Document ID: chunk:federal_register_of_legislation:F2011C00805:reg:120:p4
Version: federal_register_of_legislation:F2011C00805
Segment Type: reg
Provision Reference: reg 120 (pt 4/23)
Character Range: 244435–247298

system shall be so designed as to make it possible to measure the average volume concentrations of the CO2, CO, HC and NOx, and, in addition, in the case of vehicles equipped with compression-ignition engines, of the particulate emissions, contained in the exhaust gases emitted during the vehicle testing cycle.

         2.2.3. The mixture of air and exhaust gases shall be homogeneous at the point where the sampling probe is located (see paragraph 2.3.1.2. below).

         2.2.4. The probe shall extract a representative sample of the diluted gases.

         2.2.5.  The system shall enable the total volume of the diluted exhaust gases to be measured.

         2.2.6. The sampling system shall be gas-tight. The design of the variable-dilution sampling system and the materials that go to make it up shall be such that they do not affect the pollutant concentration in the diluted exhaust gases. Should any component in the system (heat exchanger, cyclone separator, blower, etc.) change the concentration of any of the pollutants in the diluted exhaust gases and the fault cannot be corrected, then sampling for that pollutant shall be carried out upstream from that component.

         2.2.7. If the vehicle tested is equipped with an exhaust system with several outlets, the connecting tubes shall be connected by a manifold installed as near as possible to the vehicle.

         2.2.8. The gas samples shall be collected in sampling bags of adequate capacity so as not to hinder the gas flow during the sampling period. These bags shall be made of materials which will not affect the concentration of pollutant gases (see paragraph 2.3.4.4. below).

         2.2.9. The variable-dilution system shall be so designed as to enable the exhaust gases to be sampled without appreciably changing the back-pressure at the exhaust pipe outlet (see paragraph 2.3.1.1. below).

Figure 5/1

Diagram of a variable-dilution system for measuring exhaust gas emissions

         2.3. Specific requirements

         2.3.1. Exhaust-gas collection and dilution device

         2.3.1.1. The connecting tube between the vehicle exhaust outlets and the mixing chamber shall be as short as possible; it shall in no event:

               (i) cause the static pressure at the exhaust outlets on the vehicle being tested to differ by more than  0.75 kPa at 50 km/h or more than  1.25 kPa for the whole duration of the test from the static pressures recorded when nothing is connected to the vehicle exhaust outlets. The pressure shall be measured in the exhaust outlet or in an extension having the same diameter, as near as possible to the end of the pipe;

               (ii) change the nature of the exhaust gas.

         2.3.1.2. Provision shall be made for a mixing chamber in which the vehicle exhaust gases and the dilution air are mixed so as to produce a