where:

fn[speed] = engine's angular speed as determined in
paragraph (c)(3)(ii) or (iii) of this section.
ktopgear = transmission gear ratio in the highest
available gear from Table 4 of this section (for powertrain testing
use actual top gear ratio).
vref = reference speed. Use 65 mi/hr for the transient
cycle and the 65 mi/hr highway cruise cycle, and use 55 mi/hr for
the 55 mi/hr highway cruise cycle.
[GRAPHIC] [TIFF OMITTED] TR25OC16.065

[GRAPHIC] [TIFF OMITTED] TR25OC16.066

    Example:
    This example is for a vocational Light HDV or vocational Medium
HDV with a 6-speed automatic transmission at B speed (Test 3 or 4 in
Table 2 of this section).
fnrefB = 1870 r/min = 31.17 r/s
kaB = 4.0
ktopgear = 0.61
vref = 65 mi/hr = 29.06 m/s
[GRAPHIC] [TIFF OMITTED] TR25OC16.067

    (ii) Test at least eight different vehicle configurations for
engines that will be installed in vocational Light HDV or vocational
Medium HDV. If the engine will also be installed in vocational Heavy
HDV, use good engineering judgment to select at least nine test
configurations that best represent the range of vehicles. For example,
if your engines will be installed in vocational Medium HDV and
vocational Heavy HDV, you might select Tests 1 through 6 of Table 2 of
this section to represent Class 7 vehicles and Tests 3, 6, and 9 of
Table 3 of this section to represent Class 8 vehicles. You may test
your engine using additional vehicle configurations with different
ka and Crr values to represent a wider range of
in-use vehicle configurations. Set CdA to 5.4 for all test
configurations. For powertrain testing, set Mrotating to 340
kg and Effaxle to 0.955 for all test configurations.
[GRAPHIC] [TIFF OMITTED] TR25OC16.068

corresponding designated engine speed (A, B, C, or fntest)
at 65 mi/hr for the transient cycle and the 65 mi/hr highway cruise
cycle, and at 55 mi/hr for the 55 mi/hr highway cruise cycle. These
engine speeds apply equally for engines subject to spark-ignition
standards. Use the following settings specific to each vehicle
configuration:
[GRAPHIC] [TIFF OMITTED] TR25OC16.069

    (iii) Test nine different vehicle configurations for engines that
will be installed in vocational Heavy HDV and for tractors that are not
heavy-haul tractors. Test over six different test configurations for
heavy-haul tractors. You may test your engines for additional
configurations with different ka, CdA, and
Crr values to represent a wider range of in-use vehicle
configurations. Set Crr to 6.9 for all nine defined test
configurations. For powertrain testing, set Effaxle to 0.955
for all test configurations. Set the axle ratio, ka,
[GRAPHIC] [TIFF OMITTED] TR25OC16.070

engine speed (B, fntest, or the minimum NTE exclusion speed
as determined in 40 CFR 86.1370(b)(1)) at 65 mi/hr. Use the settings
specific to each test configuration as shown in Table 3 or Table 4 of
this section, as appropriate.

Engines subject to testing under both Table 3 and Table 4 of this
section need not repeat overlapping test configurations, so complete
fuel mapping requires testing 12 (not 15) test configurations for those
engines. Note that Mrotating is needed for powertrain
testing but not for engine testing. Tables 3 and 4 follow:
[GRAPHIC] [TIFF OMITTED] TR25OC16.071

[GRAPHIC] [TIFF OMITTED] TR25OC16.072

    (iv) Use the defined values in Tables 1 through 4 of this section
to set up GEM with the correct regulatory subcategory and vehicle
weight reduction, if applicable, to achieve the target vehicle mass, M,
for each test.
    (4) Use the GEM output of instantaneous engine speed and engine
flywheel torque for each of the vehicle configurations to generate a 10
Hz transient duty cycle corresponding to each vehicle configuration
operating over each vehicle duty cycle.
    (d) Test the engine with GEM cycles. Test the engine over each of
the transient duty cycles generated in paragraph (c) of this section as
follows:
    (1) Precondition the engine either as described in 40 CFR
1037.510(a)(2)(i) for the transient duty-cycle and 40 CFR
1037.510(a)(2)(ii) for the highway cruise duty cycles using the Test 1
vehicle configuration, and then continue testing the different
configurations in the order presented in this section. Measure
emissions as described in 40 CFR part 1065; perform cycle validation
according to 40 CFR part 1065, subpart F, except as noted in this
paragraph (d)(1). If the range of reference speeds is less than 10
percent of the mean reference speed, you need to meet only the standard
error of estimate in Table 2 of 40 CFR 1065.514. For purposes of cycle
validation, treat points as being at idle if reference speed is at or
below declared idle speed. For plug-in hybrid engines, precondition the
battery and then complete all back-to-back tests for each test
configuration according to 40 CFR 1066.501 before moving to the next
test configuration. You may send signals to the engine controller
during the test, such as current transmission gear and vehicle speed,
if that allows engine operation during the test to better represent in-
use operation.
    (2) If an infrequent regeneration event occurs during a mapping
test interval, invalidate that test interval. Continue operating the
vehicle to allow the regeneration event to finish, then repeat engine
preconditioning and resume testing at the start of the invalidated test
cycle.
    (3) For each test, record measurements needed to determine fuel
mass using carbon mass balance. Record speed and torque and measure
emissions and other inputs as described in 40 CFR 1065.655(c).
Manufacturers may instead measure fuel consumption with a fuel flow
meter. For hybrid powertrains with no plug-in capability, correct for
the net energy change of the energy storage device as described in 40
CFR 1066.501. For plug-in hybrid engines, follow 40 CFR 1066.501 to

determine End-of-Test for charge-depleting operation; to do this, you
must get our advance approval for a utility factor curve. We will
approve your utility factor curve if you can show that you created it
from sufficient in-use data of vehicles in the same application as the
vehicles in which the PHEV engine will be installed.
    (4) Calculate the fuel mass flow rate, mfuel, for each
duty cycle using one of the following equations:
    (i) Determine fuel-consumption rates using emission measurements
from the raw or diluted exhaust, calculate the mass of fuel for each
duty cycle, mfuel[cycle], as follows:
    (A) For calculations that use continuous measurement of emissions
and continuous CO2 from urea, calculate
mfuel[cycle] using the following equation:
[GRAPHIC] [TIFF OMITTED] TR25OC16.073

Where:

MC = molar mass of carbon.
wCmeas = carbon mass fraction of fuel (or mixture of test
fuels) as determined in 40 CFR 1065.655(d), except that you may not
use the default properties in Table 1 of 40 CFR 1065.655 to
determine [alpha], [beta], and wC for liquid fuels.
i = an indexing variable that represents one recorded emission
value.
N = total number of measurements over the duty cycle.
nexh = exhaust molar flow rate from which you measured
emissions.
xCcombdry = amount of carbon from fuel and any injected
fluids in the exhaust per mole of dry exhaust as determined in 40
CFR 1065.655(c).
xH2Oexhdry = amount of H2O in exhaust per mole
of exhaust as determined in 40 CFR 1065.655(c).
[Delta]t = 1/frecord.
MCO2 = molar mass of carbon dioxide.
mCO2DEF = mass emission rate of CO2 resulting
from diesel exhaust fluid decomposition over the duty cycle as
determined from Sec.  1036.535(b)(10). If your engine does not
utilize diesel exhaust fluid for emission control, or if you choose
not to perform this correction, set mCO2DEF equal to 0.

    Example:
MC = 12.0107 g/mol
wCmeas = 0.867
N = 6680
nexh1= 2.876 mol/s
nexh2= 2.224 mol/s
xCcombdry1= 2.61[middot]10-\3\ mol/mol
xCcombdry2= 1.91[middot]10-\3\ mol/mol
xH2Oexhdry1= 3.53[middot]10-\2\ mol/mol
xH2Oexhdry2= 3.13[middot]10-\2\ mol/mol
frecord = 10 Hz
[Delta]t = 1/10 = 0.1 s
MCO2 = 44.0095 g/mol
mCO2DEF1 = 0.0726 g/s
mCO2DEF2 = 0.0751 g/s
[GRAPHIC] [TIFF OMITTED] TR25OC16.074

Mfueltransient = 1619.6 g
    (B) If you measure batch emissions and continuous CO2
from urea, calculate mfuel[cycle] using the following
equation:
[GRAPHIC] [TIFF OMITTED] TR25OC16.075

    (C) If you measure continuous emissions and batch CO2
from urea, calculate mfuel[cycle] using the following
equation:

[GRAPHIC] [TIFF OMITTED] TR25OC16.076

    (D) If you measure batch emissions and batch CO2 from
urea, calculate mfuel[cycle] using the following equation:
[GRAPHIC] [TIFF OMITTED] TR25OC16.077

    (ii) Manufacturers may choose to measure fuel mass flow rate.
Calculate the mass of fuel for each duty cycle,
mfuel[cycle], as follows:
[GRAPHIC] [TIFF OMITTED] TR25OC16.078

Where:

i = an indexing variable that represents one recorded value.
N = total number of measurements over the duty cycle. For batch fuel
mass measurements, set N = 1.
mfueli = the fuel mass flow rate, for each point, i,
starting from i = 1.
    [Delta]t = 1/frecord
    frecord = the data recording frequency.

    Example:
N = 6680
mfuel1 = 1.856 g/s
mfuel2 = 1.962 g/s
frecord = 10 Hz
[Delta]t = 1/10 = 0.1 s
mfueltransient = (1.856 + 1.962 + . . . +
mfuel6680)[middot]0.1
mfueltransient = 111.95 g

    (5) Correct the measured or calculated fuel mass flow rate,
mfuel, for each test result to a mass-specific net energy
content of a reference fuel as described in Sec.  1036.535(b)(11),
replacing with mifuel with mfuel in Eq. 1036.535-
3.
    (6) For engines designed for plug-in hybrid electric vehicles, the
mass of fuel for each cycle, mfuel[cycle], is the utility
factor-weighted fuel mass. This is done by calculating mfuel
for the full charge-depleting and charge-sustaining portions of the
test and weighting the results, using the following equation:
[GRAPHIC] [TIFF OMITTED] TR25OC16.079

Where:

mfuel[cycle],CD = total mass of fuel for all the tests in
the charge-depleting portion of the test.
UFDCD = utility factor fraction at distance
DCD as determined by interpolating the approved utility
factor curve.
mfuel[cycle],CS = total mass of fuel for all the tests in
the charge-sustaining portion of the test.
[GRAPHIC] [TIFF OMITTED] TR25OC16.080

Where:

v = vehicle velocity at each time step. For tests completed under
this section, v is the vehicle velocity in the GEM duty-cycle file.
For tests under 40 CFR

1037.550, v is the vehicle velocity as determined by Eq. 1037.550-1.
Note that this should include complete and incomplete charge-
depleting tests.

    (e) Determine GEM inputs. Use the results of engine testing in
paragraph (d) of this section to determine the GEM inputs for the
transient duty cycle and optionally for each of the highway cruise
cycles corresponding to each simulated vehicle configuration as
follows:
    (1) Your declared fuel mass consumption, mfueltransient.
The declared values may be at or above the values calculated in
paragraph (d) of this section, as described in Sec.  1036.535(e).
    (2) Engine output speed per unit vehicle speed,
    [GRAPHIC] [TIFF OMITTED] TR25OC16.081

by taking the average engine speed measured during the engine test
while the vehicle is moving and dividing it by the average vehicle
speed provided by GEM. Note that the engine cycle created by GEM has a
flag to indicate when the vehicle is moving.
    (3) Positive work determined accordering to 40 CFR 1065,
Wtransient.
    (4) The following table illustrates the GEM data inputs
corresponding to the different vehicle configurations:
[GRAPHIC] [TIFF OMITTED] TR25OC16.082

Subpart G--Special Compliance Provisions

Sec.  1036.601  What compliance provisions apply?

    (a) Engine and vehicle manufacturers, as well as owners, operators,
and rebuilders of engines subject to the requirements of this part, and
all other persons, must observe the provisions of this part, the
provisions of 40 CFR part 1068, and the provisions of the Clean Air
Act. The provisions of 40 CFR part 1068 apply for heavy-duty highway
engines as specified in that part, subject to the following provisions:
    (1) The exemption provisions of 40 CFR 1068.201 through 1068.230,
1068.240, and 1068.260 through 265 apply for heavy-duty motor vehicle
engines. The other exemption provisions, which are specific to nonroad
engines, do not apply for heavy-duty vehicles or heavy-duty engines.
    (2) The tampering prohibition in 40 CFR 1068.101(b)(1) applies for
alternative fuel conversions as specified in 40 CFR part 85, subpart F.
    (3) The warranty-related prohibitions in section 203(a)(4) of the
Act (42 U.S.C. 7522(a)(4)) apply to manufacturers of new heavy-duty
highway engines in addition to the prohibitions described in 40 CFR
1068.101(b)(6). We may assess a civil penalty up to $44,539 for each
engine or vehicle in violation.
    (b) Engines exempted from the applicable standards of 40 CFR part
86 under the provisions of 40 CFR part 1068 are exempt from the
standards of this part without request.
    (c) The emergency vehicle field modification provisions of 40 CFR
85.1716 apply with respect to the standards of this part.
    (d) Subpart C of this part describes how to test and certify dual-
fuel and flexible-fuel engines. Some multi-fuel engines may not fit
either of those defined terms. For such engines, we will determine
whether it is most appropriate to treat them as single-fuel engines,
dual-fuel engines, or flexible-fuel engines based on the range of
possible and expected fuel mixtures. For example, an engine might burn
natural gas but initiate combustion with a pilot injection of diesel
fuel. If the engine is designed to operate with a single fueling
algorithm (i.e., fueling rates are fixed at a given engine speed and
load condition), we would generally treat it as a single-fuel engine.
In this context, the combination of diesel fuel and natural gas would
be its own fuel type. If the engine is designed to also operate on
diesel fuel alone, we would generally treat it as a dual-fuel engine.
If the engine is designed to operate on varying mixtures of the two
fuels, we would generally treat it as a flexible-fuel engine. To the
extent that requirements vary for the different fuels or fuel mixtures,
we may apply the more stringent requirements.

Sec.  1036.605  GHG exemption for engines used in specialty vehicles.

    Engines certified to the alternative standards specified in 40 CFR
86.007-11 and 86.008-10 for use in specialty vehicles as described in
40 CFR 1037.605 are exempt from the standards of this part. See 40 CFR
part 1037 for provisions that apply to the vehicle.

Sec.  1036.610  Off-cycle technology credits and adjustments for
reducing greenhouse gas emissions.

    (a) You may ask us to apply the provisions of this section for
CO2 emission reductions resulting from powertrain
technologies that were not in common use with heavy-duty vehicles
before model year 2010 that are not reflected in the specified test
procedure. While you are not required to prove that such technologies
were not in common use with heavy-duty vehicles before model year 2010,
we will not approve your request if we determine that they do not
qualify. We will apply these provisions only for technologies that will
result in a measurable, demonstrable, and verifiable real-world

CO2 reduction. Note that prior to model year 2016, these
technologies were referred to as ``innovative technologies''.
    (b) The provisions of this section may be applied as either an
improvement factor (used to adjust emission results) or as a separate
credit, consistent with good engineering judgment. Note that the term
``credit'' in this section describes an additive adjustment to emission
rates and is not equivalent to an emission credit in the ABT program of
subpart H of this part. We recommend that you base your credit/
adjustment on A to B testing of pairs of engines/vehicles differing
only with respect to the technology in question.
    (1) Calculate improvement factors as the ratio of in-use emissions
with the technology divided by the in-use emissions without the
technology. Adjust the emission results by multiplying by the
improvement factor. Use the improvement-factor approach where good
engineering judgment indicates that the actual benefit will be
proportional to emissions measured over the test procedures specified
in this part. For example, the benefits from technologies that reduce
engine operation would generally be proportional to the engine's
emission rate.
    (2) Calculate separate credits based on the difference between the
in-use emission rate (g/ton-mile) with the technology and the in-use
emission rate without the technology. Subtract this value from your
measured emission result and use this adjusted value to determine your
FEL. We may also allow you to calculate the credits based on g/hp-hr
emission rates. Use the separate-credit approach where good engineering
judgment indicates that the actual benefit will not be proportional to
emissions measured over the test procedures specified in this part.
    (3) We may require you to discount or otherwise adjust your
improvement factor or credit to account for uncertainty or other
relevant factors.
    (c) Send your request to the Designated Compliance Officer. We
recommend that you do not begin collecting test data (for submission to
EPA) before contacting us. For technologies for which the vehicle
manufacturer could also claim credits (such as transmissions in certain
circumstances), we may require you to include a letter from the vehicle
manufacturer stating that it will not seek credits for the same
technology. Your request must contain the following items:
    (1) A detailed description of the off-cycle technology and how it
functions to reduce CO2 emissions under conditions not
represented on the duty cycles required for certification.
    (2) A list of the engine configurations that will be equipped with
the technology.
    (3) A detailed description and justification of the selected test
engines.
    (4) All testing and simulation data required under this section,
plus any other data you have considered in your analysis. You may ask
for our preliminary approval of your test plan under Sec.  1036.210.
    (5) A complete description of the methodology used to estimate the
off-cycle benefit of the technology and all supporting data, including
engine testing and in-use activity data. Also include a statement
regarding your recommendation for applying the provisions of this
section for the given technology as an improvement factor or a credit.
    (6) An estimate of the off-cycle benefit by engine model, and the
fleetwide benefit based on projected sales of engine models equipped
with the technology.
    (7) A demonstration of the in-use durability of the off-cycle
technology, based on any available engineering analysis or durability
testing data (either by testing components or whole engines).
    (d) We may seek public comment on your request, consistent with the
provisions of 40 CFR 86.1869-12(d). However, we will generally not seek
public comment on credits/adjustments based on A to B engine
dynamometer testing, chassis testing, or in-use testing.
    (e) We may approve an improvement factor or credit for any
configuration that is properly represented by your testing.
    (1) For model years before 2021, you may continue to use an
approved improvement factor or credit for any appropriate engine
families in future model years through 2020.
    (2) For model years 2021 and later, you may not rely on an approval
for model years before 2021. You must separately request our approval
before applying an improvement factor or credit under this section for
2021 and later engines, even if we approved an improvement factor or
credit for similar engine models before model year 2021. Note that
approvals for model year 2021 and later may carry over for multiple
years.

Sec.  1036.615  Engines with Rankine cycle waste heat recovery and
hybrid powertrains.

    This section specifies how to generate advanced-technology emission
credits for hybrid powertrains that include energy storage systems and
regenerative braking (including regenerative engine braking) and for
engines that include Rankine-cycle (or other bottoming cycle) exhaust
energy recovery systems. This section applies only for model year 2020
and earlier engines.
    (a) Pre-transmission hybrid powertrains. Test pre-transmission
hybrid powertrains with the hybrid engine test procedures of 40 CFR
part 1065 or with the post-transmission test procedures in 40 CFR
1037.550. Pre-transmission hybrid powertrains are those engine systems
that include features to recover and store energy during engine
motoring operation but not from the vehicle's wheels. Engines certified
with pre-transmission hybrid powertrains must be certified to meet the
diagnostic requirements of 40 CFR 86.018-10 with respect to powertrain
components and systems; if different manufacturers produce the engine
and the hybrid powertrain, the hybrid powertrain manufacturer may
separately certify its powertrain relative to diagnostic requirements.
    (b) Rankine engines. Test engines that include Rankine-cycle
exhaust energy recovery systems according to the test procedures
specified in subpart F of this part unless we approve alternate
procedures.
    (c) Calculating credits. Calculate credits as specified in subpart
H of this part. Credits generated from engines and powertrains
certified under this section may be used in other averaging sets as
described in Sec.  1036.740(c).
    (d) Off-cycle technologies. You may certify using both the
provisions of this section and the off-cycle technology provisions of
Sec.  1036.610, provided you do not double-count emission benefits.

Sec.  1036.620  Alternate CO2 standards based on model year
2011 compression-ignition engines.

    For model years 2014 through 2016, you may certify your
compression-ignition engines to the CO2 standards of this
section instead of the CO2 standards in Sec.  1036.108.
However, you may not certify engines to these alternate standards if
they are part of an averaging set in which you carry a balance of
banked credits. You may submit applications for certifications before
using up banked credits in the averaging set, but such certificates
will not become effective until you have used up (or retired) your
banked credits in the averaging set. For purposes of this section, you
are deemed to carry credits in an averaging set if you carry credits
from advanced technology that are allowed to be used in that averaging
set.

    (a) The standards of this section are determined from the measured
emission rate of the test engine of the applicable baseline 2011 engine
family or families as described in paragraphs (b) and (c) of this
section. Calculate the CO2 emission rate of the baseline
test engine using the same equations used for showing compliance with
the otherwise applicable standard. The alternate CO2
standard for light and medium heavy-duty vocational-certified engines
(certified for CO2 using the transient cycle) is equal to
the baseline emission rate multiplied by 0.975. The alternate
CO2 standard for tractor-certified engines (certified for
CO2 using the ramped-modal cycle) and all other heavy heavy-
duty engines is equal to the baseline emission rate multiplied by
0.970. The in-use FEL for these engines is equal to the alternate
standard multiplied by 1.03.
    (b) This paragraph (b) applies if you do not certify all your
engine families in the averaging set to the alternate standards of this
section. Identify separate baseline engine families for each engine
family that you are certifying to the alternate standards of this
section. For an engine family to be considered the baseline engine
family, it must meet the following criteria:
    (1) It must have been certified to all applicable emission
standards in model year 2011. If the baseline engine was certified to a
NOX FEL above the standard and incorporated the same
emission control technologies as the new engine family, you may adjust
the baseline CO2 emission rate to be equivalent to an engine
meeting the 0.20 g/hp-hr NOX standard (or your higher FEL as
specified in this paragraph (b)(1)), using certification results from
model years 2009 through 2011, consistent with good engineering
judgment.
    (i) Use the following equation to relate model year 2009-2011
NOX and CO2 emission rates (g/hp-hr):
CO2 = a x log(NOX)+b.
    (ii) For model year 2014-2016 engines certified to NOX
FELs above 0.20 g/hp-hr, correct the baseline CO2 emissions
to the actual NOX FELs of the 2014-2016 engines.
    (iii) Calculate separate adjustments for emissions over the ramped-
modal cycle and the transient cycle.
    (2) The baseline configuration tested for certification must have
the same engine displacement as the engines in the engine family being
certified to the alternate standards, and its rated power must be
within five percent of the highest rated power in the engine family
being certified to the alternate standards.
    (3) The model year 2011 U.S.-directed production volume of the
configuration tested must be at least one percent of the total 2011
U.S.-directed production volume for the engine family.
    (4) The tested configuration must have cycle-weighted BSFC
equivalent to or better than all other configurations in the engine
family.
    (c) This paragraph (c) applies if you certify all your engine
families in the primary intended service class to the alternate
standards of this section. For purposes of this section, you may
combine light heavy-duty and medium heavy-duty engines into a single
averaging set. Determine your baseline CO2 emission rate as
the production-weighted emission rate of the certified engine families
you produced in the 2011 model year. If you produce engines for both
tractors and vocational vehicles, treat them as separate averaging
sets. Adjust the CO2 emission rates to be equivalent to an
engine meeting the average NOX FEL of new engines (assuming
engines certified to the 0.20 g/hp-hr NOX standard have a
NOX FEL equal to 0.20 g/hp-hr), as described in paragraph
(b)(1) of this section.
    (d) Include the following statement on the emission control
information label: ``THIS ENGINE WAS CERTIFIED TO AN ALTERNATE
CO2 STANDARD UNDER Sec.  1036.620.''
    (e) You may not bank CO2 emission credits for any engine
family in the same averaging set and model year in which you certify
engines to the standards of this section. You may not bank any
advanced-technology credits in any averaging set for the model year you
certify under this section (since such credits would be available for
use in this averaging set). Note that the provisions of Sec.  1036.745
apply for deficits generated with respect to the standards of this
section.
    (f) You need our approval before you may certify engines under this
section, especially with respect to the numerical value of the
alternate standards. We will not approve your request if we determine
that you manipulated your engine families or test engine configurations
to certify to less stringent standards, or that you otherwise have not
acted in good faith. You must keep and provide to us any information we
need to determine that your engine families meet the requirements of
this section. Keep these records for at least five years after you stop
producing engines certified under this section.

Sec.  1036.625  In-use compliance with family emission limits (FELs).

    Section 1036.225 describes how to change the FEL for an engine
family during the model year. This section, which describes how you may
ask us to increase an engine family's FEL after the end of the model
year, is intended to address circumstances in which it is in the public
interest to apply a higher in-use FEL based on forfeiting an
appropriate number of emission credits. For example, this may be
appropriate where we determine that recalling vehicles would not
significantly reduce in-use emissions. We will generally not allow this
option where we determine the credits being forfeited would likely have
expired.
    (a) You may ask us to increase an engine family's FEL after the end
of the model year if you believe some of your in-use engines exceed the
CO2 FEL that applied during the model year (or the
CO2 emission standard if the family did not generate or use
emission credits). We may consider any available information in making
our decision to approve or deny your request.
    (b) If we approve your request under this section, you must apply
emission credits to cover the increased FEL for all affected engines.
Apply the emission credits as part of your credit demonstration for the
current production year. Include the appropriate calculations in your
final report under Sec.  1036.730.
    (c) Submit your request to the Designated Compliance Officer.
Include the following in your request:
    (1) Identify the names of each engine family that is the subject of
your request. Include separate family names for different model years.
    (2) Describe why your request does not apply for similar engine
models or additional model years, as applicable.
    (3) Identify the FEL(s) that applied during the model year and
recommend a replacement FEL for in-use engines; include a supporting
rationale to describe how you determined the recommended replacement
FEL.
    (4) Describe whether the needed emission credits will come from
averaging, banking, or trading.
    (d) If we approve your request, we will identify the replacement
FEL. The value we select will reflect our best judgment to accurately
reflect the actual in-use performance of your engines, consistent with
the testing provisions specified in this part. We may apply the higher
FELs to other engine families from the same or different model years to
the extent they used equivalent emission controls. We may include any

appropriate conditions with our approval.
    (e) If we order a recall for an engine family under 40 CFR
1068.505, we will no longer approve a replacement FEL under this
section for any of your engines from that engine family, or from any
other engine family that relies on equivalent emission controls.

Sec.  1036.630  Certification of engine GHG emissions for powertrain
testing.

    For engines included in powertrain families under 40 CFR part 1037,
you may choose to include the corresponding engine emissions in your
engine families under this part 1036 instead of (or in addition to) the
otherwise applicable engine fuel maps.
    (a) If you choose to certify powertrain fuel maps in an engine
family, the declared powertrain emission levels become standards that
apply for selective enforcement audits and in-use testing. We may
require that you provide to us the engine test cycle (not normalized)
corresponding to a given powertrain for each of the specified duty
cycles.
    (b) If you choose to certify only fuel map emissions for an engine
family and to not certify emissions over powertrain test cycles under
40 CFR 1037.550, we will not presume you are responsible for emissions
over the powertrain cycles. However, where we determine that you are
responsible in whole or in part for the emission exceedance in such
cases, we may require that you participate in any recall of the
affected vehicles. Note that this provision to limit your
responsibility does not apply if you also hold the certificate of
conformity for the vehicle.
    (c) If you split an engine family into subfamilies based on
different fuel-mapping procedures as described in Sec.  1036.230(e),
the fuel-mapping procedures you identify for certifying each subfamily
also apply for selective enforcement audits and in-use testing.

Subpart H--Averaging, Banking, and Trading for Certification

Sec.  1036.701  General provisions.

    (a) You may average, bank, and trade (ABT) emission credits for
purposes of certification as described in this subpart and in subpart B
of this part to show compliance with the standards of Sec.  1036.108.
Participation in this program is voluntary. (Note: As described in
subpart B of this part, you must assign an FCL to all engine families,
whether or not they participate in the ABT provisions of this subpart.)
    (b) The definitions of subpart I of this part apply to this subpart
in addition to the following definitions:
    (1) Actual emission credits means emission credits you have
generated that we have verified by reviewing your final report.
    (2) Averaging set means a set of engines in which emission credits
may be exchanged. See Sec.  1036.740.
    (3) Broker means any entity that facilitates a trade of emission
credits between a buyer and seller.
    (4) Buyer means the entity that receives emission credits as a
result of a trade.
    (5) Reserved emission credits means emission credits you have
generated that we have not yet verified by reviewing your final report.
    (6) Seller means the entity that provides emission credits during a
trade.
    (7) Standard means the emission standard that applies under subpart
B of this part for engines not participating in the ABT program of this
subpart.
    (8) Trade means to exchange emission credits, either as a buyer or
seller.
    (c) Emission credits may be exchanged only within an averaging set,
except as specified in Sec.  1036.740.
    (d) You may not use emission credits generated under this subpart
to offset any emissions that exceed an FCL or standard. This applies
for all testing, including certification testing, in-use testing,
selective enforcement audits, and other production-line testing.
However, if emissions from an engine exceed an FCL or standard (for
example, during a selective enforcement audit), you may use emission
credits to recertify the engine family with a higher FCL that applies
only to future production.
    (e) You may use either of the following approaches to retire or
forego emission credits:
    (1) You may retire emission credits generated from any number of
your engines. This may be considered donating emission credits to the
environment. Identify any such credits in the reports described in
Sec.  1036.730. Engines must comply with the applicable FELs even if
you donate or sell the corresponding emission credits under this
paragraph (h). Those credits may no longer be used by anyone to
demonstrate compliance with any EPA emission standards.
    (2) You may certify an engine family using an FEL (FCL for
CO2) below the emission standard as described in this part
and choose not to generate emission credits for that family. If you do
this, you do not need to calculate emission credits for those engine
families and you do not need to submit or keep the associated records
described in this subpart for that family.
    (f) Emission credits may be used in the model year they are
generated. Surplus emission credits may be banked for future model
years. Surplus emission credits may sometimes be used for past model
years, as described in Sec.  1036.745.
    (g) You may increase or decrease an FCL during the model year by
amending your application for certification under Sec.  1036.225. The
new FCL may apply only to engines you have not already introduced into
commerce.
    (h) See Sec.  1036.740 for special credit provisions that apply for
greenhouse gas credits generated under 40 CFR 86.1819-14(k)(7) or Sec.
1036.615 or 40 CFR 1037.615.
    (i) Unless the regulations explicitly allow it, you may not
calculate credits more than once for any emission reduction. For
example, if you generate CO2 emission credits for a hybrid
engine under this part for a given vehicle, no one may generate
CO2 emission credits for that same hybrid engine and vehicle
under 40 CFR part 1037. However, credits could be generated for
identical vehicles using engines that did not generate credits under
this part.
    (j) Credits you generate with compression-ignition engines in 2020
and earlier model years may be used in model year 2021 and later only
if the credit-generating engines were certified to the tractor engine
standards in Sec.  1036.108 and credits were calculated relative to the
tractor engine standards. You may otherwise use emission credits
generated in one model year without adjustment for certifying vehicles
in a later model year, even if emission standards are different.
    (k) Engine families you certify with a nonconformance penalty under
40 CFR part 86, subpart L, may not generate emission credits.

Sec.  1036.705  Generating and calculating emission credits.

    (a) The provisions of this section apply separately for calculating
emission credits for each pollutant.
    (b) For each participating family, calculate positive or negative
emission credits relative to the otherwise applicable emission standard
based on the engine family's FCL for greenhouse gases. If your engine
family is certified to both the vocational and tractor engine
standards, calculate credits separately for the vocational engines and
the tractor engines (as specified in paragraph (b)(3) of this section).
Calculate positive emission credits for a family that has an FCL below
the standard. Calculate negative emission credits for a family that has
an FCL above the standard. Sum your positive

and negative credits for the model year before rounding. Round the sum
of emission credits to the nearest megagram (Mg), using consistent
units throughout the following equations:
    (1) For vocational engines:

Emission credits (Mg) = (Std-FCL) [middot] (CF) [middot] (Volume)
[middot] (UL) [middot] (10-6)

Where:

Std = the emission standard, in g/hp-hr, that applies under subpart
B of this part for engines not participating in the ABT program of
this subpart (the ``otherwise applicable standard'').
FCL = the Family Certification Level for the engine family, in g/hp-
hr, measured over the transient duty cycle, rounded to the same
number of decimal places as the emission standard.
CF = a transient cycle conversion factor (hp-hr/mile), calculated by
dividing the total (integrated) horsepower-hour over the duty cycle
(average of vocational engine configurations weighted by their
production volumes) by 6.3 miles for engines subject to spark-
ignition standards and 6.5 miles for engines subject to compression-
ignition. This represents the average work performed by vocational
engines in the family over the mileage represented by operation over
the duty cycle.
Volume = the number of vocational engines eligible to participate in
the averaging, banking, and trading program within the given engine
family during the model year, as described in paragraph (c) of this
section.
UL = the useful life for the given engine family, in miles.

    (2) For tractor engines:

Emission credits (Mg) = (Std-FCL) [middot] (CF) [middot] (Volume)
[middot] (UL) [middot] (10-6)

Where:

Std = the emission standard, in g/hp-hr, that applies under subpart
B of this part for engines not participating in the ABT program of
this subpart (the ``otherwise applicable standard'').
FCL = the Family Certification Level for the engine family, in g/hp-
hr, measured over the ramped-modal cycle rounded to the same number
of decimal places as the emission standard.
CF = a transient cycle conversion factor (hp-hr/mile), calculated by
dividing the total (integrated) horsepower-hour over the duty cycle
(average of tractor-engine configurations weighted by their
production volumes) by 6.3 miles for engines subject to spark-
ignition standards and 6.5 miles for engines subject to compression-
ignition standards. This represents the average work performed by
tractor engines in the family over the mileage represented by
operation over the duty cycle. Note that this calculation requires
you to use the transient cycle conversion factor even for engines
certified to standards based on the ramped-modal cycle.
Volume = the number of tractor engines eligible to participate in
the averaging, banking, and trading program within the given engine
family during the model year, as described in paragraph (c) of this
section.
UL = the useful life for the given engine family, in miles.

    (3) For engine families certified to both the vocational and
tractor engine standards, we may allow you to use statistical methods
to estimate the total production volumes where a small fraction of the
engines cannot be tracked precisely.
    (4) You may not generate emission credits for tractor engines
(i.e., engines not certified to the transient cycle for CO2)
installed in vocational vehicles (including vocational tractors
certified under 40 CFR 1037.630 or exempted under 40 CFR 1037.631). We
will waive this provision where you demonstrate that less than five
percent of the engines in your tractor family were installed in
vocational vehicles. For example, if you know that 96 percent of your
tractor engines were installed in non-vocational tractors, but cannot
determine the vehicle type for the remaining four percent, you may
generate credits for all the engines in the family.
    (5) You may generate CO2 emission credits from a model
year 2021 or later medium heavy-duty engine family subject to spark-
ignition standards for exchanging with other engine families only if
the engines in the family are gasoline-fueled. You may generate
CO2 credits from these engine families only for the purpose
of offsetting CH4 and/or N2O emissions within the
same engine family as described in paragraph (d) of this section.
    (c) As described in Sec.  1036.730, compliance with the
requirements of this subpart is determined at the end of the model year
based on actual U.S.-directed production volumes. Keep appropriate
records to document these production volumes. Do not include any of the
following engines to calculate emission credits:
    (1) Engines that you do not certify to the CO2 standards
of this part because they are permanently exempted under subpart G of
this part or under 40 CFR part 1068.
    (2) Exported engines.
    (3) Engines not subject to the requirements of this part, such as
those excluded under Sec.  1036.5. For example, do not include engines
used in vehicles certified to the greenhouse gas standards of 40 CFR
86.1819.
    (4) Any other engines if we indicate elsewhere in this part 1036
that they are not to be included in the calculations of this subpart.
    (d) You may use CO2 emission credits to show compliance
with CH4 and/or N2O FELs instead of the otherwise
applicable emission standards. To do this, calculate the CH4
and/or N2O emission credits needed (negative credits) using
the equation in paragraph (b) of this section, using the FEL(s) you
specify for your engines during certification instead of the FCL. You
must use 34 Mg of positive CO2 credits to offset 1 Mg of
negative CH4 credits for model year 2021 and later engines,
and you must use 25 Mg of positive CO2 credits to offset 1
Mg of negative CH4 credits for earlier engines. You must use
298 Mg of positive CO2 credits to offset 1 Mg of negative
N2O credits.

Sec.  1036.710  Averaging.

    (a) Averaging is the exchange of emission credits among your engine
families. You may average emission credits only within the same
averaging set, except as specified in Sec.  1036.740.
    (b) You may certify one or more engine families to an FCL above the
applicable standard, subject to any applicable FEL caps and other the
provisions in subpart B of this part, if you show in your application
for certification that your projected balance of all emission-credit
transactions in that model year is greater than or equal to zero, or
that a negative balance is allowed under Sec.  1036.745.
    (c) If you certify an engine family to an FCL that exceeds the
otherwise applicable standard, you must obtain enough emission credits
to offset the engine family's deficit by the due date for the final
report required in Sec.  1036.730. The emission credits used to address
the deficit may come from your other engine families that generate
emission credits in the same model year (or from later model years as