Question

Technician A says that a ratio is a comparison between two values. Technician B says that in a compression ratio, the main values are the cylinder volumes at the two different piston positions, BDC and TDC. Who is right

Answer 1

Both technicians are right.


The compression ratio is the ratio ...
  (cylinder volume at BDC) / (cylinder volume at TDC)

Technician A might need to add that the comparison is one in which one value is divided by another (as opposed to comparison by subtraction).

Technician B might need to add that the volumes are divided one by the other. Knowing only two values doesn't tell you their ratio. Additional math must be performed.