Auto Technician A says the total volume of all the cylinders in an engine is called the compression ratio?

The volume of an engine is called displacement and is typically measured in cubic inches or liters. An eight cylinder engine that could hold 1/2 liter of water (or air) in each cylinder would be a four liter engine. As the pistons move to the top of the cylinder in an exhaust stroke, they theoretically "displace" the 1/2 liter of air in each of the cylinders.

The compression ratio is calculated during the compression stroke. If the piston occupies 90% of the enclosed cylinder space when it is at top dead center, the compression ratio is said to be 10 to 1, or 10:1. If the displacement of the cylinder was 10 cubic inches, it would have been compressed to 1 cubic inch.