Combustion Chamber Design for Two-Stroke Cross-Flow Outboard Engines

The factors considered in the new design of combustion chambers for 2-stroke cross-flow outboard engines are combustion control and trapping and air flow considerations. The former includes (1) compression ratio and the effects of surface-to-volume ratio; (2) volume location as determined relative to the piston baffle; (3) spark plug temperature; (4) knock and pressure rise control as related to flame travel and change of volume of mixture consumed; (5) octane number requirements; (6) the effect of thin rings on metal temperature and engine friction; and (7) oil-fuel mixture effects on friction and power. Trapping and air flow considerations include (1) flow path control as determined by static pressure rise; (2) pressure reversals in air column with possible back flow; and (3) fuel separation in boundary layers and effects on carburetion.