What is the purpose of pre injection on a common rail diesel?

The purpose of pre-injection in a common rail diesel system is to improve combustion efficiency and reduce emissions. By injecting a small amount of fuel before the main injection, pre-injection helps to create a more homogeneous air-fuel mixture, which leads to a smoother combustion process. This can help reduce noise, vibrations, and particulate matter in the exhaust, ultimately enhancing engine performance and compliance with environmental regulations.