Appendix 1

Test procedure for vehicle emissions testing with a Portable Emissions Measurement System (PEMS)

1.INTRODUCTION

This Appendix describes the test procedure to determine exhaust emissions from light passenger and commercial vehicles using a Portable Emissions Measurement System.

2.SYMBOLS, PARAMETERS AND UNITS

≤

smaller or equal

#

number

#/m3

number per cubic metre

%

per cent

°C

degree centigrade

g

gramme

g/s

gramme per second

h

hour

Hz

hertz

K

kelvin

kg

kilogramme

kg/s

kilogramme per second

km

kilometre

km/h

kilometre per hour

kPa

kilopascal

kPa/min

kilopascal per minute

l

litre

l/min

litre per minute

m

metre

m3

cubic-metre

mg

milligram

min

minute

pe

evacuated pressure [kPa]

qvs

volume flow rate of the system [l/min]

ppm

parts per million

ppmC1

parts per million carbon equivalent

rpm

revolutions per minute

s

second

Vs

system volume [l]

3.GENERAL REQUIREMENTS

3.1.PEMS

The test shall be carried out with a PEMS, composed of components specified in points 3.1.1 to 3.1.5. If applicable, a connection with the vehicle ECU may be established to determine relevant engine and vehicle parameters as specified in point 3.2.

3.1.1.

Analysers to determine the concentration of pollutants in the exhaust gas.

3.1.2.

One or multiple instruments or sensors to measure or determine the exhaust mass flow.

3.1.3.

A Global Positioning System to determine the position, altitude and, speed of the vehicle.

3.1.4.

If applicable, sensors and other appliances being not part of the vehicle, e.g., to measure ambient temperature, relative humidity, air pressure, and vehicle speed.

3.1.5.

An energy source independent of the vehicle to power the PEMS.

3.2.Test parameters

F1Test parameters as specified in Table 1 of this Appendix shall be measured at a constant frequency of 1,0 Hz or higher and recorded and reported in accordance with the requirements of Appendix 8 at a frequency of 1,0 Hz. If ECU parameters are available, these may be obtained at a substantially higher frequency but the recording rate shall be 1,0 Hz. The PEMS analysers, flow-measuring instruments and sensors shall comply with the requirements laid down in Appendices 2 and 3.

Table 1Test parameters

Parameter

Recommended unit

Source107

F2THC concentration100,103

ppm C1

Analyser

CH4 concentration100,103

ppm C1

Analyser

NMHC concentration100,103

ppm C1

Analyser105

CO concentration100,103

ppm

Analyser

CO2 concentration100

ppm

Analyser

NOX concentration100,103

ppm

Analyser106

PN concentration103

#/m3

Analyser

Exhaust mass flow rate

kg/s

EFM, any methods described in point 7 of Appendix 2

Ambient humidity

%

Sensor

Ambient temperature

K

Sensor

Ambient pressure

kPa

Sensor

Vehicle speed

km/h

Sensor, GPS, or ECU102

Vehicle latitude

Degree

GPS

Vehicle longitude

Degree

GPS

Vehicle altitude104,108

M

GPS or Sensor

Exhaust gas temperature104

K

Sensor

Engine coolant temperature104

K

Sensor or ECU

Engine speed104

rpm

Sensor or ECU

Engine torque104

Nm

Sensor or ECU

Torque at driven axle104

Nm

Rim torque meter

Pedal position104

%

Sensor or ECU

Engine fuel flow101

g/s

Sensor or ECU

Engine intake air flow101

g/s

Sensor or ECU

Fault status104

—

ECU

Intake air flow temperature

K

Sensor or ECU

Regeneration status104

—

ECU

Engine oil temperature104

K

Sensor or ECU

Actual gear104

#

ECU

Desired gear (e.g. gear shift indicator)104

#

ECU

Other vehicle data104

unspecified

ECU

to be measured on a wet basis or to be corrected as described in point 8.1 of Appendix 4

to be determined only if indirect methods are used to calculate exhaust mass flow rate as described in paragraphs 10.2 and 10.3 of Appendix 4

method to be chosen according to point 4.7

parameter only mandatory if measurement required by Annex IIIA, section 2.1

to be determined only if necessary to verify the vehicle status and operating conditions

may be calculated from THC and CH4 concentrations according to point 9.2 of Appendix 4

may be calculated from measured NO and NO2 concentrations

Multiple parameter sources may be used.

The preferable source is the ambient pressure sensor.

3.3.Preparation of the vehicle

The preparation of the vehicle shall include a general verification of the correct technical functioning of the test vehicle.

3.4.Installation of PEMS

F23.4.1.General:

The installation of the PEMS shall follow the instructions of the PEMS manufacturer and the local health and safety regulations. The PEMS should be installed as to minimise during the test electromagnetic interferences as well as exposure to shocks, vibration, dust and variability in temperature. The installation and operation of the PEMS shall be leak-tight and minimise heat loss. The installation and operation of PEMS shall not change the nature of the exhaust gas nor unduly increase the length of the tailpipe. To avoid the generation of particles, connectors shall be thermally stable at the exhaust gas temperatures expected during the test. It is recommended not to use elastomer connectors to connect the vehicle exhaust outlet and the connecting tube. Elastomer connectors, if used, shall have no contact with the exhaust gas to avoid artefacts at high engine load.

F13.4.2.Permissible backpressure

The installation and operation of the PEMS sampling probes shall not unduly increase the pressure at the exhaust outlet in a way that may influence the representativeness of the measurements. It is thus recommended that only one sampling probe is installed in the same plane. If technically feasible, any extension to facilitate the sampling or connection with the exhaust mass flow meter shall have an equivalent, or larger, cross sectional area than the exhaust pipe.

F13.4.3.Exhaust mass flow meter

Whenever used, the exhaust mass flow meter shall be attached to the vehicle's tailpipe(s) in accordance with the recommendations of the EFM manufacturer. The measurement range of the EFM shall match the range of the exhaust mass flow rate expected during the test. It is recommended to select the EFM in order to have the maximum expected flow rate during the test covering at least 75 % of the EFM full range. The installation of the EFM and any exhaust pipe adaptors or junctions shall not adversely affect the operation of the engine or exhaust after-treatment system. A minimum of four pipe diameters or 150 mm of straight tubing, whichever is larger, shall be placed at either side of the flow-sensing element. When testing a multi-cylinder engine with a branched exhaust manifold, it is recommended to position the exhaust mass flow meter downstream of where the manifolds combine and to increase the cross section of the piping such as to have an equivalent, or larger, cross sectional area from which to sample. If this is not feasible, exhaust flow measurements with several exhaust mass flow meters may be used. The wide variety of exhaust pipe configurations, dimensions and exhaust mass flow rates may require compromises, guided by good engineering judgement, when selecting and installing the EFM(s). It is permissible to install an EFM with a diameter smaller than that of the exhaust outlet or the total projected frontal area of multiple outlets, providing it improves measurement accuracy and does not adversely affect the operation or the exhaust after-treatment as specified in point 3.4.2. It is recommended to document the EFM set-up using photographs.

3.4.4.Global Positioning System (GPS)

The GPS antenna should be mounted, e.g. at the highest possible location, as to ensure good reception of the satellite signal. The mounted GPS antenna shall interfere as little as possible with the vehicle operation.

3.4.5.Connection with the Engine Control Unit (ECU)

If desired, relevant vehicle and engine parameters listed in Table 1 can be recorded by using a data logger connected with the ECU or the vehicle network through standards, such as ISO 15031-5 or SAE J1979, OBD-II, EOBD or WWH-OBD. If applicable, manufacturers shall disclose labels to allow the identification of required parameters.

3.4.6.Sensors and auxiliary equipment

Vehicle speed sensors, temperature sensors, coolant thermocouples or any other measurement device not part of the vehicle shall be installed to measure the parameter under consideration in a representative, reliable and accurate manner without unduly interfering with the vehicle operation and the functioning of other analysers, flow-measuring instruments, sensors and signals. Sensors and auxiliary equipment shall be powered independently of the vehicle. It is permitted to power any safety-related illumination of fixtures and installations of PEMS components outside of the vehicle’s cabin by the vehicle’s battery.

F23.5.Emissions sampling

Emissions sampling shall be representative and conducted at locations of well-mixed exhaust where the influence of ambient air downstream of the sampling point is minimal. If applicable, emissions shall be sampled downstream of the exhaust mass flow meter, respecting a distance of at least 150 mm to the flow sensing element. The sampling probes shall be fitted at least 200 mm or three times the inner diameter of the exhaust pipe, whichever is larger, upstream of the point at which the exhaust exits the PEMS sampling installation into the environment. If the PEMS feeds back a flow to the tail pipe, this shall occur downstream of the sampling probe in a manner that does not affect during engine operation the nature of the exhaust gas at the sampling point(s). If the length of the sampling line is changed, the system transport times shall be verified and if necessary corrected.

If the engine is equipped with an exhaust after-treatment system, the exhaust sample shall be taken downstream of the exhaust after-treatment system. When testing a vehicle with a branched exhaust manifold, the inlet of the sampling probe shall be located sufficiently far downstream so as to ensure that the sample is representative of the average exhaust emissions of all cylinders. In multi-cylinder engines, having distinct groups of manifolds, such as in a ‘V’ engine configuration, the sampling probe shall be positioned downstream of where the manifolds combine. If this is technically not feasible, multi-point sampling at locations of well-mixed exhaust may be used, if approved by the Type Approval Authority. In this case, the number and location of sampling probes shall match as far as possible those of the exhaust mass flow meters. In case of unequal exhaust flows, proportional sampling or sampling with multiple analysers shall be considered.

F1If the engine is equipped with an exhaust after-treatment system, the exhaust sample shall be taken downstream of the exhaust after- treatment system. When testing a vehicle with a branched exhaust manifold, the inlet of the sampling probe shall be located sufficiently far downstream so as to ensure that the sample is representative of the average exhaust emissions of all cylinders. In multi-cylinder engines having distinct groups of manifolds, such as in a ‘V’ engine configuration, the sampling probe shall be positioned downstream of the point where the manifolds combine. If this is technically not feasible, multi-point sampling at locations of well-mixed exhaust may be used. In this case, the number and location of sampling probes shall match as far as possible those of the exhaust mass flow meters. In case of unequal exhaust flows, proportional sampling or sampling with multiple analysers shall be considered.

If hydrocarbons are measured, the sampling line shall be heated to 463 ± 10 K (190 ± 10 °C). For the measurement of other gaseous components with or without cooler, the sampling line shall be kept at a minimum of 333 K (60 °C) to avoid condensation and to ensure appropriate penetration efficiencies of the various gases. For low pressure sampling systems, the temperature can be lowered corresponding to the pressure decrease provided that the sampling system ensures a penetration efficiency of 95 % for all regulated gaseous pollutants. If particles are sampled and not diluted at the tailpipe, the sampling line from the raw exhaust sample point to the point of dilution or particle detector shall be heated to a minimum of 373 K (100 °C). The residence time of the sample in the particle sampling line shall be less than 3 s until reaching first dilution or the particle detector.

All parts of the sampling system from the exhaust pipe up to the particle detector, which are in contact with raw or diluted exhaust gas, shall be designed to minimize deposition of particles. All parts shall be made from antistatic material to prevent electrostatic effects.

4.PRE-TEST PROCEDURES

4.1.PEMS leak check

After the installation of the PEMS is completed, a leak check shall be performed at least once for each PEMS-vehicle installation as prescribed by the PEMS manufacturer or as follows. The probe shall be disconnected from the exhaust system and the end plugged. The analyser pump shall be switched on. After an initial stabilization period all flow meters shall read approximately zero in the absence of a leak. Else, the sampling lines shall be checked and the fault be corrected.

The leakage rate on the vacuum side shall not exceed 0.5 per cent of the in-use flow rate for the portion of the system being checked. The analyser flows and bypass flows may be used to estimate the in-use flow rate.

Alternatively, the system may be evacuated to a pressure of at least 20 kPa vacuum (80 kPa absolute). After an initial stabilization period the pressure increase Δp (kPa/min) in the system shall not exceed:

Δp=peVs× qvs× 0.005math

Alternatively, a concentration step change at the beginning of the sampling line shall be introduced by switching from zero to span gas while maintaining the same pressure conditions as under normal system operation. If for a correctly calibrated analyser after an adequate period of time the reading is ≤ 99 per cent compared to the introduced concentration, the leakage problem shall be corrected.

F24.2.Starting and stabilizing the PEMS

The PEMS shall be switched on, warmed up and stabilized in accordance with the specifications of the PEMS manufacturer until key functional parameters, e.g., pressures, temperatures and flows have reached their operating set points before test start. To ensure correct functioning, the PEMS may be kept switched on or can be warmed up and stabilized during vehicle conditioning. The system shall be free of errors and critical warnings.

4.3.Preparing the sampling system

The sampling system, consisting of the sampling probe and sampling lines shall be prepared for testing by following the instruction of the PEMS manufacturer. It shall be ensured that the sampling system is clean and free of moisture condensation.

4.4.Preparing the Exhaust mass Flow Meter (EFM)

If used for measuring the exhaust mass flow, the EFM shall be purged and prepared for operation in accordance with the specifications of the EFM manufacturer. This procedure shall, if applicable, remove condensation and deposits from the lines and the associated measurement ports.

4.5.Checking and calibrating the analysers for measuring gaseous emissions

Zero and span calibration adjustments of the analysers shall be performed using calibration gases that meet the requirements of point 5 of Appendix 2. The calibration gases shall be chosen to match the range of pollutant concentrations expected during the RDE test. To minimize analyser drift, one should conduct the zero and span calibration of analysers at an ambient temperature that resembles, as closely as possible, the temperature experienced by the test equipment during the trip.

F14.6.Checking the analyser for measuring particle emissions

The zero level of the analyser shall be recorded by sampling HEPA filtered ambient air at an appropriate sampling point, usually at the inlet of the sampling line. The signal shall be recorded at a constant frequency which is a multiple of 1,0 Hz averaged over a period of 2 minutes; the final concentration shall be within the manufacturer's specifications, but shall not exceed 5 000 particles per cubic-centimetre.

4.7.Determining vehicle speed

Vehicle speed shall be determined by at least one of the following methods:

  1. (a)

    a GPS; if vehicle speed is determined by a GPS, the total trip distance shall be checked against the measurements of another method according to point 7 of Appendix 4.

  2. (b)

    a sensor (e.g., optical or micro-wave sensor); if vehicle speed is determined by a sensor, the speed measurements shall comply with the requirements of point 8 of Appendix 2, or alternatively, the total trip distance determined by the sensor shall be compared with a reference distance obtained from a digital road network or topographic map. The total trip distance determined by the sensor shall deviate by no more than 4 % from the reference distance.

  3. (c)

    the ECU; if vehicle speed is determined by the ECU, the total trip distance shall be validated according to point 3 of Appendix 3 and the ECU speed signal adjusted, if necessary to fulfil the requirements of point 3.3 of Appendix 3. Alternatively, the total trip distance as determined by the ECU can be compared with a reference distance obtained from a digital road network or topographic map. The total trip distance determined by the ECU shall deviate by no more than 4 % from the reference.

4.8.Check of PEMS set up

The correctness of connections with all sensors and, if applicable, the ECU shall be verified. If engine parameters are retrieved, it shall be ensured that the ECU reports values correctly (e.g., zero engine speed [rpm] while the combustion engine is in key-on-engine-off status). F2The PEMS shall function free of errors and critical warnings.

5.EMISSIONS TEST

F2F15.1.Test start

Test start (see Figure App.1.1) shall be defined by either:

  • the first ignition of the internal combustion engine;

  • or the first movement of the vehicle with speed greater than 1 km/h for OVC-HEVs and NOVC-HEVS starting with the internal combustion engine off.

Sampling, measurement and recording of parameters shall begin prior to the test start. Before the test start it shall be confirmed that all necessary parameters are recorded by the data logger.

To facilitate time alignment, it is recommended to record the parameters that are subject to time alignment either by a single data recording device or with a synchronised time stamp.

Figure App.1.1Test Start Sequence

Image_r00005

5.2.Test

Sampling, measurement and recording of parameters shall continue throughout the on-road test of the vehicle. The engine may be stopped and started, but emissions sampling and parameter recording shall continue. Any warning signals, suggesting malfunctioning of the PEMS, shall be documented and verified. If any error signal(s) appear during the test, the test shall be voided. Parameter recording shall reach a data completeness of higher than 99 %. Measurement and data recording may be interrupted for less than 1 % of the total trip duration but for no more than a consecutive period of 30 s solely in the case of unintended signal loss or for the purpose of PEMS system maintenance. Interruptions may be recorded directly by the PEMS but it is not permissible to introduce interruptions in the recorded parameter via the pre-processing, exchange or post-processing of data. If conducted, auto zeroing shall be performed against a traceable zero standard similar to the one used to zero the analyser. It is strongly recommended to initiate PEMS system maintenance during periods of zero vehicle speed.

F15.3.Test end

The end of the test (see Figure App.1.2) is reached when the vehicle has completed the trip and either when:

  • the internal combustion engine is switched off;

    or:

  • for OVC-HEVs and NOVC-HEVS finishing the test with the internal combustion engine off, the vehicle stops and the speed is lower than or equal to 1 km/h.

Excessive idling of the engine after the completion of the trip shall be avoided. The data recording shall continue until the response time of the sampling systems has elapsed. For vehicles with a signal detecting regeneration (see line 42 in the Transparency List 1 in Appendix 5 of Annex II), the OBD-check shall be performed and documented directly after data recording and before any further driven distance is driven.

Figure App.1.2Test End Sequence

Image_r00006

6.POST-TEST PROCEDURE

6.1.Checking the analysers for measuring gaseous emissions

The zero and span of the analysers of gaseous components shall be checked by using calibration gases identical to the ones applied under point 4.5 to evaluate the analyser's zero and response drift compared to the pre-test calibration. It is permissible to zero the analyser prior to verifying the span drift, if the zero drift was determined to be within the permissible range. The post-test drift check shall be completed as soon as possible after the test and before the PEMS, or individual analysers or sensors, are turned off or have switched into a non-operating mode. The difference between the pre-test and post-test results shall comply with the requirements specified in Table 2.

Table 2Permissible analyser drift over a PEMS test

F2Pollutant

Absolute Zero response drift

Absolute Span response drift109

CO2

≤ 2 000 ppm per test

≤ 2 % of reading or ≤ 2 000 ppm per test, whichever is larger

CO

≤ 75 ppm per test

≤ 2 % of reading or ≤ 75 ppm per test, whichever is larger

NOX

≤ 5 ppm per test

≤ 2 % of reading or ≤ 5 ppm per test, whichever is larger

CH4

≤ 10 ppm C1 per test

≤ 2 % of reading or ≤ 10 ppm C1 per test, whichever is larger

THC

≤ 10 ppm C1 per test

≤ 2 % of reading or ≤ 10 ppm C1 per test, whichever is larger

If the zero drift is within the permissible range, it is permissible to zero the analyser prior to verifying the span drift.

If the difference between the pre-test and post-test results for the zero and span drift is higher than permitted, all test results shall be voided and the test repeated.

F26.2.Checking the analyser for measuring particle emissions

The zero level of the analyser shall be recorded in accordance with point 4.6.

F16.3.Checking the on-road emission measurements

The span gas concentration that was used for the calibration of the analysers in accordance with paragraph 4.5 at the test start shall cover at least 90 % of the concentration values obtained from 99 % of the measurement of the valid parts of the emissions test. It is permissible that 1 % of the total number of measurements used for evaluation exceeds the used span gas by up to a factor of two. If these requirements are not met, the test shall be voided.