Sensor-based Particulate Measurement (Some Tall Tales from the Trenches)

Current evidence indicates that a relatively small number of vehicles are responsible for the majority of excess in-use emissions, e.g. about 10% of the Diesel Particulate Filter (DPF) equipped vehicles are believed to contribute about 70% of excess particulate matter (PM) emissions. But conventional I/M measurements (snap-acceleration opacity) and other similar ‘stop-and-test’ procedures are not sensitive enough to measure the difference between a properly functioning and a moderately malfunctioning DPF system, and can even be cross-sensitive to the by-products of some modern emission control systems, e.g. NO2 from Selective Catalytic Reduction. As a result, one of the key elements of a more effective next-generation emissions ‘stop-and-test’ procedure for modern vehicles would be a new ‘SMOG Check’ system. Here, using provisional data for several recent and on-going studies, we propose a sensor-array strategy based on the 3DATx parSYNC as an alternative to simply replacing one metric (opacity) with another. We present data on the effectiveness of this approach, and describe options to address cross-sensitivity. We also consider the analytical compromises required to build an instrument suitable for use in a commercial garage at a price-point that will make it viable, as well as the extended diagnostic capabilities of a multi-dimensional description of vehicle particulate emissions.