What do you want to know? Indirect injection has traditionally been used for small, high-speed engines where the rapid fuel-air mixing required is achieved by air being forced into an auxiliary combustion chamber toward the end of the compression stroke. This chamber promotes highly turbulent flow, and when the fuel is injected, high mixing rates can be achieved. The resulting pressure rise causes the combustion gases to expand into the main chamber, where combustion continues, and the resulting turbulence aids complete combustion. A direct injection design (as seen on traditional large diesel engines, and in modern small engines) puts the combustion chamber into the piston bowl, and relies on inlet port and piston design to create the necessary turbulence for combustion.