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 light truck applications. PTUs may be of the chain, geared, single- or multi-axis type and may incorporate a disconnect system that is manually or electronically shifted, although other configurations are possible. The operating points (speeds, temperatures, etc.) were chosen to mirror those of the United States Environmental Protection Agency Vehicle Chassis Dynamometer Driving Schedules (DDS).
Rationale: 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.