17 / 20
The compression ratio of a piston engine is a ratio of:
  • A
    pressures.
  • B
    area and volume.
  • C
    areas.
  • D
    volumes.

The compression ratio is the ratio of the largest volume (total volume) to the smallest volume (clearance volume). In other words, it is the ratio between the volume of the cylinder with the piston at the BDC to the volume of the cylinder with the piston at the TDC.

When the piston is at TDC, the fuel/air mixture is compressed into a very small space between the top of the piston and the top of the cylinder. This is generally labeled as the clearance volume, or to put it simply, the smallest volume. On the other hand, when the piston is at the BDC, the volume of space containing the mixture (the total volume) is much larger. The difference between the total volume and the clearance volume is called the swept volume.

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.