SAE J651_201506

The extent of test conditions on the dynamometer must be sufficient to determine the efficiency characteristics corresponding to the following range of vehicle operations in all gear ratios with locked torque converters (open converter can also be done where appropriate and noted). a Efficiency versus output speed versus input torque b Torque ratio versus output speed c Input speed versus output speed d Output torque versus output speed e Parasitic loss versus input speed (spin losses) f Cooler flow g Output torque bias (front wheel drive transaxles) This Recommended Practice had defined a test procedure and process which gave a reasonably complete description of the efficiency and performance of a 20th century automatic transmission. With the introduction of electronic controls, the number of parameters which control the transmission’s operation have expanded extensively and these need to be defined for each test. The interaction between the transmission, the environment, the engine, the cooling and other systems have also made test definition very difficult and complex. Finally, the diversity, the rapid changes, and the component complexity introduced by electric and hybrid drive system combine with the above difficulties to make it impractical to define a Recommended Practice which could provide a meaningful description of performance and efficiency of 21st century automotive transmissions. The existing Recommended Practice J651 is being stabilized to preserve the test procedures for future reference.