Indirect-injection, also referred to as pre-chamber, is one of the combustion chamber shapes used in diesel engines.
This type is provided with, in addition to the main combustion chamber, a combustion chamber referred to as a pre-chamber (pre-combustion chamber, swirl chamber), and the two chambers are connected by a narrow passage.
Fuel is injected into the pre-chamber, and, while igniting, combusting, and expanding, flows into the main combustion chamber together with uncombusted gas, were it combusts further.
With the swirl-chamber, when air inside the cylinder is sent to the pre-chamber (swirl chamber) on the compression stroke, strong swirling is generated, which rapidly mixes the injected fuel and air, allowing combustion to be performed quickly.
Accordingly, it is capable of faster rotation and has a lower fuel consumption rate than normal pre-combustion chambers.

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