Section 1066.831 - Exhaust emission test procedures for aggressive driving(a) This section describes how to test using the US06 or LA-92 driving schedule. The US06 driving schedule can be divided into two test intervals-the US06 City cycle comprises the combined portions of the cycle from 1 to 130 seconds and from 495 to 596 seconds, and the US06 Highway cycle comprises the portion of the cycle between 130 and 495 seconds. See § 1066.801 for further information on the driving schedules.(b) Take the following steps to precondition vehicles for testing under this section: (1) Drain and refill the vehicle's fuel tank(s) in any of the following cases: (i) For aggressive-driving tests that do not follow FTP or HFET testing.(ii) For a test element that starts more than 72 hours after the most recent FTP or HFET measurement (with or without evaporative emission measurements).(iii) For testing in which the test vehicle has not remained in an area where ambient temperatures were within the range specified for testing since the previous FTP or HFET.(2) Keep ambient temperatures within the ranges specified for test measurements throughout the preconditioning sequence.(3) Warm up the vehicle to a stabilized condition as follows:(i) Push or drive the vehicle onto the dynamometer.(ii) Operate the vehicle one time over one of the driving schedules specified in this paragraph (b)(3)(ii). You may ask us to use a particular preconditioning driving schedule if that is related to fuel effects on adaptive memory systems. For our testing, we will generally operate the vehicle over the same preconditioning cycle that will be used for testing in this section. You may exercise your sampling equipment, but you may not determine emissions results during preconditioning. Choose from the following driving schedules:(A) The first 505 seconds of the UDDS (bag 1).(B) The last 867 seconds of the UDDS (bag 2).(C) The HFET driving schedule.(D) US06 driving schedule or, for heavy-duty vehicles at or below 10,000 pounds GVWR with a power-to-weight ratio at or below 0.024 hp/lbm, just the highway portion of the US06 driving schedule.(E) The SC03 driving schedule.(F) The LA-92 driving schedule.(G) The Hot LA-92 driving schedule.(4) Allow the vehicle to idle for (1 to 2) minutes. This leads directly into the test measurements described in paragraph (c) of this section.(c) For testing involving the full US06 driving schedule, you may collect emissions from separate city and highway test intervals (see 40 CFR part 600 ), or you may collect emissions over the full US06 driving schedule as a single test interval. Take the following steps to measure emissions over separate city and highway test intervals:(1) At 130 seconds, simultaneously stop all US06 City, and start all US06 Highway sampling, recording, and integrating (including background sampling). At 136 seconds (before the acceleration), record the measured dynamometer roll revolutions.(2) At 495 seconds, simultaneously stop all US06 Highway, and start all US06 City sampling, recording, and integrating (including background sampling). At 500 seconds (before the acceleration), record the measured dynamometer roll revolutions.(3) Except as specified in paragraph (c)(4) of this section, treat the emissions from the first and second portions of the US06 City test interval as a single sample.(4) If you collect gaseous emissions over separate city and highway test intervals, you may still collect PM over the full US06 driving schedule as a single test interval. If you do this, calculate a composite dilution factor based on city and highway emissions using Eq. 1066.610-4 to show that you meet the dilution factor requirements of § 1066.110(b)(2)(iii)(B) .(d) For diesel-fueled vehicles, measure THC emissions on a continuous basis. For separate measurement of the city and highway test intervals as described in paragraph (c) of this section, perform separate calculations for each portion of the test cycle.(e) Follow the exhaust emission measurement procedures specified in §§ 1066.410 through 1066.425 , subject to the following exceptions and additional provisions: (1) Following the preconditioning specified in paragraph (b) of this section, place the vehicle in gear and simultaneously start sampling and recording. Begin the first acceleration 5 seconds after placing the vehicle in gear.(2) Operate the vehicle over the full US06 driving schedule, with the following exceptions that apply only for Tier 3 vehicles:(i) For heavy-duty vehicles above 10,000 pounds GVWR, operate the vehicle over the Hot LA-92 driving schedule.(ii) Heavy-duty vehicles at or below 10,000 pounds GVWR with a power-to-weight ratio at or below 0.024 hp/pound may be certified using only the highway portion of the US06 driving schedule as described in 40 CFR 86.1816.(3) Turn the engine off 2 seconds after the end of the last deceleration. Five seconds after the engine stops running, stop all sampling and recording, including background sampling. Stop any integrating devices and indicate the end of the test cycle in the recorded data. Note that the 5 second delay is intended to account for sampling system transport.(4) Correct calculated NOX emissions as described in § 1066.615(a)(1) . 79 FR 23823 , Apr. 28, 2014, as amended at 80 FR 9124 , Feb. 19, 2015; 88 FR 4709 , Jan. 24, 2023 88 FR 4709 , 3/27/2023; 89 FR 28215 , 6/17/2024