In-Use Vehicle Survey of Fuel Consumption and Emissions on Dynamometer and Road

An upgraded vehicle fuel consumption/emission test facility is shown to be able to simulate on-road performance of cars up to wide open throttle operation. A procedure is described which permits dynamometer loads to be set so as to replicate the on-road, steady speed fuel consumption of each vehicle tested. A test program involving five driving cycles (schedules), three US and two Australian, and a range of other manoeuvres has been devised, to describe a wide range of on-road driving. The tests last one week and have been carried out on a fleet of almost 40 cars. Fuel and emission data has been logged at every half second interval of the tests. The overall test results only have been reported here. It is shown that there is considerable variability in the response of individual cars to changed test cycle. For the Australian test cycle fuel consumption is typically 15% higher than to US 75 FTP city test schedule. Corresponding increases in emissions are nearly 50% for HC, 90% for CO and 30%, for NO_X. There is some evidence that vehicle designs are ‘tailored’ to the emission test cycle, and thus perform less well in more normal driving, There are indications that non-weight related improvements in recent model cars are more effective in reducing ‘on-road’ fuel consumption than reflected by the US city test schedule. Lastly the influence of ambient temperature on fuel consumption and emissions is shown to be significant.