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SAE 942274 presents a discussion on manual transmission torque losses and focuses specifically on the relationship that exists between torque loss, input speed, and torque. It also includes a discussion about other factors affecting torque loss, such as inclination angle and lube oil temperature.

Efficiency studies conducted on manual transmissions in the engine-driving mode indicate that torque losses, in other than direct-drive gears, are considerably more dependent on input torque than input speed. In other words, the transmission efficiency deteriorates as the torque demand increases. Therefore, it is advantageous to design transmissions with low speed-dependent losses to maximize fuel economy on the current EPA driving cycle. The average torque demand on the EPA cycle is 20 percent of maximum engine torque. Furthermore, significant effects on efficiency were observed when the inclination angle and lube oil temperature were increased.

For more information about manual transmission efficiency trends and characteristics capabilities at SwRI or how you can contract with SwRI, please contact Douglas Fussner at dfussner@swri.org or (210) 522-3972.

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

September 30, 2008