Cylinder (engine)

An engine cylinder is the chamber where a piston moves to convert pressure into mechanical work. This article explains parts, layouts, operation, history, and maintenance considerations.

Author: Leandro Alegsa Creation date: November 13, 2022 Last updated: May 16, 2026

Overview

The cylinder is the chamber inside an internal combustion or reciprocating engine where a piston moves to convert expanding gases into mechanical motion. In most modern engines several engine cylinders are arranged in an engine block and work together. The vertical distance a piston travels is the stroke; the cylinder's internal diameter is the bore. Together bore and stroke determine displacement and influence torque, power and efficiency.

Major parts and characteristics

A typical cylinder assembly includes a liner or bore surface, the piston crown, rings, connecting rod journal area, and the combustion chamber at the top. Cylinder heads contain openings for valves, spark plugs or fuel injectors and form the upper boundary of the combustion space. Key technical terms are compression ratio, bore, stroke and surface finish; each affects sealing, heat transfer and wear.

Arrangements and operation

Cylinders may be organized in inline, V, flat (boxer), radial or opposed layouts to balance forces and package size. Two-stroke and four-stroke cycles use the cylinder differently: valves are used in four-stroke designs, while two-stroke designs rely on ports in the cylinder walls. The piston transfers force through the connecting rod to the crankshaft and is sometimes simply described as the piston moving within the cylinder.

History and development

Early steam and internal combustion engines established the basic cylindrical chamber concept; over time materials and machining improved tolerances. Wear-resistant liners, refined casting techniques and coatings have extended service life and allowed higher compression and temperatures.

Uses, maintenance and notable distinctions

Cylinders are central to cars, motorcycles, small engines, marine and industrial powerplants. Maintenance focuses on ring wear, scoring, cylinder taper and head gasket integrity. Some modern engines employ cylinder deactivation to improve fuel economy by shutting down individual cylinders under light load. Distinctions such as the number of cylinders, firing order and bore/stroke ratio strongly affect smoothness, efficiency and character.

Summary

The cylinder is a fundamental component of reciprocating engines: a precisely finished chamber that guides the piston and forms the combustion space. Its design influences performance, emissions and durability across a wide range of applications.

Use of the term

General

a rotating part of machinery used to apply pressure to a workpiece or to impart properties to the workpiece by changing its direction (e.g. in a calender or the rotary cylinder of a printing press), also known as a roller.
the working element of a technical circuit, which is controlled by an actuator (often a valve).

For motors or pumps

the tubular chamber in which a piston moves, as used in piston pumps, steam engines and reciprocating internal combustion engines. Such machines are called reciprocating engines. Piston engines may have one or more cylinders; in double-piston engines, cylinders with a common combustion chamber are counted as one. The stroke (linear motion) of the piston in the cylinder of the reciprocating engine may be converted into rotary motion, for example of a wheel or crankshaft, by means of a connecting rod. The inversion, i.e. the conversion of a rotation into a translation, is also possible in principle. In internal combustion engines, the cylinder opens into the crankshaft housing on one side and is closed or closable by valves on the other side.

In piston steam engines, the steam usually acts alternately on both sides of the piston, and the cylinder is closed on both sides for this purpose. The steam supply is usually controlled via slide valves, but sometimes via valves.

In counter-rotating engines, the cylinder liner is open on both sides. The working medium (gas or air, gasoline-air mixture, air for direct injection) is controlled via the intake and exhaust ports.

In linear technology

electromechanical cylinders, also known as electromechanical lifting cylinders or electromechanical actuators. The basic principle of electromechanical lifting cylinders is also found in so-called telescopic lifting columns (also: lifting column or telescopic actuator).

Gas springs also have a cylinder which is filled with gas, the overpressure of which causes the gas cylinder piston to extend (the pre-stroke).

In fluid power

a drive unit for linear - more rarely also rotating - movements. The movement of the piston is transmitted to the parts to be moved via the piston rod or magnetic frictional connection. The exit of the piston rod from the pressure chamber must be sealed. A distinction is made between single-acting and double-acting cylinders (work is performed in one direction only or in both directions). Cylinders in hydraulics or pneumatics are the two fluid elements

Pneumatic cylinders and
Hydraulic cylinder

Circuit symbols for cylinders for use in pneumatic or hydraulic circuit diagrams can be found in the list of circuit symbols (fluid power).

In printing technology

one impression cylinder
Cylinder printing techniques are: Cylinder against cylinder, cylinder against surface
See also: Oscillating cylinder, cylinder press and oscillating cylinder press

Norm data (subject term): GND: 4068325-4 (OGND, AKS)

Cylinder liner of an opposed piston engine

A hydraulic cylinder on a construction machine

Author

Creation date: November 13, 2022

Last updated: May 16, 2026