SAE J47:2020 pdf free

SAE J47:2020 pdf free.Maximum Sound Level Potential for Motorcycles
The intention of this test is to have the vehicle under test reach the end point under its maximum sound conditions – at wide open throttle and at rated engine speed, or as close to rated engine speed as the powertrain and conditions permit.Vehicles with a manual clutch approach the acceleration point at a steady engine speed. All other vehicles begin accelerating from the acceleration point using a standing start procedure. Each vehicle uses a different acceleration point in the test. The acceleration point for each vehicle is established by, basically, running the test procedure in the reverse direction in order to determine how to run the test in the normal direction.
To establish the acceleration point for vehicles with a manual clutch- -the end point shall be approached in first gear from the direction opposite to the direction of the test run at a constant speed corresponding to 60% of rated engine speed. When the front of the vehicle reaches the end point, with the clutch fully engaged the throttle shall be rapidly and fully opened to accelerate the motorcycle past the microphone target point under wide open throttle. By trial, the lowest transmission gear shall be selected that will result in the vehicle traveling the shortest distance from the end point to the place where rated engine speed is reached, but which is not less than 7.5 m past the microphone target point. The location of the front of the vehicle on the vehicle path when rated engine speed is attained shall be the acceleration point for test runs to be made in the opposite direction.
When the procedure described in 6.1 results in an unusual operating condition such as wheel spin, the next higher gear shall be selected for the test, and the procedure rerun to establish the new acceleration point. In any event, the procedure shall result in the vehicle being at the end point when rated engine speed is attained without wheelspin or clutch slippage.
6.3 Vehicles without a manual clutch shall use a standing start acceleration, starting from the end point, to establish the acceleration point. With the front of the vehicle at the end point and with the transmission in the lowest selectable range, the throttle shall be rapidly and fully opened to accelerate the motorcycle past the microphone target point under wide open throttle.SAE J47 pdf free download.