**9. Conclusions**

This research work focused on the prediction of fuel consumption of a Diesel heavyduty engine in real driving cycles, by means of computer simulations. As investigated in previous works, the map-based approach (relying on tables derived through the engine steady-state analysis), to represent the IC engine characteristics within a vehicle model, can be very fast but it could also provide poor results in terms of fuel consumption and pollutants emissions, especially with new and demanding test cycles. In fact, this approach completely disregards the engine dynamics, which runs considering a simple sequence of steady-state points, with a sort of instantaneous transition from one to another.

To define a reliable simulation tool for the analysis of IC engines during transients, this work investigated the suitable coupling of a complete vehicle model to an IC engine model, interacting in real-time during an RDE.

A 0D/1D six-cylinder Diesel engine model has been developed and, with some calibration of its combustion model on the basis of the available experimental data, validated in steady-state (engine map) conditions. Hence, the study focused on the transient operation of the IC engine, which has been integrated into a complete vehicle model, by means of the Simulink® environment and coupled to vehicle models. A conventional vehicle architecture has been compared to a hybrid architecture, to highlight the performances of the two solutions and the prediction of fuel consumption by means of the usual map-based approach and the transient approach.

Future developments could focus on the prediction of pollutant emissions under transient operation. In fact, the complete transient model built could provide the input data, in terms of cylinder-out emissions, to the after-treatment simulation model coupled to the IC engine itself, which could highlight the tailpipe emissions during different RDE cycles and strategies.

**Author Contributions:** Conceptualization, T.C. and G.D.; Data curation, A.M. and G.M.; Formal analysis, A.M., G.M. and A.O.; Funding acquisition, A.O.; Investigation, M.T. and T.C.; Project administration, G.D. and A.O.; Resources, G.D. and E.P.; Supervision, A.M., T.C., G.M., G.D. and A.O.; Validation, E.P. and E.E.P.; Visualization, T.C.; Writing—original draft, A.M., E.P. and E.E.P.; Writing—review & editing, A.M., G.M. and E.E.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by European Union, gran<sup>t</sup> number 824314.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Acknowledgments:** The authors wish to thank the European Union project VISION-xEV (virtual component and system integration for efficient electrified vehicle development), which received funding from the EU Horizon 2020 research and innovation program, under gran<sup>t</sup> agreemen<sup>t</sup> No 824314. The authors are also grateful to the project partners involved the IC engine simulation activity, in particular to FPT Industrial for providing the experimental data required to validate the simulation models.

**Conflicts of Interest:** The authors declare no conflict of interest.
