Determination of GHG Emissions, Fuel Consumption and Thermal Efficiency for Real World Urban Driving using a SI Probe Car

A SI probe car, defined here as a normal commercial car equipped with GPS, in-vehicle FTIR tailpipe emission measurement and real time fuel consumption measurement systems, and temperature measurements, was used for measuring greenhouse gas emissions including CO₂, N₂O and CH₄ under real world urban driving conditions. The vehicle used was a EURO4 emission compliant SI car. Two real world driving cycles/routes were designed and employed for the tests, which were located in a densely populated area and a busy major road representing a typical urban road network. Eight trips were conducted at morning rush hours, day time non-peak traffic periods and evening off peak time respectively. The aim is to investigate the impacts of traffic conditions such as road congestion, grade and turnings on fuel consumption, engine thermal efficiency and emissions. The time aligned vehicle moving parameters with fuel consumption and emission data enabled the micro-analysis of the correlations between these parameters. The trip average data for fuel consumption, thermal efficiency and emissions etc were calculated. The impact of vehicle's transient movements and traffic events on emissions were studied. VSP (Vehicle Specific Power) has been used for the determination of engine power output. The results show that the transient emissions were dominated by sharp accelerations occurred at traffic light and pedestrian crossing. The trip average CO₂ and CH₄ emissions had a good linear correlation with vehicle's average speed which is directly related to vehicle idle periods but no clear correlation between vehicle's speed and N₂O emissions.