Khan, S. and Ayyappath, P., "Design and Development of Variable Valve Timing and Lift Mechanism for Improving the Performance of Single Cylinder Two Wheeler Gasoline Engine," SAE Technical Paper 2014-01-1699, 2014, doi:10.4271/2014-01-1699.
A small single cylinder 4 stroke gasoline engine varying capacity from 100cc to 1000cc generally used for two wheelers has a wide range of engine speeds during operation and may vary from 1000 RPM to 10000 RPM. Such variation in speed of engine demands variation in the valve timing and lift of engine at different speeds for optimum performance.The work aims at improving the performance of single cylinder two wheeler gasoline engine. The objective is to implement the novel variable valve timing and lift mechanism in the two wheeler single cylinder 4 stroke gasoline engine for the improvement in performance. The system design through kinematic calculations and 3D modeling, the prototyping with assembly, the functioning of system and its effect on the performance of engine are discussed in details. Valve timing and lift optimization was done using 1D simulation for performance prediction. The system includes a spring operated switching mechanism by which we achieve variation in valve timing and lift of intake valve at different speed range. The system is made compact to accommodate in the extremely small space of a single cylinder 110cc 4 stroke SOHC engine generally used in scooters and motorcycles. An electronic control circuit and DC motor is used to sense speed and actuate the mechanism respectively. Thus with this mechanism we achieve a variation in engine valve timing and lift at different speed range of the engine in stages. The mechanism was assembled and tested on engine dynamometer for studying operation of the mechanism on the engine at various speeds.The work explains the impact of system prototype when installed on the two wheeler engine and resulting improvement in Volumetric Efficiency and Torque of Engine, hence a reduction in fuel consumption. On the whole it concludes that this system can be implemented on small engines for better performance.