An overview of the Effect of using HHO on Spark ignition and direct injection engines combustion, performances, and emissions characteristics

: One of the major issues, the energy crisis, makes the globe dangerous and violent [1]. Every day, there is an increase in energy demand. Resources of energy are running out swiftly, and all indicators point to their impending demise. In such cases, renewable energy sources must be given more consideration. The widespread use of fossil fuels renders them unsustainable because they increase CO 2 levels and emit greenhouse gases that harm the environment [2]. With several trials of usage of HHO gas or compressed natural gas as a fuel performance improver on both internal combustion engines powered by gasoline or diesel up until this point, many advancements have been made in this field[3]. This paper comprises a survey of the numerous advancements that have occurred in this area. There was a net lead to an amplified in brake power from 2.1% to 5.8% and an increase in brake thermal efficiency from 10.27% to 35% with the addition of HHO gas. The usage of traditional fuels decreased by 20% to 30%, and HC and CO exhaust emissions decreased by an average of 14% and 18%, respectively.