Experimental measurements of the environmental impact of a Euro IV vehicle in its urban use

Passenger vehicles are one of the most significant source of pollution in the cities. The emissions production of a vehicle is strictly dependent on how the vehicle is used. This paper has the objective to characterize a Euro IV vehicle so to understand in depth the behavior in its real usage on road in terms of fuel consumption and emissions. An Honda Civic 2.0 Euro4 vehicle has been tested and the experimental results are reported. The experiments have been carried out by means of two tools: a OBD2 interface to connect a laptop PC to the vehicle for collecting engine parameters (Alessandrini et al. 2006) and the HORIBA OBS1300 equipment to measure CO, NOx, HC emissions and the exhaust gas flow, pressure and temperature. Three types of experimental tests have been made: a set of them on a dynamometer chassis and a part on road. The warm-up phase, as foreseeable, is the main source of HC (up to 550 ppm) and CO (up to 10 %Vol), while in steady conditions the emissions are often too low to be appreciated by the sensors. At full open throttle, the air-fuel ratio is no more stoichiometric, correspondingly the highest measured values of CO and NOx are encountered, being the first significantly influenced by this parameter while the NOx mostly by high combustion temperatures. Under transient conditions, typical of urban cycles, the peak values for CO are 2.6%Vol and 500 ppm for NOx, mainly due to the enrichment of the air-fuel mixture; the engine ECU (Electronic Control Unit) has a delay in counteracting the correct quantity of fuel to be injected and the mixture is purposefully enriched to give better engine performances in such critical moments. The HC are always negligible. The driver behavior as well has an important impact on the emissions and the accelerator pedal usage (and its temporal derivative) is the most relevant factor that influences fuel consumption and emissions. Several drivers have been engaged and the behavior analyzed shows how the vehicle maintains its Euro4 characteristics if never driven at full throttle regime. Transient conditions and in particular severe accelerations are the worst conditions concerning consumption and emissions