respect to drag area:
    (a) Determine whether a tractor meets standards as follows:
    (1) We will select a vehicle configuration for testing. Perform a
coastdown measurement according to Sec.  1037.528 with the vehicle in
its production configuration. If the production configuration cannot be
connected to a standard trailer, you may ask us to approve trailer
specifications different than Sec.  1037.501(g)(1) based on good
engineering judgment. Instead of the process described in Sec.
1037.528(h)(12), determine your test result as described in this
paragraph (a). You must have an equal number of runs in each direction.
    (2) Measure a yaw curve for your test vehicle using your alternate
method according to Sec.  1037.525(b)(3). You do not need to test at
the coastdown effective yaw angle. You may use a previously established
yaw curve from your certification testing if it is available.
    (3) Using the yaw curve, perform a regression using values of drag
area, CdAalt, and yaw angle, [psi]alt,
to determine the air-direction correction coefficients, a0,
a1, a2, a3, and a4, for the
following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.113

    (4) Adjust the drag area value from each coastdown run,
CdArun, from the yaw angle of each run,
[psi]run, to 4.5[deg] to represent a wind-
averaged drag area value, CdAwa by applying Eq.
1037.305-1 as follows:

[GRAPHIC] [TIFF OMITTED] TR29JN21.114

    (5) Perform additional coastdown measurements until you reach a
pass or fail decision under this paragraph (a). The minimum number of
runs to pass is 24. The minimum number of runs to fail is 100.
    (6) Calculate statistical values to characterize cumulative test
results at least once per day based on an equal number of coastdown
runs in each direction. Determine the wind-averaged drag area value for
the test CdAwa by averaging all
CdAwa-run values for all days of testing.
Determine the upper and lower bounds of the drag area value,
CdAwa-bounded, expressed to two decimal places,
using a confidence interval as follows:
[GRAPHIC] [TIFF OMITTED] TR29JN21.115

Where:

CdAwa-bounded = the upper bound,
CdAwa-upper, and lower bound,
CdAwa-lower, of the drag area value, where
CdAwa-upper is the larger number.
CdAwa = the average of all
CdAwa-run values.
[sigma] = the standard deviation of all
CdAwa-run values (see 40 CFR 1065.602(c)).
n = the total number of coastdown runs.

    (7) Determine compliance based on the values of
CdAwa-upper and CdAwa-lower
relative to the adjusted bin boundary. For purposes of this section,
the upper limit of a bin is expressed as the specified value plus 0.05
to account for rounding. For example, for a bin including values of
5.5-5.9 m2, being above the upper limit means exceeding 5.95
m2. The vehicle passes or fails relative to the adjusted bin
boundary based on one of the following criteria:
    (i) The vehicle passes if CdAwa-upper is less
than or equal to the upper limit of the bin to which you certified the
vehicle.
    (ii) The vehicle fails if CdAwa-lower is
greater than the upper limit of the bin to which you certified the
vehicle.
    (iii) The vehicle passes if you perform 100 coastdown runs and
CdAwa-upper is greater than and
CdAwa-lower is lower than the upper limit of the
bin to which you certified the vehicle.
    (iv) The vehicle fails if you choose to stop testing before
reaching a final determination under this paragraph (a)(7).
    (v) You may continue testing beyond the stopping point specified in
this paragraph (a)(7). We may consider the additional data in making
pass/fail determinations.
* * * * *

0
146. Revise Sec.  1037.320 to read as follows:

Sec.  1037.320  Audit procedures for axles and transmissions.

    Selective enforcement audit provisions apply for axles and
transmissions relative to the efficiency demonstrations of Sec. Sec.
1037.560 and 1037.565 as specified in this section. The following
provisions apply instead of 40 CFR 1068.415 through 1068.445 for the
selective enforcement audit.
    (a) A selective enforcement audit for axles or transmissions would
consist of performing measurements with a production axle or
transmission to determine mean power loss values as declared for GEM
simulations, and running GEM over one or more applicable duty cycles
based on those measured values. The axle or transmission is considered
passing for a given configuration if the new modeled emission result
for every applicable duty cycle is at or below the modeled emission
result corresponding to the declared GEM inputs.
    (b) Run GEM for each applicable vehicle configuration identified in
40 CFR 1036.540 using the applicable default engine map defined in
appendix C of 40 CFR part 1036, and the default torque curve given in
Table 1 of this section for the vehicle class as defined in Sec.
1037.140(g). For axle testing, this may require omitting several
vehicle configurations based on selecting axle ratios that correspond
to the tested axle. For transmission testing, use the test
transmission's gear ratios in place of the gear ratios defined in 40
CFR 1036.540. The GEM result for each vehicle configuration counts as a
separate test for determining whether the family passes the audit.
    (c) If the initial axle or transmission passes, the family passes
and no further testing is required. If the initial axle or transmission
does not pass, select two additional production axles or transmissions,
as applicable, to perform additional tests. Note that these could be
different axle and transmission configurations within the family. These
become official test results for the family. Use good engineering
judgment to use the results of these tests to update the declared maps
for the axle or transmission family. For example, if you fail the audit
test for any of the axles or transmissions tested, the audit result
becomes the declared map. This may also require revising any
analytically derived maps.

                       Table 1 to Sec.   1037.320--Default Torque Curves for Vehicle Class
----------------------------------------------------------------------------------------------------------------
              Light HDV                       Medium HDV               Heavy HDV           Light HDV and medium
----------------------------------------------------------------------------------------    HDV spark-ignition
                                                                                ------------------------
                            Engine       Engine      Engine       Engine      Engine       Engine      Engine
 Engine speed  (r/min)      torque     speed (r/     torque     speed (r/     torque     speed (r/     torque
                         (N[middot]m)     min)    (N[middot]m)     min)    (N[middot]m)     min)    (N[middot]m)
----------------------------------------------------------------------------------------------------------------
750....................         470          600         850          600        1200          600          433
907....................         579          750         890          750        1320          700          436
1055...................         721          850        1000          850        1490          800          445
1208...................         850          950        1200          950        1700          900          473
1358...................         876         1050        1440         1050        1950         1000          492
1507...................         866         1100        1520         1100        2090         1100          515
1660...................         870         1150        1570         1200        2100         1200          526
1809...................         868         1250        1590         1250        2100         1300          541
1954...................         869         1300        1590         1300        2093         1400          542
2105...................         878         1450        1590         1400        2092         1500          542
2258...................         850         1500        1590         1500        2085         1600          542
2405...................         800         1600        1540         1520        2075         1700          547
2556...................         734         1700        1470         1600        2010         1800          550
2600...................           0         1800        1385         1700        1910         1900          551
                         ............       1900        1300         1800        1801         2000          554
                         ............       2000        1220         1900        1640         2100          553
                         ............       2100        1040         2000        1350         2200          558
                         ............       2250         590         2100         910         2300          558
                         ............       2400           0         2250           0         2400          566
                         ............  .........  ............  .........  ............       2500          571
                         ............  .........  ............  .........  ............       2600          572
                         ............  .........  ............  .........  ............       2700          581
                         ............  .........  ............  .........  ............       2800          586
                         ............  .........  ............  .........  ............       2900          587
                         ............  .........  ............  .........  ............       3000          590
                         ............  .........  ............  .........  ............       3100          591
                         ............  .........  ............  .........  ............       3200          589
                         ............  .........  ............  .........  ............       3300          585
                         ............  .........  ............  .........  ............       3400          584
                         ............  .........  ............  .........  ............       3500          582
                         ............  .........  ............  .........  ............       3600          573
                         ............  .........  ............  .........  ............       3700          562
                         ............  .........  ............  .........  ............       3800          555
                         ............  .........  ............  .........  ............       3900          544
                         ............  .........  ............  .........  ............       4000          534
                         ............  .........  ............  .........  ............       4100          517
                         ............  .........  ............  .........  ............       4200          473
                         ............  .........  ............  .........  ............       4291          442
                         ............  .........  ............  .........  ............       4500          150
----------------------------------------------------------------------------------------------------------------

0
147. Amend Sec.  1037.501 by adding paragraph (i) to read as follows:

Sec.  1037.501  General testing and modeling provisions.

* * * * *
    (i) Note that declared GEM inputs for fuel maps and aerodynamic
drag area typically includes compliance margins to account for testing
variability; for other measured GEM inputs, the declared values are
typically the measured values without adjustment.

0
148. Amend Sec.  1037.510 by revising paragraphs (a)(2), (c)(3), (d),
and (e) to read as follows:

Sec.  1037.510  Duty-cycle exhaust testing.

* * * * *
    (a) * * *
    (2) Perform cycle-average engine fuel mapping as described in 40
CFR 1036.540. For powertrain testing under Sec.  1037.550 or Sec.
1037.555, perform testing as described in this paragraph (a)(2) to
generate GEM inputs for each simulated vehicle configuration, and test
runs representing different idle conditions. Perform testing as
follows:
    (i) Transient cycle. The transient cycle is specified in appendix I
of this part.
    (ii) Highway cruise cycles. The grade portion of the route
corresponding to the 55 mi/hr and 65 mi/hr highway cruise cycles is
specified in appendix IV of this part. Maintain vehicle speed between -
1.0 mi/hr and 3.0 mi/hr of the speed setpoint; this speed tolerance
applies instead of the approach specified in 40 CFR 1066.425(b)(1) and
(2).
    (iii) Drive idle. Perform testing at a loaded idle condition for
Phase 2 vocational vehicles. For engines with an adjustable warm idle
speed setpoint, test at the minimum warm idle speed and the maximum
warm idle speed; otherwise simply test at the engine's warm idle speed.
Warm up the powertrain using the vehicle settings for the Test 1
vehicle configuration as defined in Table 2 or 3 of 40 CFR 1036.540 by
operating it at 65 mi/hr for 600 seconds. Linearly ramp the powertrain
down to zero vehicle speed in 20 seconds. Set the engine to operate at
idle speed for 90 seconds, with the brake applied and the transmission
in drive (or clutch depressed for manual transmission), and sample
emissions to determine mean emission values (in g/s) over the last 30
seconds of idling.
    (iv) Parked idle. Perform testing at an unloaded idle condition for
Phase 2 vocational vehicles. For engines with an adjustable warm idle
speed setpoint, test at the minimum warm idle speed and the maximum
warm idle speed; otherwise simply test at the engine's warm idle speed.
Warm up the powertrain using the vehicle settings for the Test 1
vehicle configuration by

operating it at 65 mi/hr for 600 seconds. Linearly ramp the powertrain
down to zero vehicle speed in 20 seconds. Set the engine to operate at
idle speed for 780 seconds, with the transmission in park (or the
transmission in neutral with the parking brake applied for manual
transmissions), and sample emissions to determine mean emission values
(in g/s) over the last 600 seconds of idling.
* * * * *
    (c) * * *
    (3) Table 1 follows:

                          Table 1 of Sec.   1037.510--Weighting Factors for Duty Cycles
----------------------------------------------------------------------------------------------------------------
                                             Distance-weighted                Time-weighted a          Average
                                    ----------------------------------------------------------------    speed
                                                                                during non-
                                      Transient   55 mi/hr   65 mi/hr    Drive    Parked   Non-idle  idle cycles
                                         (%)       cruise     cruise   idle (%)  idle (%)     (%)     (mi/hr) b
                                                    (%)        (%)
----------------------------------------------------------------------------------------------------------------
Day Cabs...........................          19         17         64  ........  ........  ........  ...........
Sleeper Cabs.......................           5          9         86  ........  ........  ........  ...........
Heavy-haul tractors................          19         17         64  ........  ........  ........  ...........
Vocational--Regional...............          20         24         56         0        25        75        38.41
Vocational--Multi-Purpose (2b-7)...          54         29         17        17        25        58        23.18
Vocational--Multi-Purpose (8)......          54         23         23        17        25        58        23.27
Vocational--Urban (2b-7)...........          92          8          0        15        25        60        16.25
Vocational--Urban (8)..............          90         10          0        15        25        60        16.51
Vocational with conventional                 42         21         37  ........  ........  ........  ...........
 powertrain (Phase 1 only).........
Vocational Hybrid Vehicles (Phase 1          75          9         16  ........  ........  ........  ...........
 only).............................
----------------------------------------------------------------------------------------------------------------
a Note that these drive idle and non-idle weighting factors do not reflect additional drive idle that occurs
  during the transient cycle. The transient cycle does not include any parked idle.
b These values apply even for vehicles not following the specified speed traces.

    (d) For transient testing, compare actual second-by-second vehicle
speed with the speed specified in the test cycle and ensure any
differences are consistent with the criteria as specified in 40 CFR
1066.425(b) and (c). If the speeds do not conform to these criteria,
the test is not valid and must be repeated.
    (e) Run test cycles as specified in 40 CFR part 1066. For testing
vehicles equipped with cruise control over the highway cruise cycles,
you may use the vehicle's cruise control to control the vehicle speed.
For vehicles equipped with adjustable vehicle speed limiters, test the
vehicle with the vehicle speed limiter at its highest setting.
* * * * *

0
149. Amend Sec.  1037.515 by revising paragraphs (c) and (d)(2) to read
as follows:

Sec.  1037.515  Determining CO2 emissions to show compliance for
trailers.

* * * * *
    (c) Drag area. You may use [Delta]CdA values approved
under Sec.  1037.211 for device manufacturers if your trailers are
properly equipped with those devices. Determine [Delta]CdA
values for other trailers based on testing. Measure CdA and
determine [Delta]CdA values as described in Sec.
1037.526(a). You may use [Delta]CdA values from one trailer
configuration to represent any number of additional trailers based on
worst-case testing. This means that you may apply [Delta]CdA
values from your measurements to any trailer models of the same
category with drag area at or below that of the tested configuration.
For trailers in the short dry box vans and short refrigerated box vans
that are not 28 feet long, apply the [Delta]CdA value
established for a comparable 28-foot trailer model; you may use the
same devices designed for 28-foot trailers or you may adapt those
devices as appropriate for the different trailer length, consistent
with good engineering judgment. For example, 48-foot trailers may use
longer side skirts than the skirts that were tested with a 28-foot
trailer. Trailer and device manufacturers may seek preliminary approval
for these adaptations. Determine bin levels based on
[Delta]CdA test results as described in the following table:

  Table 2 of Sec.   1037.515--Bin Determinations for Trailers Based on
                        Aerodynamic Test Results
                           [[Delta]CdA in m2]
------------------------------------------------------------------------
                                                          And use the
                                                        following value
    If a trailer's measured     Designate the trailer   for [Delta]CDA .
      [Delta]CDA is . . .              as . . .               . .

------------------------------------------------------------------------
<=0.09........................  Bin I................                0.0
0.10-0.39.....................  Bin II...............                0.1
0.40-0.69.....................  Bin III..............                0.4
0.70-0.99.....................  Bin IV...............                0.7
1.00-1.39.....................  Bin V................                1.0
1.40-1.79.....................  Bin VI...............                1.4
>=1.80........................  Bin VII..............                1.8
------------------------------------------------------------------------

    (d) * * *
    (2) Apply weight reductions for other components made with light-
weight materials as shown in the following table:

       Table 3 of Sec.   1037.515--Weight Reductions for Trailers
                                [pounds]
------------------------------------------------------------------------
                                                       Weight  reduction
           Component                   Material             (pounds)
------------------------------------------------------------------------
Structure for Suspension        Aluminum.............                280
 Assembly a.
Hub and Drum (per axle).......  Aluminum.............                 80
Floor b.......................  Aluminum.............                375
Floor b.......................  Composite (wood and                  245
                                 plastic).
Floor Crossmembers b..........  Aluminum.............                250
Landing Gear..................  Aluminum.............                 50
Rear Door.....................  Aluminum.............                187
Rear Door Surround............  Aluminum.............                150
Roof Bows.....................  Aluminum.............                100
Side Posts....................  Aluminum.............                300
Slider Box....................  Aluminum.............                150
Upper Coupler Assembly........  Aluminum.............                430
------------------------------------------------------------------------
\a\ For tandem-axle suspension sub-frames made of aluminum, apply a
  weight reduction of 280 pounds. Use good engineering judgment to
  estimate a weight reduction for using aluminum sub-frames with other
  axle configurations.
\b\ Calculate a smaller weight reduction for short trailers by
  multiplying the indicated values by 0.528 (28/53).

* * * * *

0
150. Revise Sec.  1037.520 to read as follows:

Sec.  1037.520  Modeling CO2 emissions to show compliance for
vocational vehicles and tractors.

    This section describes how to use the Greenhouse gas Emissions
Model (GEM) (incorporated by reference in Sec.  1037.810) to show
compliance with the CO2 standards of Sec. Sec.  1037.105 and
1037.106 for vocational vehicles and tractors. Use GEM version 2.0.1 to
demonstrate compliance with Phase 1 standards; use GEM Phase 2, Version
3.5.1 to demonstrate compliance with Phase 2 standards. Use good
engineering judgment when demonstrating compliance using GEM. See Sec.
1037.515 for calculation procedures for demonstrating compliance with
trailer standards.
    (a) General modeling provisions. To run GEM, enter all applicable
inputs as specified by the model.
    (1) GEM inputs apply for Phase 1 standards as follows:
    (i) Model year and regulatory subcategory (see Sec.  1037.230).
    (ii) Coefficient of aerodynamic drag or drag area, as described in
paragraph (b) of this section (tractors only).
    (iii) Steer and drive tire rolling resistance, as described in
paragraph (c) of this section.
    (iv) Vehicle speed limit, as described in paragraph (d) of this
section (tractors only).
    (v) Vehicle weight reduction, as described in paragraph (e) of this
section (tractors only for Phase 1).
    (vi) Automatic engine shutdown systems, as described in Sec.
1037.660 (only for Class 8 sleeper cabs). Enter a GEM input value of
5.0 g/ton-mile, or an adjusted value as specified in Sec.  1037.660.
    (2) For Phase 2 vehicles, the GEM inputs described in paragraphs
(a)(1)(i) through (v) of this section continue to apply. Note that the
provisions in this part related to vehicle speed limiters and automatic
engine shutdown systems are available for vocational vehicles in Phase
2. The rest of this section describes additional GEM inputs for
demonstrating compliance with Phase 2 standards. Simplified versions of
GEM apply for limited circumstances as follows:
    (i) You may use default engine fuel maps for glider kits as
described in Sec.  1037.635.
    (ii) If you certify vehicles to the custom-chassis standards
specified in Sec.  1037.105(h), run GEM by identifying the vehicle type
and entering ``NA'' instead of what would otherwise apply for, tire
revolutions per mile, engine information, transmission information,
drive axle ratio, axle efficiency, and aerodynamic improvement as
specified in paragraphs (c)(1), (f), (g)(1) and (3), (i), and (m) of
this section, respectively. Incorporate other GEM inputs as specified
in this section.
    (b) Coefficient of aerodynamic drag and drag area for tractors.
Determine the appropriate drag area, CdA, for tractors as
described in this paragraph (b). Use the recommended method or an
alternate method to establish a value for CdA, expressed in
m\2\ to one decimal place, as specified in Sec.  1037.525. Where we
allow you to group multiple configurations together, measure
CdA of the worst-case configuration.
    (1) Except as specified in paragraph (b)(2) of this section,
determine the Phase 1 bin level for your vehicle based on measured
CdA values as shown in the following tables:

                      Table 1 to Sec.   1037.520--Cd Inputs for Phase 1 High-Roof Tractors
----------------------------------------------------------------------------------------------------------------
                                                                                If your
                                                                                measured  CDA   Then your CD
                 Tractor type                               Bin level               (M2) is . .   input is . . .

----------------------------------------------------------------------------------------------------------------
High-Roof Day Cabs............................  Bin I...........................           >=8.0            0.79
                                                Bin II..........................         7.1-7.9            0.72
                                                Bin III.........................         6.2-7.0            0.63
                                                Bin IV..........................         5.6-6.1            0.56
                                                Bin V...........................           <=5.5            0.51
High-Roof Sleeper Cabs........................  Bin I...........................           >=7.6            0.75
                                                Bin II..........................         6.8-7.5            0.68

                                                Bin III.........................         6.3-6.7            0.60
                                                Bin IV..........................         5.6-6.2            0.52
                                                Bin V...........................           <=5.5            0.47
----------------------------------------------------------------------------------------------------------------

                Table 2 to Sec.   1037.520--Cd Inputs for Phase 1 Low-Roof and Mid-Roof Tractors
----------------------------------------------------------------------------------------------------------------
                                                                                If your
                                                                                measured  CDA   Then your CD
                 Tractor type                               Bin level               (M2) is . .   input is . . .

----------------------------------------------------------------------------------------------------------------
Low-Roof Day and Sleeper Cabs.................  Bin I...........................           >=5.1            0.77
                                                Bin II..........................           <=5.0            0.71
Mid-Roof Day and Sleeper Cabs.................  Bin I...........................           >=5.6            0.87
                                                Bin II..........................           <=5.5            0.82
----------------------------------------------------------------------------------------------------------------

    (2) For Phase 1 low- and mid-roof tractors, you may instead
determine your drag area bin based on the drag area bin of an
equivalent high-roof tractor. If the high-roof tractor is in Bin I or
Bin II, then you may assume your equivalent low- and mid-roof tractors
are in Bin I. If the high-roof tractor is in Bin III, Bin IV, or Bin V,
then you may assume your equivalent low- and mid-roof tractors are in
Bin II.
    (3) For Phase 2 tractors other than heavy-haul tractors, determine
bin levels and CdA inputs as follows:
    (i) Determine bin levels for high-roof tractors based on
aerodynamic test results as specified in Sec.  1037.525 and summarized
in the following table:

                     Table 3 to Sec.   1037.520--Bin Determinations for Phase 2 High-Roof Tractors Based on Aerodynamic Test Results
                                                                      [CdA in m\2\]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                         Tractor type                             Bin I        Bin II      Bin III       Bin IV       Bin V        Bin VI      Bin VII
--------------------------------------------------------------------------------------------------------------------------------------------------------
Day Cabs.....................................................        >=7.2      6.6-7.1      6.0-6.5      5.5-5.9      5.0-5.4      4.5-4.9        <=4.4
Sleeper Cabs.................................................        >=6.9      6.3-6.8      5.7-6.2      5.2-5.6      4.7-5.1      4.2-4.6        <=4.1
--------------------------------------------------------------------------------------------------------------------------------------------------------

    (ii) For low- and mid-roof tractors, you may either use the same
bin level that applies for an equivalent high-roof tractor as shown in
Table 3 of this section, or you may determine your bin level based on
aerodynamic test results as described in Table 4 of this section.

               Table 4 to Sec.   1037.520--Bin Determinations for Phase 2 Low-Roof and Mid-Roof Tractors Based on Aerodynamic Test Results
                                                                      [CdA in m\2\]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                         Tractor type                             Bin I        Bin II      Bin III       Bin IV       Bin V        Bin VI      Bin VII
--------------------------------------------------------------------------------------------------------------------------------------------------------
Low-Roof Cabs................................................        >=5.4      4.9-5.3      4.5-4.8      4.1-4.4      3.8-4.0      3.5-3.7        <=3.4
Mid-Roof Cabs................................................        >=5.9      5.5-5.8      5.1-5.4      4.7-5.0      4.4-4.6      4.1-4.3        <=4.0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    (iii) Determine the CdA input according to the tractor's
bin level as described in the following table:

                                        Table 5 to Sec.   1037.520--Phase 2 CdA Tractor Inputs Based on Bin Level
--------------------------------------------------------------------------------------------------------------------------------------------------------
                         Tractor type                             Bin I        Bin II      Bin III       Bin IV       Bin V        Bin VI      Bin VII
--------------------------------------------------------------------------------------------------------------------------------------------------------
High-Roof Day Cabs...........................................         7.45         6.85         6.25         5.70         5.20         4.70         4.20
High-Roof Sleeper Cabs.......................................         7.15         6.55         5.95         5.40         4.90         4.40         3.90
Low-Roof Cabs................................................         6.00         5.60         5.15         4.75         4.40         4.10         3.80
Mid-Roof Cabs................................................         7.00         6.65         6.25         5.85         5.50         5.20         4.90
--------------------------------------------------------------------------------------------------------------------------------------------------------

    (4) Note that, starting in model year 2027, GEM internally reduces
CdA for high-roof tractors by 0.3 m2 to simulate adding a
rear fairing to the standard trailer.
    (c) Tire revolutions per mile and rolling resistance. You must have
a tire revolutions per mile (TRPM) and a tire rolling resistance level
(TRRL) for each tire configuration. For purposes of this section, you
may consider tires with the same SKU number to be the same
configuration. Determine TRRL input values separately for drive and
steer tires; determine TRPM only for drive tires.
    (1) Use good engineering judgment to determine a tire's revolutions
per mile to the nearest whole number as specified in SAE J1025
(incorporated by reference in Sec.  1037.810). Note that for tire sizes
that you do not test, we will treat your analytically derived
revolutions per mile the same as test results, and we may perform our
own testing to verify your values. We may require you to test a sample
of additional tire sizes that we select.
    (2) Measure tire rolling resistance in kg per metric ton as
specified in ISO 28580 (incorporated by reference in Sec.  1037.810),
except as specified in this paragraph (c). Use good engineering
judgment to ensure that your test results are not biased low. You may
ask us to identify a reference test laboratory to which you may
correlate your test results. Prior to beginning the test procedure in
Section 7 of ISO 28580 for a new bias-ply tire, perform a break-in
procedure by running the tire at the specified test speed, load, and
pressure for 60  2 minutes.
    (3) For each tire design tested, measure rolling resistance of at
least three different tires of that specific design and size. Perform
the test at least once for each tire. Calculate the arithmetic mean of
these results to the nearest 0.1 kg/tonne and use this value or any
higher value as your GEM input for TRRL. You must test at least one
tire size for each tire model, and may use engineering analysis to
determine the rolling resistance of other tire sizes of that model.
Note that for tire sizes that you do not test, we will treat your
analytically derived rolling resistances the same as test results, and
we may perform our own testing to verify your values. We may require
you to test a small sub-sample of untested tire sizes that we select.
    (4) If you obtain your test results from the tire manufacturer or
another third party, you must obtain a signed statement from the party
supplying those test results to verify that tests were conducted
according to the requirements of this part. Such statements are deemed
to be submissions to EPA.
    (5) For tires marketed as light truck tires that have load ranges
C, D, or E, use as the GEM input TRRL multiplied by 0.87.
    (6) For vehicles with at least three drive axles or for vehicles
with more than three axles total, use good engineering judgment to
combine tire rolling resistance into three values (steer, drive 1, and
drive 2) for use in GEM. This may require performing a weighted average
of tire rolling resistance from multiple axles based on the typical
load on each axle. For liftable axles, calculate load- and time-
weighted values to represent the load and the amount of time these
tires are in contact with the ground during typical in-use operation.
    (7) For vehicles with a single rear axle, enter ``NA'' as the TRRL
value for drive axle 2.
    (d) Vehicle speed limit. If the vehicles will be equipped with a
vehicle speed limiter, input the maximum vehicle speed to which the
vehicle will be limited (in miles per hour rounded to the nearest 0.1
mile per hour) as specified in Sec.  1037.640. Use good engineering
judgment to ensure the limiter is tamper resistant. We may require you
to obtain preliminary approval for your designs.
    (e) Vehicle weight reduction. Develop a weight-reduction as a GEM
input as described in this paragraph (e). Enter the sum of weight
reductions as described in this paragraph (e), or enter zero if there
is no weight reduction. For purposes of this paragraph (e), high-
strength steel is steel with tensile strength at or above 350 MPa.
    (1) Vehicle weight reduction inputs for wheels are specified
relative to dual-wide tires with conventional steel wheels. For
purposes of this paragraph (e)(1), an aluminum alloy qualifies as
light-weight if a dual-wide drive wheel made from this material weighs
at least 21 pounds less than a comparable conventional steel wheel. The
inputs are listed in Table 6 of this section. For example, a tractor or
vocational vehicle with aluminum steer wheels and eight (4x2) dual-wide
aluminum drive wheels would have an input of 210 pounds (2x21 + 8x21).

       Table 6 to Sec.   1037.520--Wheel-Related Weight Reductions
------------------------------------------------------------------------
                                           Weight            Weight
                                         reduction--       reduction--
     Weight-reduction technology       phase 1 (lb per   phase 2 (lb per
                                           wheel)            wheel)
------------------------------------------------------------------------
Wide-Base Single Drive Tire with . .
 .\a\
    Steel Wheel.....................                84                84
    Aluminum Wheel..................               139               147
    Light-Weight Aluminum Alloy                    147               147
     Wheel..........................
Wide-Base Single Trailer Tire with .
 . .\a\
    Steel Wheel.....................  ................                84
    Aluminum or Aluminum Alloy Wheel  ................               131
Steer Tire, Dual-wide Drive Tire, or
 Dual-wide Trailer Tire with . . .
    High-Strength Steel Wheel.......                 8                 8
    Aluminum Wheel..................                21                25
    Light-Weight Aluminum Alloy                     30                25
     Wheel..........................
------------------------------------------------------------------------
\a\ The weight reduction for wide-base tires accounts for reduced tire
  weight relative to dual-wide tires.

    (2) Weight reduction inputs for tractor components other than
wheels are specified in the following table:

     Table 7 to Sec.   1037.520--Nonwheel-Related Weight Reductions From Alternative Materials for Tractors
                                                    [Pounds]
----------------------------------------------------------------------------------------------------------------
                                                                                High-strength
                 Weight reduction technologies                     Aluminum          steel        Thermoplastic
----------------------------------------------------------------------------------------------------------------
Door..........................................................              20                6  ...............
Roof..........................................................              60               18  ...............
Cab rear wall.................................................              49               16  ...............
Cab floor.....................................................              56               18  ...............
Hood Support Structure System.................................              15                3  ...............
Hood and Front Fender.........................................  ..............  ...............               65
Day Cab Roof Fairing..........................................  ..............  ...............               18
Sleeper Cab Roof Fairing......................................              75               20               40
Aerodynamic Side Extender.....................................  ..............  ...............               10
Fairing Support Structure System..............................              35                6  ...............
Instrument Panel Support Structure............................               5                1  ...............
Brake Drums--Drive (set of 4).................................             140               74  ...............
Brake Drums--Non Drive (set of 2).............................              60               42  ...............
Frame Rails...................................................             440               87  ...............
Crossmember--Cab..............................................              15                5  ...............
Crossmember--Suspension.......................................              25                6  ...............
Crossmember--Non Suspension (set of 3)........................              15                5  ...............
Fifth Wheel...................................................             100               25  ...............
Radiator Support..............................................              20                6  ...............
Fuel Tank Support Structure...................................              40               12  ...............
Steps.........................................................              35                6  ...............
Bumper........................................................              33               10  ...............
Shackles......................................................              10                3  ...............
Front Axle....................................................              60               15  ...............
Suspension Brackets, Hangers..................................             100               30  ...............
Transmission Case.............................................              50               12  ...............
Clutch Housing................................................              40               10  ...............
Fairing Support Structure System..............................              35                6  ...............
Drive Axle Hubs (set of 4)....................................              80               20  ...............
Non Drive Hubs (2)............................................              40                5  ...............
Two-piece driveshaft..........................................              20                5  ...............
Transmission/Clutch Shift Levers..............................              20                4  ...............
----------------------------------------------------------------------------------------------------------------

    (3) Weight-reduction inputs for vocational-vehicle components other
than wheels are specified in the following table:

Table 8 to Sec.   1037.520--Nonwheel-Related Weight Reductions From Alternative Materials for Phase 2 Vocational
                                                    Vehicles
                                                  [Pounds] \a\
----------------------------------------------------------------------------------------------------------------
                                                                                Vehicle type
                                                                          --------------------------------------
                 Component                             Material                          Medium HDV
                                                                            Light HDV       \b\       Heavy HDV
----------------------------------------------------------------------------------------------------------------
Axle Hubs--Non-Drive......................  Aluminum.....................             40                      40
Axle Hubs--Non-Drive......................  High Strength Steel..........              5                       5
Axle--Non-Drive...........................  Aluminum.....................             60                      60
Axle--Non-Drive...........................  High Strength Steel..........             15                      15
Brake Drums--Non-Drive....................  Aluminum.....................             60                      60
Brake Drums--Non-Drive....................  High Strength Steel..........             42                      42
Axle Hubs--Drive..........................  Aluminum.....................             40                      80
Axle Hubs--Drive..........................  High Strength Steel..........             10                      20
Brake Drums--Drive........................  Aluminum.....................             70                     140
Brake Drums--Drive........................  High Strength Steel..........             37                      74
Suspension Brackets, Hangers..............  Aluminum.....................             67                     100
Suspension Brackets, Hangers..............  High Strength Steel..........             20                      30
----------------------------------------------------------------------------------------------------------------
Crossmember--Cab..........................  Aluminum.....................           10           15           15
Crossmember--Cab..........................  High Strength Steel..........            2            5            5
Crossmember--Non-Suspension...............  Aluminum.....................           15           15           15
Crossmember--Non-Suspension...............  High Strength Steel..........            5            5            5
Crossmember--Suspension...................  Aluminum.....................           15           25           25
Crossmember--Suspension...................  High Strength Steel..........            6            6            6
Driveshaft................................  Aluminum.....................           12           40           50
Driveshaft................................  High Strength Steel..........            5           10           12
Frame Rails...............................  Aluminum.....................          120          300          440

Frame Rails...............................  High Strength Steel..........           40           40           87
----------------------------------------------------------------------------------------------------------------
\a\ Weight-reduction values apply per vehicle unless otherwise noted.
\b\ For Medium HDV with 6x4 or 6x2 axle configurations, use the values for Heavy HDV.

    (4) Apply vehicle weight inputs for changing technology
configurations as follows:
    (i) For Class 8 tractors or for Class 8 vocational vehicles with a
permanent 6x2 axle configuration, apply a weight reduction input of 300
pounds. However, apply no weight reduction for coach buses certified to
custom-chassis standards under Sec.  1037.105(h).
    (ii) For Class 8 tractors with 4x2 axle configuration, apply a
weight reduction input of 400 pounds.
    (iii) For tractors with installed engines with displacement below
14.0 liters, apply a weight reduction of 300 pounds.
    (iv) For tractors with single-piece driveshafts with a total length
greater than 86 inches, apply a weight reduction of 43 pounds for steel
driveshafts and 63 pounds for aluminum driveshafts.
    (5) You may ask to apply the off-cycle technology provisions of
Sec.  1037.610 for weight reductions not covered by this paragraph (e).
    (f) Engine characteristics. Enter information from the engine
manufacturer to describe the installed engine and its operating
parameters as described in 40 CFR 1036.503. The fuel-mapping
information must apply for the vehicle's GVWR; for example, if you
install a medium heavy-duty engine in a Class 8 vehicle, the engine
must have additional fuel-mapping information for the heavier vehicle.
Note that you do not need fuel consumption at idle for tractors.
    (g) Vehicle characteristics. Enter the following information to
describe the vehicle and its operating parameters:
    (1) Transmission make, model, and type. Also identify the gear
ratio for every available forward gear to two decimal places, the input
torque limit for each of the forward gears, and, if applicable, the
lowest gear involving a locked torque converter. Count forward gears as
being available only if the vehicle has the hardware and software to
allow operation in those gears. For vehicles with a manual
transmission, GEM applies a 2% emission increase relative to automated
manual transmissions. If your vehicle has a dual-clutch transmission,
use good engineering judgment to determine if it can be accurately
represented in GEM as an automated manual transmission. We may require
you to perform a powertrain test with dual-clutch transmissions to show
that they can be properly simulated as an automated manual
transmission.
    (2) Drive axle make, model, and configuration. Select a drive axle
configuration to represent your vehicle for modeling.
    (i) 4x2: One drive axle and one non-drive axle. This includes
vehicles with two drive axles where one of the drive axles is
disconnectable and that disconnectable drive axle is designed to be
connected only when the vehicle is driven off-road or in slippery
conditions if at least one of the following is true:
    (A) The input and output of the disconnectable axle is mechanically
disconnected from the drive shaft and the wheels when the axle is in
4x2 configuration.
    (B) You provide power loss data generated according to Sec.
1037.560 for the combination of both drive axles, where the
disconnectable drive axle is in the disconnected configuration.
    (ii) 6x2: One drive axle and two non-drive axles.
    (iii) 6x4: Two or more drive axles, or more than three total axles.
Note that this includes, for example, a vehicle with two drive axles
out of four total axles (otherwise known as an 8x4 configuration).
    (iv) 6x4D: One non-drive axle and two drive axles where one of the
two drive axles is automatically disconnectable such that the axle can
switch between 6x2 and 6x4 configurations. You may select this
configuration only if at least one of the following is true:
    (A) The input and output of the disconnectable axle is mechanically
disconnected from the drive shaft and the wheels when the axle is in
the 6x2 configuration.
    (B) You provide power loss data generated according to Sec.
1037.560 for the combination of both drive axles, where the
disconnectable drive axle is in the disconnected configuration.
    (3) Drive axle ratio, ka. If a vehicle is designed with
two or more user-selectable axle ratios, use the drive axle ratio that
is expected to be engaged for the greatest driving distance. If the
vehicle does not have a drive axle, such as a hybrid vehicle with
direct electric drive, let ka = 1.
    (4) GEM inputs associated with powertrain testing include
powertrain family, transmission calibration identifier, test data from
Sec.  1037.550, and the powertrain test configuration (dynamometer
connected to transmission output or wheel hub). You do not need to
identify or provide inputs for transmission gear ratios, fuel map data,
or engine torque curves, which would otherwise be required under
paragraph (f) of this section.
    (h) Idle speed and idle-reduction technologies. The following
provisions apply for engine idling:
    (1) For engines with no adjustable warm idle speed, input vehicle
idle speed as the manufacturer's declared warm idle speed. For engines
with adjustable warm idle speed, input your vehicle idle speed as
follows:

------------------------------------------------------------------------
                                                          Your default
                                  And your engine is      vehicle idle
  If your vehicle is a . . .       subject to . . .       speed is . .
                                                              .\1\
------------------------------------------------------------------------
(i) Heavy HDV.................  compression-ignition    600 r/min.
                                 or spark-ignition
                                 standards.
(ii) Medium HDV tractor.......  compression-ignition    700 r/min.
                                 standards.
(iii) Light HDV or Medium HDV   compression-ignition    750 r/min.
 vocational vehicle.             standards.

(iv) Light HDV or Medium HDV..  spark-ignition          600 r/min.
                                 standards.
------------------------------------------------------------------------
\1\ If the default idle speed is above or below the engine
  manufacturer's whole range of declared warm idle speeds, use the
  manufacturer's maximum or minimum declared warm idle speed,
  respectively, instead of the default value.

    (2) Identify whether your vehicle has qualifying idle-reduction
technologies, subject to the qualifying criteria in Sec.  1037.660, as
follows:
    (i) Stop-start technology and automatic engine shutdown systems
apply for vocational vehicles. See paragraph (j) of this section for
automatic engine shutdown systems for tractors.
    (ii) Neutral idle applies for tractors and vocational vehicles.
    (i) Axle, transmission, and torque converter characterization. You
may characterize the axle, transmission, and torque converter using
axle efficiency maps as described in Sec.  1037.560, transmission
efficiency maps as described in Sec.  1037.565, and torque converter
capacity factors and torque ratios as described in Sec.  1037.570 to
replace the default values in GEM. If you obtain your test results from
the axle manufacturer, transmission manufacturer, torque converter
manufacturer or another third party, you must obtain a signed statement
from the party supplying those test results to verify that tests were
conducted according to the requirements of this part. Such statements
are deemed to be submissions to EPA.
    (j) Additional reduction technologies. Enter input values in GEM as
follows to characterize the percentage CO2 emission
reduction corresponding to certain technologies and vehicle
configurations, or enter 0:
    (1) Intelligent controls. Enter 2 for tractors with predictive
cruise control. This includes any cruise control system that
incorporates satellite-based global-positioning data for controlling
operator demand. For other tractors, enter 1.5 if they have neutral
coasting, unless good engineering judgment indicates that a lower
percentage should apply.
    (2) Accessory load. Enter the following values related to accessory
loads; if more than one item applies, enter the sum of those values:
    (i) If vocational vehicles have electrically powered pumps for
steering, enter 0.5 for vocational vehicles certified with the Regional
duty cycle, and enter 1 for other vocational vehicles.
    (ii) If tractors have electrically powered pumps for both steering
and engine cooling, enter 1.
    (iii) If vehicles have a high-efficiency air conditioning
compressor, enter 0.5 for tractors and vocational Heavy HDV, and enter
1 for other vocational vehicles. This includes all electrically powered
compressors. It also include mechanically powered compressors if the
coefficient of performance improves by 10 percent or greater over the
baseline design, consistent with the provisions for improved
evaporators and condensers in 40 CFR 86.1868-12(h)(5).
    (3) Tire-pressure systems. Enter 1.2 for vehicles with automatic
tire inflation systems on all axles (1.1 for Multi-Purpose and Urban
vocational vehicles). Enter 1.0 for vehicles with tire pressure
monitoring systems on all axles (0.9 for Multi-Purpose and Urban
vocational vehicles). If vehicles use a mix of the two systems, treat
them as having only tire pressure monitoring systems.
    (4) Extended-idle reduction. Enter values as shown in the following
table for sleeper cabs equipped with idle-reduction technology meeting
the requirements of Sec.  1037.660 that are designed to automatically
shut off the main engine after 300 seconds or less:

      Table 9 to Sec.   1037.520--GEM Input Values for AES Systems
------------------------------------------------------------------------
                                                    GEM input values
                                               -------------------------
                  Technology                                   Tamper-
                                                 Adjustable   resistant
------------------------------------------------------------------------
Standard AES system...........................            1            4
With diesel APU...............................            3            4
With battery APU..............................            5            6
With automatic stop-start.....................            3            3
With fuel-operated heater (FOH)...............            2            3
With diesel APU and FOH.......................            4            5
With battery APU and FOH......................            5            6
With stop-start and FOH.......................            4            5
------------------------------------------------------------------------

    (5) Other. Additional GEM inputs may apply as follows:
    (i) Enter 0.9 and 1.7, respectively, for school buses and coach
buses that have at least seven available forward gears.
    (ii) If we approve off-cycle technology under Sec.  1037.610 in the
form of an improvement factor, enter the improvement factor expressed
as a percentage reduction in CO2 emissions. (Note: In the
case of approved off-cycle technologies whose benefit is quantified as
a g/ton-mile credit, apply the credit to the GEM result, not as a GEM
input value.)
    (k) Vehicles with hybrid power take-off. For vocational vehicles,
determine the delta PTO emission result of your engine and hybrid power
take-off system as described in Sec.  1037.540.
    (l) [Reserved]
    (m) Aerodynamic improvements for vocational vehicles. For
vocational vehicles certified using the Regional duty cycle, enter
[Delta]CdA values to account for using aerodynamic devices
as follows:
    (1) Enter 0.2 for vocational vehicles with an installed rear
fairing if the vehicle is at least 7 m long with a minimum frontal area
of 8 m2.
    (2) For vehicles at least 11 m long with a minimum frontal area of
9 m2, enter 0.5 if the vehicle has both skirts and a front
fairing, and enter 0.3 if it has only one of those devices.
    (3) You may determine input values for these or other technologies
based on

aerodynamic measurements as described in Sec.  1037.527.
    (n) Alternate fuels. For fuels other than those identified in GEM,
perform the simulation by identifying the vehicle as being diesel-
fueled if the engine is subject to the compression-ignition standard,
or as being gasoline-fueled if the engine is subject to the spark-
ignition standards. Correct the engine or powertrain fuel map for mass-
specific net energy content as described in 40 CFR 1036.535(b).

0
151. Revise Sec.  1037.525 to read as follows:

Sec.  1037.525  Aerodynamic measurements for tractors.

    This section describes a methodology for quantifying aerodynamic
drag for use in determining input values for tractors as described in
Sec.  1037.520. This coastdown testing is the reference method for
aerodynamic measurements.
    (a) General provisions. The GEM input for a tractor's aerodynamic
performance is a Cd value for Phase 1 and a CdA
value for Phase 2. The input value is measured or calculated for a
tractor in a specific test configuration with a trailer, such as a
high-roof tractor with a box van meeting the requirements for the
standard trailer.
    (1) Aerodynamic measurements may involve any of several different
procedures. Measuring with different procedures introduces variability,
so we identify the coastdown method in Sec.  1037.528 as the primary
(or reference) procedure. You may use other procedures with our advance
approval as described in paragraph (d) of this section, but we require
that you adjust your test results from other test methods to correlate
with coastdown test results. All adjustments must be consistent with
good engineering judgment. Submit information describing how you
quantify aerodynamic drag from coastdown testing, whether or not you
use an alternate method.
    (2) Test high-roof tractors with a standard trailer as described in
Sec.  1037.501(g)(1). Note that the standard trailer for Phase 1
tractors is different from that of later model years. Note also that
GEM may model a different configuration than the test configuration,
but accounts for this internally. Test low-roof and mid-roof tractors
without a trailer; however, you may test low-roof and mid-roof tractors
with a trailer to evaluate off-cycle technologies.
    (b) Adjustments to correlate with coastdown testing. Adjust
aerodynamic drag values from alternate methods to be equivalent to the
corresponding values from coastdown measurements as follows:
    (1) Determine the functional relationship between your alternate
method and coastdown testing. Specify this functional relationship as
Falt-aero for a given alternate drag measurement method. The
effective yaw angle, [psi]eff, is assumed to be zero degrees
for Phase 1. For Phase 2, determine [psi]eff from coastdown
test results using the following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.116

Where:

CdAcoastdown([psi]eff) = the
average drag area measured during coastdown at an effective yaw
angle, [psi]eff.
    CdAalt([psi]eff) = the average
drag area calculated from an alternate drag measurement method at an
effective yaw angle, [psi]eff.

    (2) Unless good engineering judgment dictates otherwise, assume
that coastdown drag is proportional to drag measured using alternate
methods and apply a constant adjustment factor, Falt-aero,
for a given alternate drag measurement method of similar vehicles.
    (3) Determine Falt-aero by performing coastdown testing
and applying your alternate method on the same vehicles. Consider all
applicable test data including data collected during selective
enforcement audits. Unless we approve another vehicle, one vehicle must
be a Class 8 high-roof sleeper cab with a full aerodynamics package
pulling a standard trailer. Where you have more than one tractor model
meeting these criteria, use the tractor model with the highest
projected sales. If you do not have such a tractor model, you may use
your most comparable tractor model with our prior approval. In the case
of alternate methods other than those specified in this subpart, good
engineering judgment may require you to determine your adjustment
factor based on results from more than the specified minimum number of
vehicles.
    (4) Measure the drag area using your alternate method for a Phase 2
tractor used to determine Falt-aero with testing at yaw
angles of 0[deg], 1[deg], 3[deg], 4.5[deg], 6[deg], and 9[deg] (you may
include additional angles), using direction conventions described in
Figure 2 of SAE J1252 (incorporated by reference in Sec.  1037.810).
Also, determine the drag area at the coastdown effective yaw angle,
CdAalt([psi]eff), by taking the
average drag area at [psi]eff and -[psi]eff for
your vehicle using the same alternate method.
    (5) For Phase 2 testing, determine separate values of
Falt-aero for at least one high-roof day cab and one high-
roof sleeper cab for model year 2021, for at least two high-roof day
cabs and two high-roof sleeper cabs for model year 2024, and for at
least three high-roof day cabs and three high-roof sleeper cabs for
model year 2027. These test requirements are cumulative; for example,
you may meet these requirements by testing two vehicles to support
model year 2021 certification and four additional vehicles to support
model year 2023 certification. For any untested tractor models, apply
the value of Falt-aero from the tested tractor model that
best represents the aerodynamic characteristics of the untested tractor
model, consistent with good engineering judgment. Testing under this
paragraph (b)(5) continues to be valid for later model years until you
change the tractor model in a way that causes the test results to no
longer represent production vehicles. You must also determine unique
values of Falt-aero for low-roof and mid-roof tractors if
you determine CdA values based on low or mid-roof tractor
testing as shown in Table 4 of Sec.  1037.520. For Phase 1 testing, if
good engineering judgment allows it, you may calculate a single,
constant value of Falt-aero for your whole product line by
dividing the coastdown drag area, CdAcoastdown,
by drag area from your alternate method, CdAalt.
    (6) Determine Falt-aero to at least three decimal
places. For example, if your coastdown testing results in a drag area
of 6.430, but your wind tunnel method results in a drag area of 6.200,
Falt-aero would be 1.037 (or a higher value you declare).
    (7) If a tractor and trailer cannot be configured to meet the gap
requirements specified in Sec.  1037.501(g)(1)(ii), test with the
trailer positioned as close as possible to the specified gap dimension
and use good engineering judgment to correct the results to be
equivalent to a test configuration meeting the specified gap dimension.
For example, we may allow you to correct your test output using an
approved alternate method or substitute a test vehicle that is capable
of meeting the required specifications and is otherwise aerodynamically
equivalent. This allowance applies for certification, confirmatory
testing, SEA, and all other testing to demonstrate compliance with
standards.
    (8) You may ask us for preliminary approval of your coastdown
testing under Sec.  1037.210. We may witness the testing.

    (c) Yaw sweep corrections. Aerodynamic features can have a
different effectiveness for reducing wind-averaged drag than is
predicted by zero-yaw drag. The following procedures describe how to
determine a tractor's CdA values to account for wind-
averaged drag as specified in Sec.  1037.520:
    (1) Apply the following method for all Phase 2 testing with an
alternate method:
    (i) Calculate the wind-averaged drag area from the alternate
method, CdAwa-alt, using an average of
measurements at -4.5 and +4.5 degrees.
    (ii) Determine your wind-averaged drag area,
CdAwa, rounded to one decimal place, using the
following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.117

    (2) Apply the following method for Phase 2 coastdown testing other
than coastdown testing used to establish Falt-aero:
    (i) Determine your drag area at the effective yaw angle from
coastdown, CdAcoastdown([psi]eff).
    (ii) Use an alternate method to calculate the ratio of the wind-
averaged drag area, CdAwa-alt (using an average
of measurements at -4.5 and +4.5 degrees) to the drag area at the
effective yaw angle, CdAalt([psi]eff).
    (iii) Determine your wind-averaged drag area,
CdAwa, rounded to one decimal place, using the
following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.118

    (3) Different approximations apply for Phase 1. For Phase 1
testing, you may correct your zero-yaw drag area as follows if the
ratio of the zero-yaw drag area divided by yaw-sweep drag area for your
vehicle is greater than 0.8065 (which represents the ratio expected for
a typical Class 8 high-roof sleeper cab):
    (i) Determine the zero-yaw drag area, CdAzero-
yaw, and the yaw-sweep drag area for your vehicle using the same
alternate method as specified in this subpart. Measure the drag area
for 0[deg], -6[deg], and +6[deg]. Use the arithmetic mean of the -
6[deg] and +6[deg] drag areas as the 6[deg] drag area,
CdA<plus-minus>6.
    (ii) Calculate your yaw-sweep correction factor, CFys,
using the following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.119

    (iii) Calculate your corrected drag area for determining the
aerodynamic bin by multiplying the measured zero-yaw drag area by
CFys, as determined using Eq. 1037.525-4, as applicable. You
may apply the correction factor to drag areas measured using other
procedures. For example, apply CFys to drag areas measured
using the coastdown method. If you use an alternate method, apply an
alternate correction, Falt-aero, and calculate the final
drag area using the following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.120

    (iv) You may ask us to apply CFys to similar vehicles
incorporating the same design features.
    (v) As an alternative, you may calculate the wind-averaged drag
area according to SAE J1252 (incorporated by reference in Sec.
1037.810) and substitute this value into Eq. 1037.525-4 for the 6[deg] drag area.
    (d) Approval of alternate methods. You must obtain preliminary
approval before using any method other than coastdown testing to
quantify aerodynamic drag. We will approve your request if you show
that your procedures produce data that are the same as or better than
coastdown testing with respect to repeatability and unbiased
correlation. Note that the correlation is not considered to be biased
if there is a bias before correction, but you remove the bias using
Falt-aero. Send your request for approval to the Designated
Compliance Officer. Keep records of the information specified in this
paragraph (d). Unless we specify otherwise, include this information
with your request. You must provide any information we require to
evaluate whether you may apply the provisions of this section. Include
additional information related to your alternate method as described in
Sec. Sec.  1037.530 through 1037.534. If you use a method other than
those specified in this subpart, include all the following information,
as applicable:
    (1) Official name/title of the procedure.
    (2) Description of the procedure.
    (3) Cited sources for any standardized procedures that the method
is based on.
    (4) Description and rationale for any modifications/deviations from
the standardized procedures.
    (5) Data comparing the procedure to the coastdown reference
procedure.
    (6) Additional information specified for the alternate methods
described in Sec. Sec.  1037.530 through 1037.534 as applicable to this
method (e.g., source location/address, background/history).

0
152. Amend Sec.  1037.528 by revising the introductory text and
paragraphs (a), (c) introductory text, (e) introductory text, (g)(3)
introductory text, (h)(3)(i), (h)(6), and (h)(12)(v) to read as
follows:

Sec.  1037.528  Coastdown procedures for calculating drag area (CdA).

    The coastdown procedures in this section describe how to calculate
drag area, CdA, for Phase 2 tractors, trailers, and
vocational vehicles, subject to the provisions of Sec. Sec.  1037.525
through 1037.527. These procedures are considered the reference method
for tractors, but an alternate method for trailers. Follow the
provisions of Sections 1 through 9 of SAE J2263 (incorporated by
reference in Sec.  1037.810), with the clarifications and exceptions
described in this section. Several of these exceptions are from SAE
J1263 (incorporated by reference in Sec.  1037.810). The coastdown
procedures in 40 CFR 1066.310 apply instead of the provisions of this
section for Phase 1 tractors.
    (a) The terms and variables identified in this section have the
meaning given in SAE J1263 and SAE J2263 unless specified otherwise.
* * * * *
    (c) The test condition specifications described in Sections 7.1
through 7.4 of

SAE J1263 apply, with certain exceptions and additional provisions as
described in this paragraph (c). These conditions apply to each run
separately.
* * * * *
    (e) Measure wind speed, wind direction, air temperature, and air
pressure at a recording frequency of 10 Hz, in conjunction with time-
of-day data. Use at least one stationary anemometer and suitable data
loggers meeting SAE J1263 specifications, subject to the following
additional specifications for the anemometer placed along the test
surface:
* * * * *
    (g) * * *
    (3) Correct measured air direction from all the high-speed segments
using the wind speed and wind direction measurements described in
paragraph (e) of this section as follows:
* * * * *
    (h) * * *
    (3) * * *
    (i) Calculate the mean vehicle speed to represent the start point
of each speed range as the arithmetic average of measured speeds
throughout the continuous time interval that begins when measured
vehicle speed is less than 2.00 mi/hr above the nominal starting speed
point and ends when measured vehicle speed reaches 2.00 mi/hr below the
nominal starting speed point, expressed to at least two decimal places.
Calculate the timestamp corresponding to the starting point of each
speed range as the average timestamp of the interval.
* * * * *
    (6) For tractor testing, calculate the tire rolling resistance
force at high and low speeds for steer, drive, and trailer axle
positions, FTRR[speed,axle], and determine
[Delta]FTRR, the rolling resistance difference between 65
mi/hr and 15 mi/hr, for each tire as follows:
    (i) Conduct a stepwise coastdown tire rolling resistance test with
three tires for each tire model installed on the vehicle using SAE
J2452 (incorporated by reference in Sec.  1037.810) for the following
test points (which replace the test points in Table 3 of SAE J2452):

     Table 1 of Sec.   1037.528--Stepwise Coastdown Test Points for
       Determining Tire Rolling Resistance as a Function of Speed
------------------------------------------------------------------------
                                                              Inflation
                  Step Number                   Load  (% of    pressure
                                                    max)      (% of max)
------------------------------------------------------------------------
1.............................................           20          100
2.............................................           55           70
3.............................................           85          120
4.............................................           85          100
5.............................................          100           95
------------------------------------------------------------------------

    (ii) Calculate FTRR[speed,axle] using the following equation:
    [GRAPHIC] [TIFF OMITTED] TR29JN21.121

Where:

nt,[axle] = number of tires at the axle position.
p[axle] = the inflation pressure set and measured on the
tires at the axle position at the beginning of the coastdown test.
L[axle] = the load over the axle at the axle position on
the coastdown test vehicle.
[alpha][axle], [beta][axle],
a[axle], b[axle], and c[axle] =
regression coefficients from SAE J2452 that are specific to axle
position.

Example:

nt,steer = 2
psteer = 758.4 kPa
Lsteer = 51421.2 N
[alpha]steer = -0.2435
[beta]steer = 0.9576
asteer = 0.0434
bsteer = 5.4[middot]10-5
csteer = 5.53[middot]10-7
nt,drive = 8
pdrive = 689.5 kPa
Ldrive = 55958.4 N
[alpha]drive = -0.3146
[beta]drive = 0.9914
adrive = 0.0504
bdrive = 1.11[middot]10-4
cdrive = 2.86[middot]10-7
nt,trailer = 8
ptrailer = 689.5 kPa
Ltrailer = 45727.5 N
[alpha]trailer = -0.3982
[beta]trailer = 0.9756
atrailer = 0.0656
btrailer = 1.51[middot]10-4
ctrailer = 2.94[middot]10-7
vseghi = 28.86 m/s = 103.896 km/hr
vseglo = 5.84 m/s = 21.024 km/hr
[GRAPHIC] [TIFF OMITTED] TR29JN21.122

FTRRhi,steer = 365.6 N
FTRRhi,drive = 431.4 N
FTRRhi,trailer = 231.7 N
FTRRlo,steer = 297.8 N
FTRRlo,drive = 350.7 N
FTRRlo,trailer = 189.0 N

    (iii) Calculate FTRR[speed] by summing the tire rolling
resistance calculations at a given speed for each axle position:
[GRAPHIC] [TIFF OMITTED] TR29JN21.123

Example:

FTRRhi = 365.6 + 431.4 + 231.7 = 1028.7 N
FTRRlo = 297.8 + 350.7 + 189.0 = 837.5 N

    (iv) Adjust FTRR[speed] to the ambient temperature
during the coastdown segment as follows:
[GRAPHIC] [TIFF OMITTED] TR29JN21.124

Where:

    Tseg[speed] = the average ambient temperature during
the coastdown segment, in [deg]C.

Example:

FTRRhi = 1028.7 N
FTRRlo = 837.5 N
Tseghi = 25.5 [deg]C
Tseglo = 25.1 [deg]C
FTRRhi,adj = 1 + 0.006[middot](24-25.5)] = 1019.4 N
FTRRlo,adj = 837.5[middot][1 + 0.006[middot](24-25.1] =
832.0 N
    (v) Determine the difference in rolling resistance between 65 mph
and 15 mph, [Delta]FTRR, for each tire. Use good engineering
judgment to consider the multiple results. For example, you may ignore
the test results for the tires with the highest and lowest differences
and use the result from the remaining tire. Determine
[Delta]FTRR as follows:
[GRAPHIC] [TIFF OMITTED] TR29JN21.125

Example:

[Delta]FTRR = 1019.4-832.0 = 187.4 N

* * * * *
    (12) * * *
    (v) For the same set of points, recalculate the mean
CdA. This is the final result of the coastdown test,
CdAcoastdown([psi]eff).
* * * * *

0
153. Amend Sec.  1037.530 by revising paragraph (d)(7) to read as
follows:

Sec.  1037.530  Wind-tunnel procedures for calculating drag area (CdA).

* * * * *
    (d) * * *
    (7) Fan section description: fan type, diameter, power, maximum
angular speed, maximum speed, support type, mechanical drive, and
sectional total weight.
* * * * *

0
154. Amend Sec.  1037.532 by revising paragraph (a) to read as follows:

Sec.  1037.532  Using computational fluid dynamics to calculate drag
area (CdA).

* * * * *
    (a) For Phase 2 vehicles, use SAE J2966 (incorporated by reference
in Sec.  1037.810), with the following clarifications and exceptions:
    (1) Vehicles are subject to the requirement to meet standards based
on the average of testing at yaw angles of +4.5[deg] and -4.5[deg];
however, you may submit your application for certification with CFD
results based on only one of those yaw angles.
    (2) For CFD code with a Navier-Stokes based solver, follow the
additional steps in paragraph (d) of this section. For Lattice-
Boltzmann based CFD code, follow the additional steps in paragraph (e)
of this section.
    (3) Simulate a Reynolds number of 5.1 million (based on a 102-inch
trailer width) and an air speed of 65 mi/hr.
    (4) Perform an open-road simulation (not the Wind Tunnel
Simulation).
    (5) Use a free stream turbulence intensity of 0.0%.
    (6) Choose time steps that can accurately resolve intrinsic flow
instabilities, consistent with good engineering judgment.
    (7) The result must be drag area (CdA), not drag
coefficient (Cd), based on an air speed of 65 mi/hr.
    (8) Submit information as described in paragraph (g) of this
section.
* * * * *

0
155. Amend Sec.  1037.534 by revising paragraph (c)(1) and (2),
(d)(4)(i), and (f)(4)(iv) to read as follows:

Sec.  1037.534  Constant-speed procedure for calculating drag area
(CdA).

* * * * *
    (c) * * *
    (1) Measure torque at each of the drive wheels using a hub torque
meter or a rim torque meter. If testing a tractor with two drive axles,
you may disconnect one of the drive axles from receiving torque from
the driveshaft, in which case you would measure torque at only the
wheels that receive torque from the driveshaft. Set up instruments to
read engine speed for calculating angular speed at the point of the
torque measurements, or install instruments for measuring the angular
speed of the wheels directly.
    (2) Install instrumentation to measure vehicle speed at 10 Hz, with
an accuracy and resolution of 0.1 mi/hr. Also install instrumentation
for reading engine speed from the engine's onboard computer.
* * * * *
    (d) * * *
    (4) * * *
    (i) Measure the angular speed of the driveshaft, axle, or wheel
where the torque is measured, or calculate it from engine speed in
conjunction with gear and axle ratios, as applicable.
* * * * *
    (f) * * *
    (4) * * *
    (iv) Calculate CdA for each 10 second increment from the
50 mi/hr and 70 mi/hr test segments using the following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.126

Where:

CdAi[speed] = the mean drag area for each 10
second increment, i.
Faero[speed] = mean aerodynamic force over a given 10
second increment = FRL[speed] -FRL10,test.
Vair[speed] = mean aerodynamic force over a given 10
second increment.
R = specific gas constant = 287.058 J/(kg[middot]K).
T = mean air temperature.
pact = mean absolute air pressure.

Example:

FRL70 = 4310.6 N
FRL10,test = 900.1 N
Faero70 = 4310.6-900.1 = 3410.5 N
V2air70 = 1089.5 m\2\/s\2\
R = 287.058 J/(kg[middot]K)
T = 293.68 K
pact = 101300 Pa

[GRAPHIC] [TIFF OMITTED] TR29JN21.127

CdAi70 = 5.210 m\2\
* * * * *

0
156. Amend Sec.  1037.540 by revising paragraphs (b)(3) and (8),
(d)(2), (e)(2), and (f) to read as follows:

Sec.  1037.540  Special procedures for testing vehicles with hybrid
power take-off.

* * * * *
    (b) * * *
    (3) Denormalize the PTO duty cycle in appendix II of this part
using the following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.128

Where:

prefi = the reference pressure at each point i in the PTO
cycle.
pi = the normalized pressure at each point i in the PTO cycle
(relative to pmax).
pmax = the mean maximum pressure measured in paragraph
(b)(2) of this section.
pmin = the mean minimum pressure measured in paragraph
(b)(2) of this section.

* * * * *
    (8) Measured pressures must meet the cycle-validation
specifications in the following table for each test run over the duty
cycle:

  Table 1 of Sec.   1037.540--Statistical Criteria for Validating Each
                      Test Run Over the Duty Cycle
------------------------------------------------------------------------
               Parameter \a\                          Pressure
------------------------------------------------------------------------
Slope, a1.................................  0.950 <= a1 <= 1.030.
Absolute value of intercept,                <=2.0% of maximum mapped
 [verbar]a0[verbar].                         pressure.
Standard error of the estimate, SEE.......  <=10% of maximum mapped
                                             pressure.
Coefficient of determination, r2..........  >=0.970.
------------------------------------------------------------------------
\a\ Determine values for specified parameters as described in 40 CFR
  1065.514(e) by comparing measured values to denormalized pressure
  values from the duty cycle in appendix II of this part.

* * * * *
    (d) * * *
    (2) For fractions of a test, use the following equation to
calculate the time:
[GRAPHIC] [TIFF OMITTED] TR29JN21.129

Where:

i = an indexing variable that represents one recorded value.
N = number of measurement intervals.
pcircuit-1,i = normalized pressure command from circuit 1
of the PTO cycle for each point, i, starting from i = 1.
pcircuit-2,i = normalized pressure command from circuit 2
of the PTO cycle for each point, i, starting from i = 1. Let
pcircuit-2 = 0 if there is only one circuit.
pcircuit-1 = the mean normalized pressure command from
circuit 1 over the entire PTO cycle.
pcircuit-2 = the mean normalized pressure command from
circuit 2 over the entire PTO cycle. Let pcircuit-2 = 0
if there is only one circuit.
[Delta]t = the time interval between measurements. For example, at
100 Hz, [Delta]t = 0.0100 seconds.

* * * * *
    (e) * * *
    (2) Divide the CO2 mass from the PTO cycle by the
distance determined in paragraph (d)(4) of this section and the
standard payload as defined in Sec.  1037.801 to get the CO2
emission rate in g/ton-mile. For plug-in hybrid electric vehicles
follow paragraph (f)(3) of this section to calculate utility factor
weighted CO2 emissions in g/ton-mile.
* * * * *
    (f) For Phase 2, calculate the delta PTO fuel results for input
into GEM during vehicle certification as follows:
    (1) Calculate fuel consumption in grams per test,
mfuelPTO, without rounding, as described in 40 CFR
1036.540(d)(4) for both the conventional vehicle and the charge-
sustaining and charge-depleting portions of the test for the hybrid
vehicle as applicable.
    (2) Divide the fuel mass by the applicable distance determined in
paragraph (d)(4) of this section and the appropriate standard payload
as defined in Sec.  1037.801 to determine the fuel rate in g/ton-mile.
    (3) For plug-in hybrid electric vehicles calculate the utility
factor weighted fuel consumption in g/ton-mile, as follows:
    (i) Determine the utility factor fraction for the PTO system from
the table in appendix V of this part using interpolation based on the
total time of the charge-depleting portion of the test as determined in
paragraphs (c)(6) and (d)(3) of this section.
    (ii) Weight the emissions from the charge-sustaining and charge-
depleting portions of the test using the following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.130

Where:

mPTO,CD = mass of fuel per ton-mile while in charge-
depleting mode.
UFt,CD = utility factor fraction at time tCD
as determined in paragraph (f)(3)(i) of this section.
mPTO,CS = mass of fuel per ton-mile while in charge-
sustaining mode.

    (4) Calculate the difference between the conventional PTO emissions
result and the hybrid PTO emissions result for input into GEM.
* * * * *

0
157. Revise Sec.  1037.550 to read as follows:

Sec.  1037.550  Powertrain testing.

    This section describes the procedure to measure fuel consumption
and create engine fuel maps by testing a powertrain that includes an
engine coupled with a transmission, drive axle, and hybrid components
or any assembly with one or more of those hardware elements. Engine
fuel maps are part of demonstrating compliance with Phase 2 vehicle
standards under this part; the powertrain test procedure in this
section is one option for generating this fuel-mapping information as
described in 40

CFR 1036.503. Additionally, this powertrain test procedure is one
option for certifying hybrids to the engine standards in 40 CFR
1036.108.
    (a) General provisions. The following provisions apply broadly for
testing under this section:
    (1) Measure NOX emissions as described in paragraph (k)
of this section. Include these measured NOX values any time
you report to us your greenhouse gas emissions or fuel consumption
values from testing under this section.
    (2) The procedures of 40 CFR part 1065 apply for testing in this
section except as specified. This section uses engine parameters and
variables that are consistent with 40 CFR part 1065.
    (3) Powertrain testing depends on models to calculate certain
parameters. You can use the detailed equations in this section to
create your own models, or use the GEM HIL model (incorporated by
reference in Sec.  1037.810) to simulate vehicle hardware elements as
follows:
    (i) Create driveline and vehicle models that calculate the angular
speed setpoint for the test cell dynamometer,
[fnof]nref,dyno, based on the torque measurement location.
Use the detailed equations in paragraph (f) of this section, the GEM
HIL model's driveline and vehicle submodels, or a combination of the
equations and the submodels. You may use the GEM HIL model's
transmission submodel in paragraph (f) of this section to simulate a
transmission only if testing hybrid engines.
    (ii) Create a driver model or use the GEM HIL model's driver
submodel to simulate a human driver modulating the throttle and brake
pedals to follow the test cycle as closely as possible.
    (iii) Create a cycle-interpolation model or use the GEM HIL model's
cycle submodel to interpolate the duty-cycles and feed the driver model
the duty-cycle reference vehicle speed for each point in the duty-
cycle.
    (4) The powertrain test procedure in this section is designed to
simulate operation of different vehicle configurations over specific
duty cycles. See paragraphs (h) and (j) of this section.
    (5) For each test run, record engine speed and torque as defined in
40 CFR 1065.915(d)(5) with a minimum sampling frequency of 1 Hz. These
engine speed and torque values represent a duty cycle that can be used
for separate testing with an engine mounted on an engine dynamometer
under Sec.  1037.551, such as for a selective enforcement audit as
described in Sec.  1037.301.
    (6) 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 PHEV powertrains, follow 40 CFR 1066.501 to determine
End-of-Test for charge-depleting operation. You must get our approval
in advance for your utility factor curve; we will approve it 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 powertrain will be
installed.
    (b) Test configuration. Select a powertrain for testing as
described in Sec.  1037.235 or 40 CFR 1036.235 as applicable. Set up
the engine according to 40 CFR 1065.110 and 1065.405(b). Set the
engine's idle speed to the minimum warm-idle speed. If warm idle speed
is not adjustable, simply let the engine operate at its warm idle
speed.
    (1) The default test configuration consists of a powertrain with
all components upstream of the axle. This involves connecting the
powertrain's output shaft directly to the dynamometer or to a gear box
with a fixed gear ratio and measuring torque at the axle input shaft.
You may instead set up the dynamometer to connect at the wheel hubs and
measure torque at that location. The preceding sentence may apply if
your powertrain configuration requires it, such as for hybrid
powertrains or if you want to represent the axle performance with
powertrain test results.
    (2) For testing hybrid engines, connect the engine's crankshaft
directly to the dynamometer and measure torque at that location.
    (c) Powertrain temperatures during testing. Cool the powertrain
during testing so temperatures for oil, coolant, block, head,
transmission, battery, and power electronics are within the
manufacturer's expected ranges for normal operation. You may use
electronic control module outputs to comply with this paragraph (c).
You may use auxiliary coolers and fans.
    (d) Engine break in. Break in the engine according to 40 CFR
1065.405, the axle assembly according to Sec.  1037.560, and the
transmission according to Sec.  1037.565. You may instead break in the
powertrain as a complete system using the engine break in procedure in
40 CFR 1065.405.
    (e) Dynamometer setup. Set the dynamometer to operate in speed-
control mode (or torque-control mode for hybrid engine testing at idle,
including idle portions of transient duty cycles). Record data as
described in 40 CFR 1065.202. Command and control the dynamometer speed
at a minimum of 5 Hz, or 10 Hz for testing engine hybrids. Run the
vehicle model to calculate the dynamometer setpoints at a rate of at
least 100 Hz. If the dynamometer's command frequency is less than the
vehicle model dynamometer setpoint frequency, subsample the calculated
setpoints for commanding the dynamometer setpoints.
    (f) Driveline and vehicle model. Use the GEM HIL model's driveline
and vehicle submodels or the equations in this paragraph (f) to
calculate the dynamometer speed setpoint, [fnof]nref,dyno,
based on the torque measurement location. Note that the GEM HIL model
is configured to set the accessory load to zero and it comes configured
with the tire slip model disabled.
    (1) Driveline model with a transmission in hardware. For testing
with torque measurement at the axle input shaft or wheel hubs,
calculate, [fnof]nref,dyno, using the GEM HIL model's
driveline submodel or the following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.131

Where:

ka[speed] = drive axle ratio as determined in paragraph
(h) of this section. Set ka[speed] equal to 1.0 if torque
is measured at the wheel hubs.
vrefi = simulated vehicle reference speed as calculated
in paragraph (f)(3) of this section.
r[speed] = tire radius as determined in paragraph (h) of
this section.

    (2) Driveline model with a simulated transmission. For testing with
the torque measurement at the engine's crankshaft,
[fnof]nref,dyno is the dynamometer target speed from the GEM
HIL model's transmission submodel. You may request our approval to
change the transmission submodel, as long as the changes do not affect
the gear selection logic. Before testing, initialize the transmission
model with the engine's measured torque curve and the applicable
steady-state fuel map from the GEM HIL model. You may request our
approval to input your own steady-state fuel map. Configure the torque
converter to simulate neutral idle when using this procedure to
generate engine fuel maps in 40 CFR 1036.503 or to perform the
Supplemental Emission Test (SET) testing under 40 CFR 1036.505. You may
change engine commanded torque at idle to better represent CITT for
transient testing under 40 CFR 1036.510. You may change the

simulated engine inertia to match the inertia of the engine under test.
We will evaluate your requests under paragraph (f)(3) of this section
based on your demonstration that that the adjusted testing better
represents in-use operation.
    (i) The transmission submodel needs the following model inputs:
    (A) Torque measured at the engine's crankshaft.
    (B) Engine estimated torque determined from the electronic control
module or by converting the instantaneous operator demand to an
instantaneous torque in N[middot]m.
    (C) Dynamometer mode when idling (speed-control or torque-control).
    (D) Measured engine speed when idling.
    (E) Transmission output angular speed,
[fnof]ni,transmission, calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR29JN21.132

Where:

ka[speed] = drive axle ratio as determined in paragraph
(h) of this section.
vrefi = simulated vehicle reference speed as calculated
in paragraph (f)(3) of this section.
    r[speed] = tire radius as determined in paragraph (h)
of this section.

    (ii) The transmission submodel generates the following model
outputs:
    (A) Dynamometer target speed.
    (B) Dynamometer idle load.
    (C) Transmission engine load limit.
    (D) Engine speed target.
    (3) Vehicle model. Calculate the simulated vehicle reference speed,
[nu]refi, using the GEM HIL model's vehicle submodel or the equations
in this paragraph (f)(3):
[GRAPHIC] [TIFF OMITTED] TR29JN21.133

Where:

i = a time-based counter corresponding to each measurement during
the sampling period. Let vref1 = 0; start calculations at
i = 2. A 10-minute sampling period will generally involve 60,000
measurements.
T = instantaneous measured torque at the axle input, measured at the
wheel hubs, or simulated by the GEM HIL model's transmission
submodel.
E[fnof][fnof]axle = axle efficiency. Use E[fnof][fnof]axle = 0.955
for T >= 0, and use E[fnof][fnof]axle = 1/0.955 for T < 0. Use
E[fnof][fnof]axle = 1.0 if torque is measured at the wheel hubs.
M = vehicle mass for a vehicle class as determined in paragraph (h)
of this section.
g = gravitational constant = 9.80665 m/s2.
Crr = coefficient of rolling resistance for a vehicle
class as determined in paragraph (h) of this section.
Gi-1 = the percent grade interpolated at distance,
Di-1, from the duty cycle in appendix IV to this part
corresponding to measurement (i-1).
[GRAPHIC] [TIFF OMITTED] TR29JN21.134

[rho] = air density at reference conditions. Use [rho] = 1.1845 kg/
m3.
CdA = drag area for a vehicle class as determined in
paragraph (h) of this section.
Fbrake,i-1 = instantaneous braking force
applied by the driver model.
[GRAPHIC] [TIFF OMITTED] TR29JN21.135

[Delta]t = the time interval between measurements. For example, at
100 Hz, [Delta]t = 0.0100 seconds.
Mrotating = inertial mass of rotating components. Let
Mrotating = 340 kg for vocational Light HDV or vocational
Medium HDV. See paragraph (h) of this section for tractors and for
vocational Heavy HDV.

    (4) Example. The following example illustrates a calculation of
[fnof]nref,dyno using paragraph (f)(1) of this section where
torque is measured at the axle input shaft. This example is for a
vocational Light HDV or vocational Medium HDV with 6 speed automatic
transmission at B speed (Test 4 in Table 2 of 40 CFR 1036.540).

k[alpha]B = 4.0
rB = 0.399 m
T999 = 500.0 N[middot]m
Crr = 7.7 kg/tonne = 7.7[middot]10-3 kg/kg
M = 11408 kg
Cd[Alpha] = 5.4 m\2\
G999 = 0.39% = 0.0039
[GRAPHIC] [TIFF OMITTED] TR29JN21.136

Fbrake,999 = 0 N
vref,999 = 20.0 m/s
Fgrade,999 = 11408[middot]9.81[middot]sin (atan(0.0039)) =
436.5 N
[Delta]t = 0.0100 s
Mrotating = 340 kg

[GRAPHIC] [TIFF OMITTED] TR29JN21.137

    (g) Driver model. Use the GEM HIL model's driver submodel or design
a driver model to simulate a human driver modulating the throttle and
brake pedals. In either case, tune the model to follow the test cycle
as closely as possible meeting the following specifications:
    (1) The driver model must meet the speed requirements for operation
over the highway cruise cycles as described in Sec.  1037.510 and for
operation over the transient cycle as described in 40 CFR 1066.425(b).
The exceptions in 40 CFR 1066.425(b)(4) apply to the transient cycle
and the highway cruise cycles.
    (2) Send a brake signal when operator demand is zero and vehicle
speed is greater than the reference vehicle speed from the test cycle.
Include a delay before changing the brake signal to prevent dithering,
consistent with good engineering judgment.
    (3) Allow braking only if operator demand is zero.
    (4) Compensate for the distance driven over the duty cycle over the
course of the test. Use the following equation to perform the
compensation in real time to determine your time in the cycle:
[GRAPHIC] [TIFF OMITTED] TR29JN21.138

Where:

vvehicle = measured vehicle speed.
vcycle = reference speed from the test cycle. If
vcycle,i-1 < 1.0 m/s, set
vcycle,i-1 =
vvehicle,i-1.

    (h) Vehicle configurations to evaluate for generating fuel maps as
defined in 40 CFR 1036.503. Configure the driveline and vehicle models
from paragraph (f) of this section in the test cell to test the
powertrain. Simulate multiple vehicle configurations that represent the
range of intended vehicle applications. Use at least three equally
spaced axle ratios or tire sizes and three different road loads (nine
configurations), or at least four equally spaced axle ratios or tire
sizes and two different road loads (eight configurations). Select axle
ratios to represent the full range of expected vehicle installations.
    (1) Determine the vehicle model inputs for M, Mrotating,
Cd[Alpha], and Crr for a set of vehicle
configurations as described in 40 CFR 1036.540(c)(3). Instead of
selecting axle ratios and tire sizes based on the range of intended
vehicle applications as described in this paragraph (h), you may select
axle ratios and tire sizes such that the ratio of engine speed to
vehicle speed covers the range of ratios of minimum and maximum engine
speed to vehicle speed when the transmission is in top gear for the
vehicles in which the powertrain will be installed. Note that you do
not have to use the same axle ratios and tire sizes for each GEM
regulatory subcategory.
    (2) For hybrid powertrain systems where the transmission will be
simulated, use the transmission parameters defined in Table 1 of 40 CFR
1036.540 to determine transmission type and gear ratio. Use a fixed
transmission efficiency of 0.95. The GEM HIL transmission model uses a
transmission parameter file for each test that includes the
transmission type, gear ratios, lockup gear, torque limit per gear from
Table 1 of 40 CFR 1036.540, and the values from 40 CFR 1036.503(b)(4)
and (c).
    (i) [Reserved]
    (j) Duty cycles to evaluate. Operate the powertrain over each of
the duty cycles specified in Sec.  1037.510(a)(2), and for each
applicable vehicle configuration from paragraph (h) of this section.
Determine cycle-average powertrain fuel maps by testing the powertrain
using the procedures in 40 CFR 1036.540(d) with the following
exceptions:
    (1) Understand ``engine'' to mean ``powertrain''.
    (2) If the preceding duty cycle does not end at 0 mi/hr, transition
between duty cycles by decelerating at a rate of 2 mi/hr/s at 0% grade
until the vehicle reaches zero speed. Shut off the powertrain. Prepare
the powertrain and test cell for the next duty-cycle. Start the next
duty-cycle within 60 to 180 seconds after shutting off the powertrain.
Do not run the powertrain or change its physical state before starting
the next duty cycle. If the next duty cycle begins at 0 mi/hr vehicle
speed, key on the vehicle and start the duty-cycle after 10 seconds,
otherwise key on the vehicle and transition to the next duty cycle by
accelerating at a rate of 1 mi/hr/s at 0% grade for vehicle
configurations given in Table 2 of 40 CFR 1036.540 or 2 mi/hr/s at 0%
grade for vehicle configurations given in Tables 3 and 4 of 40 CFR
1036.540, then stabilize for 10 seconds at the initial duty cycle
conditions.
    (3) Calculate cycle work using GEM or the speed and torque from the
driveline and vehicle models from paragraph (f) of this section to
determine the sequence of duty cycles.
    (4) Calculate the mass of fuel consumed for idle duty cycles as
described in paragraph (n) of this section.
    (5) Warm up the powertrain as described in 40 CFR 1036.527(c)(1).
    (k) Measuring NOX emissions. Measure NOX emissions for
each 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. 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.
    (l) [Reserved]
    (m) Measured output speed validation. For each test point, validate
the measured output speed with the corresponding reference values. If
the range of reference speed is less than 10

percent of the mean reference speed, you need to meet only the standard
error of the estimate in Table 1 of this section. You may delete points
when the vehicle is stopped. If your speed measurement is not at the
location of fnref, correct your measured speed using the
constant speed ratio between the two locations. Apply cycle-validation
criteria for each separate transient or highway cruise cycle based on
the following parameters:

  Table 1 of Sec.   1037.550--Statistical Criteria for Validating Duty
                                 Cycles
------------------------------------------------------------------------
                Parameter a                         Speed control
------------------------------------------------------------------------
Slope, a;1................................  0.990 <=a1 <=1.010.
Absolute value of intercept,                <=2.0% of maximum [fnof]nref
 [verbar]a0[verbar].                         speed.
Standard error of the estimate, SEE.......  <=2.0% of maximum [fnof]nref
                                             speed.
Coefficient of determination, r2..........  >=0.990.
------------------------------------------------------------------------
a Determine values for specified parameters as described in 40 CFR
  1065.514(e) by comparing measured and reference values for
  [fnof]nref,dyno.

    (n) Fuel consumption at idle. Determine the mass of fuel consumed
at idle for the applicable duty cycles described in Sec.
1037.510(a)(2) as follows:
    (1) Measure fuel consumption with a fuel flow meter and report the
mean idle fuel mass flow rate for each duty cycle as applicable,
mifuelidle.
    (2) If you do not measure fuel mass flow rate, calculate the idle
fuel mass flow rate for each duty cycle, mifuelidle, for
each set of vehicle settings, as follows:
[GRAPHIC] [TIFF OMITTED] TR29JN21.140

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.
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.
xH2Oexhdry = the mean concentration of H2O in
exhaust per mole of dry exhaust.
miCO2DEF = the mean CO2 mass emission rate
resulting from diesel exhaust fluid decomposition over the duty
cycle as determined in 40 CFR 1036.535(b)(7). 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 = 0.867
niexh = 25.534 mol/s
xCcombdry = 2.805[middot]10-3 mol/mol
xH2Oexhdry = 3.53[middot]10-2 mol/mol
miCO2DEF = 0.0726 g/s
MCO2 = 44.0095
[GRAPHIC] [TIFF OMITTED] TR29JN21.139

mifuelidle = 0.405 g/s = 1458.6 g/hr

    (o) Create GEM inputs. Use the results of powertrain testing to
determine GEM inputs for the different simulated vehicle configurations
as follows:
    (1) Correct the measured or calculated fuel masses,
mfuel[cycle], and mean idle fuel mass flow rates,
mifuelidle, if applicable, for each test result to a mass-
specific net energy content of a reference fuel as described in 40 CFR
1036.535(f), replacing mifuel with mfuel[cycle]
where applicable in Eq. 1036.535-4.
    (2) Declare fuel masses, mfuel[cycle], in g/cycle. In
addition, declare mean fuel mass flow rate for each applicable idle
duty cycle, mifuelidle. These declared values may not be
lower than any corresponding measured values determined in this
section. If you use multiple measurement methods as allowed in 40 CFR
1036.540(d), follow 40 CFR 1036.535(g) regarding the use of direct and
indirect fuel measurements and the carbon balance error verification.
These declared values, which serve as emission standards, collectively
represent the powertrain fuel map for certification.

[GRAPHIC] [TIFF OMITTED] TR29JN21.141

    (ii) For testing with torque measurement at the wheel hubs, use Eq.
1037.550-8 setting ka equal to 1.
    (iii) For testing with torque measurement at the engine's
crankshaft:
[GRAPHIC] [TIFF OMITTED] TR29JN21.142

Where:

fnengine = average engine speed when vehicle speed is at
or above 0.100 m/s.
vref = average simulated vehicle speed at or above 0.100
m/s.

Example:

fnengine = 1870 r/min = 31.17 r/s
vref = 19.06 m/s
[GRAPHIC] [TIFF OMITTED] TR29JN21.143

    (4) Calculate positive work, W[cycle], as the work over
the duty cycle at the axle input shaft, wheel hubs, or the engine's
crankshaft, as applicable, when vehicle speed is at or above 0.100 m/s.
    (5) Calculate engine idle speed, by taking the average engine speed
measured during the transient cycle test while the vehicle speed is
below 0.100 m/s.
    (6) The following table illustrates the GEM data inputs
corresponding to the different vehicle configurations for a given duty
cycle:

[GRAPHIC] [TIFF OMITTED] TR29JN21.144

0
158. Amend Sec.  1037.551 by revising paragraph (b) to read as follows:

Sec.  1037.551  Engine-based simulation of powertrain testing.

* * * * *
    (b) Operate the engine over the applicable engine duty cycles
corresponding to the vehicle cycles specified in Sec.  1037.510(a)(2)
for powertrain testing over the applicable vehicle simulations
described in Sec.  1037.550(i). Warm up the engine to prepare for the
transient test or one of the highway cruise cycles by operating it one
time over one of the simulations of the corresponding duty cycle. Warm
up the engine to prepare for the idle test by operating it over a
simulation of the 65-mi/hr highway cruise cycle for 600 seconds. Within
60 seconds after concluding the warm up cycle, start emission sampling
while the engine operates over the duty cycle. You may perform any
number of test runs directly in succession once the engine is warmed
up. Perform cycle validation as described in 40 CFR 1065.514 for engine
speed, torque, and power.
* * * * *

0
159. Amend Sec.  1037.555 by revising paragraphs (d), (e), and (f) to
read as follows:

Sec.  1037.555  Special procedures for testing Phase 1 hybrid systems.

* * * * *
    (d) Calculate the transmission output shaft's angular speed target
for the driver model, fnref,driver, from the linear speed
associated with the vehicle cycle using the following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.145

Where:

vcyclei = vehicle speed of the test cycle for each point,
i, starting from i = 1.
ka = drive axle ratio, as declared by the manufacturer.
r = radius of the loaded tires, as declared by the manufacturer.

    (e) Use speed control with a loop rate of at least 100 Hz to
program the dynamometer to follow the test cycle, as follows:
    (1) Calculate the transmission output shaft's angular speed target
for the dynamometer, fnref,dyno, from the measured linear
speed at the dynamometer rolls using the following equation:
[GRAPHIC] [TIFF OMITTED] TR29JN21.146

[GRAPHIC] [TIFF OMITTED] TR29JN21.147

Where:

T = instantaneous measured torque at the transmission output shaft.
Fbrake = instantaneous brake force applied by the driver
model to add force to slow down the vehicle.
t = elapsed time in the driving schedule as measured by the
dynamometer, in seconds.

    (2) For each test, validate the measured transmission output
shaft's speed with the corresponding reference values according to 40
CFR 1065.514(e). You may delete points when the vehicle is stopped.
Perform the validation based on speed values at the transmission output
shaft. For steady-state tests (55 mi/hr and 65 mi/hr cruise), apply
cycle-validation criteria by treating the sampling periods from the two
tests as a continuous sampling period. Perform this validation based on
the following parameters:

  Table 1 of Sec.   1037.555--Statistical Criteria for Validating Duty
                                 Cycles
------------------------------------------------------------------------
                 Parameter                          Speed control
------------------------------------------------------------------------
Slope, a1.................................  0.950 <= a1 <= 1.030.
Absolute value of intercept,                <=2.0% of maximum test
 [verbar]a0[verbar].                         speed.
Standard error of the estimate, SEE.......  <=5% of maximum test speed.
Coefficient of determination, r\2\........  >=0.970.
------------------------------------------------------------------------

    (f) Send a brake signal when operator demand is equal to zero and
vehicle speed is greater than the reference vehicle speed from the test
cycle. Set a delay before changing the brake state to prevent the brake
signal from dithering,

consistent with good engineering judgment.
* * * * *

0
160. Revise Sec.  1037.560 to read as follows:

Sec.  1037.560  Axle efficiency test.

    This section describes a procedure for mapping axle efficiency
through a determination of axle power loss.
    (a) You may establish axle power loss maps based on testing any
number of axle configurations within an axle family as specified in
Sec.  1037.232. You may share data across a family of axle
configurations, as long as you test the axle configuration with the
lowest efficiency from the axle family; this will generally involve
testing the axle with the highest axle ratio. For vehicles with tandem
drive axles, always test each drive axle separately. For tandem axles
that can be disconnected, test both single-drive and tandem axle
configurations. This includes 4x4 axles where one of the axles is
disconnectable. Alternatively, you may analytically derive power loss
maps for untested configurations within the same axle family as
described in paragraph (h) of this section.
    (b) Prepare an axle assembly for testing as follows:
    (1) Select an axle assembly with less than 500 hours of operation
before testing. Assemble the axle in its housing, along with wheel ends
and bearings.
    (2) If you have a family of axle assemblies with different axle
ratios, you may test multiple configurations using a common axle
housing, wheel ends, and bearings.
    (3) Install the axle assembly on the dynamometer with an input
shaft angle perpendicular to the axle.
    (i) For axle assemblies with or without a locking main
differential, test the axle assembly using one of the following
methods:
    (A) Lock the main differential and test it with one electric motor
on the input shaft and a second electric motor on the output side of
the output shaft that has the speed-reduction gear attached to it.
    (B) Test with the main differential unlocked and with one electric
motor on the input shaft and electric motors on the output sides of
each of the output shafts.
    (ii) For drive-through tandem-axle setups, lock the longitudinal
and inter-wheel differentials.
    (4) Add gear oil according to the axle manufacturer's instructions.
If the axle manufacturer specifies multiple gear oils, select the one
with the highest viscosity at operating temperature. You may use a
lower-viscosity gear oil if we approve that as critical emission-
related maintenance under Sec.  1037.125. Fill the gear oil to a level
that represents in-use operation. You may use an external gear oil
conditioning system, as long as it does not affect measured values.
    (5) Install equipment for measuring the bulk temperature of the
gear oil in the oil sump or a similar location. Report temperature to
the nearest 0.1 [deg]C.
    (6) Break in the axle assembly using good engineering judgment.
Maintain gear oil temperature at or below 100 [deg]C throughout the
break-in period.
    (7) You may drain the gear oil following the break-in procedure and
repeat the filling procedure described in paragraph (b)(4) of this
section. We will follow your practice for our testing.
    (c) Measure input and output speed and torque as described in 40
CFR 1065.210(b). You must use a speed-measurement system that meets an
accuracy of 0.05% of point. Use torque transducers that
meet an accuracy requirement of 1.0 N[middot]m for unloaded
test points and 0.2% of the maximum tested axle input
torque or output torque, respectively, for loaded test points.
Calibrate and verify measurement instruments according to 40 CFR part
1065, subpart D. Command speed and torque at a minimum of 10 Hz, and
record all data, including bulk oil temperature, as 1 Hz mean values.
    (d) The test matrix consists of test points representing output
torque and wheel speed values meeting the following specifications:
    (1) Output torque includes both loaded and unloaded operation. For
measurement involving unloaded output torque, also called spin loss
testing, the wheel end is not connected to the dynamometer and is left
to rotate freely; in this condition the input torque (to maintain
constant wheel speed) equals the power loss. Test axles at a range of
output torque values, as follows:
    (i) 0, 500, 1000, 2000, 3000, and 4000 N[middot]m for single drive
axle applications for tractors and for vocational Heavy HDV with a
single drive axle.
    (ii) 0, 250, 500, 1000, 1500, and 2000 N[middot]m for tractors, for
vocational Heavy HDV with tandem drive axles, and for all vocational
Light HDV or vocational Medium HDV.
    (iii) You may exclude values that exceed your axle's maximum torque
rating.
    (2) Determine maximum wheel speed corresponding to a vehicle speed
of 65 mi/hr based on the smallest tire (as determined using Sec.
1037.520(c)(1)) that will be used with the axle. If you do not know the
smallest tire size, you may use a default size of 650 r/mi. Use wheel
angular speeds for testing that include 50 r/min and speeds in 100 r/
min increments that encompass the maximum wheel speed (150, 250, etc.).
    (3) You may test the axle assembly at additional speed and torque
setpoints.
    (e) Determine axle efficiency using the following procedure:
    (1) Maintain ambient temperature between (15 and 35) [deg]C
throughout testing. Measure ambient temperature within 1.0 m of the
axle assembly. Verify that critical axle settings (such as bearing
preload, backlash, and oil sump level) are within specifications before
and after testing.
    (2) Maintain gear oil temperature at (81 to 83) [deg]C. You may
alternatively specify a lower range by shifting both temperatures down
by the same amount. We will test your axle assembly using the same
temperature range you specify for your testing. You may use an external
gear oil conditioning system, as long as it does not affect measured
values.
    (3) Use good engineering judgment to warm up the axle assembly by
operating it until the gear oil is within the specified temperature
range.
    (4) Stabilize operation at each point in the test matrix for at
least 10 seconds, then measure the input torque, output torque, and
wheel angular speed for at least 10 seconds. Record arithmetic mean
values for all three parameters over the measurement period. Calculate
power loss as described in paragraph (f) of this section based on these
values for mean input torque, Tin, mean output torque,
Tout, and mean wheel angular speed, fnwheel, at
each test point.
    (5) Perform the map sequence described in paragraph (e)(4) of this
section three times. Remove torque from the input shaft and allow the
axle to come to a full stop before each repeat measurement.
    (6) You may need to perform additional testing at a given test
point based on a calculation of a confidence interval to represent
repeatability at a 95% confidence level for that test point. If the
confidence limit is greater than 0.10% for loaded tests or greater than
0.05% for unloaded tests, perform another repeat of measurements at
that test point and recalculate the repeatability for the whole set of
test results. Continue testing until the confidence interval is at or
below the specified values for all test points. Calculate a confidence
interval representing the repeatability in establishing a 95%
confidence level using the following equation:

[GRAPHIC] [TIFF OMITTED] TR29JN21.148

Where:

[sigma]Ploss = standard deviation of power loss values at
a given torque-speed setting (see 40 CFR 1065.602(c)).
N = number of repeat tests.
Pmax = maximum output torque setting from the test
matrix.
    Example:
[sigma]Ploss = 0.1650 kW
N = 3
P max = 314.2000 kW
[GRAPHIC] [TIFF OMITTED] TR29JN21.149

Confidence Interval = 0.0594%

    (f) Calculate the mean power loss, Ploss, at each test
point as follows:
    (1) Calculate Ploss for each measurement at each test
point as follows:
[GRAPHIC] [TIFF OMITTED] TR29JN21.150

Where:

Tin = mean input torque from paragraph (e)(4) of this
section.
fnwheel = mean wheel angular speed from paragraph (e)(4)
of this section in rad/s.
ka = drive axle ratio, expressed to at least the nearest
0.001.
Tout = mean output torque from paragraph (e)(4) of this
section. Let Tout = 0 for all unloaded tests.

    (2) Calculate Ploss as the mean power loss from all
measurements at a given test point.
    (3) The following example illustrates a calculation of
Ploss:

Tin,1 = 845.10 N[middot]m
fnwheel,1 = 100.0 r/min = 10.472 rad/s
ka = 3.731
Tout,1 = 3000.00 N[middot]m
Ploss,1 = 845.10 [middot] 10.472 [middot] 3.731 - 3000.00
[middot] 10.472
Ploss,1 = 1602.9 W = 1.6029 kW
Ploss,2 = 1601.9 W = 1.6019 kW
Ploss,3 = 1603.9 W = 1.6039 kW
[GRAPHIC] [TIFF OMITTED] TR29JN21.151

    (g) Create a table with the mean power loss, Ploss,
corresponding to each test point for input into GEM. Express wheel
angular speed in r/min to one decimal place; express output torque in
N[middot]m to two decimal places; express power loss in kW to four
decimal places.
[GRAPHIC] [TIFF OMITTED] TR29JN21.279

    (2) Record declared mean power loss values at or above the
corresponding value calculated in paragraph (f) of this section. Use
good engineering judgment to select values that will be at or above the
mean power loss values for your production axles. Vehicle manufacturers
will use these declared mean power loss values for certification. For
vehicles with tandem drive axles, the GEM input is the sum of the power
loss and output torque from the individual axles. For vehicles with a
disconnectable axle, GEM uses separate inputs for single and tandem
drive axle configurations.
    (h) You may analytically derive axle power loss maps for untested
configurations within an axle family as follows:
    (1) Test at least three axle assemblies within the same family
representing at least the smallest axle ratio, the largest axle ratio,
and an axle ratio closest to the arithmetic mean from the two other
tested axle assemblies. Test each axle assembly as described in this
section at the same speed and torque setpoints.
    (2) Perform a second-order least-squares regression between
declared power loss and axle ratio using each speed and torque setpoint
described in paragraph (d) of this section for your tested axle
assemblies. Use the declared power loss values from paragraph (g) of
this section; however, for purposes of analytically deriving power loss
maps under this paragraph (h), you must select declared values for the
largest and smallest axle ratios in the axle family that are adjusted
relative to the calculated values for mean power loss by the same
multiplier. If the coefficent of the second-order term is negative,
include testing from additional axle ratios, or increase your declared
power loss for the largest and smallest axle ratios by the same
multiplier as needed for the second-order term to become positive.
    (3) Determine Ploss of untested axles for each speed and
torque setpoint based on a linear relationship between your declared
power loss and axle ratio as follows:
    (i) Determine the slope of the correlation line by connecting the
declared power loss values for the smallest and largest axle ratios.

    (ii) Fix the intercept for the correlation line by shifting it
upward as needed so all the declared power loss values are on the
correlation line or below it. Note that for cases involving three
tested axle assemblies, the correlation line will always include the
declared power loss for the smallest and largest axle ratio.
    (4) Select declared values of Ploss for untested
configurations that are at or above the values you determined in
paragraph (h)(3) of this section.

0
161. Revise Sec.  1037.565 to read as follows:

Sec.  1037.565  Transmission efficiency test.

    This section describes a procedure for mapping transmission
efficiency through a determination of transmission power loss.
    (a) You may establish transmission power loss maps based on testing
any number of transmission configurations within a transmission family
as specified in Sec.  1037.232. You may share data across any
configurations within the family, as long as you test the transmission
configuration with the lowest efficiency from the transmission family.
Alternatively, you may ask us to approve analytically derived power
loss maps for untested configurations within the same transmission
family (see Sec.  1037.235(h)).
    (b) Prepare a transmission for testing as follows:
    (1) Select a transmission with less than 500 hours of operation
before testing.
    (2) Mount the transmission to the dynamometer such that the geared
shaft in the transmission is aligned with the input shaft from the
dynamometer.
    (3) Add transmission oil according to the transmission
manufacturer's instructions. If the transmission manufacturer specifies
multiple transmission oils, select the one with the highest viscosity
at operating temperature. You may use a lower-viscosity transmission
oil if we approve it as critical emission-related maintenance under
Sec.  1037.125. Fill the transmission oil to a level that represents
in-use operation. You may use an external transmission oil conditioning
system, as long as it does not affect measured values.
    (4) Include any internal and external pumps for hydraulic fluid and
lubricating oil in the test. Determine the work required to drive an
external pump according to 40 CFR 1065.210.
    (5) Install equipment for measuring the bulk temperature of the
transmission oil in the oil sump or a similar location.
    (6) If the transmission is equipped with a torque converter, lock
it for all testing performed in this section.
    (7) Break in the transmission using good engineering judgment.
Maintain transmission oil temperature at (87 to 93) [deg]C for
automatic transmissions and transmissions having more than two friction
clutches, and at (77 to 83) [deg]C for all other transmissions. You may
ask us to approve a different range of transmission oil temperatures if
you have data showing that it better represents in-use operation.
    (c) Measure input and output shaft speed and torque as described in
40 CFR 1065.210(b). You must use a speed measurement system that meets
an accuracy of 0.05% of point. Accuracy requirements for
torque transducers depend on the highest loaded transmission input and
output torque as described in paragraph (d)(2) of this section. Use
torque transducers for torque input measurements that meet an accuracy
requirement of 0.2% of the highest loaded transmission
input for loaded test points and 0.1% of the highest loaded
transmission input torque for unloaded test points. For torque output
measurements, torque transducers must meet an accuracy requirement of
0.2% of the highest loaded transmission output torque for
each gear ratio. Calibrate and verify measurement instruments according
to 40 CFR part 1065, subpart D. Command speed and torque at a minimum
of 10 Hz, and record all data, including bulk oil temperature, at a