(3)

Annex III is amended as follows: (a) Section 1.3.1 is replaced by the following: ‘1.3.1. ESC Test During a prescribed sequence of warmed-up engine operating conditions the amounts of the above exhaust emissions shall be examined continuously by taking a sample from the raw or diluted exhaust gas. The test cycle consists of a number of speed and power modes which cover the typical operating range of diesel engines. During each mode the concentration of each gaseous pollutant, exhaust flow and power output shall be determined, and the measured values weighted. For particulate measurement, the exhaust gas shall be diluted with conditioned ambient air using either a partial flow or full flow dilution system. The particulates shall be collected on a single suitable filter in proportion to the weighting factors of each mode. The grams of each pollutant emitted per kilowatt hour shall be calculated as described in Appendix 1 to this Annex. Additionally, NOx shall be measured at three test points within the control area selected by the Technical Service and the measured values compared to the values calculated from those modes of the test cycle enveloping the selected test points. The NOx control check ensures the effectiveness of the emission control of the engine within the typical engine operating range.’ (b) Section 1.3.3 is replaced by the following: ‘1.3.3. ETC Test During a prescribed transient cycle of warmed-up engine operating conditions, which is based closely on road-type-specific driving patterns of heavy-duty engines installed in trucks and buses, the above pollutants shall be examined either after diluting the total exhaust gas with conditioned ambient air (CVS system with double dilution for particulates) or by determining the gaseous components in the raw exhaust gas and the particulates with a partial flow dilution system. Using the engine torque and speed feedback signals of the engine dynamometer, the power shall be integrated with respect to time of the cycle resulting in the work produced by the engine over the cycle. For a CVS system, the concentration of NOx and HC shall be determined over the cycle by integration of the analyser signal, whereas the concentration of CO, CO2, and NMHC may be determined by integration of the analyser signal or by bag sampling. If measured in the raw exhaust gas, all gaseous components shall be determined over the cycle by integration of the analyser signal. For particulates, a proportional sample shall be collected on a suitable filter. The raw or diluted exhaust gas flow rate shall be determined over the cycle to calculate the mass emission values of the pollutants. The mass emission values shall be related to the engine work to get the grams of each pollutant emitted per kilowatt hour, as described in Appendix 2 to this Annex.’ (c) Section 2.1 is replaced by the following: ‘2.1. Engine Test Conditions 2.1.1. The absolute temperature (T a) of the engine air at the inlet to the engine expressed in Kelvin, and the dry atmospheric pressure (p s), expressed in kPa shall be measured and the parameter f a shall be determined according to the following provisions. In multi-cylinder engines having distinct groups of intake manifolds, for example, in a “V” engine configuration, the average temperature of the distinct groups shall be taken. (a) for compression-ignition engines: Naturally aspirated and mechanically supercharged engines: Turbocharged engines with or without cooling of the intake air: (b) for spark-ignition engines: 2.1.2. Test Validity For a test to be recognised as valid, the parameter f a shall be such that: 0,96 ≤ f a ≤ 1,06’ (d) Section 2.8 is replaced by the following: If the engine is equipped with an exhaust aftertreatment system, the emissions measured on the test cycle shall be representative of the emissions in the field. In the case of an engine equipped with a exhaust aftertreatment system that requires the consumption of a reagent, the reagent used for all tests shall comply with section 2.2.1.13 of Appendix 1 to Annex II. 2.8.1. For an exhaust aftertreatment system based on a continuous regeneration process the emissions shall be measured on a stabilised aftertreatment system. The regeneration process shall occur at least once during the ETC test and the manufacturer shall declare the normal conditions under which regeneration occurs (soot load, temperature, exhaust back-pressure, etc). In order to verify the regeneration process at least 5 ETC tests shall be conducted. During the tests the exhaust temperature and pressure shall be recorded (temperature before and after the aftertreatment system, exhaust back pressure, etc). The aftertreatment system is considered to be satisfactory if the conditions declared by the manufacturer occur during the test during a sufficient time. The final test result shall be the arithmetic mean of the different ETC test results. If the exhaust aftertreatment has a security mode that shifts to a periodic regeneration mode it should be checked following section 2.8.2. For that specific case the emission limits in table 2 of Annex I could be exceeded and would not be weighted. 2.8.2. For an exhaust aftertreatment based on a periodic regeneration process, the emissions shall be measured on at least two ETC tests, one during and one outside a regeneration event on a stabilised aftertreatment system, and the results be weighted. The regeneration process shall occur at least once during the ETC test. The engine may be equipped with a switch capable of preventing or permitting the regeneration process provided this operation has no effect on the original engine calibration. The manufacturer shall declare the normal parameter conditions under which the regeneration process occurs (soot load, temperature, exhaust back-pressure etc) and its duration time (n2). The manufacturer shall also provide all the data to determine the time between two regenerations (n1). The exact procedure to determine this time shall be agreed by the Technical Service based upon good engineering judgement. The manufacturer shall provide an aftertreatment system that has been loaded in order to achieve regeneration during an ETC test. Regeneration shall not occur during this engine conditioning phase. Average emissions between regeneration phases shall be determined from the arithmetic mean of several approximately equidistant ETC tests. It is recommended to run at least one ETC as close as possible prior to a regeneration test and one ETC immediately after a regeneration test. As an alternative, the manufacturer may provide data to show that the emissions remain constant (± 15 %) between regeneration phases. In this case, the emissions of only one ETC test may be used. During the regeneration test, all the data needed to detect regeneration shall be recorded (CO or NOx emissions, temperature before and after the aftertreatment system, exhaust back pressure etc). During the regeneration process, the emission limits in table 2 of Annex I can be exceeded. The measured emissions shall be weighted according to section 5.5 and 6.3 of Appendix 2 to this Annex and the final result shall not exceed the limits in table 2 of Annex I.’ (e) Appendix 1 is amended as follows: (i) Section 2.1 is replaced by the following: ‘2.1. Preparation of the Sampling Filter At least one hour before the test, each filter shall be placed in a partially covered petri dish which is protected against dust contamination, and placed in a weighing chamber for stabilisation. At the end of the stabilisation period each filter shall be weighed and the tare weight shall be recorded. The filter shall then be stored in a closed petri dish or sealed filter holder until needed for testing. The filter shall be used within eight hours of its removal from the weighing chamber. The tare weight shall be recorded.’ (ii) Section 2.7.4. is replaced by the following: ‘2.7.4. Particulate Sampling One filter shall be used for the complete test procedure. The modal weighting factors specified in the test cycle procedure shall be taken into account by taking a sample proportional to the exhaust mass flow during each individual mode of the cycle. This can be achieved by adjusting sample flow rate, sampling time, and/or dilution ratio, accordingly, so that the criterion for the effective weighting factors in section 5.6 is met. The sampling time per mode must be at least 4 seconds per 0,01 weighting factor. Sampling must be conducted as late as possible within each mode. Particulate sampling shall be completed no earlier than 5 seconds before the end of each mode.’ (iii) The following new section 4 is inserted: ‘4. CALCULATION OF THE EXHAUST GAS FLOW 4.1. Determination of Raw Exhaust Gas Mass Flow For calculation of the emissions in the raw exhaust, it is necessary to know the exhaust gas flow. The exhaust gas mass flow rate shall be determined in accordance with section 4.1.1 or 4.1.2. The accuracy of exhaust flow determination shall be ± 2,5 % of reading or ± 1,5 % of the engine's maximum value whichever is the greater. Equivalent methods (e.g. those described in section 4.2 of Appendix 2 to this Annex) may be used. 4.1.1. Direct measurement method Direct measurement of the exhaust flow may be done by systems such as: — pressure differential devices, like flow nozzle, — ultrasonic flowmeter, — vortex flowmeter. Precautions shall be taken to avoid measurement errors which will impact emission value errors. Such precautions include the careful installation of the device in the engine exhaust system according to the instrument manufacturers’ recommendations and to good engineering practice. Especially, engine performance and emissions shall not be affected by the installation of the device. 4.1.2. Air and fuel measurement method This involves measurement of the air flow and the fuel flow. Air flowmeters and fuel flowmeters shall be used that meet the total accuracy requirement of section 4.1. The calculation of the exhaust gas flow is as follows: q mew = q maw + q mf 4.2. Determination of Diluted Exhaust Gas Mass Flow For calculation of the emissions in the diluted exhaust using a full flow dilution system it is necessary to know the diluted exhaust gas flow. The flow rate of the diluted exhaust (qmdew ) shall be measured over each mode with a PDP-CVS, CFV-CVS or SSV-CVS in line with the general formulae given in section 4.1 of Appendix 2 to this Annex. The accuracy shall be ± 2 % of reading or better, and shall be determined according to the provisions of section 2.4 of Appendix 5 to this Annex.’ (iv) Sections 4 and 5 are replaced by the following: ‘5. CALCULATION OF THE GASEOUS EMISSIONS 5.1. Data Evaluation For the evaluation of the gaseous emissions, the chart reading of the last 30 seconds of each mode shall be averaged and the average concentrations (conc) of HC, CO and NOx during each mode shall be determined from the average chart readings and the corresponding calibration data. A different type of recording can be used if it ensures an equivalent data acquisition. For the NOx check within the control area, the above requirements apply for NOx only. The exhaust gas flow qmew or the diluted exhaust gas flow qmdew , if used optionally, shall be determined in accordance with section 2.3 of Appendix 4 to this Annex. 5.2. Dry/Wet Correction The measured concentration shall be converted to a wet basis according to the following formulae, if not already measured on a wet basis. The conversion shall be done for each individual mode. cwet = kw × cdry For the raw exhaust gas: or where: pr = water vapour pressure after cooling bath, kPa, pb = total atmospheric pressure, kPa, Ha = intake air humidity, g water per kg dry air, kf = 0,055584 × wALF – 0,0001083 × wBET – 0,0001562 × wGAM + 0,0079936 × wDEL + 0,0069978 × wEPS For the diluted exhaust gas: or, For the dilution air: KWd = 1 – KW1 For the intake air: KWa = 1 – KW2 where: H a = intake air humidity, g water per kg dry air H d = dilution air humidity, g water per kg dry air and may be derived from relative humidity measurement, dewpoint measurement, vapour pressure measurement or dry/wet bulb measurement using the generally accepted formulae. 5.3. NOx correction for humidity and temperature As the NOx emission depends on ambient air conditions, the NOx concentration shall be corrected for ambient air temperature and humidity with the factors given in the following formulae. The factors are valid in the range between 0 and 25 g/kg dry air. (a) for compression ignition engines: with: T a = temperature of the intake air, K H a = humidity of the intake air, g water per kg dry air where: H a may be derived from relative humidity measurement, dewpoint measurement, vapour pressure measurement or dry/wet bulb measurement using the generally accepted formulae. (b) for spark ignition engines k h.G = 0,6272 + 44,030 × 10–3 × H a - 0,862 × 10–3 × H a 2 where: H a may be derived from relative humidity measurement, dew point measurement, vapour pressure measurement or dry/wet bulb measurement using the generally accepted formulae. 5.4. Calculation of the emission mass flow rates The emission mass flow rate (g/h) for each mode shall be calculated as follows. For the calculation of NOx, the humidity correction factor k h,D, or k h,G, as applicable, as determined according to section 5.3, shall be used. The measured concentration shall be converted to a wet basis according to section 5.2 if not already measured on a wet basis. Values for u gas are given in Table 6 for selected components based on ideal gas properties and the fuels relevant for this Directive. (a) for the raw exhaust gas m gas = u gas × c gas × q mew where: u gas = ratio between density of exhaust component and density of exhaust gas c gas = concentration of the respective component in the raw exhaust gas, ppm q mew = exhaust mass flow rate, kg/h (b) for the diluted gas m gas = u gas × c gas,c × q mdew where: u gas = ratio between density of exhaust component and density of air c gas,c = background corrected concentration of the respective component in the diluted exhaust gas, ppm q mdew = diluted exhaust mass flow rate, kg/h where: The dilution factor D shall be calculated according to section 5.4.1 of Appendix 2 to this Annex. 5.5. Calculation of the specific emissions The emissions (g/kWh) shall be calculated for all individual components in the following way: where: m gas is the mass of individual gas P n is the net power determined according to section 8.2 in Annex II. The weighting factors used in the above calculation are according to section 2.7.1. Table 6 Values of u gas in the raw and dilute exhaust gas for various exhaust components Fuel NOx CO THC/NMHC CO2 CH4 Diesel Exhaust raw 0,001587 0,000966 0,000479 0,001518 0,000553 Exhaust dilute 0,001588 0,000967 0,000480 0,001519 0,000553 Ethanol Exhaust raw 0,001609 0,000980 0,000805 0,001539 0,000561 Exhaust dilute 0,001588 0,000967 0,000795 0,001519 0,000553 CNG Exhaust raw 0,001622 0,000987 0,000523 0,001552 0,000565 Exhaust dilute 0,001588 0,000967 0,000584 0,001519 0,000553 Propane Exhaust raw 0,001603 0,000976 0,000511 0,001533 0,000559 Exhaust dilute 0,001588 0,000967 0,000507 0,001519 0,000553 Butane Exhaust raw 0,001600 0,000974 0,000505 0,001530 0,000558 Exhaust dilute 0,001588 0,000967 0,000501 0,001519 0,000553 — u values of raw exhaust based on ideal gas properties at λ = 2, dry air, 273 K, 101,3 kPa — u values of dilute exhaust based on ideal gas properties and density of air — u values of CNG accurate within 0,2 % for mass composition of: C = 66 – 76 %; H = 22 – 25 %; N = 0 – 12 % — u value of CNG for HC corresponds to CH2,93 (for total HC use u value of CH4). 5.6. Calculation of the area control values For the three control points selected according to section 2.7.6, the NOx emission shall be measured and calculated according to section 5.6.1 and also determined by interpolation from the modes of the test cycle closest to the respective control point according to section 5.6.2. The measured values are then compared to the interpolated values according to section 5.6.3. 5.6.1. Calculation of the Specific Emission The NOx emission for each of the control points (Z) shall be calculated as follows: m NOx,Z = 0,001587 × c NOx,Z × k h,D × q mew 5.6.2. Determination of the Emission Value from the Test Cycle The NOx emission for each of the control points shall be interpolated from the four closest modes of the test cycle that envelop the selected control point Z as shown in Figure 4. For these modes (R, S, T, U), the following definitions apply: Speed(R) = Speed(T) = nRT Speed(S) = Speed(U) = nSU Per cent load(R) = Per cent load(S) Per cent load(T) = Per cent load(U). The NOx emission of the selected control point Z shall be calculated as follows: and: where: ER, ES, ET, EU = specific NOx emission of the enveloping modes calculated in accordance with section 5.6.1. MR, MS, MT, MU = engine torque of the enveloping modes. 5.6.3. Comparison of NOx Emission Values The measured specific NOx emission of the control point Z (NOx,Z) is compared to the interpolated value (EZ) as follows: 6. CALCULATION OF THE PARTICULATE EMISSIONS 6.1. Data Evaluation For the evaluation of the particulates, the total sample masses (m sep) through the filter shall be recorded for each mode. The filter shall be returned to the weighing chamber and conditioned for at least one hour, but not more than 80 hours, and then weighed. The gross weight of the filters shall be recorded and the tare weight (see section 2.1) subtracted, which results in the particulate sample mass m f. If background correction is to be applied, the dilution air mass (m d) through the filter and the particulate mass (m f,d) shall be recorded. If more than one measurement was made, the quotient m f,d/m d shall be calculated for each single measurement and the values averaged. 6.2. Partial Flow Dilution System The final reported test results of the particulate emission shall be determined through the following steps. Since various types of dilution rate control may be used, different calculation methods for q medf apply. All calculations shall be based upon the average values of the individual modes during the sampling period. 6.2.1. Isokinetic systems q medf = q mew × rd where r a corresponds to the ratio of the cross sectional areas of the isokinetic probe and the exhaust pipe: 6.2.2. Systems with measurement of CO2 or NOx concentration qmedf = qmew × rd where: c wE = wet concentration of the tracer gas in the raw exhaust c wD = wet concentration of the tracer gas in the diluted exhaust c wA = wet concentration of the tracer gas in the dilution air Concentrations measured on a dry basis shall be converted to a wet basis according to section 5.2 of this Appendix. 6.2.3. Systems with CO2 measurement and carbon balance method (14) where: c (CO2)D = CO2 concentration of the diluted exhaust c (CO2)A = CO2 concentration of the dilution air (concentrations in vol % on wet basis) This equation is based upon the carbon balance assumption (carbon atoms supplied to the engine are emitted as CO2) and determined through the following steps: qmedf = qmew × r d and 6.2.4. Systems with flow measurement qmedf = qmew × rd 6.3. Full Flow Dilution System All calculations shall be based upon the average values of the individual modes during the sampling period. The diluted exhaust gas flow q mdew shall be determined in accordance with section 4.1 of Appendix 2 to this Annex. The total sample mass m sep shall be calculated in accordance with section 6.2.1 of Appendix 2 to this Annex. 6.4. Calculation of the Particulate Mass Flow Rate The particulate mass flow rate shall be calculated as follows. If a full flow dilution system is used, q medf as determined according to section 6.2 shall be replaced with q mdew as determined according to section 6.3. i = 1, … n The particulate mass flow rate may be background corrected as follows: where D shall be calculated in accordance with section 5.4.1 of Appendix 2 to this Annex. (v) Former section 6 is renumbered as section 7. (f) Appendix 2 is amended as follows: (i) Section 3 is replaced by the following: ‘3. EMISSIONS TEST RUN At the manufacturers request, a dummy test may be run for conditioning of the engine and exhaust system before the measurement cycle. NG and LPG fuelled engines shall be run-in using the ETC test. The engine shall be run over a minimum of two ETC cycles and until the CO emission measured over one ETC cycle does not exceed by more than 10 % the CO emission measured over the previous ETC cycle. 3.1. Preparation of the sampling filters (if applicable) At least one hour before the test, each filter shall be placed in a partially covered petri dish, which is protected against dust contamination, and placed in a weighing chamber for stabilisation. At the end of the stabilisation period, each filter shall be weighed and the tare weight shall be recorded. The filter shall then be stored in a closed petri dish or sealed filter holder until needed for testing. The filter shall be used within eight hours of its removal from the weighing chamber. The tare weight shall be recorded. 3.2. Installation of the measuring equipment The instrumentation and sample probes shall be installed as required. The tailpipe shall be connected to the full flow dilution system, if used. 3.3. Starting the dilution system and the engine The dilution system and the engine shall be started and warmed up until all temperatures and pressures have stabilised at maximum power according to the recommendation of the manufacturer and good engineering practice. 3.4. Starting the particulate sampling system (diesel engines only) The particulate sampling system shall be started and running on by-pass. The particulate background level of the dilution air may be determined by passing dilution air through the particulate filters. If filtered dilution air is used, one measurement may be done prior to or after the test. If the dilution air is not filtered, measurements at the beginning and at the end of the cycle may be done and the values averaged. The dilution system and the engine shall be started and warmed up until all temperatures and pressures have stabilised according to the recommendation of the manufacturer and good engineering practice. In case of periodic regeneration aftertreatment, the regeneration shall not occur during the warm-up of the engine. 3.5. Adjustment of the dilution system The flow rates of the dilution system (full flow or partial flow) shall be set to eliminate water condensation in the system, and to obtain a maximum filter face temperature of 325 K (52 °C) or less (see section 2.3.1 of Annex V, DT). 3.6. Checking the analysers The emission analysers shall be set at zero and spanned. If sample bags are used, they shall be evacuated. 3.7. Engine starting procedure The stabilised engine shall be started according to the manufacturer's recommended starting procedure in the owner's manual, using either a production starter motor or the dynamometer. Optionally, the test may start directly from the engine preconditioning phase without shutting the engine off, when the engine has reached the idle speed. 3.8. Test cycle 3.8.1. Test sequence The test sequence shall be started, if the engine has reached idle speed. The test shall be performed according to the reference cycle as set out in section 2 of this Appendix. Engine speed and torque command set points shall be issued at 5 Hz (10 Hz recommended) or greater. Feedback engine speed and torque shall be recorded at least once every second during the test cycle, and the signals may be electronically filtered. 3.8.2. Gaseous emissions measurement 3.8.2.1. Full flow dilution system At the start of the engine or test sequence, if the cycle is started directly from the preconditioning, the measuring equipment shall be started, simultaneously: — start collecting or analysing dilution air, — start collecting or analysing diluted exhaust gas, — start measuring the amount of diluted exhaust gas (CVS) and the required temperatures and pressures, — start recording the feedback data of speed and torque of the dynamometer. HC and NOx shall be measured continuously in the dilution tunnel with a frequency of 2 Hz. The average concentrations shall be determined by integrating the analyzer signals over the test cycle. The system response time shall be no greater than 20 s, and shall be coordinated with CVS flow fluctuations and sampling time/test cycle offsets, if necessary. CO, CO2, NMHC and CH4 shall be determined by integration or by analysing the concentrations in the sample bag, collected over the cycle. The concentrations of the gaseous pollutants in the dilution air shall be determined by integration or by collecting into the background bag. All other values shall be recorded with a minimum of one measurement per second (1 Hz). 3.8.2.2. Raw exhaust measurement At the start of the engine or test sequence, if the cycle is started directly from the preconditioning, the measuring equipment shall be started, simultaneously: — start analysing the raw exhaust gas concentrations, — start measuring the exhaust gas or intake air and fuel flow rate, — start recording the feedback data of speed and torque of the dynamometer. For the evaluation of the gaseous emissions, the emission concentrations (HC, CO and NOx) and the exhaust gas mass flow rate shall be recorded and stored with at least 2 Hz on a computer system. The system response time shall be no greater than 10 s. All other data may be recorded with a sample rate of at least 1 Hz. For analogue analysers the response shall be recorded, and the calibration data may be applied online or offline during the data evaluation. For calculation of the mass emission of the gaseous components the traces of the recorded concentrations and the trace of the exhaust gas mass flow rate shall be time aligned by the transformation time as defined in section 2 of Annex I. Therefore, the response time of each gaseous emissions analyser and of the exhaust gas mass flow system shall be determined according to the provisions of section 4.2.1 and section 1.5 of Appendix 5 to this Annex and recorded. 3.8.3. Particulate sampling (if applicable) 3.8.3.1. Full flow dilution system At the start of the engine or test sequence, if the cycle is started directly from the preconditioning, the particulate sampling system shall be switched from by-pass to collecting particulates. If no flow compensation is used, the sample pump(s) shall be adjusted so that the flow rate through the particulate sample probe or transfer tube is maintained at a value within ± 5 % of the set flow rate. If flow compensation (i.e., proportional control of sample flow) is used, it must be demonstrated that the ratio of main tunnel flow to particulate sample flow does not change by more than ± 5 % of its set value (except for the first 10 seconds of sampling). Note: For double dilution operation, sample flow is the net difference between the flow rate through the sample filters and the secondary dilution air flow rate. The average temperature and pressure at the gas meter(s) or flow instrumentation inlet shall be recorded. If the set flow rate cannot be maintained over the complete cycle (within ± 5 %) because of high particulate loading on the filter, the test shall be voided. The test shall be rerun using a lower flow rate and/or a larger diameter filter. 3.8.3.2. Partial flow dilution system At the start of the engine or test sequence, if the cycle is started directly from the preconditioning, the particulate sampling system shall be switched from by-pass to collecting particulates. For the control of a partial flow dilution system, a fast system response is required. The transformation time for the system shall be determined by the procedure in section 3.3 of Appendix 5 to Annex III. If the combined transformation time of the exhaust flow measurement (see section 4.2.1) and the partial flow system is less than 0,3 sec, online control may be used. If the transformation time exceeds 0,3 sec, look ahead control based on a pre-recorded test run must be used. In this case, the rise time shall be ≤ 1 sec and the delay time of the combination ≤ 10 sec. The total system response shall be designed as to ensure a representative sample of the particulates, qmp,i, proportional to the exhaust mass flow. To determine the proportionality, a regression analysis of qmp,i versus qmew,i shall be conducted on a minimum 1 Hz data acquisition rate, and the following criteria shall be met: — The correlation coefficient R2 of the linear regression between qmp,i and qmew,i shall not be less than 0,95, — The standard error of estimate of qmp,i on qmew,i shall not exceed 5 % of qmp maximum, — qmp intercept of the regression line shall not exceed ± 2 % of qmp maximum. Optionally, a pretest may be run, and the exhaust mass flow signal of the pretest be used for controlling the sample flow into the particulate system (look-ahead control). Such a procedure is required if the transformation time of the particulate system, t50,P or the transformation time of the exhaust mass flow signal, t50,F, or both, are > 0,3 sec. A correct control of the partial dilution system is obtained, if the time trace of qmew,pre of the pretest, which controls qmp, is shifted by a look-ahead time of t50,P + t50,F. For establishing the correlation between qmp,i and qmew,i the data taken during the actual test shall be used, with qmew,i time aligned by t50,F relative to qmp,i (no contribution from t50,P to the time alignment). That is, the time shift between qmew and qmp is the difference in their transformation times that were determined in section 3.3 of Appendix 5 to Annex III. 3.8.4. Engine stalling If the engine stalls anywhere during the test cycle, the engine shall be preconditioned and restarted, and the test repeated. If a malfunction occurs in any of the required test equipment during the test cycle, the test shall be voided. 3.8.5. Operations after test At the completion of the test, the measurement of the diluted exhaust gas volume or raw exhaust gas flow rate, the gas flow into the collecting bags and the particulate sample pump shall be stopped. For an integrating analyser system, sampling shall continue until system response times have elapsed. The concentrations of the collecting bags, if used, shall be analysed as soon as possible and in any case not later than 20 minutes after the end of the test cycle. After the emission test, a zero gas and the same span gas shall be used for re-checking the analysers. The test will be considered acceptable if the difference between the pre-test and post-test results is less than 2 % of the span gas value. 3.9. Verification of the test run 3.9.1. Data shift To minimise the biasing effect of the time lag between the feedback and reference cycle values, the entire engine speed and torque feedback signal sequence may be advanced or delayed in time with respect to the reference speed and torque sequence. If the feedback signals are shifted, both speed and torque must be shifted the same amount in the same direction. 3.9.2. Calculation of the cycle work The actual cycle work Wact (kWh) shall be calculated using each pair of engine feedback speed and torque values recorded. This shall be done after any feedback data shift has occurred, if this option is selected. The actual cycle work Wact is used for comparison to the reference cycle work Wref and for calculating the brake specific emissions (see sections 4.4 and 5.2). The same methodology shall be used for integrating both reference and actual engine power. If values are to be determined between adjacent reference or adjacent measured values, linear interpolation shall be used. In integrating the reference and actual cycle work, all negative torque values shall be set equal to zero and included. If integration is performed at a frequency of less than 5 Hertz, and if, during a given time segment, the torque value changes from positive to negative or negative to positive, the negative portion shall be computed and set equal to zero. The positive portion shall be included in the integrated value. Wact shall be between – 15 % and + 5 % of Wref 3.9.3. Validation statistics of the test cycle Linear regressions of the feedback values on the reference values shall be performed for speed, torque and power. This shall be done after any feedback data shift has occurred, if this option is selected. The method of least squares shall be used, with the best fit equation having the form: y = mx + b where: y = Feedback (actual) value of speed (min-1), torque (Nm), or power (kW) m = slope of the regression line x = reference value of speed (min-1), torque (Nm), or power (kW) b = y intercept of the regression line The standard error of estimate (SE) of y on x and the coefficient of determination (r2) shall be calculated for each regression line. It is recommended that this analysis be performed at 1 Hertz. All negative reference torque values and the associated feedback values shall be deleted from the calculation of cycle torque and power validation statistics. For a test to be considered valid, the criteria of table 7 must be met. Table 7 Regression line tolerances Speed Torque Power Standard error of estimate (SE) of Y on X Max 100 min–1 Max 13 % (15 %) (15) of power map maximum engine torque Max 8 % (15 %) (15) of power map maximum engine power Slope of the regression line, m 0,95 to 1,03 0,83–1,03 0,89–1,03 (0,83–1,03) (15) Coefficient of determination, r2 min 0,9700 (min 0,9500) (15) min 0,8800 (min 0,7500) (15) min 0,9100 (min 0,7500) (15) Y intercept of the regression line, b ± 50 min–1 ± 20 Nm or ± 2 % (± 20 Nm or ± 3 %) (15) of max torque whichever is greater ± 4 kW or ± 2 % (± 4 kW or ± 3 %) (15) of max power whichever is greater Point deletions from the regression analyses are permitted where noted in Table 8. Table 8 Permitted point deletions from regression analysis Conditions Points to be deleted Full load demand and torque feedback < 95 % torque reference Torque and/or power Full load demand and speed feedback < 95 % speed reference Speed and/or power No load, not an idle point, and torque feedback > torque reference Torque and/or power No load, speed feedback ≤ idle speed + 50 min–1 and torque feedback = manufacturer defined/measured idle torque ± 2 % of max. torque Speed and/or power No load, speed feedback > idle speed + 50 min–1 and torque feedback > 105 % torque reference Torque and/or power No load and speed feedback > 105 % speed reference Speed and/or power’ (ii) The following section 4 is inserted: ‘4. CALCULATION OF THE EXHAUST GAS FLOW 4.1. Determination of the diluted exhaust gas flow The total diluted exhaust gas flow over the cycle (kg/test) shall be calculated from the measurement values over the cycle and the corresponding calibration data of the flow measurement device (V 0 for PDP, K V for CFV, C d for SSV), as determined in section 2 of Appendix 5 to Annex III). The following formulae shall be applied, if the temperature of the diluted exhaust is kept constant over the cycle by using a heat exchanger (± 6 K for a PDP-CVS, ± 11 K for a CFV-CVS or ± 11 K for a SSV-CVS), see section 2.3 of Annex V). For the PDP-CVS system: m ed = 1,293 × V 0 × N P × (p b - p 1) × 273 / (101,3 × T) where: V 0 = volume of gas pumped per revolution under test conditions, m3/rev N P = total revolutions of pump per test p b = atmospheric pressure in the test cell, kPa p 1 = pressure depression below atmospheric at pump inlet, kPa T = average temperature of the diluted exhaust gas at pump inlet over the cycle, K For the CFV-CVS system: m ed = 1,293 × t × K v × p p / T 0,5 where: t = cycle time, s K v = calibration coefficient of the critical flow venturi for standard conditions, p p = absolute pressure at venturi inlet, kPa T = absolute temperature at venturi inlet, K For the SSV-CVS system m ed = 1,293 × QSSV where: with: A 0 = collection of constants and units conversions = 0,006111 in SI units of d = diameter of the SSV throat, m C d = discharge coefficient of the SSV p p = absolute pressure at venturi inlet, kPa T = temperature at the venturi inlet, K r p = ratio of the SSV throat to inlet absolute, static pressure = rD = ratio of the SSV throat diameter, d, to the inlet pipe inner diameter = If a system with flow compensation is used (i.e. without heat exchanger), the instantaneous mass emissions shall be calculated and integrated over the cycle. In this case, the instantaneous mass of the diluted exhaust gas shall be calculated as follows. For the PDP-CVS system: m ed,i = 1,293 × V 0 × N P,i × (p b - p 1) × 273 / (101,3 × T) where: N P,i = total revolutions of pump per time interval For the CFV-CVS system: m ed,i = 1,293 × Δt i × K V × p p / T 0,5 where: Δt i = time interval, s For the SSV-CVS system: med = 1,293 × QSSV × Δti where: Δt i = time interval, s The real time calculation shall be initialised with either a reasonable value for C d, such as 0,98, or a reasonable value of Q ssv. If the calculation is initialised with Q ssv, the initial value of Q ssv shall be used to evaluate Re. During all emissions tests, the Reynolds number at the SSV throat must be in the range of Reynolds numbers used to derive the calibration curve developed in section 2.4 of Appendix 5 to this Annex. 4.2. Determination of raw exhaust gas mass flow For calculation of the emissions in the raw exhaust gas and for controlling of a partial flow dilution system, it is necessary to know the exhaust gas mass flow rate. For the determination of the exhaust mass flow rate, either of the methods described in sections 4.2.2 to 4.2.5 may be used. 4.2.1. Response time For the purpose of emissions calculation, the response time of either method described below shall be equal to or less than the requirement for the analyzer response time, as defined in section 1.5 of Appendix 5 to this Annex. For the purpose of controlling of a partial flow dilution system, a faster response is required. For partial flow dilution systems with online control, a response time of ≤ 0,3 seconds is required. For partial flow dilution systems with look ahead control based on a pre-recorded test run, a response time of the exhaust flow measurement system of ≤ 5 seconds with a rise time of ≤ 1 second is required. The system response time shall be specified by the instrument manufacturer. The combined response time requirements for exhaust gas flow and partial flow dilution system are indicated in section 3.8.3.2. 4.2.2. Direct measurement method Direct measurement of the instantaneous exhaust flow may be done by systems such as: — pressure differential devices, like flow nozzle, — ultrasonic flowmeter, — vortex flowmeter. Precautions shall be taken to avoid measurement errors which will impact emission value errors. Such precautions include the careful installation of the device in the engine exhaust system according to the instrument manufacturers' recommendations and to good engineering practice. Engine performance and emissions shall especially not be affected by the installation of the device. The accuracy of exhaust flow determination shall be at least ± 2,5 % of reading or ± 1,5 % of engine's maximum value, whichever is the greater. 4.2.3. Air and fuel measurement method This involves measurement of the air flow and the fuel flow. Air flowmeters and fuel flowmeters shall be used that meet the total exhaust flow accuracy requirement of section 4.2.2. The calculation of the exhaust gas flow is as follows: qmew = qmaw + qmf 4.2.4. Tracer measurement method This involves measurement of the concentration of a tracer gas in the exhaust. A known amount of an inert gas (e.g. pure helium) shall be injected into the exhaust gas flow as a tracer. The gas is mixed and diluted by the exhaust gas, but shall not react in the exhaust pipe. The concentration of the gas shall then be measured in the exhaust gas sample. In order to ensure complete mixing of the tracer gas, the exhaust gas sampling probe shall be located at least 1 m or 30 times the diameter of the exhaust pipe, whichever is larger, downstream of the tracer gas injection point. The sampling probe may be located closer to the injection point if complete mixing is verified by comparing the tracer gas concentration with the reference concentration when the tracer gas is injected upstream of the engine. The tracer gas flow rate shall be set so that the tracer gas concentration at engine idle speed after mixing becomes lower than the full scale of the trace gas analyser. The calculation of the exhaust gas flow is as follows: where: q mew,i = instantaneous exhaust mass flow, kg/s q vt = tracer gas flow, cm3/min c mix.i = instantaneous concentration of the tracer gas after mixing, ppm ρ e = density of the exhaust gas, kg/m3 (cf. table 3) c a = background concentration of the tracer gas in the intake air, ppm When the background concentration is less than 1 % of the concentration of the tracer gas after mixing (c mix.i) at maximum exhaust flow, the background concentration may be neglected. The total system shall meet the accuracy specifications for the exhaust gas flow, and shall be calibrated according to section 1.7 of Appendix 5 to this Annex. 4.2.5. Air flow and air-to-fuel ratio measurement method This involves exhaust mass calculation from the air flow and the air to fuel ratio. The calculation of the instantaneous exhaust gas mass flow is as follows: with: where: A/F st = stoichiometric air to fuel ratio, kg/kg λ = excess air ratio c CO2 = dry CO2 concentration, % c CO = dry CO concentration, ppm c HC = HC concentration, ppm Note: β can be 1 for fuels containing carbon and 0 for hydrogen fuel. The air flowmeter shall meet the accuracy specifications of section 2.2 of Appendix 4 to this Annex, the CO2 analyser used shall meet the specifications of section 3.3.2 of Appendix 4 to this Annex and the total system shall meet the accuracy specifications for the exhaust gas flow. Optionally, air to fuel ratio measurement equipment such as a zirconia type sensor may be used for the measurement of the excess air ratio which meets the specifications of section 3.3.6 of Appendix 4 to this Annex.’ (iii) Sections 4 and 5 are replaced by the following: ‘5. CALCULATION OF THE GASEOUS EMISSIONS 5.1. Data evaluation For the evaluation of the gaseous emissions in the diluted exhaust gas, the emission concentrations (HC, CO and NOx) and the diluted exhaust gas mass flow rate shall be recorded according to section 3.8.2.1 and stored on a computer system. For analogue analysers the response shall be recorded, and the calibration data may be applied online or offline during the data evaluation. For the evaluation of the gaseous emissions in the raw exhaust gas, the emission concentrations (HC, CO and NOx) and the exhaust gas mass flow rate shall be recorded according to section 3.8.2.2 and stored on a computer system. For analogue analysers the response shall be recorded, and the calibration data may be applied online or offline during the data evaluation. 5.2. Dry/wet correction If the concentration is measured on a dry basis, it shall be converted to a wet basis according to the following formula. For continuous measurement, the conversion shall be applied to each instantaneous measurement before any further calculation. cwet = kW × cdry The conversion equations of section 5.2 of Appendix 1 to this Annex shall apply. 5.3. NOx correction for humidity and temperature As the NOx emission depends on ambient air conditions, the NOx concentration shall be corrected for ambient air temperature and humidity with the factors given in section 5.3 of Appendix 1 to this Annex. The factors are valid in the range between 0 and 25 g/kg dry air. 5.4. Calculation of the emission mass flow rates The emission mass over the cycle (g/test) shall be calculated as follows depending on the measurement method applied. The measured concentration shall be converted to a wet basis according to section 5.2 of Appendix 1 to this Annex, if not already measured on a wet basis. The respective values for u gas shall be applied that are given in Table 6 of Appendix 1 to this Annex for selected components based on ideal gas properties and the fuels relevant for this Directive. (a) for the raw exhaust gas: where: u gas = ratio between density of exhaust component and density of exhaust gas from table 6 c gas,i = instantaneous concentration of the respective component in the raw exhaust gas, ppm q mew,i = instantaneous exhaust mass flow rate, kg/s f = data sampling rate, Hz n = number of measurements (b) for the diluted exhaust gas without flow compensation: mgas = ugas × cgas × med where: u gas = ratio between density of exhaust component and density of air from table 6 c gas = average background corrected concentration of the respective component, ppm m ed = total diluted exhaust mass over the cycle, kg (c) for the diluted exhaust gas with flow compensation: where: c e,i = instantaneous concentration of the respective component measured in the diluted exhaust gas, ppm c d = concentration of the respective component measured in the dilution air, ppm q mdew,i = instantaneous diluted exhaust gas mass flow rate, kg/s m ed = total mass of diluted exhaust gas over the cycle, kg u gas = ratio between density of exhaust component and density of air from table 6 D = dilution factor (see section 5.4.1) If applicable, the concentration of NMHC and CH4 shall be calculated by either of the methods shown in section 3.3.4 of Appendix 4 to this Annex, as follows: (a) GC method (full flow dilution system, only): cNMHC = cHC – cCH4 (b) NMC method: where: c HC(w/Cutter) = HC concentration with the sample gas flowing through the NMC c HC(w/oCutter) = HC concentration with the sample gas bypassing the NMC 5.4.1. Determination of the background corrected concentrations (full flow dilution system, only) The average background concentration of the gaseous pollutants in the dilution air shall be subtracted from measured concentrations to get the net concentrations of the pollutants. The average values of the background concentrations can be determined by the sample bag method or by continuous measurement with integration. The following formula shall be used. where: c e = concentration of the respective pollutant measured in the diluted exhaust gas, ppm c d = concentration of the respective pollutant measured in the dilution air, ppm D = dilution factor The dilution factor shall be calculated as follows: (a) for diesel and LPG fueled gas engines (b) for NG fueled gas engines where: c CO2 = concentration of CO2 in the diluted exhaust gas, % vol c HC = concentration of HC in the diluted exhaust gas, ppm C1 c NMHC = concentration of NMHC in the diluted exhaust gas, ppm C1 c CO = concentration of CO in the diluted exhaust gas, ppm F S = stoichiometric factor Concentrations measured on dry basis shall be converted to a wet basis in accordance with section 5.2 of Appendix 1 to this Annex. The stoichiometric factor shall be calculated as follows: where: α, ε are the molar ratios referring to a fuel CH α O ε Alternatively, if the fuel composition is not known, the following stoichiometric factors may be used: F S (diesel) = 13,4 F S (LPG) = 11,6 F S (NG) = 9,5 5.5. Calculation of the specific emissions The emissions (g/kWh) shall be calculated in the following way: (a) all components, except NOx: (b) NOx: where: W act = actual cycle work as determined according to section 3.9.2. 5.5.1. In case of a periodic exhaust aftertreatment system, the emissions shall be weighted as follows: where: n1 = number of ETC tests between two regenerations n2 = number of ETC during a regeneration (minimum of one ETC test) M gas,n2 = emissions during a regeneration M gas,n1 = emissions after a regeneration. 6. CALCULATION OF THE PARTICULATE EMISSION (IF APPLICABLE) 6.1. Data evaluation The particulate filter shall be returned to the weighing chamber no later than one hour after completion of the test. It shall be conditioned in a partially covered petri dish, which is protected against dust contamination, for at least one hour, but not more than 80 hours, and then weighed. The gross weight of the filters shall be recorded and the tare weight subtracted, which results in the particulate sample mass m f. For the evaluation of the particulate concentration, the total sample mass (m sep) through the filters over the test cycle shall be recorded. If background correction is to be applied, the dilution air mass (m d) through the filter and the particulate mass (m f,d) shall be recorded. 6.2. Calculation of the mass flow 6.2.1. Full flow dilution system The particulate mass (g/test) shall be calculated as follows: where: m f = particulate mass sampled over the cycle, mg m sep = mass of diluted exhaust gas passing the particulate collection filters, kg m ed = mass of diluted exhaust gas over the cycle, kg If a double dilution system is used, the mass of the secondary dilution air shall be subtracted from the total mass of the double diluted exhaust gas sampled through the particulate filters. msep = mset – mssd where: m set = mass of double diluted exhaust gas through particulate filter, kg m ssd = mass of secondary dilution air, kg If the particulate background level of the dilution air is determined in accordance with section 3.4, the particulate mass may be background corrected. In this case, the particulate mass (g/test) shall be calculated as follows: where: mPT, msep, med = see above md = mass of primary dilution air sampled by background particulate sampler, kg mf,d = mass of the collected background particulates of the primary dilution air, mg D = dilution factor as determined in section 5.4.1. 6.2.2. Partial flow dilution system The mass of particulates (g/test) shall be calculated by either of the following methods: (a) where: m f = particulate mass sampled over the cycle, mg m sep = mass of diluted exhaust gas passing the particulate collection filters, kg m edf = mass of equivalent diluted exhaust gas over the cycle, kg The total mass of equivalent diluted exhaust gas mass over the cycle shall be determined as follows: where: q medf,i = instantaneous equivalent diluted exhaust mass flow rate, kg/s q mew,i = instantaneous exhaust mass flow rate, kg/s r d,i = instantaneous dilution ratio q mdew,i = instantaneous diluted exhaust mass flow rate through dilution tunnel, kg/s q mdw,i = instantaneous dilution air mass flow rate, kg/s f = data sampling rate, Hz n = number of measurements (b) where: m f = particulate mass sampled over the cycle, mg r s = average sample ratio over the test cycle with: where: m se = sample mass over the cycle, kg m ew = total exhaust mass flow over the cycle, kg m sep = mass of diluted exhaust gas passing the particulate collection filters, kg m sed = mass of diluted exhaust gas passing the dilution tunnel, kg. Note: In case of the total sampling type system, m sep and M sed are identical. 6.3. Calculation of the Specific Emission The particulate emission (g/kWh) shall be calculated in the following way: where: W act = actual cycle work as determined according to section 3.9.2, kWh. 6.3.1. In case of a periodic regeneration aftertreatment system, the emissions shall be weighted as follows: where: n1 = number of ETC tests between two regeneration events n2 = number of ETC tests during a regeneration (minimum of one ETC) = emissions during a regeneration = emissions outside a regeneration.’ (g) Appendix 4 is amended as follows: (i) Section 1 is replaced by the following: ‘1. INTRODUCTION Gaseous components, particulates, and smoke emitted by the engine submitted for testing shall be measured by the methods described in Annex V. The respective sections of Annex V describe the recommended analytical systems for the gaseous emissions (section 1), the recommended particulate dilution and sampling systems (section 2), and the recommended opacimeters for smoke measurement (section 3). For the ESC, the gaseous components shall be determined in the raw exhaust gas. Optionally, they may be determined in the diluted exhaust gas, if a full flow dilution system is used for particulate determination. Particulates shall be determined with either a partial flow or a full flow dilution system. For the ETC, the following systems may be used — a CVS full flow dilution system for determining gaseous and particulate emissions (double dilution systems are permissible), or — a combination of raw exhaust measurement for the gaseous emissions and a partial flow dilution system for particulate emissions, or — any combination of the two principles (e.g. raw gaseous measurement and full flow particulate measurement).’ (ii) Section 2.2 is replaced by the following: ‘2.2. Other instruments Measuring instruments for fuel consumption, air consumption, temperature of coolant and lubricant, exhaust gas pressure and intake manifold depression, exhaust gas temperature, air intake temperature, atmospheric pressure, humidity and fuel temperature shall be used, as required. These instruments shall satisfy the requirements given in table 9: Table 9 Accuracy of measuring instruments Measuring Instrument Accuracy Fuel Consumption ± 2 % of Engine's Maximum Value Air Consumption ± 2 % of reading or ± 1 % of engine's maximum value whichever is greater Exhaust Gas Flow ± 2,5 % of reading or ± 1,5 % of engine's maximum value whichever is greater Temperatures ≤ 600 K (327 °C) ± 2 K Absolute Temperatures ≥ 600 K (327 °C) ± 1 % of Reading Atmospheric Pressure ± 0,1 kPa Absolute Exhaust Gas Pressure ± 0,2 kPa Absolute Intake Depression ± 0,05 kPa Absolute Other Pressures ± 0,1 kPa Absolute Relative Humidity ± 3 % Absolute Absolute Humidity ± 5 % of Reading Dilution Air Flow ± 2 % of Reading Diluted Exhaust Gas Flow ± 2 % of Reading’ (iii) Sections 2.3 and 2.4 are deleted. (iv) Sections 3 and 4 are replaced by the following: ‘3. DETERMINATION OF THE GASEOUS COMPONENTS 3.1. General analyser specifications The analysers shall have a measuring range appropriate for the accuracy required to measure the concentrations of the exhaust gas components (section 3.1.1). It is recommended that the analysers be operated such that the measured concentration falls between 15 % and 100 % of full scale. If read-out systems (computers, data loggers) can provide sufficient accuracy and resolution below 15 % of full scale, measurements below 15 % of full scale are also acceptable. In this case, additional calibrations of at least 4 non-zero nominally equally spaced points are to be made to ensure the accuracy of the calibration curves according to section 1.6.4 of Appendix 5 to this Annex. The electromagnetic compatibility (EMC) of the equipment shall be on a level as to minimise additional errors. 3.1.1. Accuracy The analyser shall not deviate from the nominal calibration point by more than ± 2 % of the reading over the whole measurement range except zero, or ± 0,3 % of full scale whichever is larger. The accuracy shall be determined according to the calibration requirements laid down in section 1.6 of Appendix 5 to this Annex. Note: For the purpose of this Directive, accuracy is defined as the deviation of the analyser reading from the nominal calibration values using a calibration gas (= true value). 3.1.2. Precision The precision, defined as 2,5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, has to be not greater than ± 1 % of full scale concentration for each range used above 155 ppm (or ppmC) or ± 2 % of each range used below 155 ppm (or ppmC). 3.1.3. Noise The analyser peak-to-peak response to zero and calibration or span gases over any 10 second period shall not exceed 2 % of full scale on all ranges used. 3.1.4. Zero drift Zero response is defined as the mean response, including noise, to a zero gas during a 30 seconds time interval. The drift of the zero response during a one hour period shall be less than 2 % of full scale on the lowest range used. 3.1.5. Span drift Span response is defined as the mean response, including noise, to a span gas during a 30 seconds time interval. The drift of the span response during a one hour period shall be less than 2 % of full scale on the lowest range used. 3.1.6. Rise time The rise time of the analyser installed in the measurement system shall not exceed 3,5 s. Note: Only evaluating the response time of the analyser alone will not clearly define the suitability of the total system for transient testing. Volumes and especially dead volumes through out the system will not only effect the transportation time from the probe to the analyser, but also effect the rise time. Also transport times inside of an analyser would be defined as analyser response time, like the converter or water traps inside NOx analysers. The determination of the total system response time is described in section 1.5 of Appendix 5 to this Annex. 3.2. Gas drying The optional gas drying device must have a minimal effect on the concentration of the measured gases. Chemical dryers are not an acceptable method of removing water from the sample. 3.3. Analysers Sections 3.3.1 to 3.3.4 describe the measurement principles to be used. A detailed description of the measurement systems is given in Annex V. The gases to be measured shall be analysed with the following instruments. For non-linear analysers, the use of linearising circuits is permitted. 3.3.1. Carbon monoxide (CO) analysis The carbon monoxide analyser shall be of the Non-Dispersive InfraRed (NDIR) absorption type. 3.3.2. Carbon dioxide (CO2) analysis The carbon dioxide analyser shall be of the Non-Dispersive InfraRed (NDIR) absorption type. 3.3.3. Hydrocarbon (HC) analysis For diesel and LPG fuelled gas engines, the hydrocarbon analyser shall be of the Heated Flame Ionisation Detector (HFID) type with detector, valves, pipework, etc. heated so as to maintain a gas temperature of 463 K ± 10 K (190 ± 10 °C). For NG fuelled gas engines, the hydrocarbon analyser may be of the non heated Flame Ionisation Detector (FID) type depending upon the method used (see section 1.3 of Annex V). 3.3.4. Non-Methane Hydrocarbon (NMHC) analysis (NG fuelled gas engines only) Non-methane hydrocarbons shall be determined by either of the following methods: 3.3.4.1. Gas chromatographic (GC) method Non-methane hydrocarbons shall be determined by subtraction of the methane analysed with a Gas Chromatograph (GC) conditioned at 423 K (150 °C) from the hydrocarbons measured according to section 3.3.3. 3.3.4.2. Non-Methane Cutter (NMC) method The determination of the non-methane fraction shall be performed with a heated NMC operated in line with an FID as per section 3.3.3 by subtraction of the methane from the hydrocarbons. 3.3.5. Oxides of Nitrogen (NOx) analysis The oxides of nitrogen analyser shall be of the ChemiLuminescent Detector (CLD) or Heated ChemiLuminescent Detector (HCLD) type with a NO2/NO converter, if measured on a dry basis. If measured on a wet basis, a HCLD with converter maintained above 328 K (55 °C) shall be used, provided the water quench check (see section 1.9.2.2 of Appendix 5 to this Annex) is satisfied. 3.3.6. Air-to-fuel measurement The air to fuel measurement equipment used to determine the exhaust gas flow as specified in section 4.2.5 of Appendix 2 to this Annex shall be a wide range air to fuel ratio sensor or lambda sensor of Zirconia type. The sensor shall be mounted directly on the exhaust pipe where the exhaust gas temperature is high enough to eliminate water condensation. The accuracy of the sensor with incorporated electronics shall be within: ± 3 % of reading λ < 2 ± 5 % of reading 2 ≤ λ < 5 ± 10 % of reading 5 ≤ λ To fulfil the accuracy specified above, the sensor shall be calibrated as specified by the instrument manufacturer. 3.4. Sampling of Gaseous Emissions 3.4.1. Raw exhaust gas The gaseous emissions sampling probes shall be fitted at least 0,5 m or 3 times the diameter of the exhaust pipe — whichever is the larger — upstream of the exit of the exhaust gas system but sufficiently close to the engine as to ensure an exhaust gas temperature of at least 343 K (70 °C) at the probe. In the case of a multi-cylinder engine with a branched exhaust manifold, the inlet of the probe shall be located sufficiently far downstream so as to ensure that the sample is representative of the average exhaust emissions from all cylinders. In multi-cylinder engines having distinct groups of manifolds, such as in a “Vee” engine configuration, it is recommended to combine the manifolds upstream of the sampling probe. If this is not practical, it is permissible to acquire a sample from the group with the highest CO2 emission. Other methods which have been shown to correlate with the above methods may be used. For exhaust emission calculation the total exhaust mass flow shall be used. If the engine is equipped with an exhaust aftertreatment system, the exhaust sample shall be taken downstream of the exhaust aftertreatment system. 3.4.2. Diluted exhaust gas The exhaust pipe between the engine and the full flow dilution system shall conform to the requirements of section 2.3.1 of Annex V (EP). The gaseous emissions sample probe(s) shall be installed in the dilution tunnel at a point where the dilution air and exhaust gas are well mixed, and in close proximity to the particulates sampling probe. Sampling can generally be done in two ways: — the pollutants are sampled into a sampling bag over the cycle and measured after completion of the test, — the pollutants are sampled continuously and integrated over the cycle; this method is mandatory for HC and NOx. 4. DETERMINATION OF THE PARTICULATES The determination of the particulates requires a dilution system. Dilution may be accomplished by a partial flow dilution system or a full flow double dilution system. The flow capacity of the dilution system shall be large enough to completely eliminate water condensation in the dilution and sampling systems. The temperature of the diluted exhaust gas shall be below 325 K (52 °C) (16) immediately upstream of the filter holders. Humidity control of the dilution air before entering the dilution system is permitted, and especially dehumidifying is useful if dilution air humidity is high. The temperature of the dilution air shall be higher than 288 K (15 °C) in close proximity to the entrance into the dilution tunnel. The partial flow dilution system has to be designed to extract a proportional raw exhaust sample from the engine exhaust stream, thus responding to excursions in the exhaust stream flow rate, and introduce dilution air to this sample to achieve a temperature below 325 K (52 °C) at the test filter. For this it is essential that the dilution ratio or the sampling ratio r dil or r s be determined such that the accuracy limits of section 3.2.1 of Appendix 5 to this Annex are fulfilled. Different extraction methods can be applied, whereby the type of extraction used dictates to a significant degree the sampling hardware and procedures to be used (section 2.2 of Annex V). In general, the particulate sampling probe shall be installed in close proximity to the gaseous emissions sampling probe, but sufficiently distant as to not cause interference. Therefore, the installation provisions of section 3.4.1 also apply to particulate sampling. The sampling line shall conform to the requirements of section 2 of Annex V. In the case of a multi-cylinder engine with a branched exhaust manifold, the inlet of the probe shall be located sufficiently far downstream so as to ensure that the sample is representative of the average exhaust emissions from all cylinders. In multi-cylinder engines having distinct groups of manifolds, such as in a “Vee” engine configuration, it is recommended to combine the manifolds upstream of the sampling probe. If this is not practical, it is permissible to acquire a sample from the group with the highest particulate emission. Other methods which have been shown to correlate with the above methods may be used. For exhaust emission calculation the total exhaust mass flow shall be used. To determine the mass of the particulates, a particulate sampling system, particulate sampling filters, a microgram balance, and a temperature and humidity controlled weighing chamber, are required. For particulate sampling, the single filter method shall be applied which uses one filter (see section 4.1.3) for the whole test cycle. For the ESC, considerable attention must be paid to sampling times and flows during the sampling phase of the test. 4.1. Particulate sampling filters The diluted exhaust shall be sampled by a filter that meets the requirements of sections 4.1.1 and 4.1.2 during the test sequence. 4.1.1. Filter specification Fluorocarbon coated glass fiber filters are required. All filter types shall have a 0,3 μm DOP (di-octylphthalate) collection efficiency of at least 99 % at a gas face velocity between 35 and 100 cm/s. 4.1.2. Filter size Particulate filters with a diameter of 47 mm or 70 mm are recommended. Larger diameter filters are acceptable (section 4.1.4), but smaller diameter filters are not permitted. 4.1.3. Filter face velocity A gas face velocity through the filter of 35 to 100 cm/s shall be achieved. The pressure drop increase between the beginning and the end of the test shall be no more than 25 kPa. 4.1.4. Filter loading The required minimum filter loadings for the most common filter sizes are shown in table 10. For larger filter sizes, the minimum filter loading shall be 0,065 mg/1 000 mm2 filter area. Table 10 Minimum Filter Loadings Filter Diameter (mm) Minimum loading (mg) 47 0,11 70 0,25 90 0,41 110 0,62 If, based on previous testing, the required minimum filter loading is unlikely to be reached on a test cycle after optimisation of flow rates and dilution ratio, a lower filter loading may be acceptable, with the agreement of the parties involved, if it can be shown to meet the accuracy requirements of section 4.2, e.g. with a 0,1 μg balance. 4.1.5. Filter holder For the emissions test, the filters shall be placed in a filter holder assembly meeting the requirements of section 2.2 of Annex V. The filter holder assembly shall be of a design that provides an even flow distribution across the filter stain area. Quick acting valves shall be located either upstream or downstream of the filter holder. An inertial pre-classifier with a 50 % cut point between 2,5 μm and 10 μm may be installed immediately upstream of the filter holder. The use of the pre-classifier is strongly recommended if an open tube sampling probe facing upstream into the exhaust flow is used. 4.2. Weighing chamber and analytical balance specifications 4.2.1. Weighing chamber conditions The temperature of the chamber (or room) in which the particulate filters are conditioned and weighed shall be maintained to within 295 K ± 3 K (22 °C ± 3 °C) during all filter conditioning and weighing. The humidity shall be maintained to a dewpoint of 282,5 K ± 3 K (9,5 °C ± 3 °C) and a relative humidity of 45 % ± 8 %. 4.2.2. Reference filter weighing The chamber (or room) environment shall be free of any ambient contaminants (such as dust) that would settle on the particulate filters during their stabilisation. Disturbances to weighing room specifications as outlined in section 4.2.1 will be allowed if the duration of the disturbances does not exceed 30 minutes. The weighing room should meet the required specifications prior to personal entrance into the weighing room. At least two unused reference filters shall be weighed within 4 hours of, but preferably at the same time as the sample filter weightings. They shall be the same size and material as the sample filters. If the average weight of the reference filters changes between sample filter weightings by more than 10 μg, then all sample filters shall be discarded and the emissions test repeated. If the weighing room stability criteria outlined in section 4.2.1 is not met, but the reference filter weightings meet the above criteria, the engine manufacturer has the option of accepting the sample filter weights or voiding the tests, fixing the weighing room control system and re-running the test. 4.2.3. Analytical balance The analytical balance used to determine the filter weight shall have a precision (standard deviation) of at least 2 μg and a resolution of at least 1 μg (1 digit = 1 μg) specified by the balance manufacturer. 4.2.4. Elimination of static electricity effects To eliminate the effects of static electricity, the filters shall be neutralized prior to weighing, e.g. by a Polonium neutralizer, a Faraday cage or a device of similar effect. 4.2.5. Specifications for flow measurement 4.2.5.1. General requirements Absolute accuracies of flow meter or flow measurement instrumentation shall be as specified in section 2.2. 4.2.5.2. Special provisions for partial flow dilution systems For partial flow dilution systems, the accuracy of the sample flow q mp is of special concern, if not measured directly, but determined by differential flow measurement: q mp = qmdew – qmdw In this case an accuracy of ± 2 % for q mdew and q mdw is not sufficient to guarantee acceptable accuracies of q mp. If the gas flow is determined by differential flow measurement, the maximum error of the difference shall be such that the accuracy of q mp is within ± 5 % when the dilution ratio is less than 15. It can be calculated by taking root-mean-square of the errors of each instrument. Acceptable accuracies of q mp can be obtained by either of the following methods: The absolute accuracies of q mdew and q mdw are ± 0,2 % which guarantees an accuracy of q mp of ≤ 5 % at a dilution ratio of 15. However, greater errors will occur at higher dilution ratios; calibration of q mdw relative to q mdew is carried out such that the same accuracies for q mp as in a) are obtained. For the details of such a calibration see section 3.2.1 of Appendix 5 to Annex III; the accuracy of q mp is determined indirectly from the accuracy of the dilution ratio as determined by a tracer gas, e.g. CO2. Again, accuracies equivalent to method a) for q mp are required; the absolute accuracy of q mdew and q mdw is within ± 2 % of full scale, the maximum error of the difference between q mdew and q mdw is within 0,2 %, and the linearity error is within ± 0,2 % of the highest q mdew observed during the test. (h) Appendix 5 is amended as follows: (i) The following section 1.2.3 is added: ‘1.2.3. Use of precision blending devices The gases used for calibration and span may also be obtained by means of precision blending devices (gas dividers), diluting with purified N2 or with purified synthetic air. The accuracy of the mixing device must be such that the concentration of the blended calibration gases is accurate to within ± 2 %. This accuracy implies that primary gases used for blending must be known to an accuracy of at least ± 1 %, traceable to national or international gas standards. The verification shall be performed at between 15 and 50 % of full scale for each calibration incorporating a blending device. Optionally, the blending device may be checked with an instrument which by nature is linear, e.g. using NO gas with a CLD. The span value of the instrument shall be adjusted with the span gas directly connected to the instrument. The blending device shall be checked at the used settings and the nominal value shall be compared to the measured concentration of the instrument. This difference shall in each point be within ± 1 % of the nominal value.’ (ii) Section 1.4 is replaced by the following: ‘1.4. Leakage test A system leakage test shall be performed. The probe shall be disconnected from the exhaust system and the end plugged. The analyser pump shall be switched on. After an initial stabilisation period all flow meters should read zero. If not, the sampling lines shall be checked and the fault corrected. The maximum allowable leakage rate on the vacuum side shall be 0,5 % of the in-use flow rate for the portion of the system being checked. The analyser flows and bypass flows may be used to estimate the in-use flow rates. Alternatively, the system may be evacuated to a pressure of at least 20 kPa vacuum (80 kPa absolute). After an initial stabilisation period the pressure increase Δp (kPa/min) in the system should not exceed: Δp = p / V s × 0,005 × q vs where: V s = system volume, l q vs = system flow rate, l/min Another method is the introduction of a concentration step change at the beginning of the sampling line by switching from zero to span gas. If after an adequate period of time the reading is about 1 % low compared to the introduced concentration, these points to calibration or leakage problems.’ (iii) The following section 1.5 is inserted: ‘1.5. Response time check of analytical system The system settings for the response time evaluation shall be exactly the same as during measurement of the test run (i.e. pressure, flow rates, filter settings on the analyzers and all other response time influences). The response time determination shall be done with gas switching directly at the inlet of the sample probe. The gas switching shall be done in less than 0,1 second. The gases used for the test shall cause a concentration change of at least 60 % FS. The concentration trace of each single gas component shall be recorded. The response time is defined to be the difference in time between the gas switching and the appropriate change of the recorded concentration. The system response time (t 90) consists of the delay time to the measuring detector and the rise time of the detector. The delay time is defined as the time from the change (t 0) until the response is 10 % of the final reading (t 10). The rise time is defined as the time between 10 % and 90 % response of the final reading (t 90 – t 10). For time alignment of the analyzer and exhaust flow signals in the case of raw measurement, the transformation time is defined as the time from the change (t 0) until the response is 50 % of the final reading (t 50). The system response time shall be ≤ 10 seconds with a rise time ≤ 3,5 seconds for all limited components (CO, NOx, HC or NMHC) and all ranges used.’ (iv) Former section 1.5 is replaced by the following: ‘1.6. Calibration 1.6.1. Instrument assembly The instrument assembly shall be calibrated and calibration curves checked against standard gases. The same gas flow rates shall be used as when sampling exhaust. 1.6.2. Warming-up time The warming-up time should be according to the recommendations of the manufacturer. If not specified, a minimum of two hours is recommended for warming up the analysers. 1.6.3. NDIR and HFID analyser The NDIR analyser shall be tuned, as necessary, and the combustion flame of the HFID analyser shall be optimised (section 1.8.1). 1.6.4. Establishment of the calibration curve — Each normally used operating range shall be calibrated — Using purified synthetic air (or nitrogen), the CO, CO2, NOx and HC analysers shall be set at zero — The appropriate calibration gases shall be introduced to the analysers, the values recorded, and the calibration curve established — The calibration curve shall be established by at least 6 calibration points (excluding zero) approximately equally spaced over the operating range. The highest nominal concentration shall be equal to or higher than 90 % of full scale — The calibration curve shall be calculated by the method of least-squares. A best-fit linear or non-linear equation may be used — The calibration points shall not differ from the least-squares best-fit line by more than ± 2 % of reading or ± 0,3 % of full scale whichever is larger — The zero setting shall be rechecked and the calibration procedure repeated, if necessary. 1.6.5. Alternative methods If it can be shown that alternative technology (e.g. computer, electronically controlled range switch, etc.) can give equivalent accuracy, then these alternatives may be used. 1.6.6. Calibration of tracer gas analyser for exhaust flow measurement The calibration curve shall be established by at least 6 calibration points (excluding zero) approximately equally spaced over the operating range. The highest nominal concentration shall be equal to or higher than 90 % of full scale. The calibration curve is calculated by the method of least squares. The calibration points shall not differ from the least-squares best-fit line by more than ± 2 % of reading or ± 0,3 % of full scale whichever is larger. The analyser shall be set at zero and spanned prior to the test run using a zero gas and a span gas whose nominal value is more than 80 % of the analyser full scale.’ (v) Former section 1.6 becomes section 1.6.7. (vi) The following section 2.4 is inserted: ‘2.4. Calibration of the Subsonic Venturi (SSV) Calibration of the SSV is based upon the flow equation for a subsonic venturi. Gas flow is a function of inlet pressure and temperature, pressure drop between the SSV inlet and throat. 2.4.1. Data analysis The air flowrate (QSSV) at each restriction setting (minimum 16 settings) shall be calculated in standard m3/min from the flowmeter data using the manufacturer's prescribed method. The discharge coefficient shall be calculated from the calibration data for each setting as follows: where: Q SSV = air flow rate at standard conditions (101,3 kPa, 273 K), m3/s T = temperature at the venturi inlet, K d = diameter of the SSV throat, m r p = ratio of the SSV throat to inlet absolute, static pressure = r D = ratio of the SSV throat diameter, d, to the inlet pipe inner diameter = To determine the range of subsonic flow, C d shall be plotted as a function of Reynolds number at the SSV throat. The Re at the SSV throat is calculated with the following formula: where: A 1 = a collection of constants and units conversions Q SSV = air flow rate at standard conditions (101,3 kPa, 273 K), m3/s d = diameter of the SSV throat, m μ = absolute or dynamic viscosity of the gas, calculated with the following formula: b = empirical constant = S = empirical constant = 110,4 K Because Q SSV is an input to the Re formula, the calculations must be started with an initial guess for Q SSV or C d of the calibration venturi, and repeated until Q SSV converges. The convergence method must be accurate to 0,1 % of point or better. For a minimum of sixteen points in the region of subsonic flow, the calculated values of C d from the resulting calibration curve fit equation must be within ± 0,5 % of the measured C d for each calibration point.’ (vii) Former section 2.4 becomes Section 2.5. (viii) Section 3 is replaced by the following: ‘3. CALIBRATION OF THE PARTICULATE MEASURING SYSTEM 3.1. Introduction The calibration of the particulate measurement is limited to the flow meters used to determine sample flow and dilution ratio. Each flow meter shall be calibrated as often as necessary to fulfil the accuracy requirements of this Directive. The calibration method that shall be used is described in section 3.2. 3.2. Flow measurement 3.2.1. Periodical calibration — To fulfil the absolute accuracy of the flow measurements as specified in section 2.2 of Appendix 4 to this Annex, the flow meter or the flow measurement instrumentation shall be calibrated with an accurate flow meter traceable to international and/or national standards. — If the sample gas flow is determined by differential flow measurement the flow meter or the flow measurement instrumentation shall be calibrated in one of the following procedures, such that the probe flow q mp into the tunnel shall fulfil the accuracy requirements of section 4.2.5.2 of Appendix 4 to this Annex: (a) The flow meter for q mdw shall be connected in series to the flow meter for q mdew, the difference between the two flow meters shall be calibrated for at least 5 set points with flow values equally spaced between the lowest q mdw value used during the test and the value of q mdew used during the test. The dilution tunnel may be bypassed. (b) A calibrated mass flow device shall be connected in series to the flowmeter for q mdew and the accuracy shall be checked for the value used for the test. Then the calibrated mass flow device shall be connected in series to the flow meter for q mdw, and the accuracy shall be checked for at least 5 settings corresponding to dilution ratio between 3 and 50, relative to q mdew used during the test. (c) The transfer tube TT shall be disconnected from the exhaust, and a calibrated flow measuring device with a suitable range to measure q mp shall be connected to the transfer tube. Then q mdew shall be set to the value used during the test, and q mdw shall be sequentially set to at least 5 values corresponding to dilution ratios q between 3 and 50. Alternatively, a special calibration flow path, may be provided, in which the tunnel is bypassed, but the total and dilution air flow through the corresponding meters as in the actual test. (d) A tracer gas, shall be fed into the exhaust transfer tube TT. This tracer gas may be a component of the exhaust gas, like CO2 or NOx. After dilution in the tunnel the tracer gas component shall be measured. This shall be carried out for 5 dilution ratios between 3 and 50. The accuracy of the sample flow shall be determined from the dilution ration r d: — The accuracies of the gas analysers shall be taken into account to guarantee the accuracy of q mp. 3.2.2. Carbon flow check — A carbon flow check using actual exhaust is recommended for detecting measurement and control problems and verifying the proper operation of the partial flow system. The carbon flow check should be run at least each time a new engine is installed, or something significant is changed in the test cell configuration. — The engine shall be operated at peak torque load and speed or any other steady state mode that produces 5 % or more of CO2. The partial flow sampling system shall be operated with a dilution factor of about 15 to 1. — If a carbon flow check is conducted, the procedure given in Appendix 6 to this Annex shall be applied. The carbon flow rates shall be calculated according to sections 2.1 to 2.3 of Appendix 6 to this Annex. All carbon flow rates should agree to within 6 % of each other. 3.2.3. Pre-test check — A pre-test check shall be performed within 2 hours before the test run in the following way: — The accuracy of the flow meters shall be checked by the same method as used for calibration (see section 3.2.1) for at least two points, including flow values of q mdw that correspond to dilution ratios between 5 and 15 for the q mdew value used during the test. — If it can be demonstrated by records of the calibration procedure under section 3.2.1 that the flow meter calibration is stable over a longer period of time, the pre-test check may be omitted. 3.3. Determination of transformation time (for partial flow dilution systems on ETC only) — The system settings for the transformation time evaluation shall be exactly the same as during measurement of the test run. The transformation time shall be determined by the following method: — An independent reference flowmeter with a measurement range appropriate for the probe flow shall be put in series with and closely coupled to the probe. This flowmeter shall have a transformation time of less than 100 ms for the flow step size used in the response time measurement, with flow restriction sufficiently low as to not affect the dynamic performance of the partial flow dilution system, and consistent with good engineering practice. — A step change shall be introduced to the exhaust flow (or air flow if exhaust flow is calculated) input of the partial flow dilution system, from a low flow to at least 90 % of full scale. The trigger for the step change should be the same one used to start the look-ahead control in actual testing. The exhaust flow step stimulus and the flowmeter response shall be recorded at a sample rate of at least 10 Hz. — From this data, the transformation time shall be determined for the partial flow dilution system, which is the time from the initiation of the step stimulus to the 50 % point of the flowmeter response. In a similar manner, the transformation times of the qmp signal of the partial flow dilution system and of the q mew,i signal of the exhaust flow meter shall be determined. These signals are used in the regression checks performed after each test (see section 3.8.3.2 of Appendix 2 to this Annex). — The calculation shall be repeated for at least 5 rise and fall stimuli, and the results shall be averaged. The internal transformation time (< 100 msec) of the reference flowmeter shall be subtracted from this value. This is the “look-ahead” value of the partial flow dilution system, which shall be applied in accordance with section 3.8.3.2 of Appendix 2 to this Annex. 3.4. Checking the partial flow conditions The range of the exhaust gas velocity and the pressure oscillations shall be checked and adjusted according to the requirements of section 2.2.1 of Annex V (EP), if applicable. 3.5. Calibration intervals The flow measurement instrumentation shall be calibrated at least every 3 months or whenever a system repair or change is made that could influence calibration.’ (i) The following Appendix 6 is added: ‘Appendix 6 CARBON FLOW CHECK 1. INTRODUCTION All but a tiny part of the carbon in the exhaust comes from the fuel, and all but a minimal part of this is manifest in the exhaust gas as CO2. This is the basis for a system verification check based on CO2 measurements. The flow of carbon into the exhaust measurement systems is determined from the fuel flow rate. The flow of carbon at various sampling points in the emissions and particulate sampling systems is determined from the CO2 concentrations and gas flow rates at those points. In this sense, the engine provides a known source of carbon flow, and observing the same carbon flow in the exhaust pipe and at the outlet of the partial flow PM sampling system verifies leak integrity and flow measurement accuracy. This check has the advantage that the components are operating under actual engine test conditions of temperature and flow. The following diagram shows the sampling points at which the carbon flows shall be checked. The specific equations for the carbon flows at each of the sample points are given below. 2. CALCULATIONS 2.1. Carbon flow rate into the engine (location 1) The carbon mass flow rate into the engine for a fuel CH α O ε is given by: where: qmf = fuel mass flow rate, kg/s 2.2. Carbon flow rate in the raw exhaust (location 2) The carbon mass flow rate in the exhaust pipe of the engine shall be determined from the raw CO2 concentration and the exhaust gas mass flow rate: where: c CO2,r = wet CO2 concentration in the raw exhaust gas, % c CO2,a = wet CO2 concentration in the ambient air, % (around 0,04 %) q mew = exhaust gas mass flow rate on wet basis, kg/s M re = molecular mass of exhaust gas If CO2 is measured on a dry basis it shall be converted to a wet basis according to section 5.2 of Appendix 1 to this Annex. 2.3. Carbon flow rate in the dilution system (location 3) The carbon flow rate shall be determined from the dilute CO2 concentration, the exhaust gas mass flow rate and the sample flow rate: where: c CO2,d = wet CO2 concentration in the dilute exhaust gas at the outlet of the dilution tunnel, % c CO2,a = wet CO2 concentration in the ambient air, % (around 0,04 %) q mdew = diluted exhaust gas mass flow rate on wet basis, kg/s q mew = exhaust gas mass flow rate on wet basis, kg/s (partial flow system only) qmp = sample flow of exhaust gas into partial flow dilution system, kg/s (partial flow system only) M re = molecular mass of exhaust gas If CO2 is measured on a dry basis, it shall be converted to wet basis according to section 5.2 of Appendix 1 to this Annex. 2.4. The molecular mass (Mre) of the exhaust gas shall be calculated as follows: where: q mf = fuel mass flow rate, kg/s q maw = intake air mass flow rate on wet basis, kg/s H a = humidity of intake air, g water per kg dry air M ra = molecular mass of dry intake air (= 28,9 g/mol) α, δ, ε, γ = molar ratios referring to a fuel CH α O δ N ε S γ Alternatively, the following molecular masses may be used: M re (diesel) = 28,9 g/mol M re (LPG) = 28,6 g/mol M re (NG) = 28,3 g/mol’