2.

Annex II is amended as follows: 1. Section 1 is amended as follows: (a) the following is added to section 1.1.: ‘Two test cycles are described that shall be applied according to the provisions of Annex I, Section 1: — the NRSC (non-road steady cycle) which shall be used for stages I, II and IIIA and for constant speed engines as well as for stages IIIB and IV in the case of gaseous pollutants, — the NRTC (non-road transient cycle) which shall be used for the measurement of particulate emissions for stages IIIB and IV and for all engines but constant speed engines. By the choice of the manufacturer this test can be used also for stage IIIA and for the gaseous pollutants in stages IIIB and IV, — for engines intended to be used in inland waterway vessels the ISO test procedure as specified by ISO 8178-4:2002 [E] and IMO MARPOL 73/78, Annex VI (NOx Code) shall be used, — for engines intended for propulsion of railcars an NRSC shall be used for the measurement of gaseous and particulate pollutants for stage III A and for stage III B, — for engines intended for propulsion of locomotives an NRSC shall be used for the measurement of gaseous and particulate pollutants for stage III A and for stage III B.’; (b) the following section is added: ‘1.3. Measurement principle: The engine exhaust emissions to be measured include the gaseous components (carbon monoxide, total hydrocarbons and oxides of nitrogen), and the particulates. Additionally, carbon dioxide is often used as a tracer gas for determining the dilution ratio of partial and full flow dilution systems. Good engineering practice recommends the general measurement of carbon dioxide as an excellent tool for the detection of measurement problems during the test run. 1.3.1. NRSC test: During a prescribed sequence of operating conditions, with the engines warmed up, the amounts of the above exhaust emissions shall be examined continuously by taking a sample from the raw exhaust gas. The test cycle consists of a number of speed and torque (load) 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. The particulate sample shall be diluted with conditioned ambient air. One sample over the complete test procedure shall be taken and collected on suitable filters. Alternatively, a sample shall be taken on separate filters, one for each mode, and cycle-weighted results computed. The grams of each pollutant emitted per kilowatt-hour shall be calculated as described in Appendix 3 to this Annex. 1.3.2. NRTC test: The prescribed transient test cycle, based closely on the operating conditions of diesel engines installed in non-road machinery, is run twice: — The first time (cold start) after the engine has soaked to room temperature and the engine coolant and oil temperatures, after treatment systems and all auxiliary engine control devices are stabilised between 20 and 30 °C. — The second time (hot start) after a twenty-minute hot soak that commences immediately after the completion of the cold start cycle. During this test sequence the above pollutants shall be examined. Using the engine torque and speed feedback signals of the engine dynamometer, the power shall be integrated with respect to the time of the cycle, resulting in the work produced by the engine over the cycle. The concentrations of the gaseous components shall be determined over the cycle, either in the raw exhaust gas by integration of the analyser signal in accordance with Appendix 3 to this Annex, or in the diluted exhaust gas of a CVS full-flow dilution system by integration or by bag sampling in accordance with Appendix 3 to this Annex. For particulates, a proportional sample shall be collected from the diluted exhaust gas on a specified filter by either partial flow dilution or full-flow dilution. Depending on the method used, the diluted or undiluted 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 give the grams of each pollutant emitted per kilowatt-hour. Emissions (g/kWh) shall be measured during both the cold and hot start cycles. Composite weighted emissions shall be computed by weighting the cold start results 10 % and the hot start results 90 %. Weighted composite results shall meet the standards. Prior to the introduction of the cold/hot composite test sequence, the symbols (Annex I, section 2.18) the test sequence (Annex III) and calculation equations (Annex III, Appendix III) shall be modified in accordance with the procedure referred to in Article 15.’ 2. Section 2 is amended as follows: (a) Section 2.2.3. is replaced by the following: ‘2.2.3. Engines with charge air cooling The charge air temperature shall be recorded and, at the declared rated speed and full load, shall be within ± 5 K of the maximum charge air temperature specified by the manufacturer. The temperature of the cooling medium shall be at least 293 K (20 °C). If a test shop system or external blower is used, the charge air temperature shall be set to within ± 5 K of the maximum charge air temperature specified by the manufacturer at the speed of the declared maximum power and full load. Coolant temperature and coolant flow rate of the charge air cooler at the above set point shall not be changed for the whole test cycle. The charge air cooler volume shall be based upon good engineering practice and typical vehicle/machinery applications. Optionally, the setting of the charge air cooler may be done in accordance with SAE J 1937 as published in January 1995.’; (b) the text in section 2.3. is replaced by the following: ‘The test engine shall be equipped with an air inlet system presenting an air inlet restriction within ± 300 Pa of the value specified by the manufacturer for a clean air cleaner at the engine operating conditions as specified by the manufacturer, which result in maximum air flow. The restrictions are to be set at rated speed and full load. A test shop system may be used, provided it duplicates actual engine operating conditions.’ (c) the text in section 2.4. Engine exhaust system is replaced by the following: ‘The test engine shall be equipped with an exhaust system with exhaust back pressure within ± 650 Pa of the value specified by the manufacturer at the engine operating conditions resulting in maximum declared power. If the engine is equipped with an exhaust after-treatment device, the exhaust pipe shall have the same diameter as found in-use for at least four pipe diameters upstream to the inlet of the beginning of the expansion section containing the after-treatment device. The distance from the exhaust manifold flange or turbocharger outlet to the exhaust after-treatment device shall be the same as in the machine configuration or within the distance specifications of the manufacturer. The exhaust backpressure or restriction shall follow the same criteria as above, and may be set with a valve. The after-treatment container may be removed during dummy tests and during engine mapping, and replaced with an equivalent container having an inactive catalyst support.’; (d) Section 2.8. is deleted. 3. Section 3 is amended as follows: (a) the title of section 3 is replaced by: (b) the following section is inserted: ‘3.1. Determination of dynamometer settings The basis of specific emissions measurement is uncorrected brake power according to ISO 14396: 2002. Certain auxiliaries, which are necessary only for the operation of the machine and may be mounted on the engine, should be removed for the test. The following incomplete list is given as an example: — air compressor for brakes — power steering compressor — air conditioning compressor — pumps for hydraulic actuators. Where auxiliaries have not been removed, the power absorbed by them at the test speeds shall be determined in order to calculate the dynamometer settings, except for engines where such auxiliaries form an integral part of the engine (e.g. cooling fans for air cool engines). The settings of inlet restriction and exhaust pipe backpressure shall be adjusted to the manufacturer's upper limits, in accordance with sections 2.3. and 2.4. The maximum torque values at the specified test speeds shall be determined by experimentation in order to calculate the torque values for the specified test modes. For engines which are not designed to operate over a range on a full load torque curve, the maximum torque at the test speeds shall be declared by the manufacturer. The engine setting for each test mode shall be calculated using the formula: If the ratio, the value of PAE may be verified by the technical authority granting type approval.’; (c) current sections 3.1 to 3.3 are renumbered 3.2 to 3.4; (d) current section 3.4. is renumbered 3.5. and replaced by the following: ‘3.5. Adjustment of the dilution ratio The particulate sampling system shall be started and running on bypass for the single filter method (optional for the multiple filter method). 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 at any time prior to, during, or after the test. If the dilution air is not filtered, the measurement must be done on one sample taken for the duration of the test. The dilution air shall be set to obtain a filter face temperature between 315 K (42 °C) and 325 K (52 °C) at each mode. The total dilution ratio shall not be less than four. NOTE: For steady-state procedure, the filter temperature may be kept at or below the maximum temperature of 325 K (52 °C) instead of respecting the temperature range of 42 °C to 52 °C. For the single and multiple filter methods, the sample mass flow rate through the filter shall be maintained at a constant proportion of the dilute exhaust mass flow rate for full flow systems for all modes. This mass ratio shall be within ± 5 % with respect to the averaged value of the mode, except for the first 10 seconds of each mode for systems without bypass capability. For partial flow dilution systems with single filter method, the mass flow rate through the filter shall be constant within ± 5 % with respect to the averaged value of the mode, except for the first 10 seconds of each mode for systems without bypass capability. For CO2 or NOx concentration controlled systems, the CO2 or NOx content of the dilution air must be measured at the beginning and at the end of each test. The pre and post test background CO2 or NOx concentration measurements of the dilution air must be within 100 ppm or 5 ppm of each other, respectively. When using a dilute exhaust gas analysis system, the relevant background concentrations shall be determined by sampling dilution air into a sampling bag over the complete test sequence. Continuous (non-bag) background concentration may be taken at the minimum of three points, at the beginning, at the end, and a point near the middle of the cycle and averaged. At the manufacturer's request background measurements may be omitted.’; (e) current sections 3.5 to 3.6 are renumbered 3.6 to 3.7; (f) current section 3.6.1. is replaced by the following: ‘3.7.1. Equipment specification according to Section 1A of Annex I: 3.7.1.1. Specification A. For engines covered by Section 1A(i) and A(iv) of Annex I, the following 8-mode cycle (6) shall be followed in dynamometer operation on the test engine: Mode No Engine speed Load Weighting factor 1 Rated 100 0,15 2 Rated 75 0,15 3 Rated 50 0,15 4 Rated 10 0,10 5 Intermediate 100 0,10 6 Intermediate 75 0,10 7 Intermediate 50 0,10 8 Idle —- 0,15 3.7.1.2. Specification B. For engines covered by Section 1A(ii) of Annex I, the following 5-mode cycle (7) shall be followed in dynamometer operation on the test engine: Mode Number Engine Speed Load Weighting Factor 1 Rated 100 0,05 2 Rated 75 0,25 3 Rated 50 0,30 4 Rated 25 0,30 5 Rated 10 0,10 The load figures are percentage values of the torque corresponding to the prime power rating defined as the maximum power available during a variable power sequence, which may be run for an unlimited number of hours per year, between stated maintenance intervals and under the stated ambient conditions, the maintenance being carried out as prescribed by the manufacturer. 3.7.1.3. Specification C. For propulsion engines (8) intended to be used in inland waterway vessels the ISO test procedure as specified by ISO 81784:2002(E) and IMO MARPOL 73/78, Annex VI (NOx Code) shall be used. Propulsion engines that operate on a fixed-pitch propeller curve shall be tested on a dynamometer using the following 4-mode steady-state cycle (9) developed to represent in-use operation of commercial marine diesel engines: Mode No Engine speed Load Weighting factor 1 100 % (Rated) 100 0,20 2 91 % 75 0,50 3 80 % 50 0,15 4 63 % 25 0,15 Fixed speed inland waterway propulsion engines with variable pitch or electrically coupled propellers shall be tested on a dynamometer using the following 4-mode steady-state cycle (10) characterised by the same load and weighting factors as the above cycle, but with engine operated in each mode at rated speed: Mode No Engine speed Load Weighting factor 1 100 % (Rated) 100 0,20 2 91 % 75 0,50 3 80 % 50 0,15 4 63 % 25 0,15 3.7.1.4. Specification D For engines covered by Section 1A(v) of Annex I, the following 3-mode cycle (11) shall be followed in dynamometer operation on the test engine: Mode No Engine speed Load Weighting factor 1 Rated 100 0,25 2 Intermediate 50 0,15 3 Idle - 0,60 ” (g) Current section 3.7.3. is replaced by the following: ‘The test sequence shall be started. The test shall be performed in the order of the mode numbers as set out above for the test cycles. During each mode of the given test cycle after the initial transition period, the specified speed shall be held to within ± 1 % of rated speed or ± 3 min-1, whichever is greater, except for low idle which shall be within the tolerances declared by the manufacturer. The specified torque shall be held so that the average over the period during which the measurements are being taken is within ± 2 % of the maximum torque at the test speed. For each measuring point a minimum time of 10 minutes is necessary. If for the testing of an engine, longer sampling times are required for reasons of obtaining sufficient particulate mass on the measuring filter the test mode period can be extended as necessary. The mode length shall be recorded and reported. The gaseous exhaust emission concentration values shall be measured and recorded during the last three minutes of the mode. The particulate sampling and the gaseous emission measurement should not commence before engine stabilisation, as defined by the manufacturer, has been achieved and their completion must be coincident. The fuel temperature shall be measured at the inlet to the fuel injection pump or as specified by the manufacturer, and the location of measurement recorded.’; (h) the current section 3.7 is renumbered 3.8. 4. The following section is inserted: ‘4. TEST RUN (NRTC TEST) 4.1. Introduction The non-road transient cycle (NRTC) is listed in Annex III, Appendix 4 as a second-by-second sequence of normalised speed and torque values applicable to all diesel engines covered by this Directive. In order to perform the test on an engine test cell, the normalised values shall be converted to the actual values for the individual engine under test, based on the engine mapping curve. This conversion is referred to as denormalisation, and the test cycle developed is referred to as the reference cycle of the engine to be tested. With these reference speed and torque values, the cycle shall be run on the test cell, and the feedback speed and torque values recorded. In order to validate the test run, a regression analysis between reference and feedback speed and torque values shall be conducted upon completion of the test. 4.1.1. The use of defeat devices or irrational control or irrational emission control strategies shall be prohibited 4.2. Engine mapping procedure When generating the NRTC on the test cell, the engine shall be mapped before running the test cycle to determine the speed vs torque curve. 4.2.1. Determination of the mapping speed range The minimum and maximum mapping speeds are defined as follows: Minimum mapping speed = idle speed Maximum mapping speed = nhi x 1,02 or speed where full load torque drops off to zero, whichever is lower (where nhi is the high speed, defined as the highest engine speed where 70 % of the rated power is delivered). 4.2.2. Engine mapping curve The engine shall be warmed up at maximum power in order to stabilise the engine parameters according to the recommendation of the manufacturer and good engineering practice. When the engine is stabilised, the engine mapping shall be performed according to the following procedures. 4.2.2.1. Transient map (a) The engine shall be unloaded and operated at idle speed. (b) The engine shall be operated at full load setting of the injection pump at minimum mapping speed. (c) The engine speed shall be increased at an average rate of 8 ± 1 min-1/s from minimum to maximum mapping speed. Engine speed and torque points shall be recorded at a sample rate of at least one point per second. 4.2.2.2. Step map (a) The engine shall be unloaded and operated at idle speed. (b) The engine shall be operated at full load setting of the injection pump at minimum mapping speed. (c) While maintaining full load, the minimum mapping speed shall be maintained for at least 15 s, and the average torque during the last 5 s shall be recorded. The maximum torque curve from minimum to maximum mapping speed shall be determined in no greater than 100 ± 20/min speed increments. Each test point shall be held for at least 15 s, and the average torque during the last 5 s shall be recorded. 4.2.3. Mapping curve generation All data points recorded under section 4.2.2. shall be connected using linear interpolation between points. The resulting torque curve is the mapping curve and shall be used to convert the normalised torque values of the engine dynamometer schedule of Annex IV into actual torque values for the test cycle, as described in section 4.3.3. 4.2.4. Alternate mapping If a manufacturer believes that the above mapping techniques are unsafe or unrepresentative for any given engine, alternate mapping techniques may be used. These alternate techniques must satisfy the intent of the specified mapping procedures to determine the maximum available torque at all engine speeds achieved during the test cycles. Deviations from the mapping techniques specified in this section for reasons of safety or representativeness shall be approved by the parties involved along with the justification for their use. In no case, however, shall the torque curve be run by descending engine speeds for governed or turbocharged engines. 4.2.5. Replicate tests An engine need not be mapped before each and every test cycle. An engine must be remapped prior to a test cycle if: — an unreasonable amount of time has transpired since the last map, as determined by engineering judgement, or, — physical changes or recalibrations have been made to the engine, which may potentially affect engine performance. 4.3. Generation of the reference test cycle 4.3.1. Reference speed The reference speed (nref) corresponds to the 100 % normalised speed values specified in the engine dynamometer schedule of Annex III, Appendix 4. It is obvious that the actual engine cycle resulting from denormalisation to the reference speed largely depends on selection of the proper reference speed. The reference speed shall be determined by the following definition: nref = low speed + 0,95 x (high speed — low speed) (the high speed is the highest engine speed where 70 % of the rated power is delivered, while the low speed is the lowest engine speed where 50 % of the rated power is delivered). 4.3.2. Denormalisation of engine speed The speed shall be denormalised using the following equation: 4.3.3. Denormalisation of engine torque The torque values in the engine dynamometer schedule of Annex III, Appendix 4 are normalised to the maximum torque at the respective speed. The torque values of the reference cycle shall be denormalised, using the mapping curve determined according to Section 4.2.2, as follows: for the respective actual speed as determined in Section 4.3.2. 4.3.4. Example of denormalisation procedure As an example, the following test point shall be denormalised: % speed = 43 % % torque = 82 % Given the following values: reference speed = 2 200/min idle speed = 600/min results in With the maximum torque of 700 Nm observed from the mapping curve at 1 288/min 4.4. Dynamometer 4.4.1. When using a load cell, the torque signal shall be transferred to the engine axis and the inertia of the dyno shall be considered. The actual engine torque is the torque read on the load cell plus the moment of inertia of the brake multiplied by the angular acceleration. The control system has to perform this calculation in real time. 4.4.2. If the engine is tested with an eddy-current dynamometer, it is recommended that the number of points, where the difference is smaller than - 5 % of the peak torque, does not exceed 30 (where T sp is the demanded torque, is the derivative of the engine speed is the rotational inertia of the eddy-current dynamometer). 4.5. Emissions test run The following flow chart outlines the test sequence. One or more practice cycles may be run as necessary to check engine, test cell and emissions systems before the measurement cycle. 4.5.1. Preparation of the sampling filters At least one hour before the test, each filter shall be placed in a petri dish, which is protected against dust contamination and allows air exchange, and placed in a weighing chamber for stabilisation. At the end of the stabilisation period, each filter shall be weighed and the 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. 4.5.2. 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. 4.5.3. Starting and preconditioning the dilution system and the engine The dilution system and the engine shall be started and warmed up. The sampling system preconditioning shall be conducted by operating the engine at a condition of rated-speed, 100 percent torque for a minimum of 20 minutes while simultaneously operating either the Partial flow Sampling System or the Full flow CVS with secondary dilution system. Dummy particulate matter emissions samples are then collected. Particulate sample filters need not be stabilised or weighed, and may be discarded. Filter media may be changed during conditioning as long as the total sampled time through the filters and sampling system exceeds 20 minutes. Flow rates shall be set at the approximate flow rates selected for transient testing. Torque shall be reduced from 100 percent torque while maintaining the rated speed condition as necessary so as not to exceed the 191 °C maximum sample zone temperature specifications. 4.5.4. Starting the particulate sampling system The particulate sampling system shall be started and run on by-pass. The particulate background level of the dilution air may be determined by sampling the dilution air prior to entrance of the exhaust into the dilution tunnel. It is preferred that background particulate sample be collected during the transient cycle if another PM sampling system is available. Otherwise, the PM sampling system used to collect transient cycle PM can be used. 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 should be carried out prior to the beginning and after the end of the cycle and the values averaged. 4.5.5. Adjustment of the dilution system The total diluted exhaust gas flow of a full-flow dilution system or the diluted exhaust gas flow through a partial flow dilution system shall be set to eliminate water condensation in the system, and to obtain a filter face temperature between 315 K (42 °C) and 325 K (52 °C). 4.5.6. Checking the analysers The emission analysers shall be set at zero and spanned. If sample bags are used, they shall be evacuated. 4.5.7. Engine starting procedure The stabilised engine shall be started within 5 min after completion of warm-up according to the starting procedure recommended by the manufacturer in the owner's manual, using either a production starter motor or the dynamometer. Optionally, the test may start within 5 min of the engine preconditioning phase without shutting the engine off, when the engine has been brought to an idle condition. 4.5.8. Cycle run 4.5.8.1. Test sequence The test sequence shall commence when the engine is started from shut down after the preconditioning phase or from idle conditions when starting directly from the preconditioning phase with the engine running. The test shall be performed according to the reference cycle as set out in Annex III, Appendix 4. Engine speed and torque command set points shall be issued at 5 Hz (10 Hz recommended) or greater. The set points shall be calculated by linear interpolation between the 1 Hz set points of the reference cycle. Feedback engine speed and torque shall be recorded at least once every second during the test cycle, and the signals may be electronically filtered. 4.5.8.2. Analyser response At the start of the engine or test sequence, if the cycle is started directly from preconditioning, the measuring equipment shall be started, simultaneously: — start collecting or analysing dilution air, if a full-flow dilution system is used, — start collecting or analysing raw or diluted exhaust gas, depending on the method used, — start measuring the amount of diluted exhaust gas and the required temperatures and pressures, — start recording the exhaust gas mass flow rate, if raw exhaust gas analysis is used, — recording the feedback data of speed and torque of the dynamometer. If raw exhaust measurement is used, the emission concentrations (HC, CO and NOx) and the exhaust gas mass flow rate shall be measured continuously and stored with at least 2 Hz on a computer system. 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. If a full flow dilution system is used, HC and NOx shall be measured continuously in the dilution tunnel with a frequency of at least 2 Hz. The average concentrations shall be determined by integrating the analyser 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 and CO2 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 collection in the background bag. All other parameters that need to be measured shall be recorded with a minimum of one measurement per second (1 Hz). 4.5.8.3. Particulate sampling At the start of the engine or test sequence, if the cycle is started directly from preconditioning, the particulate sampling system shall be switched from by-pass to collecting particulates. If a partial flow dilution system is used, the sample pump(s) shall be adjusted so that the flow rate through the particulate sample probe or transfer tube is maintained proportional to the exhaust mass flow rate. If a full flow dilution system 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 airflow 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. 4.5.8.4. 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. 4.5.8.5. Operations after test At the completion of the test, the measurement of the exhaust gas mass flow rate, the diluted exhaust gas volume, 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. The particulate filters shall be returned to the weighing chamber no later than one hour after completion of the test. They shall be conditioned in a petri dish, which is protected against dust contamination and allows air exchange, for at least one hour, and then weighed. The gross weight of the filters shall be recorded. 4.6. Verification of the test run 4.6.1. 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 by the same amount in the same direction. 4.6.2. 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. The actual cycle work Wact is used for comparison to the reference cycle work Wref and for calculating the brake specific emissions. 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. 4.6.3. 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 (N·m), or power (kW) m = slope of the regression line x = reference value of speed (min-1), torque (N·m), 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. For a test to be considered valid, the criteria of Table 1 must be met. Table 1 — Regression line tolerances Speed Torque Power Standard error of estimate (SE) of Y on X max 100 min-1 max 13 % of power map maximum engine torque max 8 % 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 Coefficient of determination, r2 min 0,9700 min 0,8800 min 0,9100 Y intercept of the regression line, b ± 50 min-1 ± 20 N·m or ± 2 % of max torque, whichever is greater ± 4 kW or ± 2 % of max power, whichever is greater For regression purposes only, point deletions are permitted where noted in Table 2 before doing the regression calculation. However, those points must not be deleted for the calculation of cycle work and emissions. An idle point is defined as a point having a normalised reference torque of 0 % and a normalised reference speed of 0 %. Point deletion may be applied to the whole or to any part of the cycle. Table 2 — Permitted point deletions from regression analysis (points to which the point deletion is applied have to be specified) Condition Speed and/or torque and/or power points which may be deleted with reference to the conditions listed in the left column First 24 (±1) s and last 25 s Speed, torque and power Wide open throttle, and torque feedback < 95 % torque reference Torque and/or power Wide open throttle, and speed feedback < 95 % speed reference Speed and/or power Closed throttle, speed feedback > idle speed + 50 min-1, and torque feedback > 105 % torque reference Torque and/or power Closed throttle, speed feedback ≤ idle speed + 50 min-1, and torque feedback = Manufacturer defined/measured idle torque ± 2 % of max torque Speed and/or power Closed throttle and speed feedback > 105 % speed reference Speed and/or power‘. 5. Appendix 1 is replaced by the following: ‘Appendix 1 MEASUREMENT AND SAMPLING PROCEDURES 1. MEASUREMENT AND SAMPLING PROCEDURES (NRSC TEST) Gaseous and particulate components emitted by the engine submitted for testing shall be measured by the methods described in Annex VI. The methods of Annex VI describe the recommended analytical systems for the gaseous emissions (Section 1.1) and the recommended particulate dilution and sampling systems (Section 1.2). 1.1. Dynamometer specification An engine dynamometer with adequate characteristics to perform the test cycle described in Annex III, Section 3.7.1. shall be used. The instrumentation for torque and speed measurement shall allow the measurement of the power within the given limits. Additional calculations may be necessary. The accuracy of the measuring equipment must be such that the maximum tolerances of the figures given in point 1.3. are not exceeded. 1.2. Exhaust gas flow The exhaust gas flow shall be determined by one of the methods mentioned in sections1.2.1. to 1.2.4. 1.2.1. Direct measurement method Direct measurement of the exhaust flow by flow nozzle or equivalent metering system (for detail see ISO 5167:2000). Note: Direct gaseous flow measurement is a difficult task. Precautions must be taken to avoid measurement errors that will impact emission value errors. 1.2.2. Air and fuel measurement method Measurement of the airflow and the fuel flow. Air flow-meters and fuel flow-meters with the accuracy defined in Section 1.3. shall be used. The calculation of the exhaust gas flow is as follows: GEXHW = GAIRW + GFUEL (for wet exhaust mass) 1.2.3. Carbon balance method Exhaust mass calculation from fuel consumption and exhaust gas concentrations using the carbon balance method (Annex III, Appendix 3). 1.2.4. Tracer measurement method This method 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 must 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 GEXHW = instantaneous exhaust mass flow (kg/s) GT = tracer gas flow (cm3/min) concmix = instantaneous concentration of the tracer gas after mixing, (ppm) ρEXH = density of the exhaust gas (kg/m3) conca = background concentration of the tracer gas in the intake air (ppm) The background concentration of the tracer gas (conc a) may be determined by averaging the background concentration measured immediately before and after the test run. When the background concentration is less than 1 % of the concentration of the tracer gas after mixing (conc mix.) 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 Appendix 2, Section 1.11.2. 1.2.5. Air flow and air to fuel ratio measurement method This method 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: where A/Fst = stoichiometric air/fuel ratio (kg/kg) λ = relative air/fuel ratio concCO2 = dry CO2 concentration ( %) concCO = dry CO concentration (ppm) concHC = HC concentration (ppm) Note: The calculation refers to a diesel fuel with a H/C ratio equal to 1,8. The air flowmeter shall meet the accuracy specifications in Table 3, the CO2 analyser used shall meet the specifications of clause 1.4.1, 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 relative air to fuel ratio in accordance with the specifications of clause 1.4.4. 1.2.6. Total dilute exhaust gas flow When using a full flow dilution system, the total flow of the dilute exhaust (GTOTW) shall be measured with a PDP or CFV or SSV (Annex VI, Section 1.2.1.2.) The accuracy shall conform to the provisions of Annex III, Appendix 2, Section 2.2. 1.3. Accuracy The calibration of all measurement instruments shall be traceable to national or international standards and comply with the requirements listed in Table 3. Table 3 — Accuracy of measuring instruments No Measuring instrument Accuracy 1 Engine speed ± 2 % of reading or ± 1 % of engine's max. value whichever is larger 2 Torque ± 2 % of reading or ± 1 % of engine's max. value whichever is larger 3 Fuel consumption ± 2 % of engine's max. value 4 Air consumption ± 2 % of reading or ± 1 % of engine's max. value whichever is larger 5 Exhaust gas flow ± 2,5 % of reading or ± 1,5 % of engine's max. value whichever is larger 6 Temperatures ≤ 600 K ± 2 K absolute 7 Temperatures > 600 K ± 1 % of reading 8 Exhaust gas pressure ± 0,2 kPa absolute 9 Intake air depression ± 0,05 kPa absolute 10 Atmospheric pressure ± 0,1 kPa absolute 11 Other pressures ± 0,1 kPa absolute 12 Absolute humidity ± 5 % of reading 13 Dilution air flow ± 2 % of reading 14 Diluted exhaust gas flow ± 2 % of reading 1.4. Determination of the gaseous components 1.4.1. General analyser specifications The analysers shall have a measuring range appropriate for the accuracy required to measure the concentrations of the exhaust gas components (section1.4.1.1). It is recommended that the analysers be operated in such a way that the measured concentration falls between 15 % and 100 % of full scale. If the full scale value is 155 ppm (or ppm C) or less or if read-out systems (computers, data loggers) that provide sufficient accuracy and resolution below 15 % of full scale are used, concentrations below 15 % of full scale are also acceptable. In this case, additional calibrations are to be made to ensure the accuracy of the calibration curves - Annex III, Appendix 2, section 1.5.5.2. The electromagnetic compatibility (EMC) of the equipment shall be on a level as to minimise additional errors. 1.4.1.1. Measurement error The analyser shall not deviate from the nominal calibration point by more than ±2 % of the reading or ± 0,3 % of full scale, whichever is larger. NOTE: For the purpose of this standard, accuracy is defined as the deviation of the analyser reading from the nominal calibration values using a calibration gas (≡ true value) 1.4.1.2. Repeatability The repeatability, defined as 2,5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, must be no greater than ± 1 % of full scale concentration for each range used above 155 ppm (or ppm C) or ± 2 % of each range used below 155 ppm (or ppm C). 1.4.1.3. 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. 1.4.1.4. Zero drift The zero drift during a one-hour period shall be less than 2 % of full scale on the lowest range used. The zero response is defined as the mean response, including noise, to a zero gas during a 30-second time interval. 1.4.1.5. Span drift The span drift during a one-hour period shall be less than 2 % of full scale on the lowest range used. Span is defined as the difference between the span response and the zero response. The span response is defined as the mean response, including noise, to a span gas during a 30-second time interval. 1.4.2. 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. 1.4.3. Analysers Sections 1.4.3.1 to 1.4.3.5 of this Appendix describe the measurement principles to be used. A detailed description of the measurement systems is given in AnnexVI. The gases to be measured shall be analysed with the following instruments. For non-linear analysers, the use of linearising circuits is permitted. 1.4.3.1. Carbon monoxide (CO) analysis The carbon monoxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type. 1.4.3.2. Carbon dioxide (CO2) analysis The carbon dioxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type. 1.4.3.3. Hydrocarbon (HC) analysis The hydrocarbon analyser shall be of the heated flame ionization detector (HFID) type with detector, valves, pipework, etc, heated so as to maintain a gas temperature of 463 K (190 °C) ± 10 K. 1.4.3.4. 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 (Annex III, Appendix 2, section 1.9.2.2) is satisfied. For both CLD and HCLD, the sampling path shall be maintained at a wall temperature of 328 K to 473 K (55 to 200 °C) up to the converter for dry measurement, and up to the analyser for wet measurement. 1.4.4. Air to fuel measurement The air to fuel measurement equipment used to determine the exhaust gas flow as specified in section 1.2.5 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. 1.4.5. Sampling for gaseous emissions The gaseous emissions sampling probes must be fitted at least 0,5 m or three times the diameter of the exhaust pipe — whichever is the larger — upstream of the exit of the exhaust gas system as far as applicable and 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 “V”-engine configuration, it is permissible to acquire a sample from each group individually and calculate an average exhaust emission. Other methods which have been shown to correlate with the above methods may be used. For exhaust emissions calculation the total exhaust mass flow of the engine must be used. If the composition of the exhaust gas is influenced by any exhaust after-treatment system, the exhaust sample must be taken upstream of this device in the tests of stage I and downstream of this device in the tests of stage II. When a full flow dilution system is used for the determination of the particulates, the gaseous emissions may also be determined in the diluted exhaust gas. The sampling probes shall be close to the particulate sampling probe in the dilution tunnel (Annex VI, section 1.2.1.2, DT and Section 1.2.2, PSP). CO and CO2 may optionally be determined by sampling into a bag and subsequent measurement of the concentration in the sampling bag. 1.5. 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 dilution system. The flow capacity of the dilution system shall be large enough to completely eliminate water condensation in the dilution and sampling systems, and maintain the temperature of the diluted exhaust gas between 315 K (42 °C) and 325 K (52 °C) immediately upstream of the filter holders. De-humidifying the dilution air before entering the dilution system is permitted, if the air humidity is high. Dilution air pre-heating above the temperature limit of 303 K (30 °C) is recommended, if the ambient temperature is below 293 K (20 °C). However, the diluted air temperature must not exceed 325 K (52 °C) prior to the introduction of the exhaust in the dilution tunnel. Note: For steady-state procedure, the filter temperature may be kept at or below the maximum temperature of 325 K (52 °C) instead of respecting the temperature range of 42 to 52 °C. For a partial flow dilution system, the particulate sampling probe must be fitted close to and upstream of the gaseous probe as defined in Section 4.4 and in accordance with Annex VI, section 1.2.1.1, figure 4-12 EP and SP. The partial flow dilution system has to be designed to split the exhaust stream into two fractions, the smaller one being diluted with air and subsequently used for particulate measurement. From that it is essential that the dilution ratio be determined very accurately. Different splitting methods can be applied, whereby the type of splitting used dictates to a significant degree the sampling hardware and procedures to be used (Annex VI, section 1.2.1.1). 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, two methods may be applied: — the single filter method uses one pair of filters (1.5.1.3 of this Appendix) for all modes of the test cycle. Considerable attention must be paid to sampling times and flows during the sampling phase of the test. However, only one pair of filters will be required for the test cycle, — the multiple filter method dictates that one pair of filters (section 1.5.1.3 of this Appendix) is used for each of the individual modes of the test cycle. This method allows more lenient sample procedures but uses more filters. 1.5.1. Particulate sampling filters 1.5.1.1. Filter specification Fluorocarbon coated glass fibre filters or fluorocarbon based membrane filters are required for certification tests. For special applications different filter materials may be used. 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 100cm/s. When performing correlation tests between laboratories or between a manufacturer and an approval authority, filters of identical quality must be used. 1.5.1.2. Filter size Particulate filters must have a minimum diameter of 47 mm (37 mm stain diameter). Larger diameter filters are acceptable (section 1.5.1.5). 1.5.1.3. Primary and back-up filters The diluted exhaust shall be sampled by a pair of filters placed in series (one primary and one back-up filter) during the test sequence. The back-up filter shall be located no more than 100mm downstream of, and shall not be in contact with, the primary filter. The filters may be weighed separately or as a pair with the filters placed stain side to stain side. 1.5.1.4. 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. 1.5.1.5. Filter loading The recommended minimum filter loadings for the most common filter sizes are shown in the following table. For larger filter sizes, the minimum filter loading shall be 0,065 mg/1 000 mm2 filter area. Filter diameter (mm) Recommended stain diameter (mm) Recommended minimum loading (mg) 47 37 0,11 70 60 0,25 90 80 0,41 110 100 0,62 For the multiple filter method, the recommended minimum filter loading for the sum of all filters shall be the product of the appropriate value above and the square root of the total number of modes. 1.5.2. Weighing chamber and analytical balance specifications 1.5.2.1. 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 (22 °C) ± 3 K during all filter conditioning and weighing. The humidity shall be maintained to a dew point of 282,5 (9,5 °C) ± 3 K and a relative humidity of 45 ± 8 %. 1.5.2.2. 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 1.5.2.1 will be allowed if the duration of the disturbances does not exceed 30 minutes. The weighing room should meet the required specifications prior to personnel entrance into the weighing room. At least two unused reference filters or reference filter pairs shall be weighed within four hours of, but preferably at the same time as the sample filter (pair) weighing. They shall be the same size and material as the sample filters. If the average weight of the reference filters (reference filter pairs) changes between sample filter weighing by more than 10μg, then all sample filters shall be discarded and the emissions test repeated. If the weighing room stability criteria outlined in section 1.5.2.1 is not met, but the reference filter (pair) weighing 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. 1.5.2.3. Analytical balance The analytical balance used to determine the weights of all filters shall have a precision (standard deviation) of 2 μg and a resolution of 1 μg (1 digit = 1 μg) specified by the balance manufacturer. 1.5.2.4. Elimination of static electricity effects To eliminate the effects of static electricity, the filters shall be neutralised prior to weighing, for example, by a Polonium neutraliser or a device of similar effect. 1.5.3. Additional specifications for particulate measurement All parts of the dilution system and the sampling system from the exhaust pipe up to the filter holder, which are in contact with raw and diluted exhaust gas, must be designed to minimise deposition or alteration of the particulates. All parts must be made of electrically conductive materials that do not react with exhaust gas components, and must be electrically grounded to prevent electrostatic effects. 2. MEASUREMENT AND SAMPLING PROCEDURES (NRTC TEST) 2.1. Introduction Gaseous and particulate components emitted by the engine submitted for testing shall be measured by the methods of Annex VI. The methods of Annex VI describe the recommended analytical systems for the gaseous emissions (Section 1.1) and the recommended particulate dilution and sampling systems (Section 1.2). 2.2. Dynamometer and test cell equipment The following equipment shall be used for emission tests of engines on engine dynamometers: 2.2.1. Engine dynamometer An engine dynamometer shall be used with adequate characteristics to perform the test cycle described in Appendix 4 to this Annex. The instrumentation for torque and speed measurement shall allow the measurement of the power within the given limits. Additional calculations may be necessary. The accuracy of the measuring equipment must be such that the maximum tolerances of the figures given in Table 3 are not exceeded. 2.2.2. 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 3: Table 3 — Accuracy of measuring instruments No. Measuring instrument accuracy 1 Engine speed ± 2 % of reading or ± 1 % of engine's max. value, whichever is larger 2 Torque ± 2 % of reading or ± 1 % of engine's max. value, whichever is larger 3 Fuel consumption ± 2 % of engine's max. value 4 Air consumption ± 2 % of reading or ± 1 % of engine's max. value, whichever is larger 5 Exhaust gas flow ± 2,5 % of reading or ± 1,5 % of engine's max. value, whichever is larger 6 Temperatures ≤ 600 K ± 2 K absolute 7 Temperatures > 600 K ± 1 % of reading 8 Exhaust gas pressure ± 0,2 kPa absolute 9 Intake air depression ± 0,05 kPa absolute 10 Atmospheric pressure ± 0,1 kPa absolute 11 Other pressures ± 0,1 kPa absolute 12 Absolute humidity ± 5 % of reading 13 Dilution air flow ± 2 % of reading 14 Diluted exhaust gas flow ± 2 % of reading 2.2.3. Raw exhaust gas flow For calculating the emissions in the raw exhaust gas and for controlling a partial flow dilution system, it is necessary to know the exhaust gas mass flow rate. For determining the exhaust mass flow rate, either of the methods described below may be used. 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 analyser response time, as defined in Appendix 2, Section 1.11.1. For the purpose of controlling a partial flow dilution system, a faster response is required. For partial flow dilution systems with online control, a response time of ≤0,3s 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 ≤5s with a rise time of ≤ 1 s 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 2.4. Direct measurement method Direct measurement of the instantaneous exhaust flow may be done by systems, such as: — pressure differential devices, like flow nozzle, (for details see ISO 5167: 2000) — 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 must not be affected by the installation of the device. The flowmeters shall meet the accuracy specifications of Table 3. Air and fuel measurement method This involves measurement of the airflow and the fuel flow with suitable flowmeters. The calculation of the instantaneous exhaust gas flow is as follows: GEXHW = GAIRW + GFUEL (for wet exhaust mass) The flowmeters shall meet the accuracy specifications of Table 3, but shall also be accurate enough to also meet the accuracy specifications for the exhaust gas flow. 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 must 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 G EXHW = instantaneous exhaust mass flow (kg/s) GT = tracer gas flow (cm3/min) conc mix = instantaneous concentration of the tracer gas after mixing (ppm) ρEXH = density of the exhaust gas (kg/m3 conc a = background concentration of the tracer gas in the intake air (ppm) The background concentration of the tracer gas (conc a) may be determined by averaging the background concentration measured immediately before the test run and after the test run. When the background concentration is less than 1 % of the concentration of the tracer gas after mixing (conc mix.) 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 Appendix 2, paragraph 1.11.2 Air flow and air to fuel ratio measurement method This involves exhaust mass calculation from the airflow and the air to fuel ratio. The calculation of the instantaneous exhaust gas mass flow is as follows: where A/Fst = stoichiometric air/fuel ratio (kg/kg) λ = relative air/fuel ratio concCO2 = dry CO2 concentration ( %) concCO = dry CO concentration (ppm) concHC = HC concentration (ppm) Note: The calculation refers to a diesel fuel with a H/C ratio equal to 1,8. The air flowmeter shall meet the accuracy specifications in Table 3, the CO2 analyser used shall meet the specifications of section 2.3.1, 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 in accordance with the specifications of section 2.3.4. 2.2.4. Diluted exhaust gas flow For calculation of the emissions in the diluted exhaust gas, it is necessary to know the diluted exhaust gas mass flow rate. 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): the corresponding methods described in Appendix 3, section2.2.1. shall be used. If the total sample mass of particulates and gaseous pollutants exceeds 0,5 % of the total CVS flow, the CVS flow shall be corrected or the particulate sample flow shall be returned to the CVS prior to the flow measuring device. 2.3. Determination of the gaseous components 2.3.1. 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 1.4.1.1). It is recommended that the analysers be operated in such a way that the measured concentration falls between 15 and 100 % of full scale. If the full scale value is 155 ppm (or ppm C) or less, or if read-out systems (computers, data loggers) that provide sufficient accuracy and resolution below 15 % of full scale are used, concentrations below 15 % of full scale are also acceptable. In this case, additional calibrations are to be made to ensure the accuracy of the calibration curves - Annex III, Appendix 2, section 1.5.5.2. The electromagnetic compatibility (EMC) of the equipment shall be of a level such as to minimise additional errors. 2.3.1.1. Measurement error The analyser shall not deviate from the nominal calibration point by more than ± 2 % of the reading or ± 0,3 % of full scale, whichever is larger. Note: For the purpose of this standard, accuracy is defined as the deviation of the analyser reading from the nominal calibration values using a calibration gas (≡ true value). 2.3.1.2. Repeatability The repeatability, defined as 2,5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, must be no greater than ± 1 % of full scale concentration for each range used above 155 ppm (or ppm C) or ± 2 % for each range used below 155 ppm (or ppm C). 2.3.1.3. 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. 2.3.1.4. Zero drift The zero drift during a one-hour period shall be less than 2 % of full scale on the lowest range used. The zero response is defined as the mean response, including noise, to a zero gas during a 30-second time interval. 2.3.1.5. Span drift The span drift during a one-hour period shall be less than 2 % of full scale on the lowest range used. Span is defined as the difference between the span response and the zero response. The span response is defined as the mean response, including noise, to a span gas during a 30-second time interval. 2.3.1.6. Rise time For raw exhaust gas analysis, the rise time of the analyser installed in the measurement system shall not exceed 2,5 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 affect the transportation time from the probe to the analyser, but also affect the rise time. Also transport times inside of an analyser would be defined as analyser response time, like the converter or water traps inside of a NOx analysers. The determination of the total system response time is described in Appendix 2, Section 1.11.1. 2.3.2. Gas drying Same specifications as for NRSC test cycle apply (Section 1.4.2) as described here below. 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. 2.3.3. Analysers Same specifications as for NRSC test cycle apply (Section 1.4.3) as described here below. The gases to be measured shall be analysed with the following instruments. For non-linear analysers, the use of linearising circuits is permitted. 2.3.3.1. Carbon monoxide (CO) analysis The carbon monoxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type. 2.3.3.2. Carbon dioxide (CO2) analysis The carbon dioxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type. 2.3.3.3. Hydrocarbon (HC) analysis The hydrocarbon analyser shall be of the heated flame ionization detector (HFID) type with detector, valves, pipework, etc, heated so as to maintain a gas temperature of 463K (190 °C) ± 10 K. 2.3.3.4. 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 (Annex III, Appendix 2, section 1.9.2.2) is satisfied. For both CLD and HCLD, the sampling path shall be maintained at a wall temperature of 328K to 473 K (55 to 200 °C) up to the converter for dry measurement, and up to the analyser for wet measurement. 2.3.4. Air to fuel measurement The air to fuel measurement equipment used to determine the exhaust gas flow as specified in section 2.2.3 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. 2.3.5. Sampling of gaseous emissions 2.3.5.1. Raw exhaust gas flow For calculation of the emissions in the raw exhaust gas the same specifications as for NRSC test cycle apply (Section 1.4.4), as described here below. The gaseous emissions sampling probes must be fitted at least 0,5 m or three times the diameter of the exhaust pipe — whichever is the larger — upstream of the exit of the exhaust gas system as far as applicable and 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 multicylinder 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 multicylinder engines having distinct groups of manifolds, such as in a “V”-engine configuration, it is permissible to acquire a sample from each group individually and calculate an average exhaust emission. Other methods which have been shown to correlate with the above methods may be used. For exhaust emissions calculation the total exhaust mass flow of the engine must be used. If the composition of the exhaust gas is influenced by any exhaust after-treatment system, the exhaust sample must be taken upstream of this device in the tests of stage I and downstream of this device in the tests of stage II. 2.3.5.2. Diluted exhaust gas flow If a full flow dilution system is used, the following specifications apply. The exhaust pipe between the engine and the full flow dilution system shall conform to the requirements of Annex VI. 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. The background concentrations shall be sampled upstream of the dilution tunnel into a sampling bag, and shall be subtracted from the emissions concentration according to Appendix 3, Section 2.2.3. 2.4. Determination of the particulates Determination of the particulates requires a dilution system. Dilution may be accomplished by a partial flow dilution system or a full flow dilution system. The flow capacity of the dilution system shall be large enough to completely eliminate water condensation in the dilution and sampling systems, and maintain the temperature of the diluted exhaust gas between 315 K (42 °C) and 325 K (52 °C) immediately upstream of the filter holders. De-humidifying the dilution air before entering the dilution system is permitted, if the air humidity is high. Dilution air pre-heating above the temperature limit of 303 K (30 °C) is recommended if the ambient temperature is below 293 K (20 °C). However, the diluted air temperature must not exceed 325 K (52 °C) prior to the introduction of the exhaust in the dilution tunnel. The particulate sampling probe shall be installed in close proximity to the gaseous emissions sampling probe, and the installation shall comply with the provisions of Section 2.3.5. To determine the mass of the particulates, a particulate sampling system, particulate sampling filters, microgram balance, and a temperature and humidity controlled weighing chamber, are required. Partial flow dilution system specifications The partial flow dilution system has to be designed to split the exhaust stream into two fractions, the smaller one being diluted with air and subsequently used for particulate measurement. For this it is essential that the dilution ratio be determined very accurately. Different splitting methods can be applied, whereby the type of splitting used dictates to a significant degree the sampling hardware and procedures to be used (Annex VI, section 1.2.1.1). 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 described in Appendix 2, Section 1.11.1. If the combined transformation time of the exhaust flow measurement (see previous section) and the partial flow system is less than 0,3 s, online control may be used. If the transformation time exceeds 0,3 s, look ahead control based on a pre-recorded test run must be used. In this case, the rise time shall be ≤ 1 s and the delay time of the combination ≤10 s. The total system response shall be designed as to ensure a representative sample of the particulates, GSE , proportional to the exhaust mass flow. To determine the proportionality, a regression analysis of GSE versus GEXHW shall be conducted on a minimum 5 Hz data acquisition rate, and the following criteria shall be met: — the correlation coefficient r of the linear regression between GSE and GEXHW shall be not less than 0,95, — the standard error of estimate of GSE on GEXHW shall not exceed 5 % of GSE maximum. — GSE intercept of the regression line shall not exceed ± 2 % of GSE maximum. Optionally, a pre-test may be run, and the exhaust mass flow signal of the pre-test 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, t 50,P or/and the transformation time of the exhaust mass flow signal, t 50,F are > 0,3 s. Acorrect control of the partial dilution system is obtained, if the time trace of GEXHW ,pre of the pre-test, which controls GSE, is shifted by a “look-ahead” time of t 50,P + t 50,F . For establishing the correlation between GSE and GEXHW the data taken during the actual test shall be used, with GEXHW time aligned by t50,F relative to GSE (no contribution from t 50,P to the time alignment). That is, the time shift between GEXHW and GSE is the difference in their transformation times that were determined in Appendix 2, Section2.6. For partial flow dilution systems, the accuracy of the sample flow GSE is of special concern, if not measured directly, but determined by differential flow measurement: GSE = GTOTW — GDILW In this case an accuracy of ± 2 % for GTOTW and GDILW is not sufficient to guarantee acceptable accuracies of GSE. If the gas flow is determined by differential flow measurement, the maximum error of the difference shall be such that the accuracy of GSE 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 GSE can be obtained by either of the following methods: (a) The absolute accuracies of GTOTW and GDILW are ± 0,2 % which guarantees an accuracy of GSE of ≤ 5 % at a dilution ratio of 15. However, greater errors will occur at higher dilution ratios. (b) Calibration of GDILW relative to GTOTW is carried out such that the same accuracies for GSE as in (a) are obtained. For the details of such a calibration see Appendix 2, Section 2.6. (c) The accuracy of GSE 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 GSE are required. (d) The absolute accuracy of GTOTW and GDILW is within ± 2 % of full scale, the maximum error of the difference between GTOTW and GDILW is within 0,2 %, and the linearity error is within ± 0,2 % of the highest GTOTW observed during the test. 2.4.1. Particulate sampling filters 2.4.1.1. Filter specification Fluorocarbon coated glass fibre filters or fluorocarbon based membrane filters are required for certification tests. For special applications different filter materials may be used. 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. When performing correlation tests between laboratories or between a manufacturer and an approval authority, filters of identical quality must be used. 2.4.1.2. Filter size Particulate filters must have a minimum diameter of 47 mm (37 mm stain diameter). Larger diameter filters are acceptable (section 2.4.1.5). 2.4.1.3. Primary and back-up filters The diluted exhaust shall be sampled by a pair of filters placed in series (one primary and one back-up filter) during the test sequence. The back-up filter shall be located no more than 100mm downstream of, and shall not be in contact with, the primary filter. The filters may be weighed separately or as a pair with the filters placed stain side to stain side. 2.4.1.4. 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 25kPa. 2.4.1.5. Filter loading The recommended minimum filter loadings for the most common filter sizes are shown in the following table. For larger filter sizes, the minimum filter loading shall be 0,065mg/1 000mm2 filter area. Filter diameter (mm) Recommended stain diameter (mm) Recommended minimum loading (mg) 47 37 0,11 70 60 0,25 90 80 0,41 110 100 0,62 2.4.2. Weighing chamber and analytical balance specifications 2.4.2.1. 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 (22 °C) ± 3 K during all filter conditioning and weighing. The humidity shall be maintained to a dewpoint of 282,5 (9,5 °C) ± 3 K and a relative humidity of 45 ± 8 %. 2.4.2.2. 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 2.4.2.1 will be allowed if the duration of the disturbances does not exceed 30 minutes. The weighing room should meet the required specifications prior to personnel entrance into the weighing room. At least two unused reference filters or reference filter pairs shall be weighed within four hours of, but preferably at the same time as the sample filter (pair) weighing. They shall be the same size and material as the sample filters. If the average weight of the reference filters (reference filter pairs) changes between sample filter weighing by more than 10μg, then all sample filters shall be discarded and the emissions test repeated. If the weighing room stability criteria outlined in section 2.4.2.1 are not met, but the reference filter (pair) weighing 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. 2.4.2.3. Analytical balance The analytical balance used to determine the weights of all filters shall have a precision (standard deviation) of 2 μg and a resolution of 1 μg (1 digit = 1 μg) specified by the balance manufacturer. 2.4.2.4. Elimination of static electricity effects To eliminate the effects of static electricity, the filters shall be neutralised prior to weighing, for example, by a Polonium neutraliser or a device having similar effect. 2.4.3. Additional specifications for particulate measurement All parts of the dilution system and the sampling system from the exhaust pipe up to the filter holder, which are in contact with raw and diluted exhaust gas, must be designed to minimise deposition or alteration of the particulates. All parts must be made of electrically conductive materials that do not react with exhaust gas components, and must be electrically grounded to prevent electrostatic effects.’ 6. Appendix 2 is amended as follows: (a) the title is amended as follows: (b) Section 1.2.2. is amended as follows: After the current text the following is added: ‘This accuracy implies that primary gases used for blending shall be known to have 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. An additional verification may be performed using another calibration gas, if the first verification has failed. 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. Other methods may be used based on good engineering practice and with the prior agreement of the parties involved. Note: A precision gas divider of accuracy is within ± 1 %, is recommended for establishing the accurate analyser calibration curve. The gas divider shall be calibrated by the instrument manufacturer.’; (c) Section 1.5.5.1 is amended as follows: (i) the first sentence is replaced by the following: ‘The analyser calibration curve is established by at least six calibration points (excluding zero) spaced as uniformly as possible.’ (ii) the third indent is replaced by the following: ‘The calibration curve must not differ by more than ± 2 % from the nominal value of each calibration point and by more than ± 0,3 % of full scale at zero.’; (d) in section 1.5.5.2, the last indent is replaced by the following: ‘The calibration curve must not differ by more than ± 4 % from the nominal value of each calibration point and by more than ± 0,3 % of full scale at zero.’; (e) the text in section 1.8.3 is replaced by the following: ‘The oxygen interference check shall be determined when introducing an analyser into service and after major service intervals. A range shall be chosen where the oxygen interference check gases will fall within the upper 50 %. The test shall be conducted with the oven temperature set as required. 1.8.3.1. Oxygen interference gases Oxygen interference check gases shall contain propane with 350 ppmC ÷ 75 ppmC hydrocarbon. The concentration value shall be determined to calibration gas tolerances by chromatographic analysis of total hydrocarbons plus impurities or by dynamic blending. Nitrogen shall be the predominant diluent with the balance oxygen. Blends required for Diesel engine testing are: O2 concentration Balance 21 (20 to 22) Nitrogen 10 (9 to 11 Nitrogen 5 (4 to 6) Nitrogen 1.8.3.2. Procedure (a) The analyser shall be zeroed. (b) The analyser shall be spanned with the 21 % oxygen blend. (c) The zero response shall be rechecked. If it has changed more than 0,5 % of full scale clauses (a) and (b) shall be repeated. (d) The 5 % and 10 % oxygen interference check gases shall be introduced. (e) The zero response shall be rechecked. If it has changed more than ± 1 % of full scale, the test shall be repeated. (f) The oxygen interference ( %O2I) shall be calculated for each mixture in (d) as follows: A = hydrocarbon concentration (ppmC) of the span gas used in (b) B = hydrocarbon concentration (ppmC) of the oxygen interference check gases used in (d) C = analyser response D = percent of full scale analyser response due to A. (g) The % of oxygen interference ( %O2I) shall be less than ± 3,0 % for all required oxygen interference check gases prior to testing. (h) If the oxygen interference is greater than ± 3,0 %, the air flow above and below the manufacturer's specifications shall be incrementally adjusted, repeating clause 1.8.1 for each flow. (i) If the oxygen interference is greater than ± 3,0 % after adjusting the air flow, the fuel flow and thereafter the sample flow shall be varied, repeating clause 1.8.1 for each new setting. (j) If the oxygen interference is still greater than ± 3,0 %, the analyser, FID fuel, or burner air shall be repaired or replaced prior to testing. This clause shall then be repeated with the repaired or replaced equipment or gases.’; (f) current paragraph 1.9.2.2. is amended as follows: (i) the first subparagraph is replaced by the following: ‘This check applies to wet gas concentration measurements only. Calculation of water quench must consider dilution of the NO span gas with water vapour and scaling of water vapour concentration of the mixture to that expected during testing. A NO span gas having a concentration of 80 to 100 % of full scale to the normal operating range shall be passed through the (H)CLD and the NO value recorded as D. The NO gas shall be bubbled through water at room temperature and passed through the (H)CLD and NO value recorded as C. The water temperature shall be determined and recorded as F. The mixture's saturation vapour pressure that corresponds to the bubbler water temperature (F) shall be determined and recorded as G. The water vapour concentration (in %) of the mixture shall be calculated as follows:’; (ii) the third subparagraph is replaced by the following: ‘and recorded as De. For diesel exhaust, the maximum exhaust water vapour concentration (in %) expected during testing shall be estimated, under the assumption of a fuel atom H/C ratio of 1,8 to 1, from the maximum CO2 concentration in the exhaust gas or from the undiluted CO2 span gas concentration (A, as measured in section 1.9.2.1) as follows:’; (g) the following section is inserted: ‘1.11. Additional calibration requirements for raw exhaust measurements over NRTC test 1.11.1. Response time check of the 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 analysers 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 as the difference in time between the gas switching and the appropriate change of the recorded concentration. The system response time (t90) 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 (t0) until the response is 10 % of the final reading (t10). The rise time is defined as the time between 10 and 90 % response of the final reading (t90 — t10). For time alignment of the analyser and exhaust flow signals in the case of raw measurement, the transformation time is defined as the time from the change (t0) until the response is 50 % of the final reading (t50). The system response time shall be ≤ 10 seconds with a rise time ≤ 2,5 seconds for all limited components (CO, NOx, HC) and all ranges used. 1.11.2. Calibration of tracer gas analyser for exhaust flow measurement The analyser for measurement of the tracer gas concentration, if used, shall be calibrated using the standard gas. The calibration curve shall be established by at least 10 calibration points (excluding zero) spaced so that a half of the calibration points are placed between 4 to 20 % of analyser's full scale and the rest are in between 20 to 100 % of the full scale. The calibration curve is calculated by the method of least squares. The calibration curve shall not differ by more than ± 1 % of the full scale from the nominal value of each calibration point, in the range from 20 to 100 % of the full scale. It shall also not differ by more than ± 2 % from the nominal value in the range from 4 to 20 % of the full scale. 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.’; (h) paragraph 2.2 is replaced by the following: ‘2.2. The calibration of gas flow-meters or flow measurement instrumentation shall be traceable to national and/or international standards. The maximum error of the measured value shall be within ± 2 % of reading. For partial flow dilution systems, the accuracy of the sample flow GSE is of special concern, if not measured directly, but determined by differential flow measurement: GSE = GTOTW — GDILW In this case an accuracy of ± 2 % for GTOTW and GDILW is not sufficient to guarantee acceptable accuracies of GSE. If the gas flow is determined by differential flow measurement, the maximum error of the difference shall be such that the accuracy of GSE 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.’; (i) the following section is added: ‘2.6. Additional calibration requirements for partial flow dilution systems 2.6.1. Periodical calibration If the sample gas flow is determined by differential flow measurement the flow meter or the flow measurement instrumentation shall be calibrated by one of the following procedures, such that the probe flow GSE into the tunnel fulfils the accuracy requirements of Appendix I section 2.4: The flow meter for GDILW is connected in series to the flow meter for GTOTW , the difference between the two flow meters is calibrated for at least five set points with flow values equally spaced between the lowest GDILW value used during the test and the value of GTOTW used during the test The dilution tunnel may be bypassed. A calibrated mass flow device is connected in series to the flowmeter for GTOTW and the accuracy is checked for the value used for the test. Then the calibrated mass flow device is connected in series to the flow meter for GDILW, and the accuracy is checked for at least five settings corresponding to the dilution ratio between 3 and 50, relative to GTOTW used during the test. The transfer tube TT is disconnected from the exhaust, and a calibrated flow measuring device with a suitable range to measure GSE is connected to the transfer tube. Then GTOTW is set to the value used during the test, and GDILW is sequentially set to at least five 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 are maintained as in the actual test. A tracer gas is fed into the 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 is measured. This shall be carried out for five dilution ratios between 3 and 50. The accuracy of the sample flow is determined from the dilution ration q: GSE = GTOTW /q The accuracies of the gas analysers shall be taken into account to guarantee the accuracy of GSE 2.6.2. Carbon flow check A carbon flow check using actual exhaust is strongly recommended for detecting measurement and control problems and verifying the proper operation of the partial flow dilution 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. 2.6.3. Pre-test check A pre-test check shall be performed within two 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 for at least two points, including flow values of GDILW that correspond to dilution ratios between five and 15 for the GTOTW value used during the test. If it can be demonstrated by records of the calibration procedure described above that the flow meter calibration is stable over a longer period of time, the pre-test check may be omitted. 2.6.4. Determination of the transformation time 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 flow meter 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 not to 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 as that 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 GSE signal of the partial flow dilution system and of the GEXHW signal of the exhaust flow meter shall be determined. These signals are used in the regression checks performed after each test (Appendix I section 2.4). The calculation shall be repeated for at least five rise-and-fall stimuli, and the results shall be averaged. The internal transformation time (<100 ms) 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 Appendix I section 2.4.’; 7. the following section is added: ‘3. CALIBRATION OF THE CVS SYSTEM 3.1. General The CVS system shall be calibrated by using an accurate flowmeter and means to change operating conditions. The flow through the system shall be measured at different flow operating settings, and the control parameters of the system shall be measured and related to the flow. Various type of flowmeters may be used, e.g. calibrated venturi, calibrated laminar flowmeter, calibrated turbine meter. 3.2. Calibration of the positive displacement pump (PDP) All the parameters related to the pump shall be simultaneously measured along with the parameters related to a calibration venturi which is connected in series with the pump. The calculated flow rate (in m3/min at pump inlet, absolute pressure and temperature) shall be plotted against a correlation function which is the value of a specific combination of pump parameters. The linear equation which relates the pump flow and the correlation function shall be determined. If a CVS has a multiple speed drive, the calibration shall be performed for each range used. Temperature stability shall be maintained during calibration. Leaks in all the connections and ducting between the calibration venturi and the CVS pump shall be maintained lower than 0,3 % of the lowest flow point (highest restriction and lowest PDP speed point). 3.2.1. Data analysis The air flowrate (Qs) at each restriction setting (minimum 6 settings) shall be calculated in standard m3/min from the flowmeter data using the manufacturer's prescribed method. The air flow rate shall then be converted to pump flow (V0) in m3/rev at absolute pump inlet temperature and pressure as follows where, Qs = air flow rate at standard conditions (101,3 kPa, 273 K) (m3/s) T = temperature at pump inlet (K) pA = absolute pressure at pump inlet (pB- p1) (kPa) n = pump speed (rev/s) To account for the interaction of pressure variations at the pump and the pump slip rate, the correlation function (X0) between pump speed, pressure differential from pump inlet to pump outlet and absolute pump outlet pressure shall be calculated as follows: where, pA = absolute outlet pressure at pump outlet (kPa) A linear least-square fit shall be performed to generate the calibration equation as follows: D0 and m are the intercept and slope constants, respectively, describing the regression lines. For a CVS system with multiple speeds, the calibration curves generated for the different pump flow ranges shall be approximately parallel, and the intercept values (D0) shall increase as the pump flow range decreases. The values calculated by the equation shall be within ± 0,5 % of the measured value of V0. Values of m will vary from one pump to another. Particulate influx over time will cause the pump slip to decrease, as reflected by lower values for m. Therefore, calibration shall be performed at pump start-up, after major maintenance, and if the total system verification (section 3.5) indicates a change in the slip rate. 3.3. Calibration of the critical flow venturi (CFV) Calibration of the CFV is based upon the flow equation for a critical venturi. Gas flow is a function of inlet pressure and temperature, as shown below: where, Kv = calibration coefficient pA = absolute pressure at venturi inlet (kPa) T = temperature at venturi inlet (K) 3.3.1. Data analysis The air flow rate (Qs) at each restriction setting (minimum 8 settings) shall be calculated in standard m3/min from the flowmeter data using the manufacturer's prescribed method. The calibration coefficient shall be calculated from the calibration data for each setting as follows: where, Qs = air flow rate at standard conditions (101,3 kPa, 273 K) (m3/s) T = temperature at the venturi inlet (K) pA = absolute pressure at venturi inlet (kPa) To determine the range of critical flow, Kv shall be plotted as a function of venturi inlet pressure. For critical (choked) flow, Kv will have a relatively constant value. As pressure decreases (vacuum increases), the venturi becomes unchoked and Kv decreases, which indicates that the CFV is operated outside the permissible range. For a minimum of eight points in the region of critical flow, the average KV and the standard deviation shall be calculated. The standard deviation shall not exceed ± 0,3 % of the average KV 3.4. 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, as shown below: where, A0 = collection of constants and units conversions d = diameter of the SSV throat (m) Cd = discharge coefficient of the SSV PA = absolute pressure at venturi inlet (kPa) T = temperature at the venturi inlet (K) 3.4.1. Data analysis The air flow rate (QSSV) at each flow 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, QSSV = 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 To determine the range of subsonic flow, Cd 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, A1 = a collection of constants and units conversions QSSV = 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: where: Because QSSV is an input to the Re formula, the calculations must be started with an initial guess for QSSV or Cd of the calibration venturi, and repeated until QSSV converges. The convergence method must be accurate to 0,1 % or better. For a minimum of sixteen points in the subsonic flow region, the calculated values of Cd from the resulting calibration curve fit equation must be within ± 0,5 % of the measured Cd for each calibration point. 3.5. Total system verification The total accuracy of the CVS sampling system and analytical system shall be determined by introducing a known mass of a pollutant gas into the system while it is being operated in the normal manner. The pollutant is analysed, and the mass calculated according to Annex III, Appendix 3, section 2.4.1 except in the case of propane where a factor of 0,000472 is used in place of 0,000479 for HC. Either of the following two techniques shall be used. 3.5.1. Metering with a critical flow orifice A known quantity of pure gas (propane) shall be fed into the CVS system through a calibrated critical orifice. If the inlet pressure is high enough, the flow rate, which is adjusted by means of the critical flow orifice, is independent of the orifice outlet pressure (critical flow). The CVS system shall be operated as in a normal exhaust emission test for about five to 10 minutes. A gas sample shall be analysed with the usual equipment (sampling bag or integrating method), and the mass of the gas calculated. The mass so determined shall be within ± 3 % of the known mass of the gas injected. 3.5.2. Metering by means of a gravimetric technique The weight of a small cylinder filled with propane shall be determined with a precision of ± 0,01 g. For about five to 10 minutes, the CVS system shall be operated as in a normal exhaust emission test, while carbon monoxide or propane is injected into the system. The quantity of pure gas discharged shall be determined by