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An experimental campaign was carried out to evaluate the influence of CNG and gasoline on the exhaust emissions and fuel consumption of a bi-fuel passenger car over on-road tests performed in the city of Naples. The chosen route is very traffic congested during the daytime of experimental measurements. An on-board analyzer was used to measure CO, CO2, NOx tailpipe concentrations and the exhaust flow rate. Throughout a carbon balance on the exhaust pollutants, the fuel consumption was estimated. The exact spatial position was acquired by a GPS which allowed to calculate vehicle speed and the traffic condition was monitored by a video camera. Whole trip realized by the vehicle was subdivided in succession of kinematic sequences and the vehicle emissions and fuel consumption were analyzed and presented as value on each kinematic sequence. Moreover, throughout a multivariate statistical analysis of sequences, the driving cycles characterizing the use of vehicle were identified.

The problem of emission evaluation control and modelling is nowadays an open question. In the framework of a Decision Support System (DSS), a new approach was developed for modeling and evaluating automotive pollutant emissions. An interesting point of this proposal was the integration of the micro simulated model to obtain driving cycle. In fact an important open issue is the very expensive costs of experimental campaigns needed to obtain driving cycle statistically representative of driving behaviour. So to overcome these high costs and to extend the real vehicle operating conditions framework, a possible solution is to integrate a microsimulation model in the general context of emission modeling. But the reliability of driving cycles coming from simulation models must be evaluated with respect to the possible influence on test bench measured emissions. In this paper, we would try to present some results related to two aspects of the problem.

In this paper some results relative to tests performed on road with a Fiat Panda Bipower, (CNG and gasoline powered), and a New Panda Twin Air with auto Start & Stop system, are presented. Gaseous emissions are measured with Portable Emission Measurement Systems (PEMS) on two different urban routes, in terms of traffic and slope characteristics during in use experiments. PEMS testing offers an easy and efficient way to evaluate the vehicle emissions over a huge variety of conditions and provides us a direct way to study the in-use emissions of combustion engines, when you want to verify the effect of the traffic and of a particular device on fuel economy and emissions reduction. Moreover now PEMS performances are very comparable to those obtained by standard laboratory instrumentation systems.