Engine configuration
Encyclopedia
Engine configuration is an engineering
term for the layout of the major components of a reciprocating piston
internal combustion engine
. These components are the cylinder
s and crankshaft
s in particular but also, sometimes, the camshaft
(s).
Many apparently 'standard' names for configurations are historic, arbitrary, or overlapping. For example, the 180° V engine
is so named because the crankshaft
is related to a V engine more closely than it is related to other opposed-piston engines such as the boxer. Others would consider it a flat engine
because of its shape.
The names W engine
and rotary engine
have each been used for several unconnected designs. The H-4
and H-6
engines produced by Subaru
are not H engine
s at all, but boxer engines.
The standard names for some configurations are historic, arbitrary, or both, with some overlap. For example, the cylinder banks of a 180° V engine
do not in any way form a V, but it is regarded as a V engine because of its crankshaft
and big end configuration, which result in performance characteristics similar to a V engine. But it is also considered a flat engine
because of its shape. On the other hand, some engines which have none of the typical V engine crankshaft design features and consequent performance characteristics are also regarded as V engines, purely because of their shape. Similarly, the Volkswagen Group
VR6 engine
is a hybrid of the V engine
and the straight engine
, and can not be definitively labeled as either.
s, although some aircraft engines have sleeve valve
s. Valves may be located in the cylinder block (side valves), or in the cylinder head (overhead valve
s). Modern engines are invariably of the latter design. There may be two, three, four or five valves per cylinder, with the intake valves outnumbering the exhaust valves in case of an odd number.
which revolves at half the crankshaft speed. This can be either chain, gear or toothed belt driven from the crankshaft, and can be located in the crankcase (where it may serve one or more banks of cylinders) or in the cylinder head.
If the camshaft is located in the crankcase, a valve train of pushrods and rocker arm
s will be required to operate overhead valves. Mechanically simpler are side valves, where the valve stems rested directly on the camshaft. However, this gives poor gas flows within the cylinder head as well as heat problems and fell out of favor for automobile use, see flathead engine
.
The majority of modern automobile engines place the camshaft on the cylinder head in an overhead camshaft
(OHC) design. There may be one or two camshafts in the cylinder head; a single camshaft design is called single overhead camshaft (SOHC). A design with two camshafts per cylinder head is called double overhead camshaft (DOHC). Note that the camshafts are counted per cylinder head, so a V engine with one camshaft in each of its two cylinder heads is still an SOHC design, and a V engine with two camshafts per cylinder head would be described as 2xDOHC, or informally as a 'quad cam' engine.
With overhead camshafts, the valvetrain
will be shorter and lighter, as no pushrods are required. Some overhead camshaft designs still have rocker arm
s; this facilitates adjustment of mechanical clearances.
If there are two camshafts in the cylinder head, the cams can sometimes bear directly on cam followers on the valve stems. This is the usual arrangement for a four-valves-per-cylinder
design. This latter arrangement is the most inertia free, allows the most unimpeded gas flows in the engine and is the usual arrangement for high performance automobile engines. It also permits the spark plug to be located in the center of the cylinder head, which promotes better combustion characteristics.
Very large engines (e.g. marine engine
s) can have either extra camshafts or extra lobes on the camshaft to enable the engine to run in either direction.
A disadvantage of overhead cams is that a much longer chain (or belt) is needed to drive the cams than with a camshaft located in the cylinder block, usually a tensioner is also needed. A break in the belt may destroy the engine if pistons touch open valves at top dead center.
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
term for the layout of the major components of a reciprocating piston
Reciprocating engine
A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...
internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
. These components are the cylinder
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
s and crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
s in particular but also, sometimes, the camshaft
Camshaft
A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.-History:An early cam was built into Hellenistic water-driven automata from the 3rd century BC. The camshaft was later described in Iraq by Al-Jazari in 1206. He employed it as part of his automata,...
(s).
Many apparently 'standard' names for configurations are historic, arbitrary, or overlapping. For example, the 180° V engine
Flat engine
A flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...
is so named because the crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
is related to a V engine more closely than it is related to other opposed-piston engines such as the boxer. Others would consider it a flat engine
Flat engine
A flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...
because of its shape.
The names W engine
W engine
A W engine is a type of reciprocating engine arranged with its 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....
and rotary engine
Rotary engine (disambiguation)
A rotary engine is a type of internal combustion piston engine used in some early aircraft, motorcycles, and cars. Virtually the whole engine rotates about a fixed crankshaft.Rotary engine may also refer to:...
have each been used for several unconnected designs. The H-4
Flat-4
A flat-4 or horizontally opposed-4 is a flat engine with four cylinders arranged horizontally in two banks of two cylinders on each side of a central crankcase...
and H-6
Flat-6
A flat-6 or horizontally opposed-6 is a flat engine with six cylinders arranged horizontally in two banks of three cylinders on each side of a central crankcase...
engines produced by Subaru
Subaru
; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...
are not H engine
H engine
An H engine is an engine configuration in which the cylinders are aligned so that if viewed from the front, they appear to be in a vertical or horizontal letter H....
s at all, but boxer engines.
Categorisation by piston motion
Engine types include:- Single-cylinder engines
- Inline engineInline engine (aviation)In aviation, an inline engine means any reciprocating engine with banks rather than rows of cylinders, including straight engines, flat engines, V engines and H engines, but excluding radial engines and rotary engines....
designs:- Straight engineStraight engineUsually found in four- and six-cylinder configurations, the straight engine, or inline engine is an internal-combustion engine with all cylinders aligned in one row, with no offset...
, with all of the cylinders placed in a single row- U engineU engineA U engine is a piston engine made up of two separate straight engines joined by gears or chains. It is similar to the H engine which couples two flat engines...
, two separate straight engines with crankshafts linked by a central gear.- The square four is a U engine where the two straight engines have two cylinders each.
- U engine
- V engineV engineA V engine, or Vee engine is a common configuration for an internal combustion engine. The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft...
, with two banks of cylinders at an angle, most commonly 60 or 90 degrees. - Flat engineFlat engineA flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...
, two banks of cylinders directly opposite each other on either side of the crankshaft.- H engineH engineAn H engine is an engine configuration in which the cylinders are aligned so that if viewed from the front, they appear to be in a vertical or horizontal letter H....
, two crankshafts.
- H engine
- W engineW engineA W engine is a type of reciprocating engine arranged with its 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....
. Combination of V and straight, giving 3 banks, or two V's intertwined giving 4 banks. - Opposed piston engineOpposed piston engineAn opposed-piston engine is a reciprocating internal combustion engine in which each cylinder has a piston at both ends, and no cylinder head.-Configurations:...
, with multiple crankshafts, an example being:- Delta engines, with three banks of cylinders and three crankshafts
- X engineX engineAn X engine is a piston engine comprising twinned V-block engines horizontally opposed to each other. Thus, the cylinders are arranged in four banks, driving a common crankshaft. Viewed head-on, this would appear as an X...
.
- Straight engine
- RadialRadial engineThe radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...
designs, including most:- Rotary engineRotary engineThe rotary engine was an early type of internal-combustion engine, usually designed with an odd number of cylinders per row in a radial configuration, in which the crankshaft remained stationary and the entire cylinder block rotated around it...
designs. Mostly seen on pre-WWII aircraft.
- Rotary engine
- Pistonless rotary enginePistonless rotary engineA pistonless rotary engine is an internal combustion engine that does not use pistons in the way a reciprocating engine does, but instead uses one or more rotors, sometimes called rotary pistons...
s, notably:- Wankel engineWankel engineThe Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle takes place in a space between the inside of an oval-like epitrochoid-shaped housing and a rotor that...
.
- Wankel engine
The standard names for some configurations are historic, arbitrary, or both, with some overlap. For example, the cylinder banks of a 180° V engine
Flat engine
A flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...
do not in any way form a V, but it is regarded as a V engine because of its crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
and big end configuration, which result in performance characteristics similar to a V engine. But it is also considered a flat engine
Flat engine
A flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...
because of its shape. On the other hand, some engines which have none of the typical V engine crankshaft design features and consequent performance characteristics are also regarded as V engines, purely because of their shape. Similarly, the Volkswagen Group
Volkswagen Group
Volkswagen Group is a German multinational automobile manufacturing group. , Volkswagen was ranked as the world’s third largest motor vehicle manufacturer and Europe's largest....
VR6 engine
VR6 engine
The VR6 engine is an internal combustion engine configuration, consisting of six cylinders. It was developed by the Volkswagen Group in the late 1980s, and evolutions of the original variant are still produced by them....
is a hybrid of the V engine
V engine
A V engine, or Vee engine is a common configuration for an internal combustion engine. The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft...
and the straight engine
Straight engine
Usually found in four- and six-cylinder configurations, the straight engine, or inline engine is an internal-combustion engine with all cylinders aligned in one row, with no offset...
, and can not be definitively labeled as either.
By valve placement
The majority of four stroke engines have poppet valvePoppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
s, although some aircraft engines have sleeve valve
Sleeve valve
The sleeve valve is a type of valve mechanism for piston engines, distinct from the usual poppet valve. Sleeve-valve engines saw use in a number of pre-World War II luxury cars and in USA in the Willys-Knight car and light truck...
s. Valves may be located in the cylinder block (side valves), or in the cylinder head (overhead valve
Overhead valve
An overhead valve engine, also informally called pushrod engine or I-head engine, is a type of piston engine that places the camshaft within the cylinder block , and uses pushrods or rods to actuate rocker arms above the cylinder...
s). Modern engines are invariably of the latter design. There may be two, three, four or five valves per cylinder, with the intake valves outnumbering the exhaust valves in case of an odd number.
By camshaft placement
Poppet valves are opened by means of a camshaftCamshaft
A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.-History:An early cam was built into Hellenistic water-driven automata from the 3rd century BC. The camshaft was later described in Iraq by Al-Jazari in 1206. He employed it as part of his automata,...
which revolves at half the crankshaft speed. This can be either chain, gear or toothed belt driven from the crankshaft, and can be located in the crankcase (where it may serve one or more banks of cylinders) or in the cylinder head.
If the camshaft is located in the crankcase, a valve train of pushrods and rocker arm
Rocker arm
Generally referred to within the internal combustion engine of automotive, marine, motorcycle and reciprocating aviation engines, the rocker arm is a reciprocating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it...
s will be required to operate overhead valves. Mechanically simpler are side valves, where the valve stems rested directly on the camshaft. However, this gives poor gas flows within the cylinder head as well as heat problems and fell out of favor for automobile use, see flathead engine
Flathead engine
A flathead engine is an internal combustion engine with valves placed in the engine block beside the piston, instead of in the cylinder head, as in an overhead valve engine...
.
The majority of modern automobile engines place the camshaft on the cylinder head in an overhead camshaft
Overhead camshaft
Overhead cam valvetrain configurations place the engine camshaft within the cylinder heads, above the combustion chambers, and drive the valves or lifters in a more direct manner compared to overhead valves and pushrods...
(OHC) design. There may be one or two camshafts in the cylinder head; a single camshaft design is called single overhead camshaft (SOHC). A design with two camshafts per cylinder head is called double overhead camshaft (DOHC). Note that the camshafts are counted per cylinder head, so a V engine with one camshaft in each of its two cylinder heads is still an SOHC design, and a V engine with two camshafts per cylinder head would be described as 2xDOHC, or informally as a 'quad cam' engine.
With overhead camshafts, the valvetrain
Valvetrain
Valvetrain is an all-encompassing term used to describe the mechanisms and parts which control the operation of the valves. A traditional reciprocating internal combustion engine uses valves to control air and fuel flow into and out of the cylinders, facilitating combustion.-Layout:Valvetrain: The...
will be shorter and lighter, as no pushrods are required. Some overhead camshaft designs still have rocker arm
Rocker arm
Generally referred to within the internal combustion engine of automotive, marine, motorcycle and reciprocating aviation engines, the rocker arm is a reciprocating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it...
s; this facilitates adjustment of mechanical clearances.
If there are two camshafts in the cylinder head, the cams can sometimes bear directly on cam followers on the valve stems. This is the usual arrangement for a four-valves-per-cylinder
Multi-valve
In automotive engineering a multi-valve or multivalve engine is one where each cylinder has more than two valves. A multi-valve engine has better breathing and can operate at higher revolutions per minute than a two-valve engine, delivering more power.- Multi-valve rationale :A multi-valve design...
design. This latter arrangement is the most inertia free, allows the most unimpeded gas flows in the engine and is the usual arrangement for high performance automobile engines. It also permits the spark plug to be located in the center of the cylinder head, which promotes better combustion characteristics.
Very large engines (e.g. marine engine
Marine engine
A marine engine is an engine that propels a ship or boat. Types of marine engine include:*Marine steam engine*Petrol engine or gasoline engine*Diesel engine*Steam turbine*Gas turbine-See also:*Marine propulsion*Engine room*Marine automobile engine...
s) can have either extra camshafts or extra lobes on the camshaft to enable the engine to run in either direction.
A disadvantage of overhead cams is that a much longer chain (or belt) is needed to drive the cams than with a camshaft located in the cylinder block, usually a tensioner is also needed. A break in the belt may destroy the engine if pistons touch open valves at top dead center.