Stratified Engine

Stratified engine combines features of the gasoline and diesel engines.   The air/fuel mixture is stratified to produce a small, rich mixture at the spark plug while providing a leaner, more efficient and cleaner-burning main mixture.   Also, the air/fuel mixture is swirled for more complete combustion. ^{Erjavec 201}

Four-stroke cycle (A) a large amount of very lean mixture is drawn through the main intake-valve on the intake stroke into the main combustion chamber.   At the same time, a small amount of rich mixture is drawn through the auxilliary intake valve into the precombustion chamber.   At the end of the compression stroke (B), the spark plug fires the rich mixture in the precombustion chamber.   As it ignites it ignites the lean mixture in the main chamber.   This reduces the formation of carbon monoxide during the power stroke (C).   Also, the peak temperature stays low enough to minimize the formation of nitrogen oxides and the mean temperature is maintained high and long enough to reduce hydrocarbon emissions.   During the exhaust stroke (D), the hot gases exit through the exhaust valve.   The advantages of this engine are (1) good part-load fuel economy, (2) efficient operation on low-octane fuel, and (3) low exhaust emissions. ^{Erjavec 201-202}