_applied sciences_  
_Editorial_  
Advanced Technologies for the Optimization of Internal Combustion Engines  
[PERSON]\({}^{\star}\)\({}^{\copyright}\) and [PERSON] \({}^{\copyright}\)  
Institute of Science and Technology for Sustainable Energy and Mobility (STEMS-CNR), Italian National Research Council, Via Marconi 4, 80125 Napoli, Italy; [EMAIL_ADDRESS]  
\({}^{\star}\) Correspondence: [EMAIL_ADDRESS]  
Even in a scenario where electric vehicles gain market share and the sale of internal combustion engines is gradually reduced, at the present time, there are still no real options that can totally replace the internal combustion (IC) engine over the entire range of its applications. In the short-to-medium term, on-road and off-road transportation will most likely be characterized by a mix of solutions, including strongly electrified powertrain configurations, as well as conventional vehicles powered by IC engines. The combustion engine will continue playing a central role; for this reason, there is a pressing need for its further optimization in terms of thermal efficiency and pollutant emissions. This goal can be achieved through more efficient and environment-friendly technologies. The aim of this Special Issue is to put together the recent research in advanced technologies for the optimization of internal combustion engines in order to help the scientific community address the efforts toward the development of higher-power engines with lower fuel consumption and pollutant emissions. This Special Issue contains \(11\) technical articles that have been peer-reviewed under the journal's rigorous review criteria. Papers [1,2] deal with water injection technology that represents a promising solution to make turbocharged spark-ignition engines operate with higher compression ratios, higher boost pressures, and stoichiometric combustions at high loads. This allows a reduction in brake-specific fuel consumption and, thus, in CO\({}_{2}\) emissions on the overall engine map. In [1], a detailed experimental analysis of a low-pressure water spray in the intake manifold (PWI technology) was presented, covering a lack of experimental data on automotive PWI systems. The obtained results evidenced how significant benefits in terms of atomization quality can be obtained by adopting injection pressure and water temperature levels compliant with standard low injection pressure technologies. An alternative way of introducing water in an SI engine is in the form of an emulsion with gasoline (water-in-gasoline emulsions (WiGE)). This solution shows some advantages compared with the standard separate injections of water and gasoline. In [2], the authors performed an experimental investigation of WiGE effects on the performance and emissions of a turbocharged port fuel injection spark-ignition engine. WiGE was produced through a prototype micro-channel emulsifier that allows using a very small amount of surfactant to create stable emulsions. Water-in-gasoline emulsions demonstrated to be a suitable technique to reduce fuel consumption at medium/high loads of turbocharged spark-ignition engines, enabling stoichiometric combustions while preserving the turbine blades from severe thermal stresses. Two contributions to this Special Issue deal with the use of alternative fuels for internal combustion engines as a promising solution for a more sustainable operation. The research work reported in [3] assessed the combustion and performance of a dual-fuel operation in a spark-ignition engine that simultaneously integrates acetone-butanol-ethanol (ABE) and hydroxy (HHO) doping in comparison with standalone gasoline operation. The implementation of the dual-fuel operation in spark-ignition engines proved to be a valuable tool for controlling emissions and reducing fuel consumption while maintaining combustion performance and thermal efficiency. In [4], an experimental study was carried out on the effects of diesel surrogates (hydrotreated vegetable oil (HVO) and oxymethylene ethers (OMEX)) on main spray and combustion characteristics.