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Difficulty: EasyEngine Principles and Internal Components

In a four-stroke internal combustion engine, the operating cycle begins by drawing a fresh charge into the cylinder. Which stroke occurs when the intake valve is open and the downward motion of the piston creates low pressure to pull in the air-fuel mixture?

  1. A
    Compression stroke
  2. Intake strokeAnswer
  3. C
    Power stroke
  4. D
    Exhaust stroke

Answer

Intake stroke
The intake stroke is the first stroke of the four-stroke cycle. As the piston travels downward from top dead center (TDC) to bottom dead center (BDC), the intake valve opens, creating a partial vacuum inside the cylinder that pulls the fresh air-fuel mixture into the combustion chamber.

Step-by-Step Solution

1
Identify the mechanical position, piston direction, and valve states described in the question.
The intake valve is open, the exhaust valve is closed, and the piston is traveling downward toward bottom dead center.
These specific mechanical conditions determine the exact phase of the four-stroke cycle.
2
Match the identified mechanical conditions to the corresponding stroke phase.
The intake stroke is the only stroke where the intake valve opens to allow the descending piston to draw in the air-fuel mixture.
Matching the valve timing and piston movement confirms the phase name.

Key Concept

Four-stroke internal combustion cycle events
Estimated Time:35s
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Topics

Engine Principles and Internal Components

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