BS ISO 9816:2018 pdf download – Passenger cars — Power-off reaction of a vehicle in a turn — Open-loop test method
8.2 Initial driving condition
8.2.1 General
For both the constant-radius and the constant-speed test methods, the initial driving condition is a steady-state circular run as defined in ISO 15037-1. For either test method, the initial runs shall be conducted from a steady-state circular condition in which a lateral acceleration of about 4 m/s 2 is achieved. In successive runs, the steady-state lateral acceleration of the initial turn shall be increased incrementally from run to run in steps of not more than 1 m/s 2 .
It is recommended that increments of 0,5 m/s 2 or less be used when the power-off response changes significantly between runs at the larger increment (1 m/s 2 ). For vehicles with manual transmission, the test shall be performed in the lowest gear possible, but not in first gear.
The engine speed shall not be higher than 80 % of the engine speed at the maximum power point, as specified by the vehicle manufacturer. If the increase in vehicle speed during a constant-radius test requires a gear change, the previous speed shall be run in both gears. For vehicles with automatic transmission, the standard drive mode shall be used. The position of the transmission lever and the selected driving programme shall be recorded in the test report (see Annex A). Cars with adaptive gear selection or CVT may use different gears or ratios at a given speed.
For such cars, engine speed shall be recorded for the purpose of determining gear ratio. It shall be recorded in the test report. For vehicles with regenerative braking capabilities the specific vehicle configuration may alter the dynamic vehicle behaviour while releasing the accelerator pedal and/or while pressing the brake pedal. Also, the different dynamic vehicle behaviour with or without active regenerative braking shall be considered while performing the tests.
The selected level of regenerative braking capability and the transmission lever position shall be documented in the test report.
8.2.2 Initial driving condition
—Constant-radius method During the initial driving condition, the vehicle shall be steered in such a manner that the reference point of the vehicle moves on a circular path of the desired radius. As it is known that the significance of the results and the ability to discriminate between different vehicles increase with increasing test speed, the standard radius of this path shall be 100 m. Smaller radii may be used.
The minimum permissible radius is 30 m, but the recommended minimum radius is 40 m. From run to run, the initial driving speeds shall be those which establish the required steady-state lateral accelerations as described in 8.2.1.
8.2.3 Initial driving condition
— Constant-speed method The standard speed for the initial driving condition is 100 km/h. If higher or lower test speeds are selected, they shall be in 20 km/h increments. From run to run, the steady-state lateral accelerations as required in 8.2.1 shall be established by either of the following two methods.
—The test runs are performed using a series of discrete turn radii, consisting of a number of marked circles or circular segments with different radii chosen to establish the required initial lateral accelerations at the selected test speed.
— The test runs are performed using a series of discrete, constant steer angles (with no constraint on initial vehicle path) chosen to establish the required initial lateral accelerations at the selected test speed. The use of an adjustable steering stop is recommended for maintaining constant steer angles.
8.3 Power-off procedure
The position of the steering wheel and the accelerator pedal shall be kept as constant as possible during the initial driving condition. The initial condition is considered to be sufficiently constant if the conditions defined in ISO 15037-1 are fulfilled. For the constant-radius method, the radius in the initial driving condition may not deviate by more than ±2 % of the desired value or ±2 m, whichever is smaller, during the time interval of 1,3 s to 0,3 s before power-off initiation.