INTRODUCTION The purpose of the study was to develop a test procedure which could form the basis of an SAE J-standard for measurement of parasitic losses (spin losses) of PTUs used in front-wheel-drive-based passenger car and light duty truck applications. The standard is intended to cover PTUs of various designs and configurations including single and multiple stage and disconnectable. The basic test procedure outlined in this paper on PTUs is based on a test methodology developed during a previous study focused on measurement of spin losses in transfer cases[1, 2, 3]. In this previous transfer case spin loss measurement study, a detailed section is dedicated to the analysis of the use of traditional methods for measurement of test unit temperature during data acquisition. The traditional method of temperature control was measurement of the transfer case temperature via a thermocouple installed in the sump of the test unit. Upon review of the initial parasitic losses data acquired using the traditional temperature monitoring/control methods at low temperature (i.e., −7°C), it was clear that the repeatability was not acceptable and another procedure would need to be developed. The previous transfer case paper outlines in detail the steps taken to develop a new test 2013-01-0361 Published 04/08/2013 Copyright © 2013 SAE International doi:10.4271/2013-01-0361 saepcmech.saejournals.org Development of a Standard Spin Loss Test Procedure for FWD- Based Power Transfer Units Michael P. Kirk Chrysler Group LLC Thomas D'Anna and William Seldon FEV Inc Andreas Perakes Ford Motor Co Craig Ross General Motors Company ABSTRACT 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. CITATION: Kirk, M., D'Anna, T., Seldon, W., Perakes, A. et al., "Development of a Standard Spin Loss Test Procedure for FWD-Based Power Transfer Units," SAE Int. J. Passeng. Cars - Mech. Syst. 6(2):2013, doi:10.4271/2013-01-0361. ____________________________________ 552Downloaded from SAE International by Univ of Nottingham - Kings Meadow Campus, Sunday, August 12, 2018procedure and compares the results of traditional methods to the newly developed Average Skin Temperature (AST) method. Use of this new unit temperature measurement methodology for the development of a test of spin loss for PTUs greatly expedited the completion of this study. POWER TRANSFER UNIT PARASITIC LOSS TESTING The traditional method for assessing the losses of transmission and driveline components is to use a single dyn