Study of Drive Trace Indices and their correlation with CO2 in Chassis Dynamometer testing

With introduction of CAFÉ norms in India, the manufacturers of all M1 Category vehicles (not exceeding 3,500kg GVW) must ascertain that they comply with Annual Corporate average CO2 target as defined in regulation. Moreover, this target will become stricter in different stages in upcoming years. Hence CO2 emissions are becoming one of the major focus parameters during vehicle development. There are various factors that can impact CO2 emissions during measurement in test cycle such as MIDC/WLTC. One such major factor is driving variations. Although speed and time tolerances are provided during the test (as part of AIS 137/AIS 175) limit the variation, even within these tolerances, drive-related effects can be significant contributors to test results variability. Monitoring and control of such variations is important to understand the true fuel economy potential of the vehicle. Drive Trace indices are standardized metrics that can be used to evaluate the driving variations. The aim of this study is to understand the different driving behaviors on drive indices and consequently on CO2. Drive indices such as Energy Rating (ER), Distance Rating (DR), Energy Economy Rating (EER), IWR (Inertial Work Rating), RMSSE (Root Mean Square Speed Error) defined in SAE J2951 document has been referred for this study. Numerous MIDC & WLTC emission test data have been used for evaluation of driving behavior. An attempt has been made to establish a correlation between the drive trace indices and CO2 (fuel economy) by using mathematical techniques. As a result, using this correlation, an attempt has been made to quantify the variation of CO2 to driving behavior.