On-board measurement is a powerful method to assess vehicular exhaust gas emission, since it enables the acquisition of instantaneous raw emission values in real-world conditions. While the vehicle emissions are subject to traffic and environment fluctuations, on-board measurement is a fast and economical way to generate data for fleet emission inventories, for instance. It is part of the mandatory testing for heavy-duty vehicles in the USA, as regulated by the USEPA.
In 2004, Petrobras (Brazilian Oil Company) first experienced on-board emission measurements while participating in an international joint project, whose objective was to obtain information regarding the light-duty vehicular gas emission contribution to pollutant levels in some of the major Latin-American cities.
Petrobras is interested to use the on-board measurement method in order to develop and evaluate fuels, including alternative ones and also to perform heavy-duty vehicles emission tests, comparing diesel, NG and hybrid buses or to test light-duty multi-fuels vehicles.
In 2006, CENPES (Petrobras Research Centre) acquired from Horiba Instruments, an on-board measurement system - OBS 2200 whose main advantages are the analyzers accuracy, mostly the HC using the FID and NOx with chemiluminescence. This paper will describe the principle of work of this on-board equipment, USA legislation and also preliminary results obtained by PETROBRAS on some vehicle tests.