The engine configuration describes the fundamental operating principles by which

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal comb ...

s are categorized. Piston engines are often categorized by their cylinder layout, valves and camshafts. Wankel engines are often categorized by the number of rotors present. Gas turbine engines are often categorized into turbojets, turbofans, turboprops and turboshafts.

Piston engines

Any design of motor/engine, be it a V or a boxer can be called an "in-line" if it's mounted in-line with the frame/chassis and in-line with the direction of travel of the vehicle. When the motor/engine is across the frame/chassis this is called a TRANSVERSE motor. Cylinder arrangement is not in the description of how the motor/engine is oriented. Therefore a V4 motor/engine can be a transverse or an in-line. Where the cylinders are arranged in two or more lines (such as in V engines or

flat engines Flat or flats may refer to: Architecture * Apartment, known as a flat in the United Kingdom, Ireland, and other Commonwealth countries Arts and entertainment * Flat (music), a symbol () which denotes a lower pitch * Flat (soldier), a two-dimensi ...

), each line of cylinders is referred to as a 'cylinder bank'. The angle between cylinder banks is called the 'bank angle'. Engines with multiple banks are shorter than straight engines of the same size, and will often have better

engine balance Engine balance refers to how the inertial forces produced by moving parts in an internal combustion engine or steam engine are neutralised with counterweights and Balance shaft#Overview, balance shafts, to prevent unpleasant and potentially dam ...

characteristics, resulting in reduced engine

vibration Vibration () is a mechanical phenomenon whereby oscillations occur about an equilibrium point. Vibration may be deterministic if the oscillations can be characterised precisely (e.g. the periodic motion of a pendulum), or random if the os ...

and potentially higher maximum engine speeds. Most engines with four or less cylinders use a

straight engine The straight engine (also called inline engine) is a configuration of multi-cylinder piston engine where all of the cylinders are arranged in a single row, rather than radially or in two or more cylinder banks. Design A straight engine is eas ...

layout, and most engines with eight cylinders or more use a

V engine A V engine, sometimes called a Vee engine, is a common configuration for internal combustion engines. It consists of two cylinder banks—usually with the same number of cylinders in each bank—connected to a common crankshaft. These cylinder ...

layout. However, there are various exceptions to this, such as the

straight-eight engine The straight-eight engine or inline-eight engine (often abbreviated as I8) is an eight-cylinder internal combustion engine with all eight cylinders mounted in a straight line along the crankcase. The type has been produced in side-valve, IO ...

s used by various luxury cars from 1919-1954,

V4 engine A V4 engine is a four-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V engine, V configuration. The V4 engine is less common compared to straight-four engines. However, V4 engines have been used in au ...

s used by some marine outboard motors,

V-twin A V-twin engine, also called a V2 engine, is a two-cylinder piston engine where the cylinders are arranged in a V configuration and share a common crankshaft. The V-twin is widely associated with motorcycles, primarily installed longitudinally ...

and

flat-twin A flat-twin engine is a two-cylinder internal combustion engine with the cylinders on opposite sides of the crankshaft. The most common type of flat-twin engine is the boxer-twin engine, where both pistons move inwards and outwards at the same ti ...

engines used by motorcycles and

flat-four engine A flat-four engine, also known as a horizontally opposed-four engine or boxer engine, is a four-cylinder piston engine with two banks of cylinders lying on opposite sides of a common crankshaft. The most common type of flat-four engine is the box ...

s used by various cars.

Single cylinder bank

Straight engine The straight engine (also called inline engine) is a configuration of multi-cylinder piston engine where all of the cylinders are arranged in a single row, rather than radially or in two or more cylinder banks. Design A straight engine is eas ...

s (also known as "inline engines") have all cylinders aligned in one row along the crankshaft with no offset. When a straight engine is mounted at an angle, it is sometimes called a "slant engine". Types of straight engines include: * Single cylinder example BMW R25 R26 R27 * Straight-2 example Sunbeam S7 *

Straight-3 A straight-three engine (also called an inline-triple or inline-three) is a three-cylinder piston engine where cylinders are arranged in a line along a common crankshaft. Less common than straight-four engine, straight-three engines have nonethel ...

, also known as "inline-triple" *

Straight-4 A straight-four engine (also referred to as an inline-four engine) is a four-cylinder piston engine where cylinders are arranged in a line along a common crankshaft. The majority of automotive four-cylinder engines use a straight-four layout ( ...

* Straight-5 *

Straight-6 A straight-six engine (also referred to as an inline-six engine; abbreviated I6 or L6) is a piston engine with six cylinders arranged in a straight line along the crankshaft. A straight-six engine has perfect primary and secondary engine balanc ...

Straight-8 The straight-eight engine or inline-eight engine (often abbreviated as I8) is an eight-cylinder internal combustion engine with all eight cylinders mounted in a straight line along the crankcase. The type has been produced in side-valve, I ...

Multiple cylinder banks

V engines

s (also known as "Vee engines") have the cylinders aligned in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft. Types of V engines include: * V2, commonly called "V-twin" * V3 * V4 * V5 * V6 * V8 * V10 * V12 * V14 * V16 * V18 VR5 and VR6 engines are very compact and light, having a narrow V angle which allows a single

cylinder block In an internal combustion engine, the engine block is the structure that contains the cylinders and other components. The engine block in an early automotive engine consisted of just the cylinder block, to which a separate crankcase was attach ...

and

cylinder head In a piston engine, the cylinder head sits above the cylinders, forming the roof of the combustion chamber. In sidevalve engines the head is a simple plate of metal containing the spark plugs and possibly heat dissipation fins. In more modern ...

. These engines use a single cylinder head so are technically a straight engine with the name "VR" coming from the combination of German words “Verkürzt” and “Reihenmotor” meaning “shortened inline engine”.

Flat engines

Flat engine A flat engine is a piston engine where the cylinders are located on either side of a central crankshaft. Flat engines are also known as horizontally opposed engines, however this is distinct from the less common opposed-piston engine design, ...

s (also known as "horizontally-opposed" engines) have the cylinders arranged in two banks on either side of a single crankshaft.

Boxer engines Boxer most commonly refers to: *Boxer (boxing), a competitor in the sport of boxing *Boxer (dog), a breed of dog Boxer or boxers may also refer to: Animal kingdom * Boxer crab * Boxer shrimp, a small group of decapod crustaceans * Boxer snipe eel ...

are a subtype of flat engines where opposing pistons move in and out in tandem. Types of flat engines include: * Flat-2, commonly called "flat-twin" *

Flat-4 A flat-four engine, also known as a horizontally opposed-four engine or boxer engine, is a four-cylinder piston engine with two banks of cylinders lying on opposite sides of a common crankshaft. The most common type of flat-four engine is the box ...

Flat-6 A flat-six engine, also known as a horizontally opposed-six, is a six-cylinder Internal combustion engine#Reciprocating engines, piston engine with three cylinders on each side of a central crankshaft. The most common type of flat-six engine is t ...

* Flat-8 * Flat-10 * Flat-12 * Flat-16

W engines

W engines have the cylinders in a configuration in which the cylinder banks resemble the letter W, in the same way those of a V engine resemble the letter V. Types of W engines include: * W8 * W12 * W16 W engines using twin "VR" engine banks are technically a V engine. These engine banks use a single cylinder head so are technically a straight bank with the name "VR" coming from the combination of German words “Verkürzt” and “Reihenmotor” meaning “shortened inline engine”.

Other layouts

Radial engine The radial engine is a reciprocating engine, reciprocating type internal combustion engine, internal combustion engine configuration in which the cylinder (engine), cylinders "radiate" outward from a central crankcase like the spokes of a wheel. ...

s have cylinders mounted radially around a central crankcase.

Rotary engine The rotary engine is an early type of internal combustion engine, usually designed with an odd number of cylinders per row in a radial configuration. The engine's crankshaft remained stationary in operation, while the entire crankcase and its ...

s have a similar configuration, except that the crankshaft is fixed and the cylinders rotate around it. (This is different from the

Wankel engine The Wankel engine (, ) is a type of internal combustion engine using an eccentric (mechanism), eccentric Pistonless rotary engine, rotary design to convert pressure into rotating motion. The concept was proven by German engineer Felix Wankel, f ...

configuration described below.) Radial and rotary engine designs were widely used in early

aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...

U engine A U engine is a piston engine made up of two separate straight engines (complete with separate crankshafts) placed side-by-side and coupled to a shared output shaft. When viewed from the front, the engine block resembles the letter "U". Althoug ...

s consist of two separate straight engines (complete with separate crankshafts) joined by gears or chains. Most U engines have four cylinders (i.e. two straight-two engines combined), such as square four engines and tandem twin engines. Similar to U engines,

H engine An H engine is a piston engine comprising two separate flat engine, flat engines (complete with separate crankshafts), most often geared to a common output shaft. The name "H engine" is due to the engine blocks resembling a letter "H" when viewe ...

s consist of two separate flat engines joined by gears or chains. H engines have been produced with between 4 and 24 cylinders. An

opposed-piston engine An opposed-piston engine is a piston engine in which each cylinder (engine), cylinder has a piston at both ends, and no cylinder head. Petrol and diesel opposed-piston engines have been used mostly in large applications such as ships, military ...

is similar to a flat engine in that pairs of pistons are co-axial but rather than sharing a crankshaft, instead share a single combustion chamber per pair of pistons. The crankshaft configuration varies amongst opposed-engine designs. One layout has a flat/boxer engine at its center and adds an additional opposed-piston to each end so there are two pistons per cylinder on each side. An

X engine An X engine is a piston engine with four banks of cylinders around a common crankshaft, such that the cylinders form an "X" shape when viewed front-on. The advantage of an X engine is that it is shorter than a V engine of the same number of c ...

is essentially two V engines joined by a common crankshaft. A majority of these were existing V-12 engines converted into an X-24 configuration. The Swashplate engine with the K-Cycle engine is where pairs of pistons are in an opposed configuration sharing a cylinder and combustion chamber. A Delta engine has three (or its multiple) cylinders having opposing pistons, aligned in three separate planes or 'banks', so that they appear to be in a Δ when viewed along the axis of the main-shaft. An example of this type of layout is the

Napier Deltic The Napier Deltic engine is a British opposed-piston valveless, supercharged uniflow scavenged, two-stroke diesel engine used in marine and locomotive applications, designed and produced by D. Napier & Son. Unusually, the cylinders were di ...

Wankel (rotary) engines

s (sometimes called 'rotary engines') can be classified based on the number of rotors present. Most production Wankel engines have two rotors, however engines with one, three and four rotors have also been produced. Wankel engines can also be classified based on whether they are

naturally aspirated A naturally aspirated engine, also known as a normally aspirated engine, and abbreviated to N/A or NA, is an internal combustion engine in which air intake depends solely on atmospheric pressure and does not have forced induction through a turboc ...

turbocharged In an internal combustion engine, a turbocharger (also known as a turbo or a turbosupercharger) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into the ...

. Most Wankel engines are fueled by petrol, however prototype engines running on diesel and hydrogen have been trialed.

Gas turbine engines

Gas turbine A gas turbine or gas turbine engine is a type of Internal combustion engine#Continuous combustion, continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas gene ...

engines— mostly used for aircraft— are usually separated into the following categories: *

Turbojet The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and ...

, gasses travel through a propelling nozzle *

Turbofan A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the add ...

, gasses travel through a ducted fan *

Turboprop A turboprop is a Gas turbine, gas turbine engine that drives an aircraft Propeller (aeronautics), propeller. A turboprop consists of an intake, reduction drive, reduction gearbox, gas compressor, compressor, combustor, turbine, and a propellin ...

, gasses travel through an unducted propeller, usually with variable pitch *

Turboshaft A turboshaft engine is a form of gas turbine that is optimized to produce shaft horsepower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the ex ...

, a gas turbine optimised for producing mechanical torque instead of thrust

References

{{Automotive engine Internal combustion engine