NPTI: New Periodic Emission Inspection to guarantee PN Emission Stability of all modern vehicles
Creators: name: Mayer, A.
name: Burtscher, H.
name: Lutz, T.
name: Hensel, V.
Publisher: name: Karlsruhe
Year: 2019

description: Periodic Technical Inspection of emission quality PTI was abandoned by most EU member states in 2014 following the EU-Directive 2014/45 which recommended to delegate emission quality to OBD. After Dieselgate this naïve dream was over and VERT proposed during the German Dieselgate Hearing Sept.2016 to re-introduce PTI for all vehicles with emission control by DPF and SCR. With the introduction of particulate filters on diesel as well as GDI engines, the measurement of particulate emissions during PTI or road-side checks however, became a nontrivial task. Opacity and smoke meters do not have sufficient sensitivity to identify particulate filter failures or tampering on new, low emission internal combustion engines. Recent studies conducted in the Netherlands, Switzerland and Belgium have shown that about 10% of passenger cars equipped with DPF have high PN emissions that could indicate a damaged or removed DPF. To address this problem, the VERT Association launched a New Periodic Technical Inspection (N-PTI) initiative to develop a simple, robust and tamper-proof method for checking the functionality of DPFs using particle number (PN) instruments. The N-PTI initiative, launched in November 2016, is supported by the European Union as well as the governments of Germany, the Netherlands, Belgium, and Switzerland. The proposed test is conducted at idle using a PN instrument. It is assumed that the process will be suitable with minor, if any, modifications for petrol engines. The test protocol is also appropriate for road-side inspections, such as by the police. The first results are promising. Instruments in their prototype stage are already capable of recognizing vehicles that have been manipulated using partial bypass that resulted in PN emissions close to maximum allowed type approval levels (i.e., 6×1011 1/km) and present a satisfactory correlation with PEMS compliant instrumentation. Work on the testing procedure and pass/fail limit is still ongoing. This work is also under the evaluation of the CITA (International Motor Vehicle Inspection Committee) Roadworthiness Technical Working Group which focuses on tampering with exhaust emission control systems. The results show a good correlation between emission levels during the type approval cycle (NEDC/ WLTC) and low idle emissions even with first generation N-PTI instruments. These results suggest that the technical specifications of NPTI instruments should have acceptable uncertainty, with low cost. The Netherlands and Germany have already started programs that will lead to the adoption of mandatory N-PTI emission testing requirements. NMI, the Dutch metrology institute, has released a draft InternationalRecommendation with the specifications of the PTI particulate number counter. The N-PTI DPF test maybecome available in the Netherlands at RDW test stations as soon as 2019, while the nationwide targetdate for the introduction of N-PTI testing is 2021. In Germany, the Federal Council passed a law inSeptember 2017 (published in the German StVZO 2017) that re-introduces PTI first by smokemeasurement but PN measurements at idle are to be required from 2021.