Cold Start SI Passenger Car Emissions from Real World Urban Congested Traffic

The tailpipe exhaust emissions were measured under real world urban driving conditions by using a EURO4 emissions compliant SI car equipped with an on-board heated FTIR for speciated gaseous emission measurements, a differential GPS for travel profiles, thermocouples for temperatures, and a MAX fuel meter for transient fuel consumption. Emissions species were measured at 0.5 Hz. The tests were designed to enable cold start to occur into congested traffic, typical of the situation of people living alongside congested roads into a large city. The cold start was monitored through temperature measurements of the TWC front and rear face temperatures and lubricating oil temperatures. The emissions are presented to the end of the cold start, defined when the downstream TWC face temperature is hotter than the front face which occurred at ~350-400oC. Journeys at various times of the day were conducted to investigate traffic flow impacts on the cold start. The test route had traffic and pedestrian crossing lights, several major road junctions and a busy shopping area. The time aligned vehicle moving parameters with pollutant emission data and fuel consumption enabled the micro-analysis of correlations between these parameters. The average cold start emissions, fuel consumption and temperature data are presented for the journeys into different levels of congestion (based on the mean speed of the cold start journey). The mean complete journey speed during was shown to reasonably correlate the emissions, which increased as mean speed reduced. The cold start congested traffic portion was separately analysed to show the much higher emissions for equivalence mean speeds. Engine vehicle specific power (VSP) output was calculated and used together with the fuel flow to determine the instantaneous and average thermal efficiency. Three way catalysts (TWC) light off was approximately 200 seconds, much longer than for the NEDC test cycle. Currently urban air quality monitoring does not include cold start into congested traffic from vehicles at houses along the road, but does have procedures where cold start occur at large car parks.