As vehicle fuel economy continues to grow in importance, the ability to accurately measure the level of efficiency on all driveline components is required. A standardized test procedure enables manufacturers and suppliers to measure component losses consistently and provides data to make comparisons. In addition, the procedure offers a reliable process to assess enablers for efficiency improvements. Previous published studies have outlined the development of a comprehensive test procedure to measure transfer case speed-dependent parasitic losses at key speed, load, and environmental conditions. This paper will take the same basic approach for the Power Transfer Units (PTUs) used on Front Wheel Drive (FWD) based All Wheel Drive (AWD) vehicles. Factors included in the assessment include single and multi-stage PTUs, fluid levels, break-in process, and temperature effects. The resultant procedure is proposed as a new SAE J-standard (Surface Vehicle Recommended Practice) for release by the AWD Standards Committee.
The overview presented in this paper includes definitions for the PTUs used in the study along with an overview of the test setup and instrumentation. This paper will outline some of the key investigations undertaken including the step size and duration, assessment of repeatability, as well as the influences of break-in and oil level.
This project was undertaken and financially supported by the Transmission Working Group of the United States Council of Automotive Research (USCAR) for the SAE AWD Standards Committee.
