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In order to simulate the real behavior of vehicles during laboratory tests, such as fuel consumption [1] and pollutant emissions [2], coast down coefficients must be set on the chassis dynamometer control system. These coefficients are used to determine load curves, which represent the resistance imposed on the vehicle movement by the wheels rolling and the air, being obtained from track tests performed according to Brazilian standard ABNT NBR 10312 [3]. However, coast down tests depend on the availability of long and flat tracks. This may entail costs for deployment or leasing of facilities with these characteristics, which may include even long commutes of human and material resources, depending on its location. This paper proposes an alternative methodology for coast down coefficients determination, from experiments on chassis dynamometer and vehicles aerodynamic specifications. It was applied to some Petrobras Research Center (Cenpes) test vehicles.

The secondary pollutants formation in the atmosphere, such as ozone (O3), comes from the reactions between volatile organic compounds (VOCs) and the photochemical oxidants in the presence of oxygen and nitrogen oxides (NOx). The understanding of VOCs reactivity emitted by light duty vehicles is very important to construct reactivity scales regarding ozone formation. In 2003, flex-fuel vehicles were released in the Brazilian market and nowadays, they represent over 50% of the total light duty vehicle fleet in the country. In 2007, new tailpipe emission limits were implemented for Non-Methane Hydrocarbons (NMHC), a group of pollutants included in VOCs. The new NMHC limit became a challenge to homologate some flex-fuel models, when fueled with ethanol. To deal with this issue, other legislation allowed the subtraction of the unburned ethanol emission from the NMHC value.

The use of CNG in light-duty vehicles is well known and widespread in Brazil, mainly in the state of Rio de Janeiro. In theory, the application of this technology could provide greater energy efficiency and lower emissions of pollutants. However, it is known that the majority of CNG kits installed do not meet the environmental requirements established by the Brazilian legislation. This work quantifies the average emissions from light-duty vehicles converted to CNG use in the Metropolitan Area of Rio de Janeiro, where 47% of the Brazilian CNG fleet runs. For this purpose, initially a field survey of gas stations was performed in this Region, in order to define the representativeness of CNG kits in terms of technology generation and brand, as well as manufacturer, model, displacement, original fuel and manufacture year of vehicles in which such kits were installed.

This paper presents the results attained in a study carried out by the PETROBRAS Research Center (CENPES), in a comparative analysis made between two flex fuel vehicles (designed for both Brazilian gasohol and hydrated ethanol in mixtures of any proportion) and similar models designed only for gasohol use. This evaluation was based on the effects of the new technology on the driveability, vehicle speed recovery performance, exhaust gas emissions (THC, CO, NOx and aldehydes), fuel economy and maintenance costs