Evaporative leakage diagnostic strategy based on OBD Ⅱ standard
WU Xinglong
Abstract：In order to meet the national and worldwide requirements for fuel evaporation system leakage monitoring,a strategy of small leakage diagnosis after engine shutdown and large leakage diagnosis during engine operation is adopted.The study focused on small leaks with a hole diameter of 0.50 mm and large leaks with a hole diameter of 2.25 mm,conducting whole vehicle tests under different environmental temperatures,fuel levels,and fuel Reid pressure(RVP)conditions,the in-use performance ratio(IUPR)of the sample vehicles is tracked and analyzed.The results show that both the small leakage diagnosis strategy and the large leakage diagnosis strategy can meet the performance index requirements;the small leakage diagnosis meets the IUPR of 0.26 required by the on-board diagnostic(OBD)Ⅱ,and the large leakage diagnosis meets the minimum IUPR of 0.62 required by the OBD Ⅱ.This diagnosis strategy can meet the monitoring requirements of both the VI OBD standard and the OBD Ⅱ standard,which shows good applicability.
Keywords：evaporation systemleakage diagnosisOBD Ⅱsmall leakagelarge leakage
Publication Date：2024-12-28
Online Publishing Date：2026-05-22(First online date of this platform, not the publication date of the document)
Pages：8( 68-75 )