Fast Emissions Analyzers for In-Vehicle and Roadside Measurements

Jamie Parnell

doi:10.4271/2021-24-0084

The use of fast response emissions analyzers to correlate spikes of emissions with engine parameters such as lambda and EGR is well known for engine test cell and chassis dynamometer work. However, the adaption of these analyzers for in-vehicle use allows engineers to identify real world situations where significant tailpipe emissions occur over short durations which may not be visible with standard PEMS equipment and to correlate these events with other engine parameters. Sampling raw exhaust gas pre muffler eliminates the extra gas mixing due to these sound deadening devices and allows high fidelity identification of emission breakthroughs during transients. Through such identification, engine calibrators can adjust ECU parameters enabling such transient emissions problems to be cured. Accurate and adequate urea dosing and EGR transients are of particular interest in diesel vehicles. In addition, combining fast measurements with GPS allows spatial determination of emissions giving rise to possible local emissions “hot spots”. Emissions map plots have been developed to help future transport planning improve local air quality. The transient emissions from passing (or “chased”) vehicles has also been studied following a sensitivity enhancement to the fast CLD, enabling high quality roadside measurements at positions where transients frequently occur (e.g. traffic lights, roundabouts). Measured roadside concentrations of nitric oxide can be seen to greatly exceed that measured by conventional air quality monitoring stations, showing the necessity for fast emissions analyzers to determine real human exposure to vehicle source toxic emissions.