What is the unit shown in the illustration commonly referred to as?

The term "fuel injector" is commonly used to describe the unit shown in the illustration. This component plays a crucial role in modern internal combustion engines by precisely delivering a specific amount of fuel into the engine's combustion chamber. Fuel injectors utilize various technologies to ensure optimal fuel atomization and mixing with air, which contributes to efficient combustion and improved engine performance.

Understanding the function of the fuel injector is essential for maintenance and troubleshooting in marine engineering, as it directly impacts fuel efficiency, emissions, and overall engine reliability. In contrast, the other options refer to different components with distinct functions: a combustion rod relates to engine mechanics; an interstage unloader is used in compressed air systems; and a governor relief valve is associated with controlling fluid flow and pressure in machinery. This highlights the specificity and importance of the fuel injector in the context of engine operations.