Cylinder head: Difference between revisions

In an [[internal combustion engine]], the '''cylinder head''' (often informally abbreviated to just '''head''') sits above the [[cylinder (engine)|cylinder]]s on top of the [[cylinder block]].<ref name="Wright 2015 p. 310">{{cite book | last=Wright | first=G. | title=Fundamentals of Medium/Heavy Duty Diesel Engines | publisher=Jones & Bartlett Learning | year=2015 | isbn=978-1-284-06705-7 | url=https://books.google.com/books?id=s5_OCwAAQBAJ&pg=PA310 | access-date=2020-11-07 | page=310}}</ref> It closes in the top of the cylinder, forming the [[combustion chamber]]. This joint is sealed by a [[head gasket]]. In most engines, the head also provides space for the passages that feed [[Atmosphere of Earth|air]] and [[fuel]] to the cylinder, and that allow the [[Exhaust gas|exhaust]] to escape. The head can also be a place to mount the [[poppet valve|valves]], [[Spark plug|spark plugs]], and [[Fuel injection|fuel injectors]].<ref>{{cite web |last1=Muhammad |first1=Waqar |title=Mechanical Boost |url=https://mechanicalboost.com/engine-cylinder-head/ |quote=[2]}}</ref>

The number of [https://mechanicalboost.com/engine-cylinder-head/ cylinder heads] in an engine is a function of the [[engine configuration]]. Almost all [[straight engine|inline (straight) engines]] today use a single cylinder head that serves all the cylinders. A [[V engine|V (or Vee)]] engine has two cylinder heads, one for each [[cylinder bank]] of the 'V'. For a few compact 'narrow-angle' V engines, such as the [[Volkswagen Group|Volkswagen]] [[VR6 engine|VR6]], the angle between the cylinder banks is so narrow that it uses a single head spanning the two banks. A [[flat engine]] (basically a V engine, where the angle between the cylinder banks is now 180°) has two heads. Most [[radial engine]]s have one head for each cylinder, although this is usually of the [[monobloc engine#Cylinder head|monobloc]] form wherein the head is made as an integral part of the cylinder. This is also common for motorcycles, and such head/cylinder components are referred to as ''barrels''.

The design of the cylinder head is key to the performance and efficiency of the internal combustion engine, as the shape of the combustion chamber, inlet passages and ports (and to a lesser extent the exhaust) determines a major portion of the [[volumetric efficiency]] and [[compression ratio]] of the engine.<ref>{{cite web |last1=Ahmed |first1=Shah |title=Mechanical Boost |url=https://mechanicalboost.com/engine-cylinder-head/ |quote=[3]}}</ref>