Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p16
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 16/108)
Character Range: 928409–931227

be performed according to paragraphs 4.2.1. and 4.2.2. of this annex and applies to both the flat belt or roller chassis dynamometers and the wind tunnel measurements.

              In the case that the alternative warm-up procedure described in paragraph 6.5.2.1. of this annex is applied, the target test mass adjustment, the weighing of the vehicle and the measurement shall all be performed without the driver in the vehicle.

              The flat belt or the chassis dynamometer test cells shall have a temperature set point of 20 °C with a tolerance of ±3 °C. At the request of the manufacturer, the set point may also be 23 °C with a tolerance of ±3 °C.

              6.4. Wind tunnel procedure

              6.4.1. Wind tunnel criteria

              The wind tunnel design, test methods and the corrections shall provide a value of (CD × Af) representative of the on-road (CD × Af) value and with a repeatability of ±0.015 m².

              For all (CD × Af) measurements, the wind tunnel criteria listed in paragraph 3.2. of this annex shall be met with the following modifications:

                  (a) The solid blockage ratio described in paragraph 3.2.4. of this annex shall be less than 25 per cent;

                  (b) The belt surface contacting any tyre shall exceed the length of that tyre's contact area by at least 20 per cent and shall be at least as wide as that contact patch;

                  (c) The standard deviation of total air pressure at the nozzle outlet described in paragraph 3.2.8. of this annex shall be less than 1 per cent;

                  (d) The restraint system blockage ratio described in paragraph 3.2.10. of this annex shall be less than 3 per cent;

                  (e) Additionally to the requirement defined in paragraph 3.2.11. of this annex, when measuring Class 1 vehicles, the precision of the measured force shall not exceed ±2.0 N.

              6.4.2. Wind tunnel measurement

              The vehicle shall be in the condition described in paragraph 6.3. of this annex.

              The vehicle shall be placed parallel to the longitudinal centre line of the tunnel with a maximum tolerance of ±10 mm.

              The vehicle shall be placed with a yaw angle of 0 ° within a tolerance of ±0.1 °.

              Aerodynamic drag shall be measured for at least for 60 seconds and at a minimum frequency of 5 Hz. Alternatively, the drag may be measured at a minimum frequency of 1 Hz and with at least 300 subsequent samples. The result shall be the arithmetic average of the drag.

              Prior to a test it shall be checked that at the aerodynamic force measured at a wind speed of 0 km/h yields a result equal to 0 Newtons.

              In the case that the vehicle has movable aerodynamic body parts, paragraph 4.2.1.5. of this