The Worldwide Harmonized Light Duty Test Procedure (WLTP), recently issued as GTR15 by UNECE-WP29, is designed to check the pollutant emission compliance of Light Duty Vehicles (LDVs) around the world and to establish the reference vehicle fuel consumption and CO₂ performance. In the course of the development of WLTP, the Joint Research Center (JRC) of the European Commission has tested gaseous emissions of twenty-one Euro 4–6 gasoline and diesel vehicles, on both the current European type approval test procedure (NEDC) and the progressive versions of the WLTP. The results, which should be regarded just as an initial and qualitative indication of the trends, demonstrated minimal average differences between CO₂ emissions over the NEDC and WLTP. On the other hand, CO₂ emissions measured at JRC on the NEDC were on average 9% higher than the respective type approval values, therefore suggesting that for the tested vehicles, CO₂ emissions over WLTP were almost 10% higher than the respective NEDC type approval values. That difference is likely to increase with application of the full WLTP test procedure. Measured THC emissions from most vehicles stayed below the legal emission limits and in general were lower under the WLTP compared to NEDC. Moving from NEDC to WLTP did not have much impact on NO_x from gasoline vehicles and CO from diesel vehicles. On the contrary, NO_x from diesel vehicles and CO from low-powered gasoline vehicles were significantly higher over the more dynamic WLTP and in several cases exceeded the emission limits. Results from this study can be considered indicative of emission patterns of modern technology vehicles and useful to both policy makers and vehicle manufacturers in developing future emission policy/technology strategies.

Although Hybrid Electric Vehicles (HEVs) represent one of the key technologies to reduce CO₂ emissions, their effective potential in real world driving conditions strongly depends on the performance of their Energy Management System (EMS) and on its capability to maximize the efficiency of the powertrain in real life as well as during Type Approval (TA) tests. Attempting to close the gap between TA and real world CO₂ emissions, the European Commission has decided to introduce from September 2017 the Worldwide Harmonized Light duty Test Procedure (WLTP), replacing the previous procedure based on the New European Driving Cycle (NEDC). The aim of this work is the analysis of the impact of different driving cycles and operating conditions on CO₂ emissions and on energy management strategies of a Euro-6 HEV through the limited number of information available from the chassis dyno tests. The vehicle was tested considering different initial battery State of Charge (SOC), ranging from 40% to 65%, and engine coolant temperatures, from −7 °C to 70 °C. The change of test conditions from NEDC to WLTP was shown to lead to a significant reduction of the electric drive and to about a 30% increase of CO₂ emissions. However, since the specific energy demand of WLTP is about 50% higher than that of NEDC, these results demonstrate that the EMS strategies of the tested vehicle can achieve, in test conditions closer to real life, even higher efficiency levels than those that are currently evaluated on the NEDC, and prove the effectiveness of HEV technology to reduce CO₂ emissions.

To assess vehicle performance on criteria compounds, carbon dioxide emissions, and fuel energy consumption, laboratory tests are generally carried out. During these tests, a vehicle is driven on a chassis dynamometer (which simulates the resistances the vehicle encounters during its motion) to follow a predefined test cycle. In addition, all conditions for running a test must strictly adhere to a predefined test procedure. The procedure is necessary to ensure that all tests are carried out in a comparable way, following the requirements set by the relevant legislation. Test results are used to assess vehicle compliance with emissions limits or to evaluate the fuel consumption that will be communicated to customers. Every region in the world follows its own approach in carrying out these types of tests. The variations in approaches have resulted in a series of drawbacks for vehicle manufacturers and regulating authorities, leading to a plethora of different conditions and results. As a step toward the harmonization of the test procedures, the United Nations Economic Commission for Europe launched a project in 2009 for the development of a worldwide harmonized light-duty test procedure (WLTP), including a new test cycle. The objective of the study reported here was to provide a brief description of WLTP and outline the plausible pathway for its introduction in European legislation.

A light-duty engine Volvo D5 was run with gasoline to demonstrate that high-octane number fuels, in compression ignition engines, are able to achieve high efficiency, low NOx and soot simultaneously. An advanced three stage injection strategy was developed. A load sweep was performed between 6 and 17 bar IMEP and 2000 rpm. Gross indicated efficiency stays fairly constant at 47% with very low NOx and soot. In the second section of the paper, diesel was compared with gasoline, while in the final part the commercial 140°UA nozzle was compared with the narrower one, 120°, used in the above-mentioned experiments.

The World-wide harmonized Light duty Test Procedure (WLTP) issued as UNECE GTR No. 15 is designed to check the emissions compliance of Light Duty Vehicles (LDVs) around the world and European Commission is planning to introduce the WLTP in the European Type Approval process starting on 1 September 2017. WLTP has greatly reduced the flexibilities that are in the NEDC procedure and has eliminated many loopholes. However a certain degree of flexibility in the test procedure is necessary, otherwise no type approval test would be valid. In order to lower the impact of those flexibilities having influence on CO₂ emissions, a European Task Force dealing with the corrections of WLTP flexibilities was established. The work presented in this paper shows the result of the practical implementation of some corrections, such as imbalances in the state of charge (SOC) of the battery, deviations against the target road load, target speed, target distance, and target soak temperature. These corrections have been applied also to NEDC tests, in order to compare their impact with WLTP corrections. The repeatability “r” (test-to-test variations) and the reproducibility “R” (lab-to-lab variations) of CO₂ results measured in different laboratories, for the same vehicles, are evaluated before and after the normalization. In summary, all corrections steps performed in this study influenced the average CO₂ emissions by approximately 1.3% and 3.8%, for WLTP and NEDC respectively, which in our opinion is an indication of the reduction of flexibilities from NEDC to WLTP. This initial analysis of the impact of the correction on the repeatability and reproducibility of test results shows promising potential, however it must be pointed out also that in several cases the application of this methodology has led to a worsening of either r and/or R. In particular, the correction of the Road Load coefficients seems to have practical issues of difficult solutions. Further tests and analyses are needed and expected for a better understanding of this issue and for the improvement of the whole procedure.