Lesson 2/Learning Event 1
FIGURE 40. PRECOMBUSTION CHAMBER.
The precombustion type of chamber is also used in the smaller, high-speed engines.
These chambers are thought to have features that improved the burning of fuel at high engine speeds. Fuel is
injected into a smaller ignition chamber to improve burning of fuel. Later, it was learned that as the fuel
injectors were improved and engines were built with higher compressions, the open-type combustion chamber
worked well at all engine speeds. The open chamber is now used in many military high-speed diesels. A few
high-speed diesels, such as the HMMWV and the CUCV, still use other types of chambers.