🔍 Key Concepts

• Unit injector design in medium- and high-speed diesel engines • Basic functions needed to get fuel from the pump into the cylinder: metering, pressurizing, atomizing • How combining components into one "unit" changes what that device must do

💭 Think About

• Think about everything that has to happen to a fuel droplet from the time it leaves the fuel gallery until it is burning inside the cylinder. Which of those jobs must still be done right at the injector? • If the injector is a self‑contained "unit" instead of part of a separate pump-and-line system, does it take over just one job or several? • Ask yourself: in a conventional system, what parts meter, what parts pressurize, and what parts atomize? How would that change when they are all combined into a single unit sitting in the cylinder head?

✅ Before You Answer

• Be clear on the difference between fuel metering (how much), fuel pressure generation (how hard), and atomization (how fine the spray is). • Verify what makes a unit injector different from a separate injection pump + high‑pressure line + injector nozzle system. • Check whether, by definition, a "unit" injector must perform one, two, or all three of these functions within the same assembly.