U.S. Code of Federal Regulations
Regulations most recently checked for updates: Nov 08, 2024
§ 1066.601 - Overview.
(a) This subpart describes calculations used to determine emission rates. See the standard-setting part and the other provisions of this part to determine which equations apply for your testing. This subpart describes how to—
(1) Use the signals recorded before, during, and after an emission test to calculate distance-specific emissions of each regulated pollutant.
(2) Perform calculations for calibrations and performance checks.
(3) Determine statistical values.
(b) You may use data from multiple systems to calculate test results for a single emission test, consistent with good engineering judgment. You may also make multiple measurements from a single batch sample, such as multiple weighing of a PM filter or multiple readings from a bag sample. Although you may use an average of multiple measurements from a single test, you may not use test results from multiple emission tests to report emissions. We allow weighted means where appropriate, such as for sampling onto a PM filter over the FTP. You may discard statistical outliers, but you must report all results.
§ 1066.605 - Mass-based and molar-based exhaust emission calculations.
(a) Calculate your total mass of emissions over a test cycle as specified in paragraph (c) of this section or in 40 CFR part 1065, subpart G, as applicable.
(b) See the standard-setting part for composite emission calculations over multiple test intervals and the corresponding weighting factors.
(c) Perform the following sequence of preliminary calculations to correct recorded concentration measurements before calculating mass emissions in paragraphs (e) and (f) of this section:
(1) For vehicles above 14,000 pounds GVWR, correct all THC and CH
(2) Correct all concentrations measured on a “dry” basis to a “wet” basis, including dilution air background concentrations.
(3) Calculate all NMHC and CH
(4) For vehicles at or below 14,000 pounds GVWR, calculate HC concentrations, including dilution air background concentrations, as described in this section, and as described in § 1066.635 for NMOG. For emission testing of vehicles above 14,000 pounds GVWR, with fuels that contain 25% or more oxygenated compounds by volume, calculate THCE and NMHCE concentrations, including dilution air background concentrations, as described in 40 CFR part 1065, subpart I.
(5) Correct all gaseous concentrations for dilution air background as described in § 1066.610.
(6) Correct NO
(7) Correct all PM filter masses for sample media buoyancy as described in 40 CFR 1065.690.
(d) Calculate g/mile emission rates using the following equation unless the standard-setting part specifies otherwise:
(e) Calculate the emission mass of each gaseous pollutant using the following equation:
(f) Calculation of the emission mass of PM, m
(1) Except as otherwise specified in this paragraph (f), calculate m
(2) If you sample PM onto a single filter as described in § 1066.815(b)(4)(i) or (b)(4)(ii) (for constant volume samplers), calculate m
(3) If you sample PM onto a single filter as described in § 1066.815(b)(4)(ii) (for partial flow dilution systems), calculate m
(4) If you sample PM onto a single filter as described in § 1066.815(b)(5)(i) or (b)(5)(ii) (for constant volume samplers), calculate m
(5) If you sample PM onto a single filter as described in § 1066.815(b)(5)(ii) (for partial flow dilution systems), calculate m
(g) This paragraph (g) describes how to correct flow and flow rates to standard reference conditions and provides an example for determining V
(1) Correct flow and flow rates to standard reference conditions as needed using the following equation:
(2) The following example provides a determination of V
Using Eq. 1066.605-8:
(h) Calculate total flow volume over a test interval, V
(1) Varying versus constant flow rates. The calculation methods depend on differentiating varying and constant flow, as follows:
(i) We consider the following to be examples of varying flows that require a continuous multiplication of concentration times flow rate: raw exhaust, exhaust diluted with a constant flow rate of dilution air, and CVS dilution with a CVS flow meter that does not have an upstream heat exchanger or electronic flow control.
(ii) We consider the following to be examples of constant exhaust flows: CVS diluted exhaust with a CVS flow meter that has an upstream heat exchanger, an electronic flow control, or both.
(2) Continuous sampling. For continuous sampling, you must frequently record a continuously updated flow signal. This recording requirement applies for both varying and constant flow rates.
(i) Varying flow rate. If you continuously sample from a varying exhaust flow rate, calculate V
Eq. 1066.605-11
(ii) Constant flow rate. If you continuously sample from a constant exhaust flow rate, use the same calculation described in paragraph (h)(2)(i) of this section or calculate the mean flow recorded over the test interval and treat the mean as a batch sample, as described in paragraph (h)(3)(ii) of this section.
(3) Batch sampling. For batch sampling, calculate total flow by integrating a varying flow rate or by determining the mean of a constant flow rate, as follows:
(i) Varying flow rate. If you proportionally collect a batch sample from a varying exhaust flow rate, integrate the flow rate over the test interval to determine the total flow from which you extracted the proportional sample, as described in paragraph (h)(2)(i) of this section.
(ii) Constant flow rate. If you batch sample from a constant exhaust flow rate, extract a sample at a proportional or constant flow rate and calculate V
§ 1066.610 - Dilution air background correction.
(a) Correct the emissions in a gaseous sample for background using the following equation:
(c) Determine the dilution factor, DF, over the test interval for partial-flow dilution sample systems using the following equation:
V
V
(d) Determine the time-weighted dilution factor, DF
§ 1066.615 - NOX intake-air humidity correction.
You may correct NO
(a) For vehicles at or below 14,000 pounds GVWR, apply a correction for vehicles with reciprocating engines operating over specific test cycles as follows:
(1) Calculate a humidity correction using a time-weighted mean value for ambient humidity over the test interval. Calculate absolute ambient humidity, H, using the following equation:
(2) Use the following equation to correct measured concentrations to a reference condition of 10.71 grams H
(b) For vehicles above 14,000 pounds GVWR, apply correction factors as described in 40 CFR 1065.670.
§ 1066.620 - Removed water correction.
Correct for removed water if water removal occurs upstream of a concentration measurement and downstream of a flow meter used to determine mass emissions over a test interval. Perform this correction based on the amount of water at the concentration measurement and on the amount of water at the flow meter.
§ 1066.625 - Flow meter calibration calculations.
This section describes the calculations for calibrating various flow meters based on mass flow rates. Calibrate your flow meter according to 40 CFR 1065.640 instead if you calculate emissions based on molar flow rates.
(a) PDP calibration. Perform the following steps to calibrate a PDP flow meter:
(1) Calculate PDP volume pumped per revolution, V
(2) Calculate a PDP slip correction factor, K
(3) Perform a least-squares regression of V
(4) Repeat the procedure in paragraphs (a)(1) through (3) of this section for every speed that you run your PDP.
(5) The following example illustrates a range of typical values for different PDP speeds:
Table 1 of § 1066.625—Example of PDP Calibration Data
(revolution/s) | (m ^{3}/s) | (m ^{3}/revolution) |
---|---|---|
12.6 | 0.841 | 0.056 |
16.5 | 0.831 | −0.013 |
20.9 | 0.809 | 0.028 |
23.4 | 0.788 | −0.061 |
(6) For each speed at which you operate the PDP, use the appropriate regression equation from this paragraph (a) to calculate flow rate during emission testing as described in § 1066.630.
(b) SSV calibration. The equations governing SSV flow assume one-dimensional isentropic inviscid flow of an ideal gas. Paragraph (b)(2)(iv) of this section describes other assumptions that may apply. If good engineering judgment dictates that you account for gas compressibility, you may either use an appropriate equation of state to determine values of Z as a function of measured pressure and temperature, or you may develop your own calibration equations based on good engineering judgment. Note that the equation for the flow coefficient, C
(1) Calculate volume flow rate at standard reference conditions, V
(2) Perform the following steps to calibrate an SSV flow meter:
(i) Using the data collected in § 1066.140, calculate C
(ii) Use the following equation to calculate C
(iii) Calculate r using the following equation:
(iv) You may apply any of the following simplifying assumptions or develop other values as appropriate for your test configuration, consistent with good engineering judgment:
(A) For raw exhaust, diluted exhaust, and dilution air, you may assume that the gas mixture behaves as an ideal gas (Z = 1).
(B) For raw exhaust, you may assume
(C) For diluted exhaust and dilution air, you may assume
(D) For diluted exhaust and dilution air, you may assume the molar mass of the mixture, M
(E) For diluted exhaust and dilution air, you may assume a constant molar mass of the mixture, M
Table 2 of § 1066.625—Examples of Dilution Air and Calibration Air Dewpoints at Which You May Assume a Constant
If calibration | assume the following
constant | for the following ranges of |
---|---|---|
≤0 | 28.96559 | ≤18 |
0 | 28.89263 | ≤21 |
5 | 28.86148 | ≤22 |
10 | 28.81911 | ≤24 |
15 | 28.76224 | ≤26 |
20 | 28.68685 | −8 to 28 |
25 | 28.58806 | 12 to 31 |
30 | 28.46005 | 23 to 34 |
^{a} The specified ranges are valid for all calibration and emission testing over the atmospheric pressure range (80.000 to 103.325) kPa.
(v) The following example illustrates the use of the governing equations to calculate C
(vi) Calculate the Reynolds number, Re
Where, using the Sutherland three-coefficient viscosity model:
Table 3 of § 1066.625—Sutherland Three-Coefficient Viscosity Model Parameters
Gas ^{1} | Temperature range within ±2% error ^{2} | Pressure limit ^{2} | |||
---|---|---|---|---|---|
kg/(m·s) | K | K | K | kPa | |
Air | 1.716·10 | 273 | 111 | 170 to 1900 | ≤1800. |
CO | 1.370·10 | 273 | 222 | 190 to 1700 | ≤3600. |
H | 1.12·10 | 350 | 1064 | 360 to 1500 | ≤10000. |
O | 1.919·10 | 273 | 139 | 190 to 2000 | ≤2500. |
N | 1.663·10 | 273 | 107 | 100 to 1500 | ≤1600. |
^{1} Use tabulated parameters only for the pure gases, as listed. Do not combine parameters in calculations to calculate viscosities of gas mixtures.
^{2} The model results are valid only for ambient conditions in the specified ranges.
(vii) Calculate
(viii) Create an equation for C
(ix) Perform a least-squares regression analysis to determine the best-fit coefficients for the equation and calculate SEE as described in 40 CFR 1065.602.
(x) If the equation meets the criterion of SEE ≤0.5% ⋅ C
(xi) If the equation does not meet the specified statistical criteria, you may use good engineering judgment to omit calibration data points; however, you must use at least seven calibration data points to demonstrate that you meet the criterion. For example, this may involve narrowing the range of flow rates for a better curve fit.
(xii) Take corrective action if the equation does not meet the specified statistical criterion even after omitting calibration data points. For example, select another mathematical expression for the C
(xiii) Once you have an equation that meets the specified statistical criterion, you may use the equation only for the corresponding range of Re
(c) CFV calibration. Some CFV flow meters consist of a single venturi and some consist of multiple venturis where different combinations of venturis are used to meter different flow rates. For CFV flow meters that consist of multiple venturis, either calibrate each venturi independently to determine a separate calibration coefficient, K
(1) To determine K
(i) Calculate an individual K
(ii) Calculate the mean and standard deviation of all the K
(iii) If the standard deviation of all the K
(iv) If the standard deviation of all the K
(v) If the number of remaining data points is less than seven, take corrective action by checking your calibration data or repeating the calibration process. If you repeat the calibration process, we recommend checking for leaks, applying tighter tolerances to measurements and allowing more time for flows to stabilize.
(vi) If the number of remaining K
(vii) If the standard deviation of the remaining K
(viii) If the standard deviation of the remaining K
(2) During exhaust emission tests, monitor sonic flow in the CFV by monitoring r. Based on the calibration data selected to meet the standard deviation criterion in paragraphs (c)(1)(iv) and (vii) of this section, in which K
§ 1066.630 - PDP, SSV, and CFV flow rate calculations.
This section describes the equations for calculating flow rates from various flow meters. After you calibrate a flow meter according to § 1066.625, use the calculations described in this section to calculate flow during an emission test. Calculate flow according to 40 CFR 1065.642 instead if you calculate emissions based on molar flow rates.
(a) PDP. (1) Based on the speed at which you operate the PDP for a test interval, select the corresponding slope, a
(2) Calculate V
(b) SSV. Calculate SSV flow rate, v
(c) CFV. If you use multiple venturis and you calibrated each venturi independently to determine a separate calibration coefficient, K
(1) To calculate V
(2) [Reserved]
§ 1066.635 - NMOG determination.
For vehicles subject to an NMOG standard, determine NMOG as described in paragraph (a) of this section. Except as specified in the standard-setting part, you may alternatively calculate NMOG results based on measured NMHC emissions as described in paragraphs (c) through (f) of this section. Note that references to the FTP in this section apply for testing over the FTP test cycle at any ambient temperature.
(a) Determine NMOG by independently measuring alcohols and carbonyls as described in 40 CFR 1065.805 and 1065.845. Use good engineering judgment to determine which alcohols and carbonyls you need to measure. This would typically require you to measure all alcohols and carbonyls that you expect to contribute 1% or more of total NMOG. Calculate the mass of NMOG in the exhaust, m
(b) The following example shows how to determine NMOG as described in paragraph (a) of this section for (OHC) compounds including ethanol (C
(c) For gasoline containing less than 25% ethanol by volume, you may calculate NMOG from measured NMHC emissions as follows:
(1) For hot-start and hot-running test cycles or intervals other than the FTP, you may determine NMOG based on the NMHC emission rate using the following equation:
(2) You may determine weighted composite NMOG for FTP testing based on the weighted composite NMHC emission rate and the volume percent of ethanol in the fuel using the following equation:
(3) You may determine NMOG for the transient portion of the FTP cold-start test for use in fuel economy and CREE calculations based on the NMHC emission rate for the test interval and the volume percent of ethanol in the fuel using the following equation:
(4) You may determine NMOG for the stabilized portion of the FTP test for either the cold-start test or the hot-start test (bag 2 or bag 4) for use in fuel economy and CREE calculations based on the corresponding NMHC emission rate and the volume percent of ethanol in the fuel using the following equation:
(5) You may determine NMOG for the transient portion of the FTP hot-start test for use in fuel economy and CREE calculations based on the NMHC emission rate for the test interval and the volume percent of ethanol in the fuel using the following equation:
(6) For PHEVs, you may determine NMOG based on testing over one full UDDS using Eq. 1066.635-3.
(d) You may take the following alternative steps when determining fuel economy and CREE under 40 CFR part 600 for testing with ethanol-gasoline blends that have up to 25% ethanol by volume:
(1) Calculate NMOG by test interval using Eq. 1066.635-3 for individual bag measurements from the FTP.
(2) For HEVs, calculate NMOG for two-bag FTPs using Eq. 1066.635-3 as described in 40 CFR 600.114.
(e) We consider NMOG values for diesel-fueled vehicles, CNG-fueled vehicles, LNG-fueled vehicles, and LPG-fueled vehicles to be equivalent to NMHC emission values for all test cycles.
(f) For all fuels not covered by paragraphs (c) and (e) of this section, manufacturers may propose a methodology to calculate NMOG results from measured NMHC emissions. We will approve adjustments based on comparative testing that demonstrates how to properly represent NMOG based on measured NMHC emissions.
§ 1066.695 - Data requirements.
Record information for each test as follows:
(a) Test number.
(b) A brief description of the test vehicle (or other system/device tested).
(c) Date and time of day for each part of the test sequence.
(d) Test results. Also include a validation of driver accuracy as described in § 1066.425(j).
(e) Driver and equipment operators.
(f) Vehicle information as applicable, including identification number, model year, applicable emission standards (including bin standards or family emission limits, as applicable), vehicle model, vehicle class, test group, durability group, engine family, evaporative/refueling emission family, basic engine description (including displacement, number of cylinders, turbocharger/supercharger used, and catalyst type), fuel system (type of fuel injection and fuel tank capacity and location), engine code, GVWR, applicable test weight, inertia weight class, actual curb weight at zero miles, actual road load at 50 mi/hr, transmission class and configuration, axle ratio, odometer reading, idle rpm, and measured drive wheel tire pressure.
(g) Dynamometer identification, inertia weight setting, indicated power absorption setting, and records to verify compliance with the driving distance and cycle-validation criteria as calculated from measured roll or shaft revolutions.
(h) Analyzer bench identification, analyzer ranges, recordings of analyzer output during zero, span, and sample readings.
(i) Associate the following information with the test record: test number, date, vehicle identification, vehicle and equipment operators, and identification of the measurements recorded.
(j) Test cell barometric pressure and humidity. You may use a central laboratory barometer if the barometric pressure in each test cell is shown to be within ±0.1% of the barometric pressure at the central barometer location.
(k) Records to verify compliance with the ambient temperature requirements throughout the test procedure and records of fuel temperatures during the running loss test.
(l) [Reserved]
(m) For CVS systems, record dilution factor for each test interval and the following additional information:
(1) For CFV and SSV testing, V
(2) For PDP testing, test measurements required to calculate V
(n) The humidity of the dilution air, if you remove H
(o) Temperature of the dilute exhaust mixture and secondary dilution air (in the case of a double-dilution system) at the inlet to the respective gas meter or flow instrumentation used for PM sampling. Determine minimum values, maximum values, mean values, and percent of time outside of the tolerance over each test interval.
(p) The maximum exhaust gas temperature over the course of the test interval within 20 cm upstream or downstream of PM sample media.
(q) If applicable, the temperatures of the heated FID, the gas in the heated sample line, and the heated filter. Determine minimum values, maximum values, average values, and percent of time outside of the tolerance over each test interval.
(r) Gas meter or flow measurement instrumentation readings used for batch sampling over each test interval. Determine minimum, maximum, and average values over each test interval.
(s) The stabilized pre-test weight and post-test weight of each particulate sample media (e.g., filter).
(t) Continuous temperature and humidity of the ambient air in which the PM sample media are stabilized. Determine minimum values, maximum values, average values, and percent of time outside of the tolerance over each test interval.
(u) For vehicles fueled by natural gas, the test fuel composition, including all carbon-containing compounds (including CO
(v) For vehicles fueled by liquefied petroleum gas, the test fuel composition, including all carbon-containing compounds (including CO
(w) For the AC17 test in § 1066.845, interior volume, climate control system type and characteristics, refrigerant used, compressor type, and evaporator/condenser characteristics.
(x) Additional information related to evaporative emissions. [Reserved]
(y) Additional information related to refueling emissions. [Reserved]