Definition and Measurement of Power Transfer Unit Speed-Dependent Parasitic Loss
This SAE Recommended Practice covers power transfer units (PTUs) used in passenger car and sport utility vehicles to support all wheel drive (AWD) operation. PTUs are typically full-time use geared devices (see 3.1). Some PTUs have additional features such as part-time on-demand capability via electronically actuated disconnect features, and other configurations are possible.
New government regulations that raise automotive fuel economy requirements and change the methods by which vehicle level fuel economy is measured drive the need for improved methods to measure component level parasitic loss. The intent of this standard is to provide the means to generate consistent component level parasitic loss data in support of modeling and analysis of vehicle-level emissions and fuel economy. This document is similar to SAE J2985, focusing however on the PTU instead of the transfer case.