FAA Aviation Mechanic Powerplant (AMP)Reciprocating EnginesMedium
In a continuous-flow fuel injection system, what is the primary function of the individual fuel discharge nozzles installed at each cylinder's intake port?
- ATo precisely time fuel injection to coincide with each cylinder's intake valve opening, like a diesel injector
- BTo continuously spray a metered fuel flow into the intake airstream near the intake valve for vaporization before entering the cylinder
- CTo atomize fuel directly into the combustion chamber during the power stroke
- DTo mechanically divide fuel flow equally among cylinders based on engine RPM
Show answer & explanationAnswer & explanation
Correct answer: B. To continuously spray a metered fuel flow into the intake airstream near the intake valve for vaporization before entering the cylinder
Continuous-flow fuel injection nozzles spray fuel continuously (not timed to valve events) into the intake port just upstream of the intake valve, where it mixes with incoming air and vaporizes before entering the cylinder. Fuel division among cylinders is handled by the flow divider, not the nozzles themselves.
Why the other options are wrong
- A. Continuous-flow systems are not timed injections; that describes a diesel-type direct injection system.
- C. Fuel is not injected directly into the combustion chamber in continuous-flow systems; it enters via the intake port.
- D. Equal fuel division among cylinders is the function of the flow divider, not the nozzles.
Fuel Injector Nozzle (Continuous-Flow)
A calibrated orifice at each cylinder's intake port that continuously sprays metered fuel into the airstream for vaporization before entering the cylinder.
- Fuel flow is continuous, not timed to valve events
- Located at intake port near intake valve, not inside cylinder
- Flow divider (not nozzles) apportions fuel equally to each cylinder
Memory trick: 'Nozzles never stop spraying — timing is the divider's job'