Fuel consumption and CO2 emissions of passenger cars over the New Worldwide Harmonized Test Protocol

AbstractIn 2014 the United Nations Economic Commission for Europe (UNECE) adopted the global technical regulation No. 15 concerning the Worldwide harmonized Light duty Test Procedure (WLTP). Having significantly contributed to its development, the European Commission is now aiming at introducing the new test procedure in the European type-approval legislation for light duty vehicles in order to replace the New European Driving Cycle (NEDC) as the certification test.The current paper aims to assess the effect of WLTP introduction on the reported CO2 emissions from passenger cars presently measured under the New European Driving Cycle and the corresponding test protocol. The most important differences between the two testing procedures, apart from the kinematic characteristics of the respective driving cycles, is the determination of the vehicle inertia and driving resistance, the gear shifting sequence, the soak and test temperature and the post-test charge balance correction applied to WLTP. In order to quantify and analyze the effect of these differences in the end value of CO2 emissions, WLTP and NEDC CO2 emission measurements were performed on 20 vehicles, covering almost the whole European market. WLTP CO2 values range from 125.5 to 217.9g/km, NEDC values range from 105.4 to 213.2g/km and the ΔCO2 between WLTP and NEDC ranges from 4.7 to 29.2g/km for the given vehicle sample. The average cold start effect over WLTP was found 6.1g/km, while for NEDC it was found 12.3g/km. For a small gasoline and a medium sized diesel passenger car, the different inertia mass and driving resistance is responsible 63% and 81% of the observed ΔCO2 between these two driving cycles respectively, whereas the other parameters (driving profile, gear shifting, test temperature) account for the remaining 37% and 19%

Assessment of real world CO2 emissions from passenger cars using simulation models and PEMS data

The European vehicle type approval procedure for CO2 emissions and fuel consumption is based on controlled laboratory conditions. In this paper, the possibility to evaluate real-world CO2 emissions with generic vehicle simulation models developed on the basis of measurements with Portable Emissions Measurement Systems (PEMS) is investigated. For this purpose, the CO2 emissions and fuel consumption for real-world driving profiles are simulated with validated vehicle models using OEM specifications and the results are compared against experimental data. The same procedure is repeated for newly developed vehicle models using generic data, such as the engine map and the powertrain losses. A comparison between the simulated CO2 emissions of the above mentioned vehicle model types and the measurements is conducted. Parameters that needed further calibration were highlighted and addressed. The error of total simulated CO2 emissions was lower than ±3% for all models and the error of the instantaneous cumulative fuel consumption remained within ±5% over the entire test