What is porting all about?
Most automotive engines are 4-stroke designs that use cams and springs to open and close the valves that let in the intake charge and let out the exhaust. Not only do the cams open and close the valves, they control when they open and how far they open, thus affecting the performance characteristics of the engine. Longer open times and higher lifts allow more flow, thus raising power output to a higher engine speed and level. Most outboard, model aircraft, chainsaw and leaf blower engines and many other small engines are 2-stroke designs. 2-strokes use a series of ports, usually opened and closed by the piston skirts, to control intake and exhaust timing and volume. The port size determines the amount that can flow through it, and the position and size determine when the port opens and closes. The rotary incorporates the 4-stroke boinger concepts of four distinct cycles, intake, compression, power, and exhaust, with the use of ports unfettered by poppet valves, which are instead opened
