A New Periodic Technical Inspection for Particle Emissions of Vehicles

Meanwhile, a high fraction of vehicles, driven by diesel engines, is equipped with very efficient particle filters in Europe. The filters have been enforced by the particle number limit for type approval testing. If the filter works properly, the emissions are very low. However, a small fraction of vehicles having broken or manipulated particle filters and therefore very high emissions can dominate the average fleet emissions of vehicles. The on-board diagnostic systems do not detect most of these filter defects. In several studies, failure rates in the order of some percent up to 20% have been observed. Therefore, identifying these high polluters is urgently needed. An option to achieve this is a periodical technical inspection. Gasoline engines may also have very high particle emissions, if there is a malfunction. Nevertheless, as a first step, the focus of current work is on diesel engines. Some data for gasoline engines will be presented, but the suggested test procedure has only been verified for diesel engines. For these, it has been shown that a test measurement can be done at low idle, which allows a fast and cheap procedure. Requirements for the test instrumentation are specified and a test procedure is suggested. A limit value is proposed which on the one hand is higher than requirements in type approval, but low enough to detect high polluters. The method suggested can be applied to passenger vehicles, as well as to heavy-duty engines and off-road applications.