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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.

This paper describes various aspects of the particle emissions from a 2-stroke motorbike. It gives an indication of issues which may face emissions engineers if (or when) such vehicles become subject to particulate legislation similar to that for light duty vehicles. A DMS500 fast particulate spectrometer was used to examine transient particle emissions from the CVS tunnel for two 2-stroke motorbikes over the European ECE R47 and urban New European Drive Cycle (NEDC) drive cycles. One was direct injected and the other was carburretted. Transient size spectra and number data from the output of a two stage, Particulate Measurement Program (PMP) compliant heated dilution system are presented for the carburretted 2-stroke motorbike running the urban phase of the NEDC. Estimates of the particle number emissions relative to the Euro 5b light-duty diesel vehicle legislation are presented.

Hydrogen is a reactive species involved with many combustion and catalysis reactions. Traditionally studies on hydrogen relied on theoretical calculation of engine out emissions. This study used a mass spectrometer to measure hydrogen emissions at engine out and tailpipe for a port fuelled injection (PFI) gasoline vehicle. Comparison of measured with calculated for engine out hydrogen showed good agreement. However, catalyst ageing affected post catalyst hydrogen levels to an extent that would be difficult to model by calculation. Study shows that for a detailed understanding of the influence of hydrogen on combustion and catalyst performance the preferred approach is measurement rather than calculation.

The emissions performance of a prototype close-coupled catalyst system has been analysed and compared with semi-close-coupled and underfloor systems. Under certain engine conditions during the stabilized region of the ECE Stage 3 drive-cycle, the close-coupled system has showed higher emissions than the semi-close-coupled or underfloor configurations. Using fast response emissions analysers and catalyst warm-up characteristics in conjunction with Computational Fluid Dynamics (CFD), the reasons for this emissions performance deficit has been attributed to flow maldistribution across the front face of the catalyst. Two flow distribution-related mechanisms for emissions breakthrough have been isolated: radial variations in mean AFR (Air-Fuel Ratio) across the catalyst can cause localized emissions breakthrough due to cylinder-to-cylinder AFR variations; and under high space velocity conditions, localized breakthrough can occur due to radial variations in gas velocity through the catalyst.

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.