A multi-position 4-stroke piston engine utilizing a novel rotary valve system was developed for handheld outdoor power equipment applications such as chainsaws, brush cutters, and string trimmers. The purpose of the project was to create a low-emission 4-stroke engine with 2-stroke performance levels including high RPM limits and power output. This was accomplished using a rotary valve system in lieu of the typical poppet valves of traditional 4-stroke engines. The prototype was then incorporated into a functional product for overall performance evaluation.
Three prototype 45cc rotary valve engines were developed and tested in both real-world usage and on laboratory engine dynamometers to measure power output and emissions levels. The rotary valve system provided the ability to achieve high RPM limits without the risk of valve float, delivered improved volumetric efficiency, and exhibited lower vibration and noise levels with improved power density over traditional 4-stroke valvetrains. Additionally, the total valvetrain part count and complexity was greatly reduced over poppet valve cylinder head designs.
This paper will discuss the goals of this exercise and the relative performance of the final prototypes.