Browse Publications Technical Papers 2019-36-0144

Comparison between the WLTC and the FTP-75 driving cycles applied to a 1.4 L light-duty vehicle running on ethanol 2019-36-0144

The forecast scenarios regarding the environmental pollution raises a question whether the current vehicle emission certification is reliable enough to assure fleet agreement with the legal limits. Type approval tests have been performed on chassis dynamometer in order to evaluate the emission factors and fuel consumption for passenger cars. Standardized procedures such as the FTP-75 proposed in the United States (currently incorporated in the Brazilian legislation) and the Worldwide harmonized Light vehicles Test Cycle (WLTC), a transient driving cycle model designed by the European Union to overcome the shortcomings of the New European Driving Cycle (NEDC), are discussed in this paper. Both cycles were performed in a chassis dynamometer with a flex-fuel passenger car running on ethanol blend (E92W08). The driver, vehicle and fuel were kept constant so the comparison between the cycles would not be compromised. The vehicle chosen was a 1.4 dm3 displaced volume FIAT sedan with maximum power of 60 kW at 5500 rpm and maximum torque of 122 Nm at 2250 rpm. The cycle dynamics and the engine operation points were assessed in this paper. The five points estimated as the most representative of both tests were selected for steady-state investigations conducted using hydrous-ethanol (E97W03), which is the ethanol blend available in Brazilian fuel stations. These points were evaluated in terms of fuel consumption and air excess factor. The results showed that the FTP-75 demanded greater average and maximum acceleration values, implying on more aggressive driving conditions. The WLTC presented a more homogeneous acceleration per speed diagram, providing higher average speed and speed standard deviation (e.g. more transient conditions) which is more like the real drive conditions. It could be seen that the WLTC covers a wider range of engine operation conditions holding more dispersed points than the FTP-75. In addition, the WLTC contained points with higher load, which made the results for fuel consumption to be higher compared to FTP-75. The engine operation points provided by the FTP-75 were excessively condensed. Therefore, it could be concluded that the FTP-75 can be a predictable test with repeated points of operation. The WLTC does not have sufficient number of trips in its schedule, which is different from the behavior expected in real-world driving conditions. Also, it could be observed that depending on the test specifications the driver can largely influence the performance of the vehicle.


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