RC Engine Size Measured

The best way to determine the displacement for a specific engine and vehicle is to view the detailed specs for that engine which should list the displacement in either cubic centimeters or cubic inches (or both). However, if you don't have the specs handy for a specific engine, you can often figure out the approximate displacement based on the name, as explained below.
RC engine size or displacement is measured in cubic centimeters (cc) or cubic inches (ci). In terms of RC engines, displacement is the volume of space a piston travels through during a single stroke.Displacement is only one factor that determines performance of the vehicle.

Typical RC Engine Displacements

Common RC engine displacements range from about .12 to .46 and larger. These numbers that begin with a decimal point are the displacement in cubic inches. Sometimes the abbreviation ci is appended to the measurement. But just remember that a .18 engine is actually .18ci or .18 cubic inches of displacement.
That same .12 to .46 range, expressed in cubic centimeters would be approximately 1.97cc to 7.5cc of displacement. Below is the small reference list (cc is rounded) to give you an idea of how cubic inches compare to cubic centimeters:

• .12ci - 2.0cc
• .15ci - 2.5cc
• .18ci - 3.0cc
• .21ci - 3.5cc
• .25ci - 4.1cc
• .27ci - 4.4cc
• .32ci - 5.2cc
• .36ci - 5.9cc
• .46ci - 7.5cc
  

Determining Size by Numbers in a Name

Studying the manufacturer’s specifications is the best way to determine engine size, but manufacturers will often include a number in the name of the vehicle or the name of the engine that represents the displacement. For example, the HPI Firestorm 10T is described as having a G3.0 engine. The 3.0 refers to the displacement of 3.0cc. That 3.0cc is the equivalent of a .18 engine.