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A study has been conducted to measure the particle number emissions from a current-generation 1.6-liter, Euro IV-compliant turbo-charged Gasoline Direct Injection (GDI) passenger car engine. A fast-response particle size spectrometer was used along with a PMP-compliant particulate measurement system to measure the effect of various engine parameters on the particulate emissions during the New European Drive Cycle (NEDC). Overall particle number is shown along with further analysis of the transient particle emissions. The cold start clearly affects particle formation with approximately 50% of the cumulative particle number being emitted within 200 seconds of the start. Even beyond 200 seconds, the particle number emissions fall as the test progresses and are generally consistent with increases in engine coolant temperature indicating that cold engine fuel preparation issues are contributing to the particle number count.

Using local emissions measurements immediately downstream of a close-coupled catalyst, spatial variations in emissions have been analysed for close-coupled catalysts with different ageing histories. Comparison of the radial emissions profiles between a uniformly-aged (oven-aged) catalyst and two vehicle-aged parts suggests that the vehicle-aged parts have substantial variations in catalyst damage across the radius of the catalyst. The radial variations in damage were confirmed by bench reactor and post-mortem studies. The radial catalyst damage profiles inferred from engine-based evaluations of vehicle aged catalysts show broad correlation with high flow areas identified by CFD predictions and high temperature regions as measured during engine tests.