Section 1, Lesson 3
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Systems: How a Carburetor Works

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Carbureted Engines

Carburetors use a venturi to suck air and fuel into an intake manifold, where it is then delivered to the cylinders. to adjust power, we control the amount of fuel-air mixture permitted to pass through the venturi, as well as the ratio of air to fuel.

Lesson Notes

In a carbureted system, fuel is sucked into the carburetor venturi where it vaporizes and is then distributed to the cylinders through an intake manifold. After combustion, exhaust gasses exit the cylinders through an exhaust manifold, and then through the exhaust pipe.

The mixture, throttle and carburetor heat controls are all attached to cables, which mechanically operate their respective valve.

Carburetors are a simple, cheap and reliable method of fuel delivery. However, they are susceptible to icing inside the venturi, which reduces, and can even eliminate, power.

Additional Resources

Flashcard Questions

  • What is the major disadvantage to a carbureted system?
  • What brings fuel from the float chamber to the venturi?
  • What distributes fuel-air mixture to each cylinder after if passes through the venturi?
  • Describe how the throttle plate operates.
  • Mechanically speaking, how does the mixture control operate?
  • What happens to air temperature inside the venturi? Why?
  • You are flying on a humid day and notice the engine starting to run rough and see a drop in RPM. Suspecting carburetor icing, you turn carburetor heat on. You notice a drop in RPM. Is this normal?
  • When you suspect an engine problem is related to carburetor ice it is imperative that you turn on the carburetor heat as quickly as possible. Why?