Comparative study of aftermarket and OEM DPFs for Periodic Technical Inspections (PTI) compliance with new PN emission limits

This study evaluates the performance of aftermarket and OEM diesel particulate filters (DPFs) using a particle number counter (PNC) during stationary Periodic Technical Inspection (PN-PTI) tests. Several European countries have already implemented regulations requiring this test to ensure that vehicles equipped with DPFs meet the stringent particle number (PN) emission limits. In this work, measurements were conducted on various vehicles with new and conditioned DPFs. The results revealed significant variability in PN emissions, with some filters failing to meet the required limits. Key contributors to elevated PN levels were identified, including filter aging and inadequate conditioning procedures. Based on the findings, the paper proposes practical recommendations and diagnostic approaches to support compliance with PN-PTI test requirements.