Section 1036.245 - Deterioration factors for exhaust emission standardsThis section describes how to determine deterioration factors, either with pre-existing test data or with new emission measurements. Apply these deterioration factors to determine whether your engines will meet the duty-cycle emission standards throughout the useful life as described in § 1036.240 . The provisions of this section and the verification provisions of § 1036.246 apply for all engine families starting in model year 2027; you may optionally use these provisions to determine and verify deterioration factors for earlier model years.
(a) You may ask us to approve deterioration factors for an engine family based on an engineering analysis of emission measurements from similar highway or nonroad engines if you have already given us these data for certifying the other engines in the same or earlier model years. Use good engineering judgment to decide whether the two engines are similar. We will approve your request if you show us that the emission measurements from other engines reasonably represent in-use deterioration for the engine family for which you have not yet determined deterioration factors.(c) If you are unable to determine deterioration factors for an engine family under paragraph (a) of this section, select engines, subsystems, or components for testing. Determine deterioration factors based on service accumulation and related testing to represent the deterioration expected from in-use engines over the useful life, including crankcase emissions. You may perform maintenance on emission-data engines as described in § 1036.125 and 40 CFR part 1065, subpart E. Use good engineering judgment for all aspects of the effort to establish deterioration factors under this paragraph (c). Send us your test plan for our preliminary approval under § 1036.210 . You may apply deterioration factors based on testing under this paragraph (c) to multiple engine families, consistent with the provisions in paragraph (a) of this section. Determine deterioration factors based on a combination of minimum required engine dynamometer aging hours and accelerated bench-aged aftertreatment as follows: (1) Select an emission-data engine and aftertreatment devices and systems that can be assembled into a certified configuration to represent the engine family. Stabilize the engine and aftertreatment devices and systems, together or separately, to prepare for emission measurements. Perform low-hour emission measurement once the engine has operated with aftertreatment long enough to stabilize the emission control. Measure emissions of all regulated pollutants while the engine operates over all applicable duty cycles on an engine dynamometer as described in subpart F of this part.(2) Perform additional service accumulation as described in paragraph (c)(3) of this section on an engine dynamometer meeting at least the following minimum specifications: Table 1 to Paragraph (c)(2) of § 1036.245 -Minimum Required Engine Dynamometer Aging Hours by Primary Intended Service Class
| Primary intended service class | Minimum engine dynamometer hours |
| Spark-ignition HDE | 300 |
| Light HDE | 1,250 |
| Medium HDE | 1,500 |
| Heavy HDE | 1,500 |
(3) Perform service accumulation in the laboratory by operating the engine or hybrid powertrain repeatedly over one of the following test sequences, or a different test sequence that we approve in advance:(i) Use duty-cycle sequence 1 for operating any engine on an engine dynamometer, as follows: (A) Operate at idle for 2 hours.(B) Operate for 105 ± 1 hours over a repeat sequence of one FTP followed by one RMC.(C) Operate over one LLC.(D) Operate at idle for 2 hours.(E) Shut down the engine for cooldown to ambient temperature.(ii) Duty-cycle sequence 2 is based on operating over the LLC and the vehicle-based duty cycles from 40 CFR part 1037 . Select the vehicle subcategory and vehicle configuration from § 1036.540 or § 1036.545 with the highest reference cycle work for each vehicle-based duty cycle. Operate the engine as follows for duty-cycle sequence 2:(A) Operate at idle for 2 hours.(B) Operate for 105 ± 1 hours over a repeat sequence of one Heavy-duty Transient Test Cycle, then one 55 mi/hr highway cruise cycle, and then one 65 mi/hr highway cruise cycle.(C) Operate over one LLC.(D) Operate at idle for 2 hours.(E) Shut down the engine for cooldown to ambient temperature.(4) Perform all the emission measurements described in paragraph (c)(1) of this section when the engine has reached the minimum service accumulation specified in paragraph (c)(2) of this section, and again after you finish service accumulation in the laboratory if your service accumulation exceeds the values specified in paragraph (c)(2) of this section.(5) Determine the deterioration factor based on a combination of actual and simulated service accumulation represented by a number of hours of engine operation calculated using the following equation: View Image
Where:
UL = useful life mileage from § 1036.104(e) .
k = 1.15 for Heavy HDE and 1.0 for all other primary intended service classes.
vagingcycle = average speed of aging cycle in paragraph (c)(3) of this section. Use 40.26 mi/hr for duty-cycle sequence 1 and 44.48 mi/hr for duty-cycle sequence 2.
Example for Heavy HDE for Duty-Cycle Sequence 1:
UL = 650,000 miles
k = 1.15
vagingcycle = 40.26 mi/hr
View Image
ttotal = 18,567 hr
(6) Perform accelerated bench aging of aftertreatment devices to represent normal engine operation over the useful life using the service accumulation hours determined in paragraph (c)(5) of this section. Design your bench aging to represent 10,000 hours of in-use engine operation for every 1,000 hours of accelerated bench aging. Use the accelerated bench-aging procedure in 40 CFR 1065.1131 through 1065.1145 or get our advance approval to use a different procedure that adequately that accounts for thermal and chemical degradation. For example, this might involve testing consistent with the analogous procedures that apply for light-duty vehicles under 40 CFR part 86, subpart S.(7) After bench-aging aftertreatment devices, install or reinstall those aftertreatment devices and systems on an emission-data engine (or an equivalent engine) that has been stabilized without aftertreatment. Ensure that the aftertreatment is installed such that the engine is in a certified configuration to represent the engine family.(8) Operate the engine with the bench-aged aftertreatment devices to stabilize emission controls for at least 100 hours on an engine dynamometer.(9) Once stabilization is complete, repeat the low-hour emission measurements.(10) Calculate deterioration factors by comparing exhaust emissions with the bench-aged aftertreatment and exhaust emissions at the low-hour test point. Create a linear curve fit if testing includes intermediate test points. Calculate deterioration factors based on measured values, without extrapolation.(d) If you determine deterioration factors as described in paragraph (c) of this section, you may apply those deterioration factors in later years for engine families that qualify for carryover certification as described in § 1036.235(d) . You may also apply those deterioration factors for additional engine families as described in paragraph (a) of this section.(e) Include the following information in your application for certification: (1) If you use test data from a different engine family, explain why this is appropriate and include all the emission measurements on which you base the deterioration factors. If the deterioration factors for the new engine family are not identical to the deterioration factors for the different engine family, describe your engineering analysis to justify the revised values and state that all your data, analyses, evaluations, and other information are available for our review upon request.(2) If you determined deterioration factors under paragraph (c) of this section, include the following information in the first year that you use those deterioration factors: (i) Describe your accelerated bench aging or other procedures to represent full-life service accumulation for the engine's emission controls.(ii) Describe how you prepared the test engine before and after installing aftertreatment systems to determine deterioration factors.(iii) Identify the power rating of the emission-data engine used to determine deterioration factors.88 FR 4487, Jan. 24, 2023, as amended at 89 FR 29742, Apr. 22, 2024 88 FR 4487, 3/27/2023; As amended at 89 FR 29742, 6/21/2024