External Chamber
Term sometimes used to describe the antechamber (swirl chamber, pre-combustion chamber) on compression - ignition ("diesel") engines of "indirect injection" design. Fuel is injected either entirely or principally into this chamber. It ignites and, while burning, is forced through a small passage into the main combustion chamber. This design gives somewhat lower maximum ignition pressures and thus permits lighter construction of the engine as well as smoother running and is thus popular for smaller commercial vehicles and private cars.