Possible impact on fuel consumption and CO2 emission by the transition of current type approval cycles to future World-wide harmonized Light duty Test Cycle (WLTC): a simulation study.

A new type approval procedure for Light Duty Vehicles, the World-wide harmonized Light vehicles Test Procedure (WLTP) and Cycle (WLTC) developed by initiative of UNECE, will enter into force by the end of 2017. In sight of the transition from NEDC to WLTP, many research activities, both experimental and numerical, have been carried out to verify the capability of current and future engine/vehicle technologies to meet the new regulations on fuel economy and green house gas emission. In this work simulation is used to estimate fuel consumption and CO2 emission of a Euro 5 city car over WLTC, ARTEMIS and FTP- 75, assuming NEDC as reference. A fuel map of a two cylinder port injection turbocharged SI engine, actually installed in the selected city car, is set up, based on a 1D model validated against experimental data. The fuel map is integrated in a vehicle/driveline model to estimate engine torque and speed required second per second along each driving cycle. Simulations have been performed assuming both idle operation and fuel cut-off strategy to highlight the effect on cycle CO2 emission of fuel cutoff when vehicle is stopped. Simulations show that for a vehicle with small engine and low mass, WLTC leads to higher CO2 emission in comparison with NEDC both without and with fuel cut-off strategy, with increases of 8.4% and 11.8%, respectively. Greater increases result over ARTEMIS and FTP-75 cycles, that is 14% and 15.4% without fuel cut-off and 14.3% and 12.7% with fuel cut-off, respectively, confirming more severe features with respect to NEDC.