California Air Resources Board

Potential Amendments to the California Exhaust Emission Standards and Test Procedures for New 2013 and Later Small Off-Road Engines; Engine-Testing Procedures (Part 1065) as of March 24, 2021.

This page consists of material released as part of the development process for the Proposed Amendments to the Small Off-Road Engine (SORE) Regulations.

For the Proposed Amendments and other rulemaking documents that the Board will consider for adoption during the public hearing in December 2021, please refer to the SORE rulemaking page.  

(Note: The potential amendments are shown in underline to indicate additions and strikeout to indicate deletions from the existing regulatory text.)

Subpart F–Performing an Emission Test in the Laboratory Over Specified Duty Cycles

§ 1065.501 Overview.

(a) Use the procedures detailed in this subpart to measure engine emissions over a specified duty cycle. Refer to subpart J of this part for field test procedures that describe how to measure emissions during in‑use engine operation. This section describes how to:

(1) Map your engine, if applicable, by recording specified speed and torque data, as measured from the engine's primary output shaft.

(2) Transform normalized duty cycles into reference duty cycles for your engine by using an engine map.

(3) Prepare your engine, equipment, and measurement instruments for an emission test.

(4) Perform pre‑test procedures to verify proper operation of certain equipment and analyzers.

(5) Record pre‑test data.

(6) Start or restart the engine and sampling systems.

(7) Sample emissions throughout the duty cycle.

(8) Record post‑test data.

(9) Perform post‑test procedures to verify proper operation of certain equipment and analyzers.

(10) Weigh PM samples.

(b) Unless we specify otherwise, you may control the regeneration timing of infrequently regenerated aftertreatment devices in a manner representative of in‑use operation, or as necessary to avoid damage to your engine or test equipment. You may control the regeneration timing using a sequence of engine operating conditions or you may initiate regeneration with an external regeneration switch or other command. This provision also allows you to ensure that a regeneration event does not occur during an emission test.

(b) (c) An emission test generally consists of measuring emissions and other parameters while an engine follows one or more duty cycles that are specified in the standard‑setting part. There are two general types of duty cycles:

(1) Transient cycles. Transient duty cycles are typically specified in the standard‑setting part as a second‑by‑second sequence of speed commands and normalized torque (or power) commands. Operate an engine over a transient cycle such that the speed and torque of the engine's primary output shaft follows the target values. Proportionally sample emissions and other parameters and use the calculations in subpart G of this part to calculate emissions. Start a transient test according to the standard‑setting part, as follows:

(i) A cold‑start transient cycle where you start to measure emissions just before starting an engine that has not been warmed up.

(ii) A hot‑start transient cycle where you start to measure emissions just before starting a warmed‑up engine.

(iii) A hot running transient cycle where you start to measure emissions after an engine is started, warmed up, and running.

(2) Steady‑state cycles. Steady‑state duty cycles are typically specified in the standard‑setting part as a list of discrete operating points (modes or notches), where each operating point has one value of a normalized speed command and one value of a normalized torque (or power) command. Ramped‑modal cycles for steady‑state testing also list test times for each mode and transition times between modes where speed and torque are linearly ramped between modes, even for cycles with % power. Start a steady‑state cycle as a hot running test, where you start to measure emissions after an engine is started, warmed up and running. You may run a steady‑state duty cycle as a discrete‑mode cycle or a ramped‑modal cycle, as follows:

(i) Discrete‑mode cycles. Before emission sampling, stabilize an engine at the first discrete modeof the duty cycle specified in the standard‑setting part. Sample emissions and other parameters for that mode in the same manner as a transient cycle, with the exception that reference speed and torque values are constant. Recordmean values datafor that mode, transition to the next mode,and then stabilize the engine at the next mode. Continue to sample each mode discretely as a separate test intervals and calculate weighted emission results according to the standard‑setting part. composite brake‑specific emission results according to § 1065.650(g)(2).

(A) Use appropriate measurements or analysis to determine the time required to stabilize the engine. You may make this determination before starting the test based on prior experience, or you may make this determination in real time based on automated stability criteria. If needed, you may continue to operate the engine after reaching stability to get laboratory equipment ready for sampling.

(B) Collect PM on separate PM sample media for each mode.

(C) The minimum sample time is 60 seconds. We recommend that you sample both gaseous and PM emissions over the same test interval. If you sample gaseous and PM emissions over different test intervals, there must be no change in engine operation between the two test intervals. These two test intervals may completely or partially overlap, they may run consecutively, or they may be separated in time.

(ii) Ramped‑modal cycles. Perform ramped‑modal cycles similar to the way you would perform transient cycles, except that ramped‑modal cycles involve mostly steady‑state engine operation. Generate a ramped‑modal duty cycle as a sequence of second‑by‑second (1 Hz) reference speed and torque points. Run the ramped‑modal duty cycle in the same manner as a transient cycle and use the 1 Hz reference speed and torque values to validate the cycle, even for cycles with % power. Proportionally sample emissions and other parameters during the cycle and use the calculations in subpart G of this part to calculate emissions.

(c) (d) Other subparts in this part identify how to select and prepare an engine for testing (subpart E), how to perform the required engine service accumulation (subpart E), and how to calculate emission results (subpart G).

(d) (e) Subpart J of this part describes how to perform field testing.

§ 1065.510 Engine mapping.

(a) Applicability, scope, and frequency. An engine map is a data set that consists of a series of paired data points that represent the maximum brake torque versus engine speed, measured at the engine's primary output shaft. Map your engine if the standard‑setting part requires engine mapping to generate a duty cycle for your engine configuration. Map your engine while it is connected to a dynamometer or other device that can absorb work output from the engine's primary output shaft according to § 1065.110. Configure any auxiliary work inputs and outputs such as hybrid, turbo‑compounding, or thermoelectric systems to represent their in‑use configurations, and use the same configuration for emission testing. See Figure 1 of § 1065.210. This may involve configuring initial states of charge and rates and times of auxiliary‑work inputs and outputs. We recommend that you contact the Designated Compliance Officer before testing to determine how you should configure any auxiliary‑work inputs and outputs. Use the most recent engine map to transform a normalized duty cycle from the standard‑setting part to a reference duty cycle specific to your engine. Normalized duty cycles are specified in the standard‑setting part. You may update an engine map at any time by repeating the engine‑mapping procedure. You must map or re‑map an engine before a test if any of the following apply:

(1) If you have not performed an initial engine map.

(2) If the atmospheric pressure near the engine's air inlet is not within ± 5 kPa of the atmospheric pressure recorded at the time of the last engine map.

(3) If the engine or emission‑control system has undergone changes that might affect maximum torque performance. This includes changing the configuration of auxiliary work inputs and outputs.

(4) If you capture an incomplete map on your first attempt or you do not complete a map within the specified time tolerance. You may repeat mapping as often as necessary to capture a complete map within the specified time.

(b) Mapping variable‑speed engines. Map variable‑speed engines as follows:

(1) Record the atmospheric pressure.

(2) Warm up the engine by operating it. We recommend operating the engine at any speed and at approximately 75% of its expected maximum power. Continue the warm‑up until the engine coolant, block, or head absolute temperature is within ± 2% of its mean value for at least 2 min or until the engine thermostat controls engine temperature.

(3) Operate the engine at its warm idle speed as follows:

(i) For engines with a low‑speed governor, set the operator demand to minimum, use the dynamometer or other loading device to target a torque of zero on the engine's primary output shaft, and allow the engine to govern the speed. Measure this warm idle speed; we recommend recording at least 30 values of speed and using the mean of those values.

(ii) For engines without a low‑speed governor, operate the engine at warm idle speed and zero torque on the engine's primary output shaft. You may use the dynamometer to target a torque of zero on the engine's primary output shaft, and manipulate the operator demand to control the speed to target the manufacturer‑declared value for the lowest engine speed possible with minimum load (also known as manufacturer‑declared warm idle speed). You may alternatively use the dynamometer to target the manufacturer‑declared warm idle speed and manipulate the operator demand to control the torque on the engine's primary output shaft to zero.

(iii) For variable‑speed engines with or without a low‑speed governor, if a nonzero idle torque is representative of in‑use operation, you may use the dynamometer or operator demand to target the manufacturer‑declared idle torque instead of targeting zero torque as specified in paragraphs (b)(3)(i) and (ii) of this section. Control speed as specified in paragraph (b)(3)(i) or (ii) of this section, as applicable. If you use this option for engines with a low‑speed governor to measure the warm idle speed with the manufacturer‑declared torque at this step, you may use this as the warm‑idle speed for cycle generation as specified in paragraph (b)(6) of this section. However, if you identify multiple warm idle torques under paragraph (f)(4)(i) of this section, measure the warm idle speed at only one torque level for this paragraph (b)(3).

(4) Set operator demand to maximum and control engine speed at (95 ± 1) % of its warm idle speed determined above for at least 15 seconds. For engines with reference duty cycles whose lowest speed is greater than warm idle speed, you may start the map at (95 ± 1) % of the lowest reference speed.

(5) Perform one of the following:

(i) For any engine subject only to steady‑state duty cycles (i.e., discrete‑mode or ramped‑modal), you may perform an engine map by using discrete speeds. Select at least 20 evenly spaced setpoints from 95% of warm idle speed to the highest speed above maximum power at which 50% of maximum power occurs. We refer to this 50% speed as the check point speed as described in paragraph (b)(5)(iii) of this section. At each setpoint, stabilize speed and allow torque to stabilize. Record the mean speed and torque at each setpoint. We recommend that you stabilize an engine for at least 15 seconds at each setpoint and record the mean feedback speed and torque of the last (4 to 6) seconds. Record the mean speed and torque at each setpoint. Use linear interpolation to determine intermediate speeds and torques. Use this series of speeds and torques to generate the power map as described in paragraph (e) of this section.

(ii) For any variable‑speed engine, you may perform an engine map by using a continuous sweep of speed by continuing to record the mean feedback speed and torque at 1 Hz or more frequently and increasing speed at a constant rate such that it takes (4 to 6) min to sweep from 95% of warm idle speed to the check point speed as described in paragraph (b)(5)(iii) of this section. Use good engineering judgment to dDetermine when to stop recording data to ensure that the sweep is complete. In most cases, this means that you can stop the sweep at any point after the power falls to 50% of the maximum value. From the series of mean speed and maximum torque values, use linear interpolation to determine intermediate values. Use this series of speeds and torques to generate the power map as described in paragraph (e) of this section.

(iii) The check point speed of the map is the highest speed above maximum power at which 50% of maximum power occurs. If this speed is unsafe or unachievable (e.g., for ungoverned engines or engines that do not operate at that point), use good engineering judgment to map up to the maximum safe speed or maximum achievable speed. For discrete mapping, if the engine cannot be mapped to the check point speed, make sure the map includes at least 20 points from 95% of warm idle to the maximum mapped speed. For continuous mapping, if the engine cannot be mapped to the check point speed, verify that the sweep time from 95% of warm idle to the maximum mapped speed is (4 to 6) min.

(iv) Note that under § 1065.10(c)(1) we may allow you to disregard portions of the map when selecting maximum test speed if the specified procedure would result in a duty cycle that does not represent in‑use operation.

(6) Use one of the following methods to determine warm high‑idle speed for engines with a high‑speed governor if they are subject to transient testing with a duty cycle that includes reference speed values above 100%:

(i) You may use a manufacturer‑declared warm high‑idle speed if the engine is electronically governed. For engines with a high‑speed governor that shuts off torque output at a manufacturer‑specified speed and reactivates at a lower manufacturer‑specified speed (such as engines that use ignition cut‑off for governing), declare the middle of the specified speed range as the warm high‑idle speed.

(ii) Measure the warm high‑idle speed using the following procedure:

(A) Set operator demand to maximum and use the dynamometer to target zero torque on the engine's primary output shaft. If the mean feedback torque is within ±1% of T_{max mapped}, you may use the observed mean feedback speed at that point as the measured warm high‑idle speed.

(B) If the engine is unstable as a result of in‑use production components (such as engines that use ignition cut‑off for governing, as opposed to unstable dynamometer operation), you must use the mean feedback speed from paragraph (b)(6)(ii)(A) of this section as the measured warm high‑idle speed. The engine is considered unstable if any of the 1 Hz speed feedback values are not within ±2% of the calculated mean feedback speed. We recommend that you determine the mean as the value representing the midpoint between the observed maximum and minimum recorded feedback speed.

(C) If your dynamometer is not capable of achieving a mean feedback torque within ±1% of T_{max mapped}, operate the engine at a second point with operator demand set to maximum with the dynamometer set to target a torque equal to the recorded mean feedback torque on the previous point plus 20% of T_{max mapped}. Use this data point and the data point from paragraph (b)(6)(ii)(A) of this section to extrapolate the engine speed where torque is equal to zero.

(D) You may use a manufacturer‑declared T_max instead of the measured T_{max mapped}. If you do this, or if you are able to determine mean feedback speed as described in paragraphs (b)(6)(ii)(A) and (B) of this section, you may measure the warm high‑idle speed before running the speed sweep specified in paragraph (b)(5) of this section.

(6) (7) For engines with a low‑speed governor, if a nonzero idle torque is representative of in‑use operation, operate the engine at warm idle with the manufacturer‑declared idle torque. Set the operator demand to minimum, use the dynamometer to target the declared idle torque, and allow the engine to govern the speed. Measure this speed and use it as the warm idle speed for cycle generation in § 1065.512. We recommend recording at least 30 values of speed and using the mean of those values. If you identify multiple warm idle torques under paragraph (f)(4)(i) of this section, measure the warm idle speed at each torque. You may map the idle governor at multiple load levels and use this map to determine the measured warm idle speed at the declared idle torque(s).

(c) Negative torque mapping. If your engine is subject to a reference duty cycle that specifies negative torque values (i.e., engine motoring), generate a motoring map by any of the following procedures:

(1) Multiply the positive torques from your map by −40%. Use linear interpolation to determine intermediate values.

(2) Map the amount of negative torque required to motor the engine by repeating paragraph (b) of this section with minimum operator demand. You may start the negative torque map at either the minimum or maximum speed from paragraph (b) of this section.

(3) Determine the amount of negative torque required to motor the engine at the following two points near the ends of the engine's speed range. Operate the engine at these two points at minimum operator demand. Use linear interpolation to determine intermediate values.

(i) Low‑speed point. For engines without a low‑speed governor, determine the amount of negative torque at warm idle speed. For engines with a low‑speed governor, motor the engine above warm idle speed so the governor is inactive and determine the amount of negative torque at that speed.

(ii) High‑speed point. For engines without a high‑speed governor, determine the amount of negative torque at the maximum safe speed or the maximum representative speed. For engines with a high‑speed governor, determine the amount of negative torque at a speed at or above n_hi per § 1065.610(c)(2).

(d) Mapping constant‑speed engines. For constant‑speed engines, generate a map as follows:

(1) Record the atmospheric pressure.

(2) Warm up the engine by operating it. We recommend operating the engine at approximately 75% of the engine's expected maximum power. Continue the warm‑up until the engine coolant, block, or head absolute temperature is within ±2% of its mean value for at least 2 min or until the engine thermostat controls engine temperature.

(3) You may operate the engine with a production constant‑speed governor or simulate a constant‑speed governor by controlling engine speed with an operator demand control system described in § 1065.110. Use either isochronous or speed‑droop governor operation, as appropriate.

(4) With the governor or simulated governor controlling speed using operator demand, operate the engine at no‑load governed speed (at high speed, not low idle) for at least 15 seconds.

(5) Record at 1 Hz the mean of feedback speed and torque. Use the dynamometer to increase torque at a constant rate. Unless the standard‑setting part specifies otherwise, complete the map such that it takes (2 to 4) min to sweep from no‑load governed speed to the speed below maximum mapped power at which the engine develops 90% of maximum mapped power. You may map your engine to lower speeds. Stop recording after you complete the sweep. Use this series of speeds and torques to generate the power map as described in paragraph (e) of this section.

(i) For constant‑speed engines subject only to steady‑state testing, you may perform an engine map by using a series of discrete torques. Select at least five evenly spaced torque setpoints from no‑load to 80% of the manufacturer‑declared test torque or to a torque derived from your published maximum power level if the declared test torque is unavailable. Starting at the 80% torque point, select setpoints in 2.5% or smaller intervals, stopping at the endpoint torque. The endpoint torque is defined as the first discrete mapped torque value greater than the torque at maximum observed power where the engine outputs 90% of the maximum observed power; or the torque when engine stall has been determined (i.e. sudden deceleration of engine speed while adding torque). You may continue mapping at higher torque setpoints. At each setpoint, allow torque and speed to stabilize. Record the mean feedback speed and torque at each setpoint. From this series of mean feedback speed and torque values, use linear interpolation to determine intermediate values. Use this series of mean feedback speeds and torques to generate the power map as described in paragraph (e) of this section.

(ii) For any constant‑speed engine, you may perform an engine map with a continuous torque sweep by continuing to record the mean feedback speed and torque at 1 Hz or more frequently. Use the dynamometer to increase torque. Increase the reference torque at a constant rate from no‑load to the endpoint torque as defined in paragraph (d)(5)(i) of this section. You may continue mapping at higher torque setpoints. Unless the standard‑setting part specifies otherwise, target a torque sweep rate equal to the manufacturer‑declared test torque (or a torque derived from your published power level if the declared test torque is not known) divided by 180 seconds. Stop recording after you complete the sweep. Verify that the average torque sweep rate over the entire map is within ±7% of the target torque sweep rate. Use linear interpolation to determine intermediate values from this series of mean feedback speed and torque values. Use this series of mean feedback speeds and torques to generate the power map as described in paragraph (e) of this section.

(iii) For any isochronous governed (0% speed droop) constant‑speed engine, you may map the engine with two points as described in this paragraph (d)(5)(iii). After stabilizing at the no‑load governed speed in paragraph (d)(4) of this section, record the mean feedback speed and torque. Continue to operate the engine with the governor or simulated governor controlling engine speed using operator demand, and control the dynamometer to target a speed of 99.5% of the recorded mean no‑load governed speed. Allow speed and torque to stabilize. Record the mean feedback speed and torque. Record the target speed. The absolute value of the speed error (the mean feedback speed minus the target speed) must be no greater than 0.1% of the recorded mean no‑load governed speed. From this series of two mean feedback speed and torque values, use linear interpolation to determine intermediate values. Use this series of two mean feedback speeds and torques to generate a power map as described in paragraph (e) of this section. Note that the measured maximum test torque as determined in §1065.610 (b)(1) will be the mean feedback torque recorded on the second point.

(e) Power mapping. For all engines, create a power‑versus‑speed map by transforming torque and speed values to corresponding power values. Use the mean values from the recorded map data. Do not use any interpolated values. Multiply each torque by its corresponding speed and apply the appropriate conversion factors to arrive at units of power (kW). Interpolate intermediate power values between these power values, which were calculated from the recorded map data.

(f) Measured and declared test speeds and torques. You must select test speeds and torques for cycle generation as required in this paragraph (f). “Measured” values are either directly measured during the engine mapping process or they are determined from the engine map. “Declared” values are specified by the manufacturer. When both measured and declared values are available, you may use declared test speeds and torques instead of measured speeds and torques if they meet the criteria in this paragraph (f). Otherwise, you must use measured speeds and torques derived from the engine map.

(1) Measured speeds and torques. Determine the applicable speeds and torques for the duty cycles you will run:

(i) Measured maximum test speed for variable‑speed engines according to § 1065.610.

(ii) Measured maximum test torque for constant‑speed engines according to § 1065.610.

(iii) Measured “A,”, “B”, and “C” speeds for variable‑speed engines according to § 1065.610.

(iv) Measured intermediate speed for variable‑speed engines according to § 1065.610.

(v) For variable‑speed engines with a low‑speed governor, measure warm idle speed according to § 1065.510(b) and use this speed for cycle generation in § 1065.512. For engines with no low‑speed governor, instead use the manufacturer‑declared warm idle speed.

(2) Required declared speeds. You must declare the lowest engine speed possible with minimum load (i.e., manufacturer‑declared warm idle speed). This is applicable only to variable‑speed engines with no low‑speed governor. For engines with no low‑speed governor, the declared warm idle speed is used for cycle generation in § 1065.512. Declare this speed in a way that is representative of in‑use operation. For example, if your engine is typically connected to an automatic transmission or a hydrostatic transmission, declare this speed at the idle speed at which your engine operates when the transmission is engaged.

(3) Optional declared speeds. You may use declared speeds instead of measured speeds as follows:

(i) You may use a declared value for maximum test speed for variable‑speed engines if it is within (97.5 to 102.5)% of the corresponding measured value. You may use a higher declared speed if the length of the “vector” at the declared speed is within 2.0% of the length of the “vector” at the measured value. The term vector refers to the square root of the sum of normalized engine speed squared and the normalized full‑load power (at that speed) squared, consistent with the calculations in § 1065.610.

(ii) You may use a declared value for intermediate, “A,”, “B”, or “C” speeds for steady‑state tests if the declared value is within (97.5 to 102.5)% of the corresponding measured value.

(4) Required declared torques. If a nonzero idle or minimum torque is representative of in‑use operation, you must declare the appropriate torque as follows:

(i) For variable‑speed engines, declare a warm idle torque that is representative of in‑use operation. For example, if your engine is typically connected to an automatic transmission or a hydrostatic transmission, declare the torque that occurs at the idle speed at which your engine operates when the transmission is engaged. Use this value for cycle generation. You may use multiple warm idle torques and associated idle speeds in cycle generation for representative testing. For example, for cycles that start the engine and begin with idle, you may start a cycle in idle with the transmission in neutral with zero torque and later switch to a different idle with the transmission in drive with the Curb‑Idle Transmission Torque (CITT). For variable‑speed engines intended primarily for propulsion of a vehicle with an automatic transmission where that engine is subject to a transient duty cycle with idle operation, you must declare a CITT. You must specify a CITT based on typical applications at the mean of the range of idle speeds you specify at stabilized temperature conditions.

(ii) For constant‑speed engines, declare a warm minimum torque that is representative of in‑use operation. For example, if your engine is typically connected to a machine that does not operate below a certain minimum torque, declare this torque and use it for cycle generation.

(5) Optional declared torques.

(i) For variable‑speed engines you may declare a maximum torque over the engine operating range. You may use the declared value for measuring warm high‑idle speed as specified in this section.

(ii) For constant‑speed engines you may declare a maximum test torque. You may use the declared value for cycle generation if it is within (95 to 100)% of the measured value.

(g) [Reserved]

(h) Other mapping procedures. You may use other mapping procedures if you believe the procedures specified in this section are unsafe or unrepresentative for your engine. Any alternate techniques you use must satisfy the intent of the specified mapping procedures, which is to determine the maximum available torque at all engine speeds that occur during a duty cycle. Identify any deviations from this section's mapping procedures when you submit data to us.

§ 1065.512 Duty cycle generation.

(a) Generate duty cycles according to this section if the standard‑setting part requires engine mapping to generate a duty cycle for your engine configuration. The standard‑setting part generally defines applicable duty cycles in a normalized format. A normalized duty cycle consists of a sequence of paired values for speed and torque or for speed and power.

(b) Transform normalized values of speed, torque, and power using the following conventions:

(1) Engine speed for variable‑speed engines. For variable‑speed engines, normalized speed may be expressed as a percentage between warm idle speed, f_nidle, and maximum test speed, f_ntest, or speed may be expressed by referring to a defined speed by name, such as “warm idle,” “intermediate speed,” or “A,” “B,” or “C” speed. Section 1065.610 describes how to transform these normalized values into a sequence of reference speeds, f_nref. Running duty cycles with negative or small normalized speed values near warm idle speed may cause low‑speed idle governors to activate and the engine torque to exceed the reference torque even though the operator demand is at a minimum. In such cases, we recommend controlling the dynamometer so it gives priority to follow the reference torque instead of the reference speed and let the engine govern the speed. Note that the cycle‑validation criteria in § 1065.514 allow an engine to govern itself. This allowance permits you to test engines with enhanced‑idle devices and to simulate the effects of transmissions such as automatic transmissions. For example, an enhanced‑idle device might be an idle speed value that is normally commanded only under cold‑start conditions to quickly warm up the engine and aftertreatment devices. In this case, negative and very low normalized speeds will generate reference speeds below this higher enhanced idle speed. You may do either of the following when using enhanced‑idle devices: and we recommend controlling

(i) Control the dynamometer so it gives priority to follow the reference torque, controlling the operator demand so it gives priority to follow reference speed and let the engine govern the speed when the operator demand is at minimum.

(ii) While running an engine where the electronic control module broadcasts an enhanced‑idle speed that is above the denormalized speed, use the broadcast speed as the reference speed. Use these new reference points for duty‑cycle validation. This does not affect how you determine denormalized reference torque in paragraph (b)(2) of this section.

(2) Engine torque for variable‑speed engines. For variable‑speed engines, normalized torque is expressed as a percentage of the mapped torque at the corresponding reference speed. Section 1065.610 describes how to transform normalized torques into a sequence of reference torques, T_ref. Section 1065.610 also describes special requirements for modifying transient duty cycles for variable‑speed engines intended primarily for propulsion of a vehicle with an automatic transmission. Section 1065.610 also describes under what conditions you may command T_ref greater than the reference torque you calculated from a normalized duty cycle. This provision permits you to command T_ref values that are limited by a declared minimum torque. For any negative torque commands, command minimum operator demand and use the dynamometer to control engine speed to the reference speed, but if reference speed is so low that the idle governor activates, we recommend using the dynamometer to control torque to zero, CITT, or a declared minimum torque as appropriate. Note that you may omit power and torque points during motoring from the cycle‑validation criteria in § 1065.514. Also, use the maximum mapped torque at the minimum mapped speed as the maximum torque for any reference speed at or below the minimum mapped speed.

(3) Engine torque for constant‑speed engines. For constant‑speed engines, normalized torque is expressed as a percentage of maximum test torque, T_test. Section 1065.610 describes how to transform normalized torques into a sequence of reference torques, T_ref. Section 1065.610 also describes under what conditions you may command T_ref greater than the reference torque you calculated from the normalized duty cycle. This provision permits you to command T_ref values that are limited by a declared minimum torque.

(4) Engine power. For all engines, normalized power is expressed as a percentage of mapped power at maximum test speed, f_ntest, unless otherwise specified by the standard‑setting part. Section 1065.610 describes how to transform these normalized values into a sequence of reference powers, P_ref. Convert these reference powers to corresponding torques for operator demand and dynamometer control. Use the reference speed associated with each reference power point for this conversion. As with cycles specified with % torque, issue torque commands more frequently and linearly interpolate between these reference torque values generated from cycles with % power.

(5) Ramped‑modal cycles. For ramped modal cycles, generate reference speed and torque values at 1 Hz and use this sequence of points to run the cycle and validate it in the same manner as with a transient cycle. During the transition between modes, linearly ramp the denormalized reference speed and torque values between modes to generate reference points at 1 Hz. Do not linearly ramp the normalized reference torque values between modes and then denormalize them. Do not linearly ramp normalized or denormalized reference power points. These cases will produce nonlinear torque ramps in the denormalized reference torques. If the speed and torque ramp runs through a point above the engine's torque curve, continue to command the reference torques and allow the operator demand to go to maximum. Note that you may omit power and either torque or speed points from the cycle‑validation criteria under these conditions as specified in § 1065.514.

(c) For variable‑speed engines, command reference speeds and torques sequentially to perform a duty cycle. Issue speed and torque commands at a frequency of at least 5 Hz for transient cycles and at least 1 Hz for steady‑state cycles (i.e., discrete‑mode and ramped‑modal). Linearly interpolate between the 1 Hz reference values specified in the standard‑setting part to determine more frequently issued reference speeds and torques. During an emission test, record the feedback speeds and torques at a frequency of at least 5 Hz for transient cycles and at least 1 Hz for steady‑state cycles. For transient cycles, you may record the feedback speeds and torques at lower frequencies (as low as 1 Hz) if you record the average value over the time interval between recorded values. Calculate the average values based on feedback values updated at a frequency of at least 5 Hz. Use these recorded values to calculate cycle‑validation statistics and total work.

(d) For constant‑speed engines, operate the engine with the same production governor you used to map the engine in § 1065.510 or simulate the in‑use operation of a governor the same way you simulated it to map the engine in § 1065.510. Command reference torque values sequentially to perform a duty cycle. Issue torque commands at a frequency of at least 5 Hz for transient cycles and at least 1 Hz for steady‑state cycles (i.e., discrete‑mode, ramped‑modal). Linearly interpolate between the 1 Hz reference values specified in the standard‑setting part to determine more frequently issued reference torque values. During an emission test, record the feedback speeds and torques at a frequency of at least 5 Hz for transient cycles and at least 1 Hz for steady‑state cycles. For transient cycles, you may record the feedback speeds and torques at lower frequencies (as low as 1 Hz) if you record the average value over the time interval between recorded values. Calculate the average values based on feedback values updated at a frequency of at least 5 Hz. Use these recorded values to calculate cycle‑validation statistics and total work.

(e) You may perform practice duty cycles with the test engine to optimize operator demand and dynamometer controls to meet the cycle‑validation criteria specified in § 1065.514.

§ 1065.514 Cycle-validation criteria for operation over specified duty cycles.

Validate the execution of your duty cycle according to this section unless the standard‑setting part specifies otherwise. This section describes how to determine if the engine's operation during the test adequately matched the reference duty cycle. This section applies only to speed, torque, and power from the engine's primary output shaft. Other work inputs and outputs are not subject to cycle‑validation criteria. You must compare the original reference duty cycle points generated as described in § 1065.512 to the corresponding feedback values recorded during the test. You may compare reference duty cycle points recorded during the test to the corresponding feedback values recorded during the test as long as the recorded reference values match the original points generated in § 1065.512. The number of points in the validation regression are based on the number of points in the original reference duty cycle generated in § 1065.512. For example, if the original cycle has 1199 reference points at 1 Hz, then the regression will have up to 1199 pairs of reference and feedback values at the corresponding moments in the test. The feedback speed and torque signals may be filtered—either in real‑time while the test is run or afterward in the analysis program. Any filtering that is used on the feedback signals used for cycle validation must also be used for calculating work. Feedback signals for control loops may use different filtering.

(a) Testing performed by EPA CARB. Our tests must meet the specifications of paragraph (f) of this section, unless we determine that failing to meet the specifications is related to engine performance rather than to shortcomings of the dynamometer or other laboratory equipment.

(b) Testing performed by manufacturers. Emission tests that meet the specifications of paragraph (f) of this section satisfy the standard‑setting part's requirements for duty cycles. You may ask to use a dynamometer or other laboratory equipment that cannot meet those specifications. We will approve your request as long as using the alternate equipment does not adversely affect your ability to show compliance with the applicable emission standards.

(c) Time‑alignment. Because time lag between feedback values and the reference values may bias cycle‑validation results, you may advance or delay the entire sequence of feedback engine speed and torque pairs to synchronize them with the reference sequence. If you advance or delay feedback signals for cycle validation, you must make the same adjustment for calculating work. You may use linear interpolation between successive recorded feedback signals to time shift an amount that is a fraction of the recording period.

(d) Omitting additional points. Besides engine cranking, you may omit additional points from cycle‑validation statistics as described in the following table:

Table 1 of § 1065.514—Permissible Criteria for Omitting Points From from Duty‑Cycle Regression Statistics

(e) Statistical parameters. Use the remaining points to calculate regression statistics for a floating intercept as described in § 1065.602. Round calculated regression statistics to the same number of significant digits as the criteria to which they are compared. Refer to Table 2 of § 1065.514 for the default criteria and refer to the standard‑setting part to determine if there are other criteria for your engine. Calculate the following regression statistics:

(1) Slopes for feedback speed, a_1fn, feedback torque, a_1T, and feedback power a_1P.

(2) Intercepts for feedback speed, a_0fn, feedback torque, a_0T, and feedback power a_0P.

(3) Standard error of the estimates of error for feedback speed, SEE_fn, feedback torque, SEE_T, and feedback power SEE_P.

(4) Coefficients of determination for feedback speed, r²_fn, feedback torque, r²_T, and feedback power r²_P.

(f) Cycle‑validation criteria. Unless the standard‑setting part specifies otherwise, use the following criteria to validate a duty cycle:

(1) For variable‑speed engines, apply all the statistical criteria in Table 2 of this section.

(2) For constant‑speed engines, apply only the statistical criteria for torque in Table 2 of this section.

(3) For discrete‑mode steady‑state testing, apply cycle‑validation criteria by treating the sampling periods from the series of test modes as a continuous sampling period, analogous to ramped‑modal testing and apply statistical criteria as described in paragraph (f)(1) or (f)(2) of this section. Note that if the gaseous and particulate test intervals are different periods of time, separate validations are required for the gaseous and particulate test intervals. Table 2 follows:

Table 2 of § 1065.514—Default Statistical Criteria for Validating Duty Cycles

§ 1065.516 Sample system decontamination and preconditioning.

This section describes how to manage the impact of sampling system contamination on emission measurements. Decontaminate and precondition your sampling system as appropriate for your application. Contamination occurs when a regulated pollutant accumulates in the sample system in a high enough concentration to cause release during emission tests. Hydrocarbons and PM are generally the only regulated pollutants that contaminate sample systems. Note that although this section focuses on avoiding excessive contamination of sampling systems, you must also avoid loss of sample to a sampling system that is too clean. The goal of decontamination is not to perfectly clean the sampling system, but rather to achieve equilibrium between the sampling system and the exhaust so emission components are neither lost to nor entrained from the sampling system.

(a) You may perform contamination checks as follows to determine if decontamination is needed:

(1) For dilute exhaust sampling systems, measure hydrocarbon and PM emissions by sampling with the CVS dilution air turned on, without an engine connected to it.

(2) For raw analyzers and systems that collect PM samples from raw exhaust, measure hydrocarbon and PM emissions by sampling purified air or nitrogen.

(3) When calculating zero emission levels, apply all applicable corrections, including initial THC contamination and diluted (CVS) exhaust background corrections.

(4) Sampling systems are considered contaminated if either of the following conditions applies:

(i) The hydrocarbon emission level exceeds 2% of the flow‑weighted mean concentration expected at the HC standard.

(ii) The PM emission level exceeds 5% of the level expected at the standard and exceeds 20 µg on a 47 mm PTFE membrane filter.

(b) To precondition or decontaminate sampling systems, use the following recommended procedure.  If you show that the following procedure is not appropriate for your application, you may request that we approve a different procedure:

(1) Start the engine and operate it at a condition that generates high exhaust temperatures at the sample probe inlet.

(2) Operate any dilution systems at their expected flow rates. Prevent aqueous condensation in the dilution systems.

(3) Operate any PM sampling systems at their expected flow rates.

(4) Sample PM for at least 10 min using any sample media. You may change sample media at any time during this process and you may discard them without weighing them.

(5) You may purge any gaseous sampling systems that do not require decontamination during this procedure.

(6) You may conduct calibrations or verifications on any idle equipment or analyzers during this procedure.

(c) If your sampling system is still contaminated following the procedures specified in paragraph (b) of this section, you may use more aggressive procedures to decontaminate the sampling system, as long as the decontamination does not cause the sampling system to be cleaner than an equilibrium condition such that artificially low emission measurements may result.

§ 1065.518 Engine preconditioning.

(a) This section applies for engines where measured emissions are affected by prior operation. Note that §1065.520(e) allows you to run practice duty cycles before the emission test; this section recommends how to do this for the purpose of preconditioning the engine. Follow the standard‑setting part if it specifies a different engine preconditioning procedure.

(b) The intent of engine preconditioning is to manage the representativeness of emissions and emission controls over the duty cycle and to reduce bias.

(c) This paragraph (c) specifies the engine preconditioning procedures for different types of duty cycles. You must identify the amount of preconditioning before starting to precondition. You must run the predefined amount of preconditioning. You may measure emissions during preconditioning. You may not abort an emission test sequence based on emissions measured during preconditioning. For confirmatory testing, you may ask us to run more preconditioning cycles than we specify in this paragraph (c); we will agree to this only if you show that additional preconditioning cycles are required to meet the intent of paragraph (b) of this section, for example, due to the effect of DPF regeneration on NH₃ storage in the SCR catalyst. Perform preconditioning as follows, noting that the specific cycles for preconditioning are the same ones that apply for emission testing:

(1) Cold‑start transient cycle. Precondition the engine by running at least one hot‑start transient cycle. We will precondition your engine by running two hot‑start transient cycles. Immediately after completing each preconditioning cycle, shut down the engine and complete the engine‑off soak period. Immediately after completing the last preconditioning cycle, shut down the engine and begin the cold soak as described in §1065.530(a)(1).

(2) Hot‑start transient cycle. Precondition the engine by running at least one hot‑start transient cycle. We will precondition your engine by running two hot‑start transient cycles. Immediately after completing each preconditioning cycle, shut down the engine, then start the next cycle (including the emission test) as soon as practical. For any repeat cycles, start the next cycle within 60 seconds after completing the last preconditioning cycle (this is optional for manufacturer testing).

(3) Hot‑running transient cycle. Precondition the engine by running at least one hot‑running transient cycle. We will precondition your engine by running two hot‑running transient cycles. Do not shut down the engine between cycles. Immediately after completing each preconditioning cycle, start the next cycle (including the emission test) as soon as practical. For any repeat cycles, start the next cycle within 60 seconds after completing the last preconditioning cycle (this is optional for manufacturer testing). See §1065.530(a)(1)(iii) for additional instructions if the cycle begins and ends under different operating conditions.

(4) Discrete‑mode cycle for steady‑state testing. Precondition the engine at the same operating condition as the next test mode, unless the standard‑setting part specifies otherwise. We will precondition your engine by running it for at least five minutes before sampling.

(5) Ramped‑modal cycle for steady‑state testing. Precondition the engine by running at least the second half of the ramped‑modal cycle, based on the number of test modes. We will precondition your engine by running one complete ramped‑modal cycle. Do not shut down the engine between cycles. Immediately after completing each preconditioning cycle, start the next cycle (including the emission test) as soon as practical. For any repeat cycles, start the next cycle within 60 seconds after completing the last preconditioning cycle. See §1065.530(a)(1)(iii) for additional instructions if the cycle begins and ends under different operating conditions.

(d) You may conduct calibrations or verifications on any idle equipment or analyzers during engine preconditioning.

§ 1065.520 Pre-test verification procedures and pre-test data collection.

(a) If your engine must comply with a PM standard For tests in which you measure PM emissions, follow the procedures for PM sample preconditioning and tare weighing according to § 1065.590.

(b) Unless the standard‑setting part specifies different tolerances, verify at some point before the test that ambient conditions are within the tolerances specified in this paragraph (b). For purposes of this paragraph (b), “before the test” means any time from a point just prior to engine starting (excluding engine restarts) to the point at which emission sampling begins.

(1) Ambient temperature of (20 to 30) °C. See § 1065.530(j) for circumstances under which ambient temperatures must remain within this range during the test.

(2) Atmospheric pressure of (80.000 to 103.325) kPa and within ±5 kPa of the value recorded at the time of the last engine map. You are not required to verify atmospheric pressure prior to a hot start test interval for testing that also includes a cold start.

(3) Dilution air conditions as specified in § 1065.140, except in cases where you preheat your CVS before a cold start test. We recommend verifying dilution air conditions just prior to the start of each test interval.

(c) You may test engines at any intake‑air humidity, and we may test engines at any intake‑air humidity.

(d) Verify that auxiliary‑work inputs and outputs are configured as they were during engine mapping, as described in§ 1065.510(a).

(e) You may perform a final calibration of the speed, torque, and proportional‑flow control systems, which may include performing practice duty cycles.

(f) You may perform the following recommended procedure to precondition sampling systems:

(1) Start the engine and use good engineering judgment to bring it to one of the following:

(i) 100% torque at any speed above its peak‑torque speed.

(ii) 100% operator demand.

(2) Operate any dilution systems at their expected flow rates. Prevent aqueous condensation in the dilution systems.

(3) Operate any PM sampling systems at their expected flow rates.

(4) Sample PM for at least 10 min using any sample media. You may change sample media during preconditioning. You may discard preconditioning samples without weighing them.

(5) You may purge any gaseous sampling systems during preconditioning.

(6) You may conduct calibrations or verifications on any idle equipment or analyzers during preconditioning.

(7) Proceed with the test sequence described in § 1065.530(a)(1).

(g) (f) Verify the amount of nonmethane hydrocarbon contamination in the exhaust and background HC sampling systems within 8 hours before the start of the first test interval of each duty‑cycle sequence for laboratory tests. You may verify the contamination of a background HC sampling system by reading the last bag fill and purge using zero gas. For any NMHC measurement system that involves separately measuring methane CH₄ and subtracting it from a THC measurement or for any CH₄ measurement system that uses an NMC, verify the amount of THC contamination using only the THC analyzer response. There is no need to operate any separate methane CH₄ analyzer for this verification,; however, you may measure and correct for THC contamination in the CH₄ sample train path for the cases where NMHC is determined by subtracting CH₄ from THCor, where CH₄ is determined, using an NMC as configured in § 1065.365(d), (e), and (f); and using the calculations in § 1065.660(b)(2). Perform this verification as follows:

(1) Select the HC analyzer range for measuring the flow‑weighted mean concentration expected at the HC standard.

(2) Zero the HC analyzer at the analyzer zero or sample port. Note that FID zero and span balance gases may be any combination of purified air or purified nitrogen that meets the specifications of § 1065.750. We recommend FID analyzer zero and span gases that contain approximately the flow‑weighted mean concentration of O₂ expected during testing.

(3) Span the HC analyzer using span gas introduced at the analyzer span or sample port. Span on a carbon number basis of one (C₁). For example, if you use a C₃H₈ span gas of concentration 200 µmol/mol, span the FID to respond with a value of 600 µmol/mol.

(4) Overflow zero gas at the HC probe inlet or into a tee near the probe outlet.

(5) Measure the THC concentration in the sampling and background systems as follows:

(i) For continuous sampling, record the mean THC concentration as overflow zero air gas flows.

(ii) For batch sampling, fill the sample medium (e.g., bag) and record its mean THC concentration.

(iii) For the background system, record the mean THC concentration of the last fill and purge.

(6) Record this value as the initial THC concentration, x_{THC[THC‑FID]init}, and use it to correct measured values as described in § 1065.660.

(7) You may correct the measured initial THC concentration for drift as follows:

(i) For batch and continuous HC analyzers, after determining the initial THC concentration, flow zero gas to the analyzer zero or sample port. When the analyzer reading is stable, record the mean analyzer value.

(ii) Flow span gas to the analyzer span or sample port. When the analyzer reading is stable, record the mean analyzer value.

(iii) Use mean analyzer values from paragraphs (f)(2), (f)(3), (f)(7)(i), and (f)(7)(ii) of this section to correct the initial THC concentration recorded in paragraph (f)(6) of this section for drift, as described in §1065.550.

(7) (8)  If any of the x_{THC[THC‑FID]init} values exceed the greatest of the following values, determine the source of the contamination and take corrective action, such as purging the system during an additional preconditioning cycle or replacing contaminated portions:

(i) 2% of the flow‑weighted mean wet, net concentration expected at the HC (THC or NMHC) standard.

(ii) 2% of the flow‑weighted mean wet, net concentration of HC (THC or NMHC) measured during testing.

(iii) 2 µmol/mol.

(8) (9) If corrective action does not resolve the deficiency, you may request to use the contaminated system as an alternate procedure under § 1065.10.

§ 1065.525 Engine starting, restarting, and shutdown, and optional repeating of void discrete modes.

(a) Start For test intervals that require emission sampling during engine starting, start the engine using one of the following methods:

(1) Start the engine as recommended in the owner’s manual using a production starter motor or air‑start system and either an adequately charged battery, a suitable power supply, or a suitable compressed air source.

(2) Use the dynamometer to start the engine. To do this, motor the engine within ±25% of its typical in‑use cranking speed. Stop cranking within 1 second of starting the engine.

(b) If the engine does not start after 15 seconds of cranking, stop cranking and determine why the engine failed to start, unless the owners manual or the service‑repair manual describes the longer cranking time as normal.

(c) Respond to engine stalling with the following steps:

(1) If the engine stalls during warm‑up before emission sampling begins, restart the engine and continue warm‑up.

(2) If the engine stalls during preconditioning before emission sampling begins, restart the engine and restart the preconditioning sequence.

(3) Void the entire test if the engine stalls at any time after emission sampling begins, except as described in § 1065.526. If you do not void the entire test, you must void the individual test mode or test interval in which the engine stalls.

(4) Except as described in paragraph (d) of this section, void the test if the engine stalls at any time after emission sampling begins.

(d) Shut down the engine according to the manufacturer's specifications.

§ 1065.526 Repeating void modes or test intervals.

(a) Test modes and test intervals can be voided because of instrument malfunctions, engine stalling, or emissions exceeding instrument ranges, and other unexpected deviations from the specified procedures. This section specifies circumstances for which a test mode or test interval can be repeated without repeating the entire test.

(b) This section is intended to result in replicate test modes and test intervals that are identical to what would have occurred if the cause of the voiding had not occurred. It does not allow you to repeat test modes or test intervals in any circumstances that would be inconsistent with good engineering judgment where doing so would produce inconsistent or unrepresentative results. For example, the procedures specified here for repeating a mode or interval may not apply for certain engines that include hybrid energy storage features or emission controls that involve physical or chemical storage of pollutants. This section applies for circumstances in which emission concentrations exceed the analyzer range only if it is due to operator error or analyzer malfunction. It does not apply for circumstances in which the emission concentrations exceed the range because they were higher than expected.

(c) If one of the modes of a discrete‑mode test is voided as provided in this section, you may void the results for that individual mode and continue the test as follows:

(1) If the engine has stalled or been shut down, restart the engine.

(2) Use good engineering judgment to restart Restart the test sequence duty cycle using the appropriate steps in § 1065.530(b).

(3) Precondition Stabilize the engine by operating it at the previous mode for approximately the same amount of time it operated at that mode for the previous emission measurement. mode at which the duty cycle was interrupted and continue with the duty cycle as specified in the standard‑setting part.

(4) Advance to the mode at which the duty cycle was interrupted and continue with the duty cycle as specified in the standard‑setting part.

(d) If an individual mode of a discrete‑mode duty cycle sequence is voided after running the full duty cycle, you may void results for that mode and repeat testing for that mode as follows:

(1) Restart the test sequence using the appropriate steps in §1065.530(b).

(2) Stabilize the engine by operating it at that mode.

(3) Sample emissions over an appropriate test interval.

(4) If you sampled gaseous and PM emissions over separate test intervals for a voided mode, you must void both test intervals and repeat sampling of both gaseous and PM emissions for that mode.

(d) (e) If a transient or ramped‑modal cycle test interval is voided as provided in this section, you may repeat the test interval as follows:

(1) Use good engineering judgment to restrart Restart (as applicable) and precondition the engine and emission sampling system to the same condition as would apply for normal testing. This may require you to complete the voided test interval. For example, you may generally repeat a hot‑start test of a heavy‑duty highway engine after completing the voided hot‑start test and allowing the engine to soak for 20 minutes.

(2) Complete the remainder of the test according to the provisions in this subpart.

(e) (f) Keep records from the voided test mode or test interval in the same manner as required for unvoided tests, and include a description of the reason for voiding the test mode or test interval.

§ 1065.530 Emission test sequence.

(a) Time the start of testing as follows:

(1) Perform one of the following if you precondition sampling systems as described in § 1065.520(f) the engine as described in § 1065.518:

(i) For cold‑start duty cycles, shut down the engine. Unless the standard‑setting part specifies that you may only perform a natural engine cooldown, you may perform a forced engine cooldown. Use good engineering judgment to set up Set up appropriate systems to send cooling air across the engine, to send cool oil through the engine lubrication system, to remove heat from coolant through the engine cooling system, and to remove heat from any exhaust aftertreatment systems. In the case of a forced aftertreatment cooldown, good engineering judgment would indicate that you do not start flowing cooling air until the aftertreatment system has cooled below its catalytic activation temperature. For platinum‑group metal catalysts, this temperature is about 200 °C. Once the aftertreatment system has naturally cooled below its catalytic activation temperature, good engineering judgment would indicate that you use clean air with a temperature of at least 15°C, and direct the air through the aftertreatment system in the normal direction of exhaust flow. Do not use any cooling procedure that results in unrepresentative emissions (see § 1065.10(c)(1)). You may start a cold‑start duty cycle when the temperatures of an engine's lubricant, coolant, and aftertreatment systems are all between (20 and 30)°C.

(ii) For hot‑start emission measurements, shut down the engine. Start the hot‑start duty cycle as specified in the standard‑setting part immediately after completing the last preconditioning cycle. For any repeat cycles, start the hot‑start transient emission test within 60 seconds after completing the last preconditioning cycle (this is optional for manufacturer testing).

(iii) For testing that involves hot‑stabilized emission measurements, such as any steady‑state testing, you may continue to operate the engine at maximum test speed and 100% torque if that is the first operating point. Otherwise, operate the engine at warm idle or the first operating point of the duty cycle. In any case, start the emission test within 10 min after you complete the preconditioning procedure. such as any steady‑state testing with a ramped‑modal cycle, start the hot‑stabilized emission test within 60 seconds after completing the last preconditioning cycle (the time between cycles is optional for manufacturer testing). If the hot‑stabilized cycle begins and ends with different operating conditions, add a linear transition period of 20 seconds between hot‑stabilized cycles where you linearly ramp the (denormalized) reference speed and torque values over the transition period. See § 1065.501(c)(2)(i) for discrete‑mode cycles.

(2) If you do not precondition sampling systems the engine as described in §1065.518, perform one of the following:

(i) For cold‑start duty cycles, prepare the engine according to paragraph (a)(1)(i) of this section.

(ii) For hot‑start emission measurements, first operate the engine at any speed above peak‑torque speed and at (65 to 85)% of maximum mapped power until either the engine coolant, block, or head absolute temperature is within ±2% of its mean value for at least 2 min or until the engine thermostat controls engine temperature. Shut down the engine. Start the duty cycle within 20 min of engine shutdown.

(iii) For testing that involves hot‑stabilized emission measurements, bring the engine either to warm idle or the first operating point of the duty cycle. Start the test within 10 min of achieving temperature stability. Determine temperature stability either as the point at which the engine thermostat controls engine temperature or as the point at which the engine coolant, block, or head absolute temperature is within ±2% of its mean value for at least 2 min, or as the point at which the engine thermostat controls engine temperature. based on the following parameters:

(A) Engine coolant or block or head absolute temperatures for water‑cooled engines.

(B) Oil sump absolute temperature for air‑cooled engines with an oil sump.

(C) Cylinder head absolute temperature or exhaust gas temperature for air‑cooled engines with no oil sump.

(b) Take the following steps before emission sampling begins:

(1) For batch sampling, connect clean storage media, such as evacuated bags or tare‑weighed filters.

(2) Start all measurement instruments according to the instrument manufacturer's instructions and using good engineering judgment and as necessary and appropriate for your application.

(3) Start dilution systems, sample pumps, cooling fans, and the data‑collection system.

(4) Pre‑heat or pre‑cool heat exchangers in the sampling system to within their operating temperature tolerances for a test.

(5) Allow heated or cooled components such as sample lines, filters, chillers, and pumps to stabilize at their operating temperatures.

(6) Verify that there are no significant vacuum‑side leaks according to § 1065.345.

(7) Adjust the sample flow rates to desired levels, using bypass flow, if desired.

(8) Zero or re‑zero any electronic integrating devices, before the start of any test interval.

(9) Select gas analyzer ranges. You may automatically or manually switch gas analyzer ranges during a test only if switching is performed by changing the span over which the digital resolution of the instrument is applied. During a test you may not switch the gains of an analyzer's analog operational amplifier(s).

(10) Zero and span all continuous analyzers using NIST SI‑traceable gases that meet the specifications of § 1065.750. Span FID analyzers on a carbon number basis of one (1), C₁. For example, if you use a C₃H₈ span gas of concentration 200 µmol/mol, span the FID to respond with a value of 600 µmol/mol. Span FID analyzers consistent with the determination of their respective response factors, RF, and penetration fractions, PF, according to § 1065.365.

(11) We recommend that you verify gas analyzer responses after zeroing and spanning by sampling a calibration gas that has a concentration near one‑half of the span gas concentration. Based on the results and good engineering judgment, you may decide whether or not, determine whether it is necessary or appropriate to re‑zero, re‑span, or re‑calibrate a gas analyzer before starting a test.

(12) If you correct for dilution air background concentrations of engine exhaust constituents, start measuring and recording background concentrations.

(13) Drain any condensate from the intake air system and close any intake air condensate drains that are not normally open during in‑use operation.

(12) Drain any accumulated condensate from the intake air system before starting a duty cycle, as described in § 1065.125(e)(1). If engine and aftertreatment preconditioning cycles are run before the duty cycle, treat the preconditioning cycles and any associated soak period as part of the duty cycle for the purpose of opening drains and draining condensate. Note that you must close any intake air condensate drains that are not representative of those normally open during in‑use operation.

(c) Start testing as follows:

(1) If an engine is already running and warmed up, and starting is not part of the duty cycle, perform the following for the various duty cycles:

(i) Transient and steady‑state ramped‑modal cycles. Simultaneously start running the duty cycle, sampling exhaust gases, recording data, and integrating measured values.

(ii) Steady‑state discrete‑mode cycles. Control the engine operation to match the first mode in the test cycle. This will require controlling engine speed and load, engine load, or other operator demand settings, as specified in the standard‑setting part. Follow the instructions in the standard‑setting part to determine how long to stabilize engine operation at each mode, how long to sample emissions at each mode, and how to transition between modes.

(2) If engine starting is part of the duty cycle, initiate data logging, sampling of exhaust gases, and integrating measured values before attempting to start the engine. Initiate the duty cycle when the engine starts.

(c) Start and run each test interval as described in this paragraph (c). The procedure varies depending on whether the test interval is part of a discrete‑mode cycle, and whether the test interval includes engine starting. Note that the standard‑setting part may apply different requirements for running test intervals.

(1) For steady‑state discrete‑mode duty cycles, start the duty cycle with the engine warmed‑up and running as described in § 1065.501(c)(2)(i). Run each mode in the sequence specified in the standard‑setting part. This will require controlling engine speed, engine load, or other operator demand settings as specified in the standard‑setting part. Simultaneously start any electronic integrating devices, continuous data recording, and batch sampling. We recommend that you stabilize the engine for at least 5 minutes for each mode. Once sampling begins, sample continuously for at least 1 minute. Note that longer sample times may be needed for accurately measuring very low emission levels.

(2) For transient and steady‑state ramped‑modal duty cycles that do not include engine starting, start the test interval with the engine running as soon as practical after completing engine preconditioning. Simultaneously start any electronic integrating devices, continuous data recording, batch sampling, and execution of the duty cycle.

(3) If engine starting is part of the test interval, simultaneously start any electronic integrating devices, continuous data recording, and batch sampling before attempting to start the engine. Initiate the sequence of points in the duty cycle when the engine starts.

(4) For batch sampling systems, you may advance or delay the start and end of sampling at the beginning and end of the test interval to improve the accuracy of the batch sample, as appropriate for your application.

(d) At the end of each test interval, continue to operate all sampling and dilution systems to allow the sampling system's response time to elapse. Then stop all sampling and recording, including the recording of background samples. Finally, stop any integrating devices and indicate the end of the duty cycle in the recorded data.

(e) Shut down the engine if you have completed testing or if it is part of the duty cycle.

(f) If testing involves another duty cycle after a soak period with the engine off, start a timer when the engine shuts down, and repeat the steps in paragraphs (b) through (e) of this section as needed.

(g) Take the following steps after emission sampling is complete:

(1) For any proportional batch sample, such as a bag sample or PM sample, verify that proportional sampling was maintained according to § 1065.545. Void any samples that did not maintain proportional sampling according to § 1065.545.

(2) Place any used PM samples into covered or sealed containers and return them to the PM‑stabilization environment. Follow the PM sample post‑conditioning and total weighing procedures in § 1065.595.

(3) As soon as practical after the duty cycle is complete, or during the soak period if practical, perform the following:

(i) Zero and span all batch gas analyzers no later than 30 minutes after the duty cycle is complete, or during the soak period if practical.

(ii) Analyze any conventional gaseous batch samples no later than 30 minutes after the duty cycle is complete, or during the soak period if practical.

(iii) Analyze background samples no later than 60 minutes after the duty cycle is complete.

(iv) Analyze non‑conventional gaseous batch samples, such as ethanol (NMHCE) as soon as practical using good engineering judgment.

(4) After quantifying exhaust gases, verify drift as follows:

(i) For batch and continuous gas analyzers, record the mean analyzer value after stabilizing a zero gas to the analyzer. Stabilization may include time to purge the analyzer of any sample gas, plus any additional time to account for analyzer response.

(ii) Record the mean analyzer value after stabilizing the span gas to the analyzer. Stabilization may include time to purge the analyzer of any sample gas, plus any additional time to account for analyzer response.

(iii) Use these data to validate and correct for drift as described in § 1065.550.

(5) If you perform carbon balance error verification, verify carbon balance error as specified in the standard‑setting part and §1065.543. Calculate and report the three carbon balance error quantities for each test interval; carbon mass absolute error for a test interval (ε_aC), carbon mass rate absolute error for a test interval (ε_aCrate), and carbon mass relative error for a test interval (ε_rC). For duty cycles with multiple test intervals, you may calculate and report the composite carbon mass relative error, ε_rCcomp, for the whole duty cycle. If you report ε_rCcomp, you must still calculate and report ε_aC, ε_aCrate, and ε_rC for each test interval.

(h) Unless the standard‑setting part specifies otherwise, determine whether or not the test meets the cycle‑validation criteria in § 1065.514.

(1) If the criteria void the test, you may retest using the same denormalized duty cycle, or you may re‑map the engine, denormalize the reference duty cycle based on the new map and retest the engine using the new denormalized duty cycle.

(2) If the criteria void the test for a constant‑speed engine only during commands of maximum test torque, you may do the following:

(i) Determine the first and last feedback speeds at which maximum test torque was commanded.

(ii) If the last speed is greater than or equal to 90% of the first speed, the test is void. You may retest using the same denormalized duty cycle, or you may re‑map the engine, denormalize the reference duty cycle based on the new map and retest the engine using the new denormalized duty cycle.

(iii) If the last speed is less than 90% of the first speed, reduce maximum test torque by 5%, and proceed as follows:

(A) Denormalize the entire duty cycle based on the reduced maximum test torque according to § 1065.512.

(B) Retest the engine using the denormalized test cycle that is based on the reduced maximum test torque.

(C) If your engine still fails the cycle criteria, reduce the maximum test torque by another 5% of the original maximum test torque.

(D) If your engine fails after repeating this procedure four times, such that your engine still fails after you have reduced the maximum test torque by 20% of the original maximum test torque, notify us and we will consider specifying a more appropriate duty cycle for your engine under the provisions of § 1065.10(c).

(i) [Reserved]

(j) Measure and record ambient temperature, pressure, and humidity, as appropriate. For testing the following engines, you must record ambient temperature continuously to verify that it remains within the pre‑test temperature range as specified in § 1065.520(b):

(1) Air‑cooled engines.

(2) Engines equipped with auxiliary emission control devices that sense and respond to ambient temperature.

(3) Any other engine for which good engineering judgment indicates this is necessary to remain consistent with § 1065.10(c)(1).

§ 1065.543 Carbon balance error verification.

(a) Carbon balance error verification compares independently calculated quantities of carbon flowing into and out of an engine system. The engine system includes aftertreatment devices as applicable. Calculating carbon intake considers carbon‑carrying streams flowing into the system, including intake air, fuel, and optionally any other fluids injected into the exhaust, if applicable. Carbon flow out of the system comes from exhaust emission calculations. Note that this verification is not valid if you calculate exhaust molar flow rate using fuel rate and chemical balance as described in §1065.655(f)(3) because carbon flows into and out of the system are not independent. Ensure that carbon mass in and carbon mass out data signals align.

(b) Perform the carbon balance error verification after emission sampling is complete for a test interval or duty cycle as described in §1065.530(g). Testing must include measured values as needed to determine intake air, fuel flow, and carbon‑related gaseous exhaust emissions. You may optionally account for the flow of carbon‑carrying fluids other than intake air and fuel into the system.

Perform carbon balance error verification as follows:

(1) Calculate carbon balance error quantities as described in §1065.643. The three quantities for individual test intervals are carbon mass absolute error, ε_aC, carbon mass rate absolute error, ε_aC_rate, and carbon mass relative error, εrC. Determine ε_aC, ε_aC_rate, and ε_rC for all test intervals. You may determine composite carbon mass relative error, ε_rC_comp, as a fourth quantity that optionally applies for duty cycles with multiple test intervals.

(2) You meet verification criteria for an individual test interval if the absolute values of carbon balance error quantities are at or below the following limit values:

(i) Calculate the carbon mass absolute error limit, L_εaC, in grams to three decimal places for comparision to the absolute value of εaC, using the following equation:

L_εaC = c ∙ P_max
Eq. 1065.543‑1

Where:
c = power‑specific carbon mass absolute error coefficient = 0.007 g/kW.
P_max= maximum power from the engine map generated according to §1065.510. If measured.
P_maxis not available, use a manufacturer‑declared value for P_max.

Example:
c = 0.007 g/kW
P_max= 230.0 kW
L_εaC = 0.007·230.0 = 1.610 g

(ii) Calculate the carbon mass rate absolute error limit, L_εaCrate, in grams per hour to three decimal places for comparison to the absolute value of εaCrate, using the following equation:

L_εaCrate = d ∙ P_max
Eq. 1065.543‑2

Where:
d = power‑specific carbon mass rate absolute error coefficient = 0.31 g/(kW∙hr).
P_max= maximum power from the engine map generated according to §1065.510. If measured.
P_maxis not available, use a manufacturer‑declared value for P_max.

Example:
d = 0.31 g/(kW∙hr)
P_max= 230.0 kW
L_εaCrate = 0.31· 230.0 = 71.300 g/hr

(iii) The carbon mass relative error limit, L_εrC, is 0.020 for comparision to the absolute value of

εrC, and optionally the absolute value of ε_rC_comp.

(c) A failed carbon balance error verification might indicate one or more problems requiring corrective action, as follows:

§ 1065.545 Validation of proportional flow control for batch sampling.

For any proportional batch sample such as a bag or PM filter, demonstrate that proportional sampling was maintained using one of the following, noting that you may omit up to 5% of the total number of data points as outliers:

(a) For any pair of flow meters rates, use recorded sample and total flow rates, where total flow rate means the raw exhaust flow rate for raw exhaust sampling and the dilute exhaust flow rate for CVS sampling, or their 1 Hz means, with the statistical calculations in § 1065.602 forcing the intercept through zero. Total flow rate means the raw exhaust flow rate for raw exhaust sampling and the dilute exhaust flow rate for CVS sampling,  Determine the standard error of the estimate, SEE, of the sample flow rate versus the total flow rate. For each test interval, demonstrate that SEE was less than or equal to 3.5% of the mean sample flow rate.

(b) For any pair of flow meters, use recorded sample and total flow rates, where total flow rate means the raw exhaust flow rate for raw exhaust sampling and the dilute exhaust flow rate for CVS sampling, or their 1 Hz means, to demonstrate that each flow rate was constant within ±2.5% of its respective mean or target flow rate. Total flow rate means the raw exhaust flow rate for raw exhaust sampling and the dilute exhaust flow rate for CVS sampling. You may use the following options instead of recording the respective flow rate of each type of meter:

(1) Critical‑flow venturi option. For critical‑flow venturis, you may use recorded venturi‑inlet conditions or their 1 Hz means. Demonstrate that the flow density at the venturi inlet was constant within ±2.5% of the mean or target density over each test interval. For a CVS critical‑flow venturi, you may demonstrate this by showing that the absolute temperature at the venturi inlet was constant within ±4% of the mean or target absolute temperature over each test interval.

(2) Positive‑displacement pump option. You may use recorded pump‑inlet conditions or their 1 Hz means. Demonstrate that the flow density at the pump inlet was constant within ±2.5% of the mean or target density over each test interval. For a CVS pump, you may demonstrate this by showing that the absolute temperature at the pump inlet was constant within ±2% of the mean or target absolute temperature over each test interval.

(c) Using good engineering judgment, demonstrated Demonstrate with an engineering analysis that the proportional‑flow control system inherently ensures proportional sampling under all circumstances expected during testing. For example, you might use CFVs for both sample flow and total dilute exhaust (CVS) flow and demonstrate that they always have the same inlet pressures and temperatures and that they always operate under critical‑flow conditions.

§ 1065.546 Validation of minimum dilution ration for PM batch sampling.

Use continuous flows and/or tracer gas concentrations for transient and ramped modal cycles to validate verify the minimum dilution ratios for PM batch sampling as specified in § 1065.140(e)(2) over the test interval. You may use mode‑average values instead of continuous measurements for discrete mode steady‑state duty cycles. Determine the minimum primary and minimum overall dilution ratios using one of the following methods (you may use a different method for each stage of dilution):

(a) Determine minimum dilution ratio based on molar flow data. This involves determination of at least two of the following three quantities: Raw exhaust flow (or previously diluted flow), dilution air flow, and dilute exhaust flow. You may determine the raw exhaust flow rate based on the measured intake air molar flow rate or fuel flow rate and the raw exhaustchemical balance terms as given in § 1065.655(f). You may determine the raw exhaust flow rate based on the measured intake air and dilute exhaust molar flow rates and the dilute exhaust chemical balance terms as given in § 1065.655(g). You may alternatively estimate the molar raw exhaust flow rate based on intake air, fuel rate measurements, and fuel properties, consistent with good engineering judgment.

(b) Determine minimum dilution ratio based on tracer gas (e.g., CO₂) concentrations in the raw (or previously diluted) and dilute exhaust corrected for any removed water.

(c) Use good engineering judgment to develop your own If you show that the methods described in this section are inappropriate for your application, you may request that we approve another method of determining dilution ratios.

§ 1065.550 Gas analyzer range validation, drift validation, and drift correction.

(a) Range validation. If an analyzer operated above 100% of its range at any time during the test, perform the following steps:

(1) For batch sampling, re‑analyze the sample using the lowest analyzer range that results in a maximum instrument response below 100%. Report the result from the lowest range from which the analyzer operates below 100% of its range.

(2) For continuous sampling, repeat the entire test using the next higher analyzer range. If the analyzer again operates above 100% of its range, repeat the test using the next higher range. Continue to repeat the test until the analyzer always operates at less than 100% of its range.

(b) Drift validation and drift correction. Calculate two sets of brake‑specific emission results for each test interval. Calculate one set using the data before drift correction and calculate the other set after correcting all the data for drift according to § 1065.672. Use the two sets of brake‑specific emission results to validate the duty cycle for drift as follows:

(1) The duty cycle is validated for drift if you satisfy one of the following criteria:

(i) For each test interval of the duty cycle and for each measured exhaust constituent, the difference between the uncorrected and the corrected brake‑specific emission values over the test interval is within ±4% of the uncorrected value or applicable emission standard, whichever is greater. This requirement also applies for CO₂, whether or not an emission standard applies for CO₂. Where no emission standard applies for CO₂, the difference must be within ±4% of the uncorrected value. See paragraph (b)(4) of this section for exhaust constituents other than CO₂ for which no emission standard applies.

(ii) For the entire duty cycle and for each measured exhaust constituent, the difference between the uncorrected and corrected composite brake‑specific emission values over the entire duty cycle is within ± 4% of the uncorrected value or the applicable emission standard, whichever is greater. Note that for purposes of drift validation using composite brake‑specific emission values over the entire duty cycle, leave unaltered any negative emission results over a given test interval (i.e., do not set them to zero). A third calculation of composite brake‑specific emission values is required for final reporting. This calculation uses drift‑corrected mass (or mass rate) values from each test interval and sets any negative mass (or mass rate) values to zero before calculating the composite brake‑specific emission values over the entire duty cycle. This requirement also applies for CO₂, whether or not an emission standard applies for CO₂. Where no emission standard applies for CO₂, the difference must be within ± 4% of the uncorrected value. See paragraph (b)(4) of this section for exhaust constituents other than CO₂ for which no emission standard applies.

(2) For standards consisting of combined, individual measurements of exhaust constituents (such as NO_X + NMHC or separate NO and NO₂ measurements to comply with a NO_X standard), the duty cycle shall be validated for drift if you satisfy one of the following:

(i) For each test interval of the duty cycle and for each individually measured exhaust constituent (e.g. NO, NO₂, NO_X, or NMHC), the difference between the uncorrected and the corrected brake‑specific emission values over the test interval is within ± 4% of the uncorrected value; or

(ii) For each test interval of the duty cycle or for the entire duty cycle the difference between the combined (e.g. NO_X + NMHC) uncorrected and combined (e.g. NO_X + NMHC) corrected composite brake‑specific emissions values over each test interval of the duty cycle or the entire duty cycle is within ± 4% of the uncorrected value or the applicable emissions standard, whichever is greater.

(3) If the test is not validated for drift, you may consider the test results for the duty cycle to be valid only if, using good engineering judgment, the observed drift does not affect your ability to demonstrate compliance with the applicable emission standards. For example, if the drift‑corrected value is less than the standard by at least two times the absolute difference between the uncorrected and corrected values, you may consider the data to be valid for demonstrating compliance with the applicable standard.

(4) The provisions of this paragraph (b)(4) apply for measurement of pollutants other than CO₂ for which no emission standard applies (for purposes of this provision, standards consisting of combined, individual measurements are considered to be standards for each individual pollutant). You may use measurements that do not meet the drift validation criteria specified in paragraph (b)(1). For example, this allowance may be appropriate for measuring and reporting very low concentrations of CH₄ and N₂O as long as no emission standard applies for these compounds.

(b) Drift verification. Gas analyzer drift verification is required for all gaseous exhaust constituents for which an emission standard applies. It is also required for CO₂ even if there is no CO₂ emission standard. It is not required for other gaseous exhaust constituents for which only a reporting requirement applies (such as CH₄ and N₂O).

(1) Verify drift using one of the following methods:

(i) For regulated exhaust constituents determined from the mass of a single component, perform drift verification based on the regulated constituent. For example, when NO_X mass is determined with a dry sample measured with a CLD and the removed water is corrected based on measured CO₂, CO, THC, and NO_X concentrations, you must verify the calculated NO_X value.

(ii) For regulated exhaust constituents determined from the masses of multiple subcomponents, perform the drift verification based on either the regulated constituent or all the mass subcomponents. For example, when NO_X is measured with separate NO and NO₂ analyzers, you must verify either the NO_X value or both the NO and NO₂ values.

(iii) For regulated exhaust constituents determined from the concentrations of multiple gaseous emission subcomponents prior to performing mass calculations, perform drift verification on the regulated constituent. You may not verify the concentration subcomponents (e.g., THC and CH₄ for NMHC) separately. For example, for NMHC measurements, perform drift verification on NMHC; do not verify THC and CH₄ separately.

(2) Drift verification requires two sets of emission calculations. For each set of calculations, include all the constituents in the drift verification. Calculate one set using the data before drift correction and calculate the other set after correcting all the data for drift according to § 1065.672. Note that for purposes of drift verification, you must leave unaltered any negative emission results over a given test interval (i.e., do not set them to zero). These unaltered results are used when verifying either test interval results or composite brake‑specific emissions over the entire duty cycle for drift. For each constituent to be verified, both sets of calculations must include the following:

(i) Calculated mass (or mass rate) emission values over each test interval.

(ii) If you are verifying each test interval based on brake‑specific values, calculate brake‑specific emission values over each test interval.

(iii) If you are verifying over the entire duty cycle, calculate composite brake‑specific emission values.

(3) The duty cycle is verified for drift if you satisfy the following criteria:

(i) For each regulated gaseous exhaust constituent, you must satisfy one of the following:

(A) For each test interval of the duty cycle, the difference between the uncorrected and the corrected brake‑specific emission values of the regulated constituent must be within ±4% of the uncorrected value or the applicable emissions standard, whichever is greater. Alternatively, the difference between the uncorrected and the corrected emission mass (or mass rate) values of the regulated constituent must be within ±4% of the uncorrected value or the composite work (or power) multiplied by the applicable emissions standard, whichever is greater. For purposes of verifying each test interval, you may use either the reference or actual composite work (or power).

(B) For each test interval of the duty cycle and for each mass subcomponent of the regulated constituent, the difference between the uncorrected and the corrected brake‑specific emission values must be within ±4% of the uncorrected value. Alternatively, the difference between the uncorrected and the corrected emissions mass (or mass rate) values must be within ±4% of the uncorrected value.

(C) For the entire duty cycle, the difference between the uncorrected and the corrected composite brake‑specific emission values of the regulated constituent must be within ±4% of the uncorrected value or applicable emission standard, whichever is greater.

(D) For the entire duty cycle and for each subcomponent of the regulated constituent, the difference between the uncorrected and the corrected composite brake‑specific emission values must be within ±4% of the uncorrected value.

(ii) Where no emission standard applies for CO₂, you must satisfy one of the following:

(A) For each test interval of the duty cycle, the difference between the uncorrected and the corrected brake‑specific CO₂ values must be within ±4% of the uncorrected value; or the difference between the uncorrected and the corrected CO₂ mass (or mass rate) values must be within ±4% of the uncorrected value.

(B) For the entire duty cycle, the difference between the uncorrected and the corrected composite brake‑specific CO₂ values must be within ±4% of the uncorrected value.

(4) If the test is not verified for drift as described in paragraph (b)(1) of this section, you may consider the test results for the duty cycle to be valid only if the observed drift does not affect your ability to demonstrate compliance with the applicable emission standards. For example, if the drift‑corrected value is less than the standard by at least two times the absolute difference between the uncorrected and corrected values, you may consider the data to be verified for demonstrating compliance with the applicable standard.

§ 1065.590 PM sampling media (e.g., filters) preconditioning and tare weighing.

Before an emission test, take the following steps to prepare PM sampling media (e.g., filters) and equipment for PM measurements:

(a) Make sure the balance and PM‑stabilization environments meet the periodic verifications in § 1065.390.

(b) Visually inspect unused sample media (e.g., filters) for defects and discard defective media.

(c) To handle PM sampling media (e.g., filters), use electrically grounded tweezers or a grounding strap, as described in § 1065.190.

(d) Place unused sample media (e.g., filters) in one or more containers that are open to the PM‑stabilization environment. If you are using filters, you may place them in the bottom half of a filter cassette.

(e) Stabilize sample media (e.g., filters) in the PM‑stabilization environment. Consider an unused sample medium stabilized as long as it has been in the PM‑stabilization environment for a minimum of 30 min, during which the PM‑stabilization environment has been within the specifications of § 1065.190.

(f) Weigh the sample media (e.g., filters) automatically or manually, as follows:

(1) For automatic weighing, follow the automation system manufacturer's instructions to prepare samples for weighing. This may include placing the samples in a special container.

(2) For manual weighing, use good engineering judgment to determined Determine if substitution weighing is necessary to show that an engine meets the applicable standard. You If substitution weighing is necessary, you may follow the substitution weighing procedure in paragraph (j) of this section, or you may develop your own procedure. If you show the procedure in paragraph (j) of this section is not appropriate for your application, you may request that we approve a difference procedure.

(g) Correct the measured mass of each sample medium (e.g., filter) for buoyancy as described in § 1065.690. These buoyancy‑corrected values are subsequently subtracted from the post‑test mass of the corresponding sample media (e.g., filters) and collected PM to determine the mass of PM emitted during the test.

(h) You may repeat measurements to determine the mean mass of each sample medium (e.g., filter). Use good engineering judgment to exclude Exclude outliers from the calculation of mean mass values as appropriate for your application.

(i) If you use filters as sample media, load unused filters that have been tare‑weighed into clean filter cassettes and place the loaded cassettes in a clean, covered or sealed container before removing them from the stabilization environment for transport to the test site for sampling. We recommend that you keep filter cassettes clean by periodically washing or wiping them with a compatible solvent applied using a lint‑free cloth. Depending upon your cassette material, ethanol (C₂H₅OH) might be an acceptable solvent. Your cleaning frequency will depend on your engine's level of PM and HC emissions.

(j) Substitution weighing involves measurement of a reference weight before and after each weighing of PM sampling media (e.g., filters). While substitution weighing requires more measurements, it corrects for a balance's zero‑drift and it relies on balance linearity only over a small range. This is most advantageous when quantifying net PM masses that are less than 0.1% of the sample medium's mass. However, it may not be advantageous when net PM masses exceed 1% of the sample medium's mass. If you utilize substitution weighing, it must be used for both pre‑test and post‑test weighing. The same substitution weight must be used for both pre‑test and post‑test weighing. Correct the mass of the substitution weight for buoyancy if the density of the substitution weight is less than 2.0 g/cm³. The following steps are an example of substitution weighing:

(1) Use electrically grounded tweezers or a grounding strap, as described in § 1065.190.

(2) Use a static neutralizer as described in § 1065.190 to minimize static electric charge on any object before it is placed on the balance pan.

(3) Select and weigh a substitution weight that meets the requirements for calibration weights found in § 1065.790. The substitution weight must also have the same density as the weight you use to span the microbalance, and be similar in mass to an unused sample medium (e.g., filter). A 47 mm PTFE membrane filter will typically have a mass in the range of 80 to 100 mg.

(4) Record the stable balance reading, then remove the calibration substitution weight.

(5) Weigh an unused sample medium (e.g., a new filter), record the stable balance reading and record the balance environment's dewpoint, ambient temperature, and atmospheric pressure.

(6) Reweigh the calibration substitution weight and record the stable balance reading.

(7) Calculate the arithmetic mean of the two calibration substitution‑weight readings that you recorded immediately before and after weighing the unused sample. Subtract that mean value from the unused sample reading, then add the true mass of the calibration substitution weight as stated on the calibration substitution‑weight certificate. Record this result. This is the unused sample's tare weight without correcting for buoyancy.

(8) Repeat these substitution‑weighing steps for the remainder of your unused sample media.

(9) Once weighing is completed, follow the instructions given in paragraphs (g) through (i) of this section.

§ 1065.595 PM sample post‑conditioning and total weighing.

After testing is complete, return the sample media (e.g., filters) to the weighing and PM‑stabilization environments.

(a) Make sure the weighing and PM‑stabilization environments meet the ambient condition specifications in § 1065.190(e)(1). If those specifications are not met, leave the test sample media (e.g., filters) covered until proper conditions have been met.

(b) In the PM‑stabilization environment, remove PM samples from sealed containers. If you use filters, you may remove them from their cassettes before or after stabilization. We recommend always removing the top portion of the cassette before stabilization. When you remove a filter from a cassette, separate the top half of the cassette from the bottom half using a cassette separator designed for this purpose.

(c) To handle PM samples, use electrically grounded tweezers or a grounding strap, as described in § 1065.190.

(d) Visually inspect the sampling media (e.g., filters) and collected particulate. If either the sample media (e.g., filters) or particulate sample appear to have been compromised, or the particulate matter contacts any surface other than the filter, the sample may not be used to determine particulate emissions. In the case of contact with another surface, clean the affected surface before continuing.

(e) To stabilize PM samples, place them in one or more containers that are open to the PM‑stabilization environment, as described in § 1065.190. If you expect that a sample medium's (e.g., filter's) total surface concentration of PM will be less than 400 µg, assuming a 38 mm diameter filter stain area, expose the filter to a PM‑stabilization environment meeting the specifications of § 1065.190 for at least 30 minutes before weighing. If you expect a higher PM concentration or do not know what PM concentration to expect, expose the filter to the stabilization environment for at least 60 minutes before weighing. Note that 400 µg on sample media (e.g., filters) is an approximate net mass of 0.07 g/kW·hr for a hot‑start test with compression‑ignition engines tested according to 40 CFR part 86, subpart N, or 50 mg/mile for light‑duty vehicles tested according to 40 CFR part 86, subpart B.

(f) Repeat the procedures in § 1065.590(f) through (i) to determine post‑test mass of the sample media (e.g., filters).

(g) Subtract each buoyancy‑corrected tare mass of the sample medium (e.g., filter) from its respective buoyancy‑corrected mass. The result is the net PM mass, m_PM. Use m_PM in emission calculations in § 1065.650.