Feasibility Study of a New Test Procedure to Identify High Emitters of Particulate Matter during Periodic Technical Inspection

The Diesel Particulate Filter (DPF) is the most effective way to reduce particulate matter emissions from diesel vehicles and is fitted on every passenger car since the EURO5 emission standard. Unfortunately, this essential after-treatment device can be damaged over time or could be defective from the manufacturing, negatively impacting its filtration efficiency. It is also sometimes illegally removed. Today in Europe, the presence and effectiveness of the DPF cannot be determined at the Periodic Technical Inspection (PTI), during which an opacity measurement of the exhaust gases is performed during a free acceleration test. Therefore, this work presents the results of the feasibility study of a new test procedure using devices measuring a particulate matter concentration (PN). The test consists of a PN measurement at low idle, which shows good correlation with NEDC PN emissions. This test procedure is afterwards compared to the opacity test on more than 300 EURO5 and EURO6 diesel vehicles. Two different PN measurement devices have been used and compared. This measurement campaign allowed to observe the negative influence of mileage and of the age of the vehicle on the PN emissions. With the proposed rejection threshold of 250 000 particles/cm³ also found in other studies, 15 % of the tested vehicles would fail while less than 1 % failed the opacity test. The identification and repair of those high emitters is of utmost importance since they increase the studied fleet emissions by a factor of 30. This study is a first step towards major changes in the PTI worldwide.