Emissions of modern light duty ethanol flex-fuel vehicles over different operating and environmental conditions

In 2012 some 2.8 million toe of bioethanol were introduced in the European gasoline market. The introduction of ethanol blendstocks in the European fuels market should take place without undermining pollutant emissions or vehicle engine performance. According to the Euro 5 certification procedure the properties of three different ethanol blends supplied in the European market (E5, E75, E85) should be taken into account when testing for exhaust emissions. In this study the latest procedure established for emissions certification is assessed, shedding light on the gaseous regulated emissions and CO2 - energy/fuel consumption performance of two Flex Fuel Vehicles with different fueling strategies (Direct/Port Fuel Injection) and different Euro standards (Euro 4 and Euro 5). Both legislative and non-legislative “real-world” driving cycles were used in the study. The analysis is completed with a comparison with existing emission factors for Flex Fuel Vehicles in Europe. At 22 °C CO emissions decreased over all conditions tested with the use of the high ethanol content fuel (E85), compared to the E5 performance. Total HC emissions were practically unaffected by the fuel type. NOx emissions decreased for both vehicles over the New European Driving Cycle, while over the Common Artemis Driving Cycle the vehicles exhibited different NOx behavior. At −7 °C both regulated CO and total HC emissions increased with E75 fuel. However, the Euro 5 vehicle exhibited emission performance below the current legislative limits for both CO/total HC over the cold-start urban part of the cycle. Results were found to be in line with existing emission factors used in Europe for ethanol-fueled vehicles.