Improvement of Gasoline Engine Performance and Fuel Economy Through New Hollow Head Valve

In recent years, the international emission standards for vehicles have become increasingly stringent, introducing new homologation cycles and limiting emission worldwide. In the next future, CO₂ target and RDE regulation will force engine manufactures to further increase the efficiency of the engines making them operate with air to fuel ratio (\(\lambda \)) equal to 1 on entire calibration map. For gasoline engines, the knock tendency is the main barrier for the operation with stoichiometric mixture at high loads, which is an important driver to decrease fuel consumption and improve catalytic converter efficiency. One possible way to prevent knocking is to reduce the engine combustion chamber temperature. This paper presents an optimized hollow head valve able to improve knocking tendency by reducing significantly valve combustion face temperature. An innovative design and manufacturing process enabled to achieve outstanding cooling effect, as demonstrated by thermometric testing. Engine calibration testing with hollow head valves proved a remarkable gain in \(\lambda \) and spark advance, if compared to hollow stem. This effect translates into a clear advantage for engine manufacturers, enabling them to improve fuel consumption.