Comparison of constant-volume sampler and bag mini-diluter emissions measurements of a plug-in hybrid electric vehicle

Abstract

Abstract

The impending introduction of dual-fuel plug-in hybrid vehicles (PHEVs) will impose significant challenges on current vehicle emissions testing equipment and protocols. One reason is the all-electric range and random start of the combustion engine. A second reason is the period of low or zero flow rate of exhaust volume. The present paper systematically evaluates these challenges by testing a Toyota prototype with an industry-standard, constant-volume sampler system in parallel with bag mini diluter equipment. Both systems exhibit technical difficulties when testing the PHEV. Discrepancies between the two methods can be corrected with software manipulations for a charge-sustaining operation. However, there are clear mechanisms of possible error in CO₂ emissions collected during charge-depleting operation for both technologies. These findings indicate that alternative methods, including continuous sampling methods, may be required for accurate vehicle certification.