![Displacement](https://upload.wikimedia.org/wikipedia/commons/8/8a/Displacement.gif)
Engine displacement is the measure of the
cylinder
A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base.
A cylinder may also be defined as an infin ...
volume
Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). The de ...
swept by all of the pistons of a
piston engine
A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...
, excluding the
combustion chamber
A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process.
Interna ...
s. It is commonly used as an expression of an engine's size, and by extension as a loose indicator of the
power
Power most often refers to:
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power
* Power (social and political), the ability to influence people or events
** Abusive power
Power may a ...
an engine might be capable of producing and the amount of fuel it should be expected to consume. For this reason displacement is one of the measures often used in advertising, as well as regulating, motor vehicles.
It is usually expressed using the
metric
Metric or metrical may refer to:
* Metric system, an internationally adopted decimal system of measurement
* An adjective indicating relation to measurement in general, or a noun describing a specific type of measurement
Mathematics
In mathema ...
units of
cubic centimetre
A cubic centimetre (or cubic centimeter in US English) (SI unit symbol: cm3; non-SI abbreviations: cc and ccm) is a commonly used unit of volume that corresponds to the volume of a cube that measures 1 cm × 1 cm × 1 cm. One cu ...
s (cc or cm
3, equivalent to
millilitres
The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3). ...
) or
litre
The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3). ...
s (l or L), orparticularly in the United States
cubic inches (CID, cu in, or in
3).
Definition
The overall displacement for a typical reciprocating piston engine is calculated by multiplying together three values; the distance travelled by the piston (the
stroke length), the
circular area of the cylinder, and the number of cylinders in the whole engine.
The formula is:
:
Using this formula for non-typical types of engine, such as the
Wankel design and the oval-piston type used in
Honda NR
The Honda NR (New Racing) was a V-four motorcycle series started by Honda in 1979 with the 500cc NR500 Grand Prix racer that used oval pistons. This was followed during the 1980s by a 750cc endurance racer version known as the NR750. The ov ...
motorcycles, can sometimes yield misleading results when attempting to compare engines. Manufacturers and regulators may develop and use specialised formulae to determine a comparative nominal displacement for variant engine types.
Governmental regulations
In several countries fees and taxes levied on road vehicles by transport authorities are scaled in proportion to engine displacement. In countries where this is practised, vehicle manufacturers often seek to increase power output through higher-revving engines or
turbocharging
In an internal combustion engine, a turbocharger (often called a turbo) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake gas, forcing more air into the engine in order to pro ...
, instead of increasing the displacement.
Examples of countries where the road taxes are based upon engine displacement:
* In some European countries, and which predates the EU, there is one charge for engines over 1.0 litre, and another at the level of about 1.6 litres.
* In the United Kingdom, cars registered after 1 March 2001 are taxed based on the exhaust emissions. However, cars registered before this date are taxed based on engine displacement. Cars under 1549 cm
3 qualify for a lower tax rate.
* In Japan, the engine displacement is one of the factors (along with overall vehicle size and power output) used to determine the vehicle size class and therefore the cost of road tax for the vehicle
* In France and some other EU countries,
moped
A moped ( ) is a type of small motorcycle, generally having a less stringent licensing requirement than full motorcycles or automobiles. The term used to mean a similar vehicle except with both bicycle pedals and a motorcycle engine. Mopeds typic ...
s with a displacement of less than can be driven with minimum qualifications. This led to all light motorbikes having a displacement of about 49.9 cm
3.
* In many areas of the United States, Canada (except Quebec
), Australia and New Zealand, the road taxes are not based on engine displacement. However, the engine displacement is often used in low-powered scooters or mopeds to determine whether a licence is required to operate the vehicle. A common threshold is .
Wankel engines are able to produce higher power levels for a given displacement. Therefore, they are generally taxed as 1.5 times their stated physical displacement (1.3 litres becomes effectively 2.0, 2.0 becomes effectively 3.0), although actual power outputs can be higher than suggested by this conversion factor.
Automotive model names
Historically, many car model names have included their engine displacement. Examples include the 1923–1930
Cadillac Series 353 (powered by a 353
Cubic inch
The cubic inch (symbol in3) is a unit of volume in the Imperial units and United States customary units systems. It is the volume of a cube with each of its three dimensions (length, width, and height) being one inch long which is equivalent ...
/5.8-litre engine), and the 1963–1968
BMW 1800
As of March 1 ( O.S. February 18), when the Julian calendar acknowledged a leap day and the Gregorian calendar did not, the Julian calendar fell one day further behind, bringing the difference to 12 days until February 28 ( O.S. February 16) ...
(a 1.8-litre engine) and
Lexus LS 400 with a 3,968 cc engine. This was especially common in US
muscle cars
Muscle car is a description according to '' Merriam-Webster Dictionary'' that came to use in 1966 for "a group of American-made two-door sports coupes with powerful engines designed for high-performance driving." The '' Britannica Dictionary'' ...
, like the
Ford Mustang
The Ford Mustang is a series of American automobiles manufactured by Ford. In continuous production since 1964, the Mustang is currently the longest-produced Ford car nameplate. Currently in its sixth generation, it is the fifth-best selli ...
Boss 302 and 429, and later GT 5.0L, The
Plymouth Roadrunner
The Plymouth Road Runner is a mid-size car with a focus on performance built by Plymouth in the United States between 1968 and 1980. By 1968, some of the original muscle cars were moving away from their roots as relatively cheap, fast cars as t ...
440, and the
Chevrolet Chevelle
The Chevrolet Chevelle is a mid-sized automobile that was produced by Chevrolet in three generations for the 1964 through 1978 model years. Part of the General Motors (GM) A-body platform, the Chevelle was one of Chevrolet's most successful ...
SS 396 and 454.
However, trends towards turbocharging and hybrid/electric drivetrains since 2010 have resulted in far fewer model names being based on the engine displacement.
See also
*
Active Fuel Management
Active Fuel Management (formerly known as displacement on demand (DoD)) is a trademarked name for the automobile variable displacement technology from General Motors. It allows a V6 or V8 engine to "turn off" half of the cylinders under light-lo ...
*
Bore (engine)
In a piston engine, the bore (or cylinder bore) is the diameter of each cylinder.
Engine displacement is calculated based on bore, stroke length and the number of cylinders:
displacement =
The stroke ratio, determined by dividing the bore by ...
*
Compression ratio
The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values.
A fundamental specification for such engines, it is measured two ways: the stati ...
*
Stroke (engine)
In the context of an internal combustion engine, the term stroke has the following related meanings:
* A phase of the engine's cycle (e.g. compression stroke, exhaust stroke), during which the piston travels from top to bottom or vice versa.
* Th ...
*
Variable displacement Variable displacement is an automobile engine technology that allows the engine displacement to change, usually by deactivating cylinders, for improved fuel economy. The technology is primarily used in large, multi-cylinder engines. Many automobil ...
References
{{DEFAULTSORT:Engine Displacement
Displacement
Displacement may refer to:
Physical sciences
Mathematics and Physics
*Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...