ANNEX 4B

Test procedure for compression-ignition (CI) engines and positive-ignition (PI) engines fuelled with natural gas (NG) or liquefied petroleum gas (LPG) incorporating the world-wide harmonised heavy duty certification (WHDC, global technical regulation (gtr) No 4)

1. APPLICABILITY

This annex is not applicable for the purpose of type approval according to this Regulation for the time being. It will be made applicable in the future.

2. RESERVED. (1)

3. DEFINITIONS, SYMBOLS AND ABBREVIATIONS

3.1. Definitions

For the purpose of this Regulation,

3.1.1. “continuous regeneration” means the regeneration process of an exhaust after-treatment system that occurs either permanently or at least once per WHTC hot start test. Such a regeneration process will not require a special test procedure.

3.1.2. “delay time” means the difference in time between the change of the component to be measured at the reference point and a system response of 10 per cent of the final reading (t10) with the sampling probe being defined as the reference point. For the gaseous components, this is the transport time of the measured component from the sampling probe to the detector.

3.1.3. “deNOx system” means an exhaust after-treatment system designed to reduce emissions of oxides of nitrogen (NOx) (e.g. passive and active lean NOx catalysts, NOx adsorbers and selective catalytic reduction (SCR) systems).

3.1.4. “diesel engine” means an engine which works on the compression-ignition principle.

3.1.5. “drift” means the difference between the zero or span responses of the measurement instrument after and before an emissions test.

3.1.6. “engine family” means a manufacturers grouping of engines which, through their design as defined in paragraph 5.2 of this Annex, have similar exhaust emission characteristics; all members of the family shall comply with the applicable emission limit values.

3.1.7. “engine system” means the engine, the emission control system and the communication interface (hardware and messages) between the engine system electronic control unit(s) (ECU) and any other powertrain or vehicle control unit.

3.1.8. “engine type” means a category of engines which do not differ in essential engine characteristics.

3.1.9. “exhaust after-treatment system” means a catalyst (oxidation or 3-way), particulate filter, deNOx system, combined deNOx particulate filter or any other emission-reducing device that is installed downstream of the engine. This definition excludes exhaust gas recirculation (EGR), which is considered an integral part of the engine.

3.1.10. “full flow dilution method” means the process of mixing the total exhaust flow with diluent prior to separating a fraction of the diluted exhaust stream for analysis.

3.1.11. “gaseous pollutants” means carbon monoxide, hydrocarbons and/or non-methane hydrocarbons (assuming a ratio of CH1,85 for diesel, CH2,525 for LPG and CH2.93 for NG, and an assumed molecule CH3O0,5 for ethanol fuelled diesel engines), methane (assuming a ratio of CH4 for NG) and oxides of nitrogen (expressed in nitrogen dioxide (NO2) equivalent).

3.1.12. “high speed (n hi)” means the highest engine speed where 70 per cent of the declared maximum power occurs.

3.1.13. “low speed (n lo)” means the lowest engine speed where 55 per cent of the declared maximum power occurs.

3.1.14. “maximum power (Pmax)” means the maximum power in kW as specified by the manufacturer.

3.1.15. “maximum torque speed” means the engine speed at which the maximum torque is obtained from the engine, as specified by the manufacturer.

3.1.16. “normalised torque” means engine torque in per cent normalised to the maximum available torque at an engine speed.

3.1.17. “operator demand” means an engine operator's input to control engine output. The operator may be a person (i.e. manual), or a governor (i.e. automatic) that mechanically or electronically signals an input that demands engine output. Input may be from an accelerator pedal or signal, a throttle-control lever or signal, a fuel lever or signal, a speed lever or signal, or a governor setpoint or signal.

3.1.18. “parent engine” means an engine selected from an engine family in such a way that its emissions characteristics are representative for that engine family.

3.1.19. “particulate after-treatment device” means an exhaust after-treatment system designed to reduce emissions of particulate pollutants (PM) through a mechanical, aerodynamic, diffusional or inertial separation.

3.1.20. “partial flow dilution method” means the process of separating a part from the total exhaust flow, then mixing it with an appropriate amount of diluent prior to the particulate sampling filter.

3.1.21. “particulate matter (PM)” means any material collected on a specified filter medium after diluting exhaust with a clean filtered diluent to a temperature between 315 K (42 °C) and 325 K (52 °C); this is primarily carbon, condensed hydrocarbons, and sulphates with associated water.

3.1.22. “periodic regeneration” means the regeneration process of an exhaust after-treatment system that occurs periodically in typically less than 100 hours of normal engine operation. During cycles where regeneration occurs, emission standards may be exceeded.

3.1.23. “ramped steady state test cycle” means a test cycle with a sequence of steady state engine test modes with defined speed and torque criteria at each mode and defined ramps between these modes (WHSC).

3.1.24. “rated speed” means the maximum full load speed allowed by the governor as specified by the manufacturer in his sales and service literature, or, if such a governor is not present, the speed at which the maximum power is obtained from the engine, as specified by the manufacturer in his sales and service literature.

3.1.25. “response time” means the difference in time between the change of the component to be measured at the reference point and a system response of 90 per cent of the final reading (t90) with the sampling probe being defined as the reference point, whereby the change of the measured component is at least 60 per cent full scale (FS) and takes place in less than 0,1 second. The system response time consists of the delay time to the system and of the rise time of the system.

3.1.26. “rise time” means the difference in time between the 10 per cent and 90 per cent response of the final reading (t 90 – t 10).

3.1.27. “span response” means the mean response to a span gas during a 30 s time interval.

3.1.28. “specific emissions” means the mass emissions expressed in g/kWh.

3.1.29. “test cycle” means a sequence of test points each with a defined speed and torque to be followed by the engine under steady state (WHSC) or transient operating conditions (WHTC).

3.1.30. “transformation time” means the difference in time between the change of the component to be measured at the reference point and a system response of 50 per cent of the final reading (t 50) with the sampling probe being defined as the reference point. The transformation time is used for the signal alignment of different measurement instruments.

3.1.31. “transient test cycle” means a test cycle with a sequence of normalised speed and torque values that vary relatively quickly with time (WHTC).

3.1.32. “useful life” means the relevant period of distance and/or time over which compliance with the relevant gaseous and particulate emission limits has to be assured.

3.1.33. “zero response” means the mean response to a zero gas during a 30 s time interval.

3.2. General symbols

Symbol Unit Term a 1 — Slope of the regression a 0 — y intercept of the regression A/F st — Stoichiometric air to fuel ratio c ppm/Vol per cent Concentration c d ppm/Vol per cent Concentration on dry basis c w ppm/Vol per cent Concentration on wet basis c b ppm/Vol per cent Background concentration C d — Discharge coefficient of SSV c gas ppm/Vol per cent Concentration on the gaseous components d m Diameter d V m Throat diameter of venturi D 0 m3/s PDP calibration intercept D — Dilution factor Δt s Time interval e gas g/kWh Specific emission of gaseous components e PM g/kWh Specific emission of particulates e r g/kWh Specific emission during regeneration e w g/kWh Weighted specific emission E CO2 per cent CO2 quench of NOx analyser E E per cent Ethane efficiency E H2O per cent Water quench of NOx analyser E M per cent Methane efficiency E NOx per cent Efficiency of NOx converter f Hz Data sampling rate f a — Laboratory atmospheric factor F s — Stoichiometric factor H a g/kg Absolute humidity of the intake air H d g/kg Absolute humidity of the diluent i — Subscript denoting an instantaneous measurement (e.g. 1 Hz) k c — Carbon specific factor k f,d m3/kg fuel Combustion additional volume of dry exhaust k f,w m3/kg fuel Combustion additional volume of wet exhaust k h,D — Humidity correction factor for NOx for CI engines k h,G — Humidity correction factor for NOx for PI engines k r,u — Upward regeneration adjustment factor k r,d — Downward regeneration adjustment factor k w,a — Dry to wet correction factor for the intake air k w,d — Dry to wet correction factor for the diluent k w,e — Dry to wet correction factor for the diluted exhaust gas k w,r — Dry to wet correction factor for the raw exhaust gas K V — CFV calibration function λ — Excess air ratio m b mg Particulate sample mass of the diluent collected m d kg Mass of the diluent sample passed through the particulate sampling filters m ed kg Total diluted exhaust mass over the cycle m edf kg Mass of equivalent diluted exhaust gas over the test cycle m ew kg Total exhaust mass over the cycle m gas g Mass of gaseous emissions over the test cycle m f mg Particulate sampling filter mass m p mg Particulate sample mass collected m PM g Mass of particulate emissions over the test cycle m se kg Exhaust sample mass over the test cycle m sed kg Mass of diluted exhaust gas passing the dilution tunnel m sep kg Mass of diluted exhaust gas passing the particulate collection filters m ssd kg Mass of secondary diluent M Nm Torque M a g/mol Molar mass of the intake air M d g/mol Molar mass of the diluent M e g/mol Molar mass of the exhaust M f Nm Torque absorbed by auxiliaries/equipment to be fitted M gas g/mol Molar mass of gaseous components M r Nm Torque absorbed by auxiliaries/equipment to be removed n — Number of measurements nr — Number of measurements with regeneration n min–1 Engine rotational speed n hi min–1 High engine speed n lo min–1 Low engine speed n pref min–1 Preferred engine speed n p r/s PDP pump speed p a kPa Saturation vapour pressure of engine intake air p b kPa Total atmospheric pressure p d kPa Saturation vapour pressure of the diluent P f kW Power absorbed by auxiliaries/equipment to be fitted p p kPa Absolute pressure p r kW Water vapour pressure after cooling bath p s kPa Dry atmospheric pressure P kW Power P r kW Power absorbed by auxiliaries/equipment to be removed q mad kg/s Intake air mass flow rate on dry basis q maw kg/s Intake air mass flow rate on wet basis q mCe kg/s Carbon mass flow rate in the raw exhaust gas q mCf kg/s Carbon mass flow rate into the engine q mCp kg/s Carbon mass flow rate in the partial flow dilution system q mdew kg/s Diluted exhaust gas mass flow rate on wet basis q mdw kg/s Diluent mass flow rate on wet basis q medf kg/s Equivalent diluted exhaust gas mass flow rate on wet basis q mew kg/s Exhaust gas mass flow rate on wet basis q mex kg/s Sample mass flow rate extracted from dilution tunnel q mf kg/s Fuel mass flow rate q mp kg/s Sample flow of exhaust gas into partial flow dilution system q vCVS m3/s CVS volume rate q vs dm3/min System flow rate of exhaust analyser system q vt cm3/min Tracer gas flow rate r2 — Coefficient of determination r d — Dilution ratio r D — Diameter ratio of SSV r h — Hydrocarbon response factor of the FID r m — Methanol response factor of the FID r p — Pressure ratio of SSV r s — Average sample ratio ρ kg/m3 Density ρ e kg/m3 Exhaust gas density σ — Standard deviation s Standard deviation T K Absolute temperature T a K Absolute temperature of the intake air t s Time t 10 s Time between step input and 10 per cent of final reading t 50 s Time between step input and 50 per cent of final reading t 90 s Time between step input and 90 per cent of final reading u — Ratio between the densities (or molar masses) of the gas components and the exhaust gas divided by 1 000 V 0 m3/r PDP gas volume pumped per revolution V s dm3 System volume of exhaust analyser bench W act kWh Actual cycle work of the test cycle W ref kWh Reference cycle work of the test cycle X 0 m3/r PDP calibration function

3.3. Symbols and abbreviations for the fuel composition

w ALF hydrogen content of fuel, per cent mass w BET carbon content of fuel, per cent mass w GAM sulphur content of fuel, per cent mass w DEL nitrogen content of fuel, per cent mass w EPS oxygen content of fuel, per cent mass α molar hydrogen ratio (H/C) γ molar sulphur ratio (S/C) δ molar nitrogen ratio (N/C) ε molar oxygen ratio (O/C)

referring to a fuel CH α O ε N δ S γ

3.4. Symbols and abbreviations for the chemical components

C1 Carbon 1 equivalent hydrocarbon CH4 Methane C2H6 Ethane C3H8 Propane CO Carbon monoxide CO2 Carbon dioxide DOP Di-octylphtalate HC Hydrocarbons H2O Water NMHC Non-methane hydrocarbons NOx Oxides of nitrogen NO Nitric oxide NO2 Nitrogen dioxide PM Particulate matter

3.5. Abbreviations

CFV Critical Flow Venturi CLD Chemiluminescent Detector CVS Constant Volume Sampling deNOx NOx after-treatment system EGR Exhaust gas recirculation FID Flame Ionisation Detector GC Gas Chromatograph HCLD Heated Chemiluminescent Detector HFID Heated Flame Ionisation Detector LPG Liquefied Petroleum Gas NDIR Non-Dispersive Infrared (Analyser) NG Natural Gas NMC Non-Methane Cutter PDP Positive Displacement Pump Per cent FS Per cent of full scale PFS Partial Flow System SSV Subsonic Venturi VGT Variable Geometry Turbine

4. GENERAL REQUIREMENTS

The engine system shall be so designed, constructed and assembled as to enable the engine in normal use to comply with the provisions of this Annex during its useful life, as defined in this Regulation, including when installed in the vehicle.

5. PERFORMANCE REQUIREMENTS

5.1. Emission of gaseous and particulate pollutants

The emissions of gaseous and particulate pollutants by the engine shall be determined on the WHTC and WHSC test cycles, as described in paragraph 7. The measurement systems shall meet the linearity requirements in paragraph 9.2 and the specifications in paragraph 9.3 (gaseous emissions measurement), paragraph 9.4 (particulate measurement) and in Appendix 3.

Other systems or analysers may be approved by the type approval authority, if it is found that they yield equivalent results in accordance with paragraph 5.1.1.

5.1.1. Equivalency

The determination of system equivalency shall be based on a seven-sample pair (or larger) correlation study between the system under consideration and one of the systems of this Annex.

“Results” refer to the specific cycle weighted emissions value. The correlation testing is to be performed at the same laboratory, test cell, and on the same engine, and is preferred to be run concurrently. The equivalency of the sample pair averages shall be determined by F-test and t-test statistics as described in Appendix 4, paragraph A.4.3, obtained under the laboratory test cell and the engine conditions described above. Outliers shall be determined in accordance with ISO 5725 and excluded from the database. The systems to be used for correlation testing shall be subject to the approval by the type approval authority.

5.2. Engine family

5.2.1. General

An engine family is characterised by design parameters. These shall be common to all engines within the family. The engine manufacturer may decide which engines belong to an engine family, as long as the membership criteria listed in paragraph 5.2.3 are respected. The engine family shall be approved by the type approval authority. The manufacturer shall provide to the type approval authority the appropriate information relating to the emission levels of the members of the engine family.

5.2.2. Special cases

In some cases there may be interaction between parameters. This shall be taken into consideration to ensure that only engines with similar exhaust emission characteristics are included within the same engine family. These cases shall be identified by the manufacturer and notified to the type approval authority. It shall then be taken into account as a criterion for creating a new engine family.

In case of devices or features, which are not listed in paragraph 5.2.3 and which have a strong influence on the level of emissions, this equipment shall be identified by the manufacturer on the basis of good engineering practice, and shall be notified to the type approval authority. It shall then be taken into account as a criterion for creating a new engine family.

In addition to the parameters listed in paragraph 5.2.3, the manufacturer may introduce additional criteria allowing the definition of families of more restricted size. These parameters are not necessarily parameters that have an influence on the level of emissions.

5.2.3. Parameters defining the engine family

5.2.3.1. Combustion cycle

(a) 2-stroke cycle

(b) 4-stroke cycle

(c) Rotary engine

(d) Others

5.2.3.2. Configuration of the cylinders

5.2.3.2.1. Position of the cylinders in the block

(a) V

(b) In line

(c) Radial

(d) Others (F, W, etc.)

5.2.3.2.2. Relative position of the cylinders

Engines with the same block may belong to the same family as long as their bore centre-to-centre dimensions are the same.

5.2.3.3. Main cooling medium

(a) air

(b) water

(c) oil

5.2.3.4. Individual cylinder displacement

5.2.3.4.1. Engine with a unit cylinder displacement ≥ 0,75 dm3

In order for engines with a unit cylinder displacement of ≥ 0,75 dm3 to be considered to belong to the same engine family, the spread of their individual cylinder displacements shall not exceed 15 per cent of the largest individual cylinder displacement within the family.

5.2.3.4.2. Engine with a unit cylinder displacement < 0,75 dm3

In order for engines with a unit cylinder displacement of < 0,75 dm3 to be considered to belong to the same engine family, the spread of their individual cylinder displacements shall not exceed 30 per cent of the largest individual cylinder displacement within the family.

5.2.3.4.3. Engine with other unit cylinder displacement limits

Engines with an individual cylinder displacement that exceeds the limits defined in paragraphs 5.2.3.4.1 and 5.2.3.4.2 may be considered to belong to the same family with the approval of the type approval authority. The approval shall be based on technical elements (calculations, simulations, experimental results etc.) showing that exceeding the limits does not have a significant influence on the exhaust emissions.

5.2.3.5. Method of air aspiration

(a) Naturally aspirated

(b) Pressure charged

(c) Pressure charged with charge cooler

5.2.3.6. Fuel type

(a) Diesel

(b) Natural gas (NG)

(c) Liquefied petroleum gas (LPG)

(d) Ethanol

5.2.3.7. Combustion chamber type

(a) Open chamber

(b) Divided chamber

(c) Other types

5.2.3.8. Ignition Type

(a) Positive ignition

(b) Compression ignition

5.2.3.9. Valves and porting

(a) Configuration

(b) Number of valves per cylinder

5.2.3.10. Fuel supply type

(a) Liquid fuel supply type (i) Pump and (high pressure) line and injector (ii) In-line or distributor pump (iii) Unit pump or unit injector (iv) Common rail (v) Carburettor(s) (vi) Others

(b) Gas fuel supply type (i) Gaseous (ii) Liquid (iii) Mixing units (iv) Others

(c) Other types

5.2.3.11. Miscellaneous devices

(a) Exhaust gas recirculation (EGR)

(b) Water injection

(c) Air injection

(d) Others

5.2.3.12. Electronic control strategy

The presence or absence of an electronic control unit (ECU) on the engine is regarded as a basic parameter of the family.

In the case of electronically controlled engines, the manufacturer shall present the technical elements explaining the grouping of these engines in the same family, i.e. the reasons why these engines can be expected to satisfy the same emission requirements.

These elements can be calculations, simulations, estimations, description of injection parameters, experimental results, etc.

Examples of controlled features are:

(a) Timing

(b) Injection pressure

(c) Multiple injections

(d) Boost pressure

(e) VGT

(f) EGR

5.2.3.13. Exhaust after-treatment systems

The function and combination of the following devices are regarded as membership criteria for an engine family:

(a) Oxidation catalyst

(b) Three-way catalyst

(c) DeNOx system with selective reduction of NOx (addition of reducing agent)

(d) Other DeNOx systems

(e) Particulate trap with passive regeneration

(f) Particulate trap with active regeneration

(g) Other particulate traps

(h) Other devices

When an engine has been certified without after-treatment system, whether as parent engine or as member of the family, then this engine, when equipped with an oxidation catalyst, may be included in the same engine family, if it does not require different fuel characteristics.

If it requires specific fuel characteristics (e.g. particulate traps requiring special additives in the fuel to ensure the regeneration process), the decision to include it in the same family shall be based on technical elements provided by the manufacturer. These elements shall indicate that the expected emission level of the equipped engine complies with the same limit value as the non-equipped engine.

When an engine has been certified with after-treatment system, whether as parent engine or as member of a family, whose parent engine is equipped with the same after-treatment system, then this engine, when equipped without after-treatment system, shall not be added to the same engine family.

5.2.4. Choice of the parent engine

5.2.4.1. Compression ignition engines

Once the engine family has been agreed by the type approval authority, the parent engine of the family shall be selected using the primary criterion of the highest fuel delivery per stroke at the declared maximum torque speed. In the event that two or more engines share this primary criterion, the parent engine shall be selected using the secondary criterion of highest fuel delivery per stroke at rated speed.

5.2.4.2. Positive ignition engines

Once the engine family has been agreed by the type approval authority, the parent engine of the family shall be selected using the primary criterion of the largest displacement. In the event that two or more engines share this primary criterion, the parent engine shall be selected using the secondary criterion in the following order of priority:

(a) the highest fuel delivery per stroke at the speed of declared rated power;

(b) the most advanced spark timing;

(c) the lowest EGR rate.

5.2.4.3. Remarks on the choice of the parent engine

The type approval authority may conclude that the worst-case emission of the family can best be characterised by testing additional engines. In this case, the engine manufacturer shall submit the appropriate information to determine the engines within the family likely to have the highest emissions level.

If engines within the family incorporate other features which may be considered to affect exhaust emissions, these features shall also be identified and taken into account in the selection of the parent engine.

If engines within the family meet the same emission values over different useful life periods, this shall be taken into account in the selection of the parent engine.

6. TEST CONDITIONS

6.1. Laboratory test conditions

The absolute temperature (T a) of the engine intake air expressed in Kelvin, and the dry atmospheric pressure (p s), expressed in kPa shall be measured and the parameter f a shall be determined according to the following provisions. In multi-cylinder engines having distinct groups of intake manifolds, such as in a “Vee” engine configuration, the average temperature of the distinct groups shall be taken. The parameter f a shall be reported with the test results. For better repeatability and reproducibility of the test results, it is recommended that the parameter f a be such that: 0,93 ≤ f a ≤ 1,07.

(a) Compression-ignition engines: Naturally aspirated and mechanically supercharged engines: (1) Turbocharged engines with or without cooling of the intake air: (2)

(b) Positive ignition engines: (3)

6.2. Engines with charge air-cooling

The charge air temperature shall be recorded and shall be, at the rated speed and full load, 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 laboratory system or external blower is used, the coolant flow rate shall be set to achieve a charge air temperature within ± 5 K of the maximum charge air temperature specified by the manufacturer at the rated speed 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, unless this results in unrepresentative overcooling of the charge air. The charge air cooler volume shall be based upon good engineering practice and shall be representative of the production engine's in-use installation. The laboratory system shall be designed to minimise accumulation of condensate. Any accumulated condensate shall be drained and all drains shall be completely closed before emission testing.

If the engine manufacturer specifies pressure-drop limits across the charge-air cooling system, it shall be ensured that the pressure drop across the charge-air cooling system at engine conditions specified by the manufacturer is within the manufacturer's specified limit(s). The pressure drop shall be measured at the manufacturer's specified locations.

6.3. Engine power

The basis of specific emissions measurement is engine power and cycle work as determined in accordance with paragraphs 6.3.1 to 6.3.5.

6.3.1. General engine installation

The engine shall be tested with the auxiliaries/equipment listed in Appendix 7.

If auxiliaries/equipment are not installed as required, their power shall be taken into account in accordance with paragraphs 6.3.2 to 6.3.5.

6.3.2. Auxiliaries/equipment to be fitted for the emissions test

If it is inappropriate to install the auxiliaries/equipment required according to Appendix 7 on the test bench, the power absorbed by them shall be determined and subtracted from the measured engine power (reference and actual) over the whole engine speed range of the WHTC and over the test speeds of the WHSC.

6.3.3. Auxiliaries/equipment to be removed for the test

Where the auxiliaries/equipment not required according to Appendix 7 cannot be removed, the power absorbed by them may be determined and added to the measured engine power (reference and actual) over the whole engine speed range of the WHTC and over the test speeds of the WHSC. If this value is greater than 3 per cent of the maximum power at the test speed it shall be demonstrated to the type approval authority.

6.3.4. Determination of auxiliary power

The power absorbed by the auxiliaries/equipment needs only be determined, if

(a) auxiliaries/equipment required according to Appendix 7, are not fitted to the engine and/or

(b) auxiliaries/equipment not required according to Appendix 7, are fitted to the engine.

The values of auxiliary power and the measurement/calculation method for determining auxiliary power shall be submitted by the engine manufacturer for the whole operating area of the test cycles, and approved by the type approval authority.

6.3.5. Engine cycle work

The calculation of reference and actual cycle work (see paragraphs 7.4.8 and 7.8.6) shall be based upon engine power according to paragraph 6.3.1. In this case, P f and P r of equation 4 are zero, and P equals P m.

If auxiliaries/equipment are installed according to paragraphs 6.3.2 and/or 6.3.3, the power absorbed by them shall be used to correct each instantaneous cycle power value P m,i, as follows:

(4)

where:

P m,i is the measured engine power, kW P f,i is the power absorbed by auxiliaries/equipment to be fitted, kW P r,i is the power absorbed by auxiliaries/equipment to be removed, kW

6.4. Engine air intake system

An engine air intake system or a test laboratory system shall be used presenting an air intake restriction within ± 300 Pa of the maximum value specified by the manufacturer for a clean air cleaner at the rated speed and full load. The static differential pressure of the restriction shall be measured at the location specified by the manufacturer.

6.5. Engine exhaust system

An engine exhaust system or a test laboratory system shall be used presenting an exhaust backpressure within 80 to 100 per cent of the maximum value specified by the manufacturer at the rated speed and full load. If the maximum restriction is 5 kPa or less, the set point shall be no less than 1,0 kPa from the maximum. The exhaust system shall conform to the requirements for exhaust gas sampling, as set out in paragraphs 9.3.10 and 9.3.11.

6.6. Engine with exhaust after-treatment system

If the engine is equipped with an exhaust after-treatment system, the exhaust pipe shall have the same diameter as found in-use, or as specified by the manufacturer, for at least four pipe diameters upstream of the expansion section containing the after-treatment device. The distance from the exhaust manifold flange or turbocharger outlet to the exhaust after-treatment system shall be the same as in the vehicle 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. For variable-restriction after-treatment devices, the maximum exhaust restriction is defined at the after-treatment condition (de-greening/aging and regeneration/loading level) specified by the manufacturer. If the maximum restriction is 5 kPa or less, the set point shall be no less than 1,0 kPa from the maximum. 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.

The emissions measured on the test cycle shall be representative of the emissions in the field. In the case of an engine equipped with a exhaust after-treatment system that requires the consumption of a reagent, the reagent used for all tests shall be declared by the manufacturer.

Engines equipped with exhaust after-treatment systems with continuous regeneration do not require a special test procedure, but the regeneration process needs to be demonstrated according to paragraph 6.6.1.

For engines equipped with exhaust after-treatment systems that are regenerated on a periodic basis, as described in paragraph 6.6.2, emission results shall be adjusted to account for regeneration events. In this case, the average emission depends on the frequency of the regeneration event in terms of fraction of tests during which the regeneration occurs.

6.6.1. Continuous regeneration

The emissions shall be measured on an after-treatment system that has been stabilised so as to result in repeatable emissions behaviour. The regeneration process shall occur at least once during the WHTC hot start test and the manufacturer shall declare the normal conditions under which regeneration occurs (soot load, temperature, exhaust back-pressure, etc.).

In order to demonstrate that the regeneration process is continuous, at least three WHTC hot start tests shall be conducted. For the purpose of this demonstration, the engine shall be warmed up in accordance with paragraph 7.4.1, the engine be soaked according to paragraph 7.6.3 and the first WHTC hot start test be run. The subsequent hot start tests shall be started after soaking according to paragraph 7.6.3. During the tests, exhaust temperatures and pressures shall be recorded (temperature before and after the after-treatment system, exhaust back pressure, etc.).

If the conditions declared by the manufacturer occur during the tests and the results of the three (or more) WHTC hot start tests do not scatter by more than ± 25 per cent or 0,005 g/kWh, whichever is greater, the after-treatment system is considered to be of the continuous regeneration type, and the general test provisions of paragraph 7.6 (WHTC) and paragraph 7.7 (WHSC) apply.

If the exhaust after-treatment system has a security mode that shifts to a periodic regeneration mode, it shall be checked according to paragraph 6.6.2. For that specific case, the applicable emission limits may be exceeded and would not be weighted.

6.6.2. Periodic regeneration

For an exhaust after-treatment based on a periodic regeneration process, the emissions shall be measured on at least three WHTC hot start tests, one with and two without a regeneration event on a stabilised after-treatment system, and the results be weighted in accordance with equation 5.

The regeneration process shall occur at least once during the WHTC hot start test. The engine may be equipped with a switch capable of preventing or permitting the regeneration process provided this operation has no effect on the original engine calibration.

The manufacturer shall declare the normal parameter conditions under which the regeneration process occurs (soot load, temperature, exhaust back-pressure, etc.) and its duration. The manufacturer shall also provide the frequency of the regeneration event in terms of number of tests during which the regeneration occurs compared to number of tests without regeneration. The exact procedure to determine this frequency shall be based upon in use data using good engineering judgement, and shall be agreed by the type approval or certification authority.

The manufacturer shall provide an after-treatment system that has been loaded in order to achieve regeneration during a WHTC test. For the purpose of this testing, the engine shall be warmed up in accordance with paragraph 7.4.1, the engine be soaked according to paragraph 7.6.3 and the WHTC hot start test be started. Regeneration shall not occur during the engine warm-up.

Average specific emissions between regeneration phases shall be determined from the arithmetic mean of several approximately equidistant WHTC hot start test results (g/kWh). As a minimum, at least one WHTC hot start test as close as possible prior to a regeneration test and one WHTC hot start test immediately after a regeneration test shall be conducted. As an alternative, the manufacturer may provide data to show that the emissions remain constant (±25 per cent or 0,005 g/kWh, whichever is greater) between regeneration phases. In this case, the emissions of only one WHTC hot start test may be used.

During the regeneration test, all the data needed to detect regeneration shall be recorded (CO or NOx emissions, temperature before and after the after-treatment system, exhaust back pressure, etc.).

During the regeneration test, the applicable emission limits may be exceeded.

The test procedure is schematically shown in figure 2.

The WHTC hot start emissions shall be weighted as follows:

(5)

where:

n is the number of WHTC hot start tests without regeneration nr is the number of WHTC hot start tests with regeneration (minimum one test) is the average specific emission without regeneration, g/kWh is the average specific emission with regeneration, g/kWh

For the determination of , the following provisions apply:

(a) If regeneration takes more than one hot start WHTC, consecutive full hot start WHTC tests shall be conducted and emissions continued to be measured without soaking and without shutting the engine off, until regeneration is completed, and the average of the hot start WHTC tests be calculated.

(b) If regeneration is completed during any hot start WHTC, the test shall be continued over its entire length.

In agreement with the type approval authority, the regeneration adjustment factors may be applied either multiplicative (c) or additive (d) based upon good engineering analysis.

(c) The multiplicative adjustment factors shall be calculated as follows: (upward) (6) (downward) (6a)

(d) The additive adjustment factors shall be calculated as follows: (upward) (7) (downward) (8)

With reference to the specific emission calculations in paragraph 8.6.3, the regeneration adjustment factors shall be applied, as follows:

(e) for a test without regeneration, k r,u shall be multiplied with or be added to, respectively, the specific emission e in equations 69 or 70,

(f) for a test with regeneration, k r,d shall be multiplied with or be subtracted from, respectively, the specific emission e in equations 69 or 70.

At the request of the manufacturer, the regeneration adjustment factors

(g) may be extended to other members of the same engine family,

(h) may be extended to other engine families using the same after-treatment system with the prior approval of the type approval or certification authority based on technical evidence to be supplied by the manufacturer, that the emissions are similar.

6.7. Cooling system

An engine cooling system with sufficient capacity to maintain the engine at normal operating temperatures prescribed by the manufacturer shall be used.

6.8. Lubricating oil

The lubricating oil shall be specified by the manufacturer and be representative of lubricating oil available on the market; the specifications of the lubricating oil used for the test shall be recorded and presented with the results of the test.

6.9. Specification of the reference fuel

The reference fuel is specified in Appendix 2 of this Annex for CI engines and in Annexes 6 and 7 for CNG and LPG fuelled engines.

The fuel temperature shall be in accordance with the manufacturer’s recommendations.

6.10. Crankcase emissions

No crankcase emissions shall be discharged directly into the ambient atmosphere, with the following exception: engines equipped with turbochargers, pumps, blowers, or superchargers for air induction may discharge crankcase emissions to the ambient atmosphere if the emissions are added to the exhaust emissions (either physically or mathematically) during all emission testing. Manufacturers taking advantage of this exception shall install the engines so that all crankcase emission can be routed into the emissions sampling system.

For the purpose of this paragraph, crankcase emissions that are routed into the exhaust upstream of exhaust after-treatment during all operation are not considered to be discharged directly into the ambient atmosphere.

Open crankcase emissions shall be routed into the exhaust system for emission measurement, as follows:

(a) The tubing materials shall be smooth-walled, electrically conductive, and not reactive with crankcase emissions. Tube lengths shall be minimised as far as possible.

(b) The number of bends in the laboratory crankcase tubing shall be minimised, and the radius of any unavoidable bend shall be maximised.

(c) The laboratory crankcase exhaust tubing shall be heated, thin-walled or insulated and shall meet the engine manufacturer’s specifications for crankcase back pressure.

(d) The crankcase exhaust tubing shall connect into the raw exhaust downstream of any after-treatment system, downstream of any installed exhaust restriction, and sufficiently upstream of any sample probes to ensure complete mixing with the engine’s exhaust before sampling. The crankcase exhaust tube shall extend into the free stream of exhaust to avoid boundary-layer effects and to promote mixing. The crankcase exhaust tube’s outlet may orient in any direction relative to the raw exhaust flow.

7. TEST PROCEDURES

7.1. Principles of emissions measurement

To measure the specific emissions, the engine shall be operated over the test cycles defined in paragraphs 7.2.1 and 7.2.2. The measurement of specific emissions requires the determination of the mass of components in the exhaust and the corresponding engine cycle work. The components are determined by the sampling methods described in paragraphs 7.1.1 and 7.1.2.

7.1.1. Continuous sampling

In continuous sampling, the component’s concentration is measured continuously from raw or dilute exhaust. This concentration is multiplied by the continuous (raw or dilute) exhaust flow rate at the emission sampling location to determine the component’s mass flow rate. The component’s emission is continuously summed over the test cycle. This sum is the total mass of the emitted component.

7.1.2. Batch sampling

In batch sampling, a sample of raw or dilute exhaust is continuously extracted and stored for later measurement. The extracted sample shall be proportional to the raw or dilute exhaust flow rate. Examples of batch sampling are collecting diluted gaseous components in a bag and collecting particulate matter (PM) on a filter. The batch sampled concentrations are multiplied by the total exhaust mass or mass flow (raw or dilute) from which it was extracted during the test cycle. This product is the total mass or mass flow of the emitted component. To calculate the PM concentration, the PM deposited onto a filter from proportionally extracted exhaust shall be divided by the amount of filtered exhaust.

7.1.3. Measurement procedures

This annex applies two measurement procedures that are functionally equivalent. Both procedures may be used for both the WHTC and the WHSC test cycle:

(a) the gaseous components are sampled continuously in the raw exhaust gas, and the particulates are determined using a partial flow dilution system;

(b) the gaseous components and the particulates are determined using a full flow dilution system (CVS system).

Any combination of the two principles (e.g. raw gaseous measurement and full flow particulate measurement) is permitted.

7.2. Test cycles

7.2.1. Transient test cycle WHTC

The transient test cycle WHTC is listed in Appendix 1 as a second-by-second sequence of normalised speed and torque values. 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. The conversion is referred to as denormalisation, and the test cycle so developed as the reference cycle of the engine to be tested. With those reference speed and torque values, the cycle shall be run on the test cell, and the actual speed, torque and power values shall be recorded. In order to validate the test run, a regression analysis between reference and actual speed, torque and power values shall be conducted upon completion of the test.

For calculation of the brake specific emissions, the actual cycle work shall be calculated by integrating actual engine power over the cycle. For cycle validation, the actual cycle work shall be within prescribed limits of the reference cycle work.

For the gaseous pollutants, continuous sampling (raw or dilute exhaust gas) or batch sampling (dilute exhaust gas) may be used. The particulate sample shall be diluted with a conditioned diluent (such as ambient air), and collected on a single suitable filter. The WHTC is shown schematically in figure 3.

7.2.2. Ramped steady state test cycle WHSC

The ramped steady state test cycle WHSC consists of a number of normalised speed and load modes which shall be converted to the reference values for the individual engine under test based on the engine-mapping curve. The engine shall be operated for the prescribed time in each mode, whereby engine speed and load shall be changed linearly within 20 ± 1 seconds. In order to validate the test run, a regression analysis between reference and actual speed, torque and power values shall be conducted upon completion of the test.

The concentration of each gaseous pollutant, exhaust flow and power output shall be determined over the test cycle. The gaseous pollutants may be recorded continuously or sampled into a sampling bag. The particulate sample shall be diluted with a conditioned diluent (such as ambient air). One sample over the complete test procedure shall be taken, and collected on a single suitable filter.

For calculation of the brake specific emissions, the actual cycle work shall be calculated by integrating actual engine power over the cycle.

The WHSC is shown in table 1. Except for mode 1, the start of each mode is defined as the beginning of the ramp from the previous mode.

Table 1

WHSC test cycle

Mode Normalised speed (per cent) Normalised torque (per cent) Mode length(s) incl. 20 s ramp 1 0 0 210 2 55 100 50 3 55 25 250 4 55 70 75 5 35 100 50 6 25 25 200 7 45 70 75 8 45 25 150 9 55 50 125 10 75 100 50 11 35 50 200 12 35 25 250 13 0 0 210 Sum 1 895

7.3. General test sequence

The following flow chart outlines the general guidance that should be followed during testing. The details of each step are described in the relevant paragraphs. Deviations from the guidance are permitted where appropriate, but the specific requirements of the relevant paragraphs are mandatory.

For the WHTC, the test procedure consists of a cold start test following either natural or forced cool-down of the engine, a hot soak period and a hot start test.

For the WHSC, the test procedure consists of a hot start test following engine preconditioning at WHSC mode 9.

7.4. Engine mapping and reference cycle

Pre-test engine measurements, pre-test engine performance checks and pre-test system calibrations shall be made prior to the engine mapping procedure in line with the general test sequence shown in paragraph 7.3.

As basis for WHTC and WHSC reference cycle generation, the engine shall be mapped under full load operation for determining the speed vs. maximum torque and speed vs. maximum power curves. The mapping curve shall be used for denormalising engine speed (paragraph 7.4.6) and engine torque (paragraph 7.4.7).

7.4.1. Engine warm-up

The engine shall be warmed up between 75 per cent and 100 per cent of its maximum power or according to the recommendation of the manufacturer and good engineering judgment. Towards the end of the warm up it shall be operated in order to stabilise the engine coolant and lube oil temperatures to within ± 2 per cent of its mean values for at least 2 minutes or until the engine thermostat controls engine temperature.

7.4.2. Determination of the mapping speed range

The minimum and maximum mapping speeds are defined as follows:

Minimum mapping speed = idle speed Maximum mapping speed = n hi × 1,02 or speed where full load torque drops off to zero, whichever is smaller.

7.4.3. Engine mapping curve

When the engine is stabilised according to paragraph 7.4.1, the engine mapping shall be performed according to the following procedure.

(a) The engine shall be unloaded and operated at idle speed.

(b) The engine shall be operated with maximum operator demand 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, or at a constant rate such that it takes 4 to 6 min to sweep 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.

When selecting option (b) in paragraph 7.4.7 for determining negative reference torque, the mapping curve may directly continue with minimum operator demand from maximum to minimum mapping speed.

7.4.4. 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 shall 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 paragraph for reasons of safety or representativeness shall be approved by the type approval authority along with the justification for their use. In no case, however, the torque curve shall be run by descending engine speeds for governed or turbocharged engines.

7.4.5. Replicate tests

An engine need not be mapped before each and every test cycle. An engine shall be remapped prior to a test cycle if:

(a) an unreasonable amount of time has transpired since the last map, as determined by engineering judgement, or

(b) physical changes or recalibrations have been made to the engine which potentially affect engine performance.

7.4.6. Denormalisation of engine speed

For generating the reference cycles, the normalised speeds of Appendix 1 (WHTC) and table 1 (WHSC) shall be denormalised using the following equation:

(9)

For determination of n pref, the integral of the maximum torque shall be calculated from n idle to n 95h from the engine mapping curve, as determined in accordance with paragraph 7.4.3.

The engine speeds in figures 4 and 5 are defined, as follows:

n lo is the lowest speed where the power is 55 per cent of maximum power n pref is the engine speed where the integral of max. mapped torque is 51 per cent of the whole integral between n idle and n 95h n hi is the highest speed where the power is 70 per cent of maximum power n idle is the idle speed n 95h is the highest speed where the power is 95 per cent of maximum power

For engines (mainly positive ignition engines) with a steep governor droop curve, where fuel cut off does not permit to operate the engine up to n hi or n 95h, the following provisions apply:

n hi in equation 9 is replaced with n Pmax × 1,02 n 95h is replaced with n Pmax × 1,02

7.4.7. Denormalisation of engine torque

The torque values in the engine dynamometer schedule of Appendix 1 (WHTC) and in table 1 (WHSC) are normalised to the maximum torque at the respective speed. For generating the reference cycles, the torque values for each individual reference speed value as determined in paragraph 7.4.6 shall be denormalised, using the mapping curve determined according to paragraph 7.4.3, as follows:

(10)

where:

M norm,i is the normalised torque, per cent M max,i is the maximum torque from the mapping curve, Nm M f,i is the torque absorbed by auxiliaries/equipment to be fitted, Nm M r,i is the torque absorbed by auxiliaries/equipment to be removed, Nm

If auxiliaries/equipment are fitted in accordance with paragraph 6.3.1 and Appendix 7, M f and M r are zero.

The negative torque values of the motoring points (m in Appendix 1) shall take on, for purposes of reference cycle generation, reference values determined in either of the following ways:

(a) negative 40 per cent of the positive torque available at the associated speed point;

(b) mapping of the negative torque required to motor the engine from maximum to minimum mapping speed;

(c) determination of the negative torque required to motor the engine at idle and at n hi and linear interpolation between these two points.

7.4.8. Calculation of reference cycle work

Reference cycle work shall be determined over the test cycle by synchronously calculating instantaneous values for engine power from reference speed and reference torque, as determined in paragraphs 7.4.6 and 7.4.7. Instantaneous engine power values shall be integrated over the test cycle to calculate the reference cycle work W ref (kWh). If auxiliaries are not fitted in accordance with paragraph 6.3.1, the instantaneous power values shall be corrected using equation (4) in paragraph 6.3.5.

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 actual cycle work, any negative torque values shall be set equal to zero and included. If integration is performed at a frequency of less than 5 Hz, 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.

7.5. Pre-test procedures

7.5.1. Installation of the measurement equipment

The instrumentation and sample probes shall be installed as required. The tailpipe shall be connected to the full flow dilution system, if used.

7.5.2. Preparation of measurement equipment for sampling

The following steps shall be taken before emission sampling begins:

(a) Leak checks shall be performed within 8 hours prior to emission sampling according to paragraph 9.3.4.

(b) For batch sampling, clean storage media shall be connected, such as evacuated bags.

(c) All measurement instruments shall be started according to the instrument manufacturer’s instructions and good engineering judgment.

(d) Dilution systems, sample pumps, cooling fans, and the data-collection system shall be started.

(e) The sample flow rates shall be adjusted to desired levels, using bypass flow, if desired.

(f) Heat exchangers in the sampling system shall be pre-heated or pre-cooled to within their operating temperature ranges for a test.

(g) Heated or cooled components such as sample lines, filters, coolers, and pumps shall be allowed to stabilise at their operating temperatures.

(h) Exhaust dilution system flow shall be switched on at least 10 minutes before a test sequence.

(i) Any electronic integrating devices shall be zeroed or re-zeroed, before the start of any test interval.

7.5.3. Checking the gas analysers

Gas analyser ranges shall be selected. Emission analysers with automatic or manual range switching are permitted. During the test cycle, the range of the emission analysers shall not be switched. At the same time the gains of an analyser’s analogue operational amplifier(s) may not be switched during the test cycle.

Zero and span response shall be determined for all analysers using internationally-traceable gases that meet the specifications of paragraph 9.3.3. FID analysers shall be spanned on a carbon number basis of one (C1).

7.5.4. Preparation of the particulate sampling filter

At least one hour before the test, the 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, the filter shall be weighed and the tare weight shall be recorded. The filter shall then be stored in a closed petri dish or sealed filter holder until needed for testing. The filter shall be used within eight hours of its removal from the weighing chamber.

7.5.5. 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).

7.5.6. Starting the particulate sampling system

The particulate sampling system shall be started and operated on by-pass. The particulate background level of the diluent may be determined by sampling the diluent prior to the entrance of the exhaust gas into the dilution tunnel. The measurement may be done prior to or after the test. If the measurement is done both at the beginning and at the end of the cycle, the values may be averaged. If a different sampling system is used for background measurement, the measurement shall be done in parallel to the test run.

7.6. WHTC cycle run

7.6.1. Engine cool-down

A natural or forced cool-down procedure may be applied. For forced cool-down, good engineering judgment shall be used to set up systems to send cooling air across the engine, to send cool oil through the engine lubrication system, to remove heat from the coolant through the engine cooling system, and to remove heat from an exhaust after-treatment system. In the case of a forced after-treatment system cool down, cooling air shall not be applied until the after-treatment system has cooled below its catalytic activation temperature. Any cooling procedure that results in unrepresentative emissions is not permitted.

7.6.2. Cold start test

The cold-start test shall be started when the temperatures of the engine’s lubricant, coolant, and after-treatment systems are all between 293 and 303 K (20 and 30 °C). The engine shall be started using one of the following methods:

(a) the engine shall be started as recommended in the owners manual using a production starter motor and adequately charged battery or a suitable power supply, or

(b) the engine shall be started by using the dynamometer. The engine shall be motored within ± 25 per cent of its typical in-use cranking speed. Cranking shall be stopped within 1 second after the engine is running. If the engine does not start after 15 seconds of cranking, cranking shall be stopped and the reason for the failure to start determined, unless the owners manual or the service-repair manual describes the longer cranking time as normal.

7.6.3. Hot soak period

Immediately upon completion of the cold start test, the engine shall be conditioned for the hot start test using a 10 ± 1 minutes hot soak period.

7.6.4. Hot start test

The engine shall be started at the end of the hot soak period as defined in paragraph 7.6.3. using the starting methods given in paragraph 7.6.2.

7.6.5. Test sequence

The test sequence of both cold start and hot start test shall commence at the start of the engine. After the engine is running, cycle control shall be initiated so that engine operation matches the first set point of the cycle.

The WHTC shall be performed according to the reference cycle as set out in paragraph 7.4. 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. Actual engine speed and torque shall be recorded at least once every second during the test cycle (1 Hz), and the signals may be electronically filtered.

7.6.6. Collection of emission relevant data

At the start of the test sequence, the measuring equipment shall be started, simultaneously:

(a) start collecting or analysing diluent air, if a full flow dilution system is used;

(b) start collecting or analysing raw or diluted exhaust gas, depending on the method used;

(c) start measuring the amount of diluted exhaust gas and the required temperatures and pressures;

(d) start recording the exhaust gas mass flow rate, if raw exhaust gas analysis is used;

(e) start recording the feedback data of speed and torque of the dynamometer.

If raw exhaust measurement is used, the emission concentrations ((NM)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, CO2, and NMHC may be determined by integration of continuous measurement signals or by analysing the concentrations in the sample bag, collected over the cycle. The concentrations of the gaseous pollutants in the diluent shall be determined prior to the point where the exhaust enters into the dilution tunnel by integration or by collecting into the background bag. All other parameters that need to be measured shall be recorded with a minimum of one measurement per second (1 Hz).

7.6.7. Particulate sampling

At the start of the test sequence, 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 controlled, so that the flow rate through the particulate sample probe or transfer tube is maintained proportional to the exhaust mass flow rate as determined in accordance with paragraph 9.4.6.1.

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 ±2,5 per cent of the set flow rate. If flow compensation (i.e. proportional control of sample flow) is used, it shall be demonstrated that the ratio of main tunnel flow to particulate sample flow does not change by more than ±2,5 per cent of its set value (except for the first 10 seconds of sampling). 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 ±2,5 per cent because of high particulate loading on the filter, the test shall be voided. The test shall be rerun using a lower sample flow rate.

7.6.8. Engine stalling and equipment malfunction

If the engine stalls anywhere during the cold start test, the test shall be voided. The engine shall be preconditioned and restarted according to the requirements of paragraph 7.6.2, and the test repeated.

If the engine stalls anywhere during the hot start test, the hot start test shall be voided. The engine shall be soaked according to paragraph 7.6.3, and the hot start test repeated. In this case, the cold start test need not be repeated.

If a malfunction occurs in any of the required test equipment during the test cycle, the test shall be voided and repeated in line with the above provisions.

7.7. WHSC cycle run

7.7.1. Preconditioning the dilution system and the engine

The dilution system and the engine shall be started and warmed up in accordance with paragraph 7.4.1. After warm-up, the engine and sampling system shall be preconditioned by operating the engine at mode 9 (see paragraph 7.2.2, table 1) for a minimum of 10 minutes while simultaneously operating the dilution system. Dummy particulate emissions samples may be collected. Those sample filters need not be stabilised or weighed, and may be discarded. Flow rates shall be set at the approximate flow rates selected for testing. The engine shall be shut off after preconditioning.

7.7.2. Engine starting

5 ± 1 minutes after completion of preconditioning at mode 9 as described in paragraph 7.7.1, the engine shall be started according to the manufacturer’s recommended starting procedure in the owner’s manual, using either a production starter motor or the dynamometer in accordance with paragraph 7.6.2.

7.7.3. Test sequence

The test sequence shall commence after the engine is running and within one minute after engine operation is controlled to match the first mode of the cycle (idle).

The WHSC shall be performed according to the order of test modes listed in table 1 of paragraph 7.2.2.

7.7.4. Collection of emission relevant data

At the start of the test sequence, the measuring equipment shall be started, simultaneously:

(a) start collecting or analysing diluent, if a full flow dilution system is used;

(b) start collecting or analysing raw or diluted exhaust gas, depending on the method used;

(c) start measuring the amount of diluted exhaust gas and the required temperatures and pressures;

(d) start recording the exhaust gas mass flow rate, if raw exhaust gas analysis is used;

(e) start recording the feedback data of speed and torque of the dynamometer.

If raw exhaust measurement is used, the emission concentrations ((NM)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, CO2, and NMHC may be determined by integration of continuous measurement signals or by analysing the concentrations in the sample bag, collected over the cycle. The concentrations of the gaseous pollutants in the diluent shall be determined prior to the point where the exhaust enters into the dilution tunnel by integration or by collecting into the background bag. All other parameters that need to be measured shall be recorded with a minimum of one measurement per second (1 Hz).

7.7.5. Particulate sampling

At the start of the test sequence, 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 controlled, so that the flow rate through the particulate sample probe or transfer tube is maintained proportional to the exhaust mass flow rate as determined in accordance with paragraph 9.4.6.1.

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 ±2,5 per cent of the set flow rate. If flow compensation (i.e. proportional control of sample flow) is used, it shall be demonstrated that the ratio of main tunnel flow to particulate sample flow does not change by more than ±2,5 per cent of its set value (except for the first 10 seconds of sampling). 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 ±2,5 per cent because of high particulate loading on the filter, the test shall be voided. The test shall be rerun using a lower sample flow rate.

7.7.6. Engine stalling and equipment malfunction

If the engine stalls anywhere during the cycle, the test shall be voided. The engine shall be preconditioned according to paragraph 7.7.1 and restarted according to paragraph 7.7.2, and the test repeated.

If a malfunction occurs in any of the required test equipment during the test cycle, the test shall be voided and repeated in line with the above provisions.

7.8. Post-test procedures

7.8.1. 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.

7.8.2. Verification of proportional sampling

For any proportional batch sample, such as a bag sample or PM sample, it shall be verified that proportional sampling was maintained according to paragraphs 7.6.7 and 7.7.5. Any sample that does not fulfil the requirements shall be voided.

7.8.3. PM conditioning and weighing

The particulate filter shall be placed into covered or sealed containers or the filter holders shall be closed, in order to protect the sample filters against ambient contamination. Thus protected, the filter shall be returned to the weighing chamber. The filter shall be conditioned for at least one hour, and then weighed according to paragraph 9.4.5. The gross weight of the filter shall be recorded.

7.8.4. Drift verification

As soon as practical but no later than 30 minutes after the test cycle is complete or during the soak period, the zero and span responses of the gaseous analyser ranges used shall be determined. For the purpose of this paragraph, test cycle is defined as follows:

(a) for the WHTC: the complete sequence cold — soak — hot;

(b) for the WHTC hot start test (paragraph 6.6): the sequence soak — hot;

(c) for the multiple regeneration WHTC hot start test (paragraph 6.6): the total number of hot start tests;

(d) for the WHSC: the test cycle.

The following provisions apply for analyser drift:

(a) the pre-test zero and span and post-test zero and span responses may be directly inserted into equation 66 of paragraph 8.6.1 without determining drift;

(b) if the drift difference between the pre-test and post-test results is less than 1 per cent of full scale, the measured concentrations may be used uncorrected or may be corrected for drift according to paragraph 8.6.1;

(c) if the drift difference between the pre-test and post-test results is equal to or greater than 1 per cent of full scale, the test shall be voided or the measured concentrations shall be corrected for drift according to paragraph 8.6.1.

7.8.5. Analysis of gaseous bag sampling

As soon as practical, the following shall be performed:

(a) gaseous bag samples shall be analysed no later than 30 minutes after the hot start test is complete or during the soak period for the cold start test;

(b) background samples shall be analysed no later than 60 minutes after the hot start test is complete.

7.8.6. Validation of cycle work

Before calculating actual cycle work, any points recorded during engine starting shall be omitted. Actual cycle work shall be determined over the test cycle by synchronously using actual speed and actual torque values to calculate instantaneous values for engine power. Instantaneous engine power values shall be integrated over the test cycle to calculate the actual cycle work W act (kWh). If auxiliaries/equipment are not fitted in accordance with paragraph 6.3.1, the instantaneous power values shall be corrected using equation (4) in paragraph 6.3.5.

The same methodology as described in paragraph 7.4.8 shall be used for integrating actual engine power.

The actual cycle work W act is used for comparison to the reference cycle work W ref and for calculating the brake specific emissions (see paragraph 8.6.3).

W act shall be between 85 per cent and 105 per cent of W ref.

7.8.7. Validation statistics of the test cycle

Linear regressions of the actual values (n act, M act, P act) on the reference values (n ref, M ref, P ref) shall be performed for both the WHTC and the WHSC.

To minimise the biasing effect of the time lag between the actual and reference cycle values, the entire engine speed and torque actual signal sequence may be advanced or delayed in time with respect to the reference speed and torque sequence. If the actual signals are shifted, both speed and torque shall be shifted the same amount in the same direction.

The method of least squares shall be used, with the best-fit equation having the form:

(11)

where:

y is the actual value of speed (min–1), torque (Nm), or power (kW) a1 is the slope of the regression line x is the reference value of speed (min–1), torque (Nm), or power (kW) a0 is the y intercept of the regression line

The standard error of estimate (SEE) 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 Hz. For a test to be considered valid, the criteria of table 2 (WHTC) or table 3 (WHSC) shall be met.

Table 2

Regression line tolerances for the WHTC

Speed Torque Power Standard error of estimate (SEE) of y on x maximum 5 per cent of maximum test speed maximum 10 per cent of maximum engine torque maximum 10 per cent of maximum engine power Slope of the regression line, a1 0,95 to 1,03 0,83 – 1,03 0,89 – 1,03 Coefficient of determination, r2 minimum 0,970 minimum 0,850 minimum 0,910 y intercept of the regression line, a0 maximum 10 per cent of idle speed ± 20 Nm or ± 2 per cent of maximum torque whichever is greater ± 4 kW or ± 2 per cent of maximum power whichever is greater





Table 3

Regression line tolerances for the WHSC

Speed Torque Power Standard error of estimate (SEE) of y on x maximum 1 per cent of maximum test speed maximum 2 per cent of maximum engine torque maximum 2 per cent of maximum engine power Slope of the regression line, a1 0,99 to 1,01 0,98 – 1,02 0,98 – 1,02 Coefficient of determination, r2 minimum 0,990 minimum 0,950 minimum 0,950 y intercept of the regression line, a0 maximum 1 per cent of maximum test speed ± 20 Nm or ± 2 per cent of maximum torque whichever is greater ± 4 kW or ± 2 per cent of maximum power whichever is greater

For regression purposes only, point omissions are permitted where noted in table 4 before doing the regression calculation. However, those points shall not be omitted for the calculation of cycle work and emissions. Point omission may be applied to the whole or to any part of the cycle.

Table 4

Permitted point omissions from regression analysis

Event Conditions Permitted point omissions Minimum operator demand (idle point) n ref = 0 per cent and M ref = 0 per cent and M act > (M ref – 0,02M max. mapped torque) and M act < (M ref + 0,02M max. mapped torque) speed and power Minimum operator demand (motoring point) M ref < 0 per cent power and torque Minimum operator demand n act ≤ 1,02 n ref and M act > M ref or n act > n ref and M act ≤ M ref' or n act > 1,02 n ref and M ref < M act ≤ (M ref + 0,02M max. mapped torque) power and either torque or speed Maximum operator demand n act < n ref and M act ≥ M ref or n act ≥ 0,98 n ref and M act < M ref or n act < 0,98 n ref and M ref > M act ≥ (M ref – 0,02M max. mapped torque) power and either torque or speed

8. EMISSION CALCULATION

The final test result shall be rounded in one step to the number of places to the right of the decimal point indicated by the applicable emission standard plus one additional significant figure, in accordance with ASTM E 29-06B. No rounding of intermediate values leading to the final break-specific emission result is permitted.

Examples of the calculation procedures are given in Appendix 6.

Emissions calculation on a molar basis, in accordance with Annex 7 of gtr No [xx] concerning the exhaust emission test protocol for Non-Road Mobile Machinery (NRMM), is permitted with the prior agreement of the type approval authority.

8.1. Dry/wet correction

If the emissions are measured on a dry basis, the measured concentration shall be converted to a wet basis according to the following equation:

(12)

where:

c d is the dry concentration in ppm or per cent volume kw is the dry/wet correction factor (k w,a, k w,e, or k w,d depending on respective equation used)

8.1.1. Raw exhaust gas

(13)

or

(14)

or

(15)

with

(16)

and

(17)

where:

H a is the intake air humidity, g water per kg dry air w ALF is the hydrogen content of the fuel, per cent mass q mf,i is the instantaneous fuel mass flow rate, kg/s q mad,I is the instantaneous dry intake air mass flow rate, kg/s p r is the water vapour pressure after cooling bath, kPa p b is the total atmospheric pressure, kPa w DEL is the nitrogen content of the fuel, per cent mass w EPS is the oxygen content of the fuel, per cent mass α is the molar hydrogen ratio of the fuel c CO2 is the dry CO2 concentration, per cent c CO is the dry CO concentration, per cent

Equations (13) and (14) are principally identical with the factor 1,008 in equations (13) and (15) being an approximation for the more accurate denominator in equation (14).

8.1.2. Diluted exhaust gas

(18)

or

(19)

with

(20)

where:

α is the molar hydrogen ratio of the fuel c CO2w is the wet CO2 concentration, per cent c CO2d is the dry CO2 concentration, per cent H d is the diluent humidity, g water per kg dry air H a is the intake air humidity, g water per kg dry air D is the dilution factor (see paragraph 8.5.2.3.2)

8.1.3. Diluent

(21)

with

(22)

where:

H d is the diluent humidity, g water per kg dry air

8.2. NOx correction for humidity

As the NOx emission depends on ambient air conditions, the NOx concentration shall be corrected for humidity with the factors given in paragraph 8.2.1 or 8.2.2. The intake air humidity Ha may be derived from relative humidity measurement, dew point measurement, vapour pressure measurement or dry/wet bulb measurement using generally accepted equations.

8.2.1. Compression-ignition engines

(23)

where:

H a is the intake air humidity, g water per kg dry air

8.2.2. Positive ignition engines

(24)

where:

H a is the intake air humidity, g water per kg dry air

8.3. Particulate filter buoyancy correction

The sampling filter mass shall be corrected for its buoyancy in air. The buoyancy correction depends on sampling filter density, air density and the density of the balance calibration weight, and does not account for the buoyancy of the PM itself. The buoyancy correction shall be applied to both tare filter mass and gross filter mass.

If the density of the filter material is not known, the following densities shall be used:

(a) teflon coated glass fiber filter: 2 300 kg/m3

(b) teflon membrane filter: 2 144 kg/m3

(c) teflon membrane filter with polymethylpentene support ring: 920 kg/m3

For stainless steel calibration weights, a density of 8 000 kg/m3 shall be used. If the material of the calibration weight is different, its density shall be known.

The following equation shall be used:

(25)

with

(26)

where:

m uncor is the uncorrected particulate filter mass, mg ρ a is the density of the air, kg/m3 ρ w is the density of balance calibration weight, kg/m3 ρ f is the density of the particulate sampling filter, kg/m3 p b is the total atmospheric pressure, kPa T a is the air temperature in the balance environment, K 28,836 is the molar mass of the air at reference humidity (282,5 K), g/mol 8,3144 is the molar gas constant

The particulate sample mass mp used in paragraphs 8.4.3 and 8.5.3 shall be calculated as follows:

(27)

where:

m f,G is the buoyancy corrected gross particulate filter mass, mg m f,T is the buoyancy corrected tare particulate filter mass, mg

8.4. Partial flow dilution (PFS) and raw gaseous measurement

The instantaneous concentration signals of the gaseous components are used for the calculation of the mass emissions by multiplication with the instantaneous exhaust mass flow rate. The exhaust mass flow rate may be measured directly, or calculated using the methods of intake air and fuel flow measurement, tracer method or intake air and air/fuel ratio measurement. Special attention shall be paid to the response times of the different instruments. These differences shall be accounted for by time aligning the signals. For particulates, the exhaust mass flow rate signals are used for controlling the partial flow dilution system to take a sample proportional to the exhaust mass flow rate. The quality of proportionality shall be checked by applying a regression analysis between sample and exhaust flow in accordance with paragraph 9.4.6.1. The complete test set up is schematically shown in figure 6.

8.4.1. Determination of exhaust gas mass flow

8.4.1.1. Introduction

For calculation of the emissions in the raw exhaust gas and for controlling of a partial flow dilution system, it is necessary to know the exhaust gas mass flow rate. For the determination of the exhaust mass flow rate, either of the methods described in paragraphs 8.4.1.3 to 8.4.1.7 may be used.

8.4.1.2. Response time

For the purpose of emissions calculation, the response time of either method described in paragraphs 8.4.1.3 to 8.4.1.7 shall be equal to or less than the analyser response time of ≤ 10 s, as required in paragraph 9.3.5.

For the purpose of controlling of a partial flow dilution system, a faster response is required. For partial flow dilution systems with online control, the response time shall be ≤ 0,3 s. For partial flow dilution systems with look-ahead control based on a pre-recorded test run, the response time of the exhaust flow measurement system shall be ≤ 5 s with a rise time of ≤ 1 s. The system response time shall be specified by the instrument manufacturer. The combined response time requirements for the exhaust gas flow and partial flow dilution system are indicated in paragraph 9.4.6.1.

8.4.1.3. Direct measurement method

Direct measurement of the instantaneous exhaust flow shall be done by systems, such as:

(a) pressure differential devices, like flow nozzle, (details see ISO 5167);

(b) ultrasonic flowmeter;

(c) vortex flowmeter.

Precautions shall be taken to avoid measurement errors which will impact emission value errors. Such precautions include the careful installation of the device in the engine exhaust system according to the instrument manufacturers’ recommendations and to good engineering practice. Especially, engine performance and emissions shall not be affected by the installation of the device.

The flowmeters shall meet the linearity requirements of paragraph 9.2.

8.4.1.4. 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 shall be as follows:

(28)

where:

q mew,i is the instantaneous exhaust mass flow rate, kg/s q maw,i is the instantaneous intake air mass flow rate, kg/s q mf,i is the instantaneous fuel mass flow rate, kg/s

The flowmeters shall meet the linearity requirements of paragraph 9.2, but shall be accurate enough to also meet the linearity requirements for the exhaust gas flow.

8.4.1.5. Tracer measurement method

This involves measurement of the concentration of a tracer gas in the exhaust.

A known amount of an inert gas (e.g. pure helium) shall be injected into the exhaust gas flow as a tracer. The gas is mixed and diluted by the exhaust gas, but shall not react in the exhaust pipe. The concentration of the gas shall then be measured in the exhaust gas sample.

In order to ensure complete mixing of the tracer gas, the exhaust gas sampling probe shall be located at least 1 m or 30 times the diameter of the exhaust pipe, whichever is larger, downstream of the tracer gas injection point. The sampling probe may be located closer to the injection point if complete mixing is verified by comparing the tracer gas concentration with the reference concentration when the tracer gas is injected upstream of the engine.

The tracer gas flow rate shall be set so that the tracer gas concentration at engine idle speed after mixing becomes lower than the full scale of the trace gas analyser.

The calculation of the exhaust gas flow shall be as follows:

(29)

where:

q mew,i is the instantaneous exhaust mass flow rate, kg/s q vt is tracer gas flow rate, cm3/min c mix,i is the instantaneous concentration of the tracer gas after mixing, ppm ρ e is the density of the exhaust gas, kg/m3 (cf. table 4) c b is the background concentration of the tracer gas in the intake air, ppm

The background concentration of the tracer gas (c b) 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 per cent of the concentration of the tracer gas after mixing (c mix.i) at maximum exhaust flow, the background concentration may be neglected.

The total system shall meet the linearity requirements for the exhaust gas flow of paragraph 9.2.

8.4.1.6. Airflow and air to fuel ratio measurement method

This involves exhaust mass calculation from the air flow and the air to fuel ratio. The calculation of the instantaneous exhaust gas mass flow is as follows:

(30)

with

(31)

(32)

where:

q maw,i is the instantaneous intake air mass flow rate, kg/s A/F st is the stoichiometric air to fuel ratio, kg/kg λ i is the instantaneous excess air ratio c CO2d is the dry CO2 concentration, per cent c COd is the dry CO concentration, ppm c HCw is the wet HC concentration, ppm

Airflowmeter and analysers shall meet the linearity requirements of paragraph 9.2, and the total system shall meet the linearity requirements for the exhaust gas flow of paragraph 9.2.

If an air to fuel ratio measurement equipment such as a zirconia-type sensor is used for the measurement of the excess air ratio, it shall meet the specifications of paragraph 9.3.2.7.

8.4.1.7. Carbon balance method

This involves exhaust mass calculation from the fuel flow and the gaseous exhaust components that include carbon. The calculation of the instantaneous exhaust gas mass flow is as follows:

(33)

with

(34)

and

(35)

where:

q mf,i is the instantaneous fuel mass flow rate, kg/s H a is the intake air humidity, g water per kg dry air w BET is the carbon content of the fuel, per cent mass w ALF is the hydrogen content of the fuel, per cent mass w DEL is the nitrogen content of the fuel, per cent mass w EPS is the oxygen content of the fuel, per cent mass c CO2d is the dry CO2 concentration, per cent c CO2d,a is the dry CO2 concentration of the intake air, per cent c CO is the dry CO concentration, ppm c HCw is the wet HC concentration, ppm

8.4.2. Determination of the gaseous components

8.4.2.1. Introduction

The gaseous components in the raw exhaust gas emitted by the engine submitted for testing shall be measured with the measurement and sampling systems described in paragraph 9.3 and Appendix 3. The data evaluation is described in paragraph 8.4.2.2.

Two calculation procedures are described in paragraphs 8.4.2.3 and 8.4.2.4, which are equivalent for the reference fuel of Appendix 2. The procedure in paragraph 8.4.2.3 is more straightforward, since it uses tabulated u values for the ratio between component and exhaust gas density. The procedure in paragraph 8.4.2.4 is more accurate for fuel qualities that deviate from the specifications in Appendix 2, but requires elementary analysis of the fuel composition.

8.4.2.2. Data evaluation

The emission relevant data shall be recorded and stored in accordance with paragraph 7.6.6.

For calculation of the mass emission of the gaseous components, the traces of the recorded concentrations and the trace of the exhaust gas mass flow rate shall be time aligned by the transformation time as defined in paragraph 3.1.30. Therefore, the response time of each gaseous emissions analyser and of the exhaust gas mass flow system shall be determined according to paragraphs 8.4.1.2 and 9.3.5, respectively, and recorded.

8.4.2.3. Calculation of mass emission based on tabulated values

The mass of the pollutants (g/test) shall be determined by calculating the instantaneous mass emissions from the raw concentrations of the pollutants and the exhaust gas mass flow, aligned for the transformation time as determined in accordance with paragraph 8.4.2.2, integrating the instantaneous values over the cycle, and multiplying the integrated values with the u values from table 5. If measured on a dry basis, the dry/wet correction according to paragraph 8.1 shall be applied to the instantaneous concentration values before any further calculation is done.

For the calculation of NOx, the mass emission shall be multiplied, where applicable, with the humidity correction factor k h,D, or k h,G, as determined according to paragraph 8.2.

The following equation shall be applied:

(in g/test) (36)

where:

u gas is the respective value of the exhaust component from table 5 c gas,i is the instantaneous concentration of the component in the exhaust gas, ppm q mew,i is the instantaneous exhaust mass flow, kg/s f is the data sampling rate, Hz n is the number of measurements

Table 5

Raw exhaust gas u values and component densities

Fuel ρ e Gas NOx CO HC CO2 O2 CH4 ρ gas [kg/m3] 2,053 1,250 (2) 1,9636 1,4277 0,716 u gas (3) Diesel 1,2943 0,001586 0,000966 0,000479 0,001517 0,001103 0,000553 Ethanol 1,2757 0,001609 0,000980 0,000805 0,001539 0,001119 0,000561 CNG (4) 1,2661 0,001621 0,000987 0,000528 (5) 0,001551 0,001128 0,000565 Propane 1,2805 0,001603 0,000976 0,000512 0,001533 0,001115 0,000559 Butane 1,2832 0,001600 0,000974 0,000505 0,001530 0,001113 0,000558 LPG (6) 1,2811 0,001602 0,000976 0,000510 0,001533 0,001115 0,000559

8.4.2.4. Calculation of mass emission based on exact equations

The mass of the pollutants (g/test) shall be determined by calculating the instantaneous mass emissions from the raw concentrations of the pollutants, the u values and the exhaust gas mass flow, aligned for the transformation time as determined in accordance with paragraph 8.4.2.2 and integrating the instantaneous values over the cycle. If measured on a dry basis, the dry/wet correction according to paragraph 8.1 shall be applied to the instantaneous concentration values before any further calculation is done.

For the calculation of NOx, the mass emission shall be multiplied with the humidity correction factor k h,D, or k h,G, as determined according to paragraph 8.2.

The following equation shall be applied:

(in g/test) (37)

where:

u gas,i is calculated from equation 38 or 39 c gas,i is the instantaneous concentration of the component in the exhaust gas, ppm q mew,i is the instantaneous exhaust mass flow, kg/s f is the data sampling rate, Hz n is the number of measurements

The instantaneous u values shall be calculated as follows:

(38)

or

(39)

with

(40)

where:

M gas is the molar mass of the gas component, g/mol (cf. Appendix 6) M e,i is the instantaneous molar mass of the exhaust gas, g/mol ρ gas is the density of the gas component, kg/m3 ρ e,i is the instantaneous density of the exhaust gas, kg/m3

The molar mass of the exhaust, M e, shall be derived for a general fuel composition CH α O ε N δ S γ under the assumption of complete combustion, as follows:

(41)

where:

q maw,i is the instantaneous intake air mass flow rate on wet basis, kg/s q mf,i is the instantaneous fuel mass flow rate, kg/s H a is the intake air humidity, g water per kg dry air M a is the molar mass of the dry intake air = 28,965 g/mol

The exhaust density ρ e shall be derived, as follows:

(42)

where:

q mad,i is the instantaneous intake air mass flow rate on dry basis, kg/s q mf,i is the instantaneous fuel mass flow rate, kg/s H a is the intake air humidity, g water per kg dry air k fw is the fuel specific factor of wet exhaust (equation 16) in paragraph 8.1.1.

8.4.3. Particulate determination

8.4.3.1. Data evaluation

The particulate mass shall be calculated according to equation 27 of paragraph 8.3. For the evaluation of the particulate concentration, the total sample mass (m sep) through the filter over the test cycle shall be recorded.

With the prior approval of the type approval authority, the particulate mass may be corrected for the particulate level of the diluent, as determined in paragraph 7.5.6, in line with good engineering practice and the specific design features of the particulate measurement system used.

8.4.3.2. Calculation of mass emission

Depending on system design, the mass of particulates (g/test) shall be calculated by either of the methods in paragraphs 8.4.3.2.1 or 8.4.3.2.2 after buoyancy correction of the particulate sample filter according to paragraph 8.3.

8.4.3.2.1. Calculation based on sample ratio

(43)

where:

m p is the particulate mass sampled over the cycle, mg r s is the average sample ratio over the test cycle

with

(44)

where:

m se is the sample mass over the cycle, kg m ew is the total exhaust mass flow over the cycle, kg m sep is the mass of diluted exhaust gas passing the particulate collection filters, kg m sed is the mass of diluted exhaust gas passing the dilution tunnel, kg

In case of the total sampling type system, m sep and m sed are identical.

8.4.3.2.2. Calculation based on dilution ratio

(45)

where:

m p is the particulate mass sampled over the cycle, mg m sep is the mass of diluted exhaust gas passing the particulate collection filters, kg m edf is the mass of equivalent diluted exhaust gas over the cycle, kg

The total mass of equivalent diluted exhaust gas mass over the cycle shall be determined as follows:

(46)

(47)

(48)

where:

q medf,i is the instantaneous equivalent diluted exhaust mass flow rate, kg/s q mew,i is the instantaneous exhaust mass flow rate, kg/s r d,i is the instantaneous dilution ratio q mdew,i is the instantaneous diluted exhaust mass flow rate, kg/s q mdw,i is the instantaneous diluent mass flow rate, kg/s f is the data sampling rate, Hz n is the number of measurements

8.5. Full flow dilution measurement (CVS)

The concentration signals, either by integration over the cycle or by bag sampling, of the gaseous components shall be used for the calculation of the mass emissions by multiplication with the diluted exhaust mass flow rate. The exhaust mass flow rate shall be measured with a constant volume sampling (CVS) system, which may use a positive displacement pump (PDP), a critical flow venturi (CFV) or a subsonic venturi (SSV) with or without flow compensation.

For bag sampling and particulate sampling, a proportional sample shall be taken from the diluted exhaust gas of the CVS system. For a system without flow compensation, the ratio of sample flow to CVS flow shall not vary by more than ±2,5 per cent from the set point of the test. For a system with flow compensation, each individual flow rate shall be constant within ±2,5 per cent of its respective target flow rate.

The complete test set up is schematically shown in figure 7.

8.5.1. Determination of the diluted exhaust gas flow

8.5.1.1. Introduction

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) by either of the methods described in paragraphs 8.5.1.2 to 8.5.1.4. If the total sample flow of particulates (m sep) exceeds 0,5 per cent of the total CVS flow (m ed), the CVS flow shall be corrected for m sep or the particulate sample flow shall be returned to the CVS prior to the flow measuring device.

8.5.1.2. PDP-CVS system

The calculation of the mass flow over the cycle is as follows, if the temperature of the diluted exhaust is kept within ± 6 K over the cycle by using a heat exchanger:

(49)

where:

V 0 is the volume of gas pumped per revolution under test conditions, m3/rev n P is the total revolutions of pump per test p p is the absolute pressure at pump inlet, kPa T is the average temperature of the diluted exhaust gas at pump inlet, K

If a system with flow compensation is used (i.e. without heat exchanger), the instantaneous mass emissions shall be calculated and integrated over the cycle. In this case, the instantaneous mass of the diluted exhaust gas shall be calculated as follows:

(50)

where:

n P,i is the total revolutions of pump per time interval

8.5.1.3. CFV-CVS system

The calculation of the mass flow over the cycle is as follows, if the temperature of the diluted exhaust is kept within ± 11 K over the cycle by using a heat exchanger:

(51)

where:

t is the cycle time, s K V is the calibration coefficient of the critical flow venturi for standard conditions, p p is the absolute pressure at venturi inlet, kPa T is the absolute temperature at venturi inlet, K

If a system with flow compensation is used (i.e. without heat exchanger), the instantaneous mass emissions shall be calculated and integrated over the cycle. In this case, the instantaneous mass of the diluted exhaust gas shall be calculated as follows:

(52)

where:

Δti is the time interval, s

8.5.1.4. SSV-CVS system

The calculation of the mass flow over the cycle shall be as follows, if the temperature of the diluted exhaust is kept within ± 11 K over the cycle by using a heat exchanger:

(53)

with

(54)

where:

A 0 is 0,006111 in SI units of d V is the diameter of the SSV throat, m C d is the discharge coefficient of the SSV p p is the absolute pressure at venturi inlet, kPa T is the temperature at the venturi inlet, K r p is the ratio of the SSV throat to inlet absolute static pressure, r D is the ratio of the SSV throat diameter, d, to the inlet pipe inner diameter D

If a system with flow compensation is used (i.e. without heat exchanger), the instantaneous mass emissions shall be calculated and integrated over the cycle. In this case, the instantaneous mass of the diluted exhaust gas shall be calculated as follows:

(55)

where:

Δt i is the time interval, s

The real time calculation shall be initialised with either a reasonable value for C d, such as 0,98, or a reasonable value of Q ssv. If the calculation is initialised with Q ssv, the initial value of Q ssv shall be used to evaluate the Reynolds number.

During all emissions tests, the Reynolds number at the SSV throat shall be in the range of Reynolds numbers used to derive the calibration curve developed in paragraph 9.5.4.

8.5.2. Determination of the gaseous components

8.5.2.1. Introduction

The gaseous components in the diluted exhaust gas emitted by the engine submitted for testing shall be measured by the methods described in Appendix 3. Dilution of the exhaust shall be done with filtered ambient air, synthetic air or nitrogen. The flow capacity of the full flow system shall be large enough to completely eliminate water condensation in the dilution and sampling systems. Data evaluation and calculation procedures are described in paragraphs 8.5.2.2 and 8.5.2.3.

8.5.2.2. Data evaluation

The emission relevant data shall be recorded and stored in accordance with paragraph 7.6.6.

8.5.2.3. Calculation of mass emission

8.5.2.3.1. Systems with constant mass flow

For systems with heat exchanger, the mass of the pollutants shall be determined from the following equation:

(in g/test) (56)

where:

u gas is the respective value of the exhaust component from table 6 c gas is the average background corrected concentration of the component, ppm m ed is the total diluted exhaust mass over the cycle, kg

If measured on a dry basis, the dry/wet correction according to paragraph 8.1 shall be applied.

For the calculation of NOx, the mass emission shall be multiplied, if applicable, with the humidity correction factor k h,D, or k h,G, as determined according to paragraph 8.2.

The u values are given in table 6. For calculating the u gas values, the density of the diluted exhaust gas has been assumed to be equal to air density. Therefore, the u gas values are identical for single gas components, but different for HC.

Table 6

Diluted exhaust gas u values and component densities

Fuel ρ de Gas NOx CO HC CO2 O2 CH4 ρ gas [kg/m3] 2,053 1,250 (7) 1,9636 1,4277 0,716 u gas (8) Diesel 1,293 0,001588 0,000967 0,000480 0,001519 0,001104 0,000553 Ethanol 1,293 0,001588 0,000967 0,000795 0,001519 0,001104 0,000553 CNG (9) 1,293 0,001588 0,000967 0,000517 (10) 0,001519 0,001104 0,000553 Propane 1,293 0,001588 0,000967 0,000507 0,001519 0,001104 0,000553 Butane 1,293 0,001588 0,000967 0,000501 0,001519 0,001104 0,000553 LPG (11) 1,293 0,001588 0,000967 0,000505 0,001519 0,001104 0,000553

Alternatively, the u values may be calculated using the exact calculation method generally described in paragraph 8.4.2.4, as follows:

(57)

where:

M gas is the molar mass of the gas component, g/mol (cf. Appendix 6) M e is the molar mass of the exhaust gas, g/mol M d is the molar mass of the diluent = 28,965 g/mol D is the dilution factor (see paragraph 8.5.2.3.2)

8.5.2.3.2. Determination of the background corrected concentrations

The average backgrou