The increasing demand for fossil fuels, rising fuel prices, and stringent emission regulations have intensified the search for alternative and supplementary fuels for internal combustion engines. This research focuses on the design, fabrication, and experimental evaluation of an HHO cell system integrated into a two-wheeler spark ignition engine as a supplementary fuel source. The project aims to investigate the feasibility of on-demand hydrogen–oxygen (HHO) gas generation through water electrolysis and its impact on engine performance, fuel efficiency, and exhaust emissions.

In this study, an HHO dry cell electrolyzer was designed and retrofitted to a 100–125 cc petrol two-wheeler engine. The system includes stainless steel electrode plates, an electrolyte solution, a bubbler unit for safety, a pulse width modulation (PWM) controller to regulate current supply, and an electrical connection powered by the vehicle battery. The generated HHO gas was supplied directly into the engine intake manifold to enhance combustion characteristics.

Experimental testing was conducted under various load conditions to measure parameters such as fuel consumption, brake thermal efficiency, and exhaust emissions (CO and HC levels). Comparative analysis between conventional petrol operation and petrol + HHO operation was performed. The results indicate improved combustion efficiency due to faster flame propagation and higher calorific value of hydrogen, leading to marginal improvement in mileage and noticeable reduction in carbon monoxide and hydrocarbon emissions.

The findings suggest that HHO-assisted combustion can act as a supplementary fuel technique for two-wheelers without major engine modification. Although complete replacement of petrol is not feasible due to electrical energy limitations, the system demonstrates potential for improving fuel economy and reducing environmental impact. Further optimization of cell design, electrolyte concentration, and electrical efficiency can enhance system viability for practical applications.