An automotive technician is analyzing the mechanical timing of a four-stroke internal comb… — Armed Services Vocational Aptitude Battery (ASVAB)

An automotive technician is analyzing the mechanical timing of a four-stroke internal combustion engine. To complete all four strokes of the operating cycle (intake, compression, power, and exhaust) within a cylinder, how many complete revolutions must the crankshaft make?

Two revolutions ( $720^\circ$ )Answer
B
Four revolutions ( $1440^\circ$ )
C
One revolution ( $360^\circ$ )
D
One-half revolution ( $180^\circ$ )

Answer

Two complete revolutions (

720^\circ

)

In a four-stroke internal combustion engine, each stroke (intake, compression, power, exhaust) moves the piston from top dead center (TDC) to bottom dead center (BDC) or vice versa. Each linear stroke rotates the crankshaft through

180^\circ

of an arc (half a turn). Completing all four distinct strokes requires

4 \times 180^\circ = 720^\circ

of total rotation, which equals exactly two complete revolutions of the crankshaft.

Step-by-Step Solution

Determine the degrees of crankshaft rotation produced during a single piston stroke

Each individual stroke moves the piston between top dead center (TDC) and bottom dead center (BDC), rotating the crankshaft

180^\circ

(one half-turn).

A single linear sweep of the piston through the cylinder corresponds to half of a circular revolution of the crankshaft journal throw.

Calculate the total rotational degrees required for all four strokes in the cycle

4 \text{ strokes} \times 180^\circ = 720^\circ

The complete four-stroke cycle requires the sequential execution of intake, compression, power, and exhaust strokes.

Convert total rotational degrees into complete revolutions

\frac{720^\circ}{360^\circ \text{ per revolution}} = 2 \text{ complete revolutions}

One full circular revolution corresponds to

360^\circ

Key Concept

Kinematic relationship between piston strokes and crankshaft rotation in a four-stroke internal combustion engine

Estimated Time:1m 0s

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