🔍 Key Concepts

• Closed-type fuel injection nozzle construction and operation • Differences between hole-type, multi-hole, and pintle-type nozzles • How fuel pressure acts on the needle valve in a closed nozzle

💭 Think About

• Think about what makes a nozzle "closed" versus "open" and how the needle valve is kept seated until injection begins. • Consider which nozzle design is typically used in direct-injection engines and how the fuel is distributed into the combustion space. • Ask yourself which nozzle type has a projecting tip that could be more exposed to carbon buildup in the combustion chamber.

✅ Before You Answer

• Verify how a needle valve in a closed nozzle actually opens (what forces act on it). • Check which nozzle type(s) are commonly used with precombustion chambers versus direct injection. • Consider which design is more or less self-cleaning and why the flow pattern through the orifice(s) matters.