(1) Measure NO_X emissions as described in paragraph (k) of this section. Include these measured NO_X 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 § 1037.810) to simulate vehicle hardware elements as follows:

(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 § 1037.551, such as for a selective enforcement audit as described in § 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.

(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.

(1) Driveline model with a transmission in hardware . For testing with torque measurement at the axle input shaft or wheel hubs, calculate, ƒ_nref,dyno, using the GEM HIL model's driveline submodel or the following equation:

(2) Driveline model with a simulated transmission . For testing with the torque measurement at the engine's crankshaft, ƒ_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·m.

(C) Dynamometer mode when idling (speed-control or torque-control).

(D) Measured engine speed when idling.

(E) Transmission output angular speed, ƒ_{ni,transmission}, calculated as follows:

Where:

k_a[speed] = drive axle ratio as determined in paragraph (h) of this section.

v_refi = 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.

(3) Vehicle model . Calculate the simulated vehicle reference speed, νrefi, using the GEM HIL model's vehicle submodel or the equations in this paragraph (f)(3):

Where:

i = a time-based counter corresponding to each measurement during the sampling period. Let v_ref1 = 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.

Eƒƒaxle = axle efficiency. Use Eƒƒaxle = 0.955 for T ≥ 0, and use Eƒƒaxle = 1/0.955 for T < 0. Use Eƒƒaxle = 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.

C_rr = coefficient of rolling resistance for a vehicle class as determined in paragraph (h) of this section.

G_i-1 = the percent grade interpolated at distance, D_i-1, from the duty cycle in appendix IV to this part corresponding to measurement (i-1).

ρ = air density at reference conditions. Use ρ = 1.1845 kg/m³.

C_dA = drag area for a vehicle class as determined in paragraph (h) of this section.

F_brake,i-1 = instantaneous braking force applied by the driver model.

Δt = the time interval between measurements. For example, at 100 Hz, Δt = 0.0100 seconds.

M_rotating = inertial mass of rotating components. Let M_rotating = 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 ƒ_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).

G₉₉₉ = 0.39% = 0.0039

M_rotating = 340 kg

(1) The driver model must meet the speed requirements for operation over the highway cruise cycles as described in § 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:

(1) Determine the vehicle model inputs for M, M_rotating, C_d, and C_rr 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).

(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).

(1) Measure fuel consumption with a fuel flow meter and report the mean idle fuel mass flow rate for each duty cycle as applicable, ṁ̅_fuelidle.

(2) If you do not measure fuel mass flow rate, calculate the idle fuel mass flow rate for each duty cycle, ṁ̅_fuelidle, for each set of vehicle settings, as follows:

Example:

M_C = 12.0107 g/mol

w_Cmeas = 0.867

ṅ̅_exh = 25.534 mol/s

x_Ccombdry = 2.805·10⁻³ mol/mol

x_H2Oexhdry = 3.53·10⁻² mol/mol

ṁ̅_CO2DEF = 0.0726 g/s

M_CO2 = 44.0095

ṁ̅_fuelidle = 0.405 g/s = 1458.6 g/hr

(1) Correct the measured or calculated fuel masses, m_fuel[cycle], and mean idle fuel mass flow rates, ṁ̅_fuelidle, 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 ṁ̅_fuel with m_fuel[cycle] where applicable in Eq. 1036.535-4.

(2) Declare fuel masses, m_fuel[cycle], in g/cycle. In addition, declare mean fuel mass flow rate for each applicable idle duty cycle, ṁ̅_fuelidle. 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.

(iii) For testing with torque measurement at the engine's crankshaft:

Where:

f̄_nengine = average engine speed when vehicle speed is at or above 0.100 m/s.

v̄_ref = average simulated vehicle speed at or above 0.100 m/s.

Example:

f̄_nengine = 1870 r/min = 31.17 r/s

v̄_ref = 19.06 m/s

(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: