Document ID: chunk:federal_register_of_legislation:F2024L00447:reg:0:p39
Version: federal_register_of_legislation:F2024L00447
Segment Type: reg
Provision Reference: reg 0 (pt 39/57)
Character Range: 199238–202290

speed from different sources

To time align vehicle speed with the exhaust mass flow rate, it is first necessary to establish one valid speed trace. In case vehicle speed is obtained from multiple sources (e.g., the GNSS, a sensor or the ECU), the speed values shall be time aligned by cross-correlation.
              3.3.2. Vehicle speed with exhaust mass flow rate

Vehicle speed shall be time aligned with the exhaust mass flow rate by cross-correlation between the exhaust mass flow rate and the product of vehicle speed and positive acceleration.
              3.3.3. Further signals

The time alignment of signals whose values change slowly and within a small value range, e.g. ambient temperature, can be omitted.
              4. Emission measurements during stop of the combustion engine

Any instantaneous emissions or exhaust flow measurements obtained while the combustion engine is deactivated shall be recorded in the data exchange file.
              5. Correction of measured values

              5.0. Drift correction

         where:

cref,z   is the reference concentration of the zero gas (usually zero) [ppm]

cref,s   is the reference concentration of the span gas [ppm]

cpre,z   is the pre-test analyser concentration of the zero gas [ppm]

cpre,s   is the pre-test analyser concentration of the span gas [ppm]

cpost,z  is the post-test analyser concentration of the zero gas [ppm]

cpost,s  is the post-test analyser concentration of the span gas [ppm]

cgas     is the sample gas concentration [ppm]

       5.1. Dry-wet correction

If the emissions are measured on a dry basis, the measured concentrations shall be converted to a wet basis as:
where:
cwet  is the wet concentration of a pollutant in ppm or per cent volume

cdry  is the dry concentration of a pollutant in ppm or per cent volume

kw    is the dry-wet correction factor

              The following equation shall be used to calculate kw:

              where:

              where:

Ha    is the intake air humidity [g water per kg dry air]

cCO2  is the dry CO2 concentration [%]

cCO   is the dry CO concentration [%]

α     is the molar hydrogen ratio of the fuel (H/C)

       5.2. Correction of NOX for ambient humidity and temperature

              NOX emissions shall not be corrected for ambient temperature and humidity.

       5.3. Correction of negative emission results

Negative instantaneous results shall not be corrected.

       6. Determination of the instantaneous gaseous exhaust components

       6.1. Introduction

The components in the raw exhaust shall be measured with the measurement and sampling analysers described in Annex 5. The raw concentrations of relevant components shall be measured in accordance with Annex 4. The data shall be time corrected and aligned in accordance with paragraph 3 of this annex.

       6.2. Calculating NMHC and CH4 concentrations

For methane measurement using a NMC-FID, the calculation of NMHC depends on the calibration gas/method used for the zero/span calibration adjustment. When