Cubic Inch

The cubic inch is a unit of measurement for volume in the Imperial units and United States systems. It is the volume of a cube with each of its three dimensions (length, width, and depth) being one inch long. The cubic inch of a motor, in most cases, is a reference to the size of the motor. Cubic inches or Cu  is the imperial equivalent of cc or cubic centimeters for internal combustion engines. Technically speaking, it is the sum of the volumetric displacement of the pistons as the engine makes one complete rotation. Most engine sizes nowadays are communicated in liters instead of cubic inches. Motorcycle engine sizes are usually given in cubic centimeters, and in the world of drag racing “there ain't no substitute for cubic inches” which means that the bigger an engine, the more power you can make.


Cubic Inch displacement (CID) can be determined by using the following formula: CID= (GPM x 231)/RPM. If you’re not sure about your Gallons per Minute (GPM) or Revolutions per Minute (RPM) calculations, you can also measure the gear chamber on your gear pump. In an automobile, it is used to describe the internal volume or 'displacement' of the engine cylinders. So a 386 cu in, eight cylinder engine has eight cylinders each of 48.25 cu in. A 2000cc (or 2 litre) engine has a displacement of 122 cu in based on the fact that 1 cu in = 16.387 cc. It is also important to take into account engine displacement, another way to explain the size and power of an engine. It depends on three factors: the number of cylinders, bore (interior diameter of a cylinder), and stroke (interior length of a cylinder). The formula for displacement in this form is D = (π/4)B²SN. Here is a calculator, and a great resource to help you do all these calculations instantly. 

Displacement and Hydraulic Systems

Displacement in hydraulics is a power variable that indicates how much fluid is moved by a hydraulic pump in one cycle. Displacement is measured in cubic inches per revolution or cubic centimeters per revolution. When trying to properly understand how displacement will affect every area of your hydraulic system it can get a little tricky. There are a multitude of options when it comes to hydraulic pumps, valves, motors and cylinders so it’s important to know which items to chose based on power and displacement properties to make sure your system will be working properly. Our staff is happy to help answer any questions you might have.

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