Diesel engines use precombustion chambers located between the combustion chamber and the injection. The pre-chambers can be considered as part of the combustion chamber, but are separated from it by holes. Their task is to ignite the injected fuel already here in the pre-chamber at the end of the compression, thus passing the combustion into the combustion chamber, which results in a faster and more perfect combustion.
Description precombustion chamber
What is a precombustion chamber?