Editing Inlet manifold (section)

{{Short description|Automotive technology}}
{{More citations needed|date=February 2019}}[[File:1961 Ferrari 250 TR 61 Spyder Fantuzzi engine.jpg|thumb|Carburetors used as intake runners]]
[[File:Manly 1919 Fig 133 Fordson intake.png|thumb|A cutaway view of the intake of the original Fordson tractor (including the intake manifold, [[carburetor#Vaporizers|vaporizer]], [[carburetor]], and fuel lines)]]

An '''inlet manifold''' or '''intake manifold''' (in [[American English]]) is the part of an [[internal combustion engine]] that supplies the [[fuel]]/[[air]] mixture to the [[cylinder (engine)|cylinder]]s.<ref>{{Cite web|date=2018-11-10|title=What Is an Intake Manifold? • STATE OF SPEED|url=https://stateofspeed.com/2018/11/10/what-is-an-intake-manifold/|access-date=2022-02-03|website=STATE OF SPEED|language=en-US}}</ref>  The word ''[[manifold (engineering)|manifold]]'' comes from the Old English word ''manigfeald'' (from the Anglo-Saxon ''manig'' [many] and ''feald'' [repeatedly]) and refers to the multiplying of one (pipe) into many.<ref>manifold, (adv.) "in the proportion of many to one, by many times". AD1526 ''Oxford English Dictionary'',</ref> <!-- Consider displace it to "Manifold (fluid mechanics)" page -->

In contrast, an [[exhaust manifold]] collects the [[exhaust gas]]es from multiple cylinders into a smaller number of pipes&nbsp;– often down to one pipe.

The primary function of the intake manifold is to ''evenly'' distribute the combustion mixture (or just air in a direct injection engine) to each intake port in the cylinder head(s).  Even distribution is important to optimize the efficiency and performance of the engine.  It may also serve as a mount for the carburetor, throttle body, fuel injectors and other components of the engine.

Due to the downward movement of the [[piston]]s and the restriction caused by the throttle valve, in a reciprocating  [[spark ignition]] [[piston engine]], a partial [[vacuum]] (lower than [[atmospheric pressure]]) exists in the intake manifold. This [[manifold vacuum]] can be substantial, and can be used as a source of [[automobile ancillary power]] to drive auxiliary systems: power assisted [[brake]]s, emission control devices, [[cruise control]], [[ignition system|ignition]] advance, [[windshield wiper]]s, [[power window]]s, ventilation system valves, etc.

This vacuum can also be used to draw any piston blow-by gases from the engine's [[crankcase]]. This is known as a positive [[crankcase ventilation system]], in which the gases are burned with the fuel/air mixture.

The intake manifold has historically been manufactured from [[aluminium]] or cast iron, but use of composite plastic materials is gaining popularity (e.g. most Chrysler 4-cylinders, [[Ford Zetec engine|Ford Zetec]] 2.0, Duratec 2.0 and 2.3, and GM's [[GM Ecotec engine|Ecotec]] series).