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An on-board version of a fast response chemiluminsescence analyzer with a 3-millisecond response time enables the recording of high temporal resolution transient NOx emissions during cold start and pull-away, gear changes, speed bumps and other real world transient conditions. Tests were initially performed on a 1.6 litre turbo GDI vehicle before comparison with a diesel vehicle. The data has been correlated with on-board engine data available from the vehicle’s electronic control unit to study the underlying causes of these short-duration events. Exhaust gas was generally sampled from downstream of the after treatment system but before the silencer (muffler) to preserve all high frequency detail and to allow accurate integration of pollutant concentration and engine exhaust mass flow.

A study has been conducted to measure the transient HC, NOx, CO, CO2 and particulate emissions from a modern 1.6-liter, Euro IV-stage turbocharged Gasoline Direct Injection (GDI) passenger car engine. The tests were conducted using ultra-fast-response analyzers with millisecond response times so that the real-time effects of the individual combustion events and the ECU's start strategy could be studied. The results show that through the use of an aggressive cold start calibration strategy, the catalyst is very efficient after light-off at about 30s. However, during this same period, there are signs of partial misfires and rich AFR excursions, both of which contribute to the overall tailpipe emissions. The data from the fast-response analyzers allowed clear discrimination between rich events and partial misfires and would allow appropriate calibration actions to be taken.