GB/T 23920-2022Low-speed vehicles—Determination method of maximum speed (English PDF)

4.1 Vehicles

4.1.1 Vehicles shall be filled with fuel according to the regulations in the instructions for use.

4.1.2 The adjustment of the fuel supply system shall be such that the engine power and speed comply with the manufacturer's regulations. Any device that can cause changes in the engine speed and/or vehicle speed through adjustment shall be adjusted to the state that enables the engine speed and/or vehicle speed to reach the maximum.

4.1.3 The tire with the maximum outer diameter allowed by the manufacturer shall be used; the inflation pressure shall be the tire pressure value recommended by the vehicle manufacturer for road driving.

4.4 Environmental conditions

4.4.1 The maximum difference between the air density in the test and the air density in the standard environment shall not exceed 10%; the atmospheric pressure during the test shall not be lower than 91 kPa; the temperature shall not be lower than 273 K, and not higher than 313 K (where the test environmental temperature is 0 °C ~ 40 °C). Calculate the air density according to Formula (1).

Where: dT - air density of the test environment, in kilograms per cubic meter (kg/m³); d0 - air density of the standard environment, d0 = 1.205 kg/m³;

HT - atmospheric pressure of the test environment, in kilopascals (kPa);

H0 - atmospheric pressure of the standard ambient, H0 = 100 kPa;

T0 - temperature of the standard environment, T0 = 293 K (20 °C); TT - temperature of the test environment, in Kelvins (K).

4.4.2 The road test shall be carried out under environmental conditions where the relative humidity is not greater than 95%, and the wind speed in the horizontal direction of the driving path does not exceed 3 m/s.

4.5 Vehicle loading mass and load distribution

4.5.1 As required, measure the actual maximum running speed of the vehicle under no-load or maximum design total mass state.

4.5.2 When loading at the maximum design total mass, the loaded mass shall be evenly distributed, and the loaded object shall be fixed firmly to ensure that there is no shaking or overturning during the test; its mass shall not be changed due to changes in conditions such as humidity and loss, so as to ensure that the size and distribution of the loaded mass remain unchanged. The occupant (calculated as 65 kg) can be replaced by the weight of the same mass.

5.1 Test preparation

Before the test, the test vehicle shall be fully preheated so that the engine, transmission system, lubricating oil, etc. reach the specified stable temperature state.

5.2 Road test

5.2.1 Put the test vehicle in the highest forward gear, fully open the accelerator to reach a stable maximum speed, and try to drive into the test runway.

5.2.2 Carry out the test along the to-and-from direction, and try to use the same path of the test section.

5.2.3 Along the to-and-from direction, measure the actual maximum running speed of the vehicle within a distance of at least 100 m. Record the time for the vehicle to travel a distance of 100 m.

5.2.4 Carry out two consecutive measurements in the to-and-from direction, and the speed change of the vehicle in the same direction during the test shall not exceed 2%. Otherwise, the number of tests shall be increased, and the values with far deviations shall be discarded.

5.2.5 Fill in the relevant measured values required in Table A.1 of Appendix A, and calculate the average vehicle speed for each to-and-from trip.

5.2.6 Take the larger of the average vehicle speeds of two consecutive to-and-from trips as the measured actual maximum running speed of the vehicle.

5.3 Drum dynamometer test

5.3.1 For the test vehicle, an equivalent inertia of the chassis dynamometer shall be set according to the requirements of A.5.1 and A.6 in GB 21377-2015, and the running resistance shall be set according to the requirements of Appendix B.

5.3.2 Place the vehicle on the chassis dynamometer, with proper protection. Put the vehicle in the highest forward gear and fully open the accelerator to reach the maximum speed.

5.3.3 Measure the actual maximum speed of the vehicle within a distance equivalent to at least 100 m. Record the time when the vehicle travels a distance of 100 m on the test bench, and directly read the average value during this period as the maximum speed value.

5.3.4 Take two consecutive measurements. Fill in the relevant measurements required in Table A.2 of Appendix A.