Editing Diesel engine (section)

=== Combustion cycle ===
[[File:Uniflow 2-stroke diesel static.svg|thumb|right|Schematic of a two-stroke diesel engine with a roots blower]]
[[File:Detroit Diesel timing.jpg|thumb|Detroit Diesel timing]]

[[Four-stroke engine]]s use the combustion cycle described earlier. Most smaller diesels, for vehicular use, for instance, typically use the four-stroke cycle. This is due to several factors, such as the two-stroke design's narrow powerband which is not particularly suitable for automotive use and the necessity for complicated and expensive built-in lubrication systems and scavenging measures.<ref name=enginebuilder>{{cite web | url = https://www.enginebuildermag.com/2015/01/cars-get-two-stroke-diesels/ | archive-url = https://web.archive.org/web/20221209084324/https://www.enginebuildermag.com/2015/01/cars-get-two-stroke-diesels/ | archive-date = 2022-12-09 | date = 2015-01-11 | title = Could Our Cars Get Two Stroke Diesels? | first = Sterling | last = Shriber | work = Engine Builder | publisher = Babcox Media Inc. }}</ref> The cost effectiveness (and proportion of added weight) of these technologies has less of an impact on larger, more expensive engines, while engines intended for shipping or stationary use can be run at a single speed for long periods.<ref name=enginebuilder/>

[[Two-stroke diesel engine|Two-stroke engines]] use a combustion cycle which is completed in two strokes instead of four strokes. Filling the cylinder with air and compressing it takes place in one stroke, and the power and exhaust strokes are combined. The compression in a two-stroke diesel engine is similar to the compression that takes place in a four-stroke diesel engine: As the piston passes through bottom centre and starts upward, compression commences, culminating in fuel injection and ignition. Instead of a full set of valves, two-stroke diesel engines have simple intake ports, and exhaust ports (or exhaust valves). When the piston approaches bottom dead centre, both the intake and the exhaust ports are "open", which means that there is atmospheric pressure inside the cylinder. Therefore, some sort of pump is required to blow the air into the cylinder and the combustion gasses into the exhaust. This process is called ''scavenging''. The pressure required is approximately 10-30&nbsp;kPa.<ref name="Mau_1984_50" />

Due to the lack of discrete exhaust and intake strokes, all two-stroke diesel engines use a [[scavenge blower]] or some form of compressor to charge the cylinders with air and assist in scavenging.<ref name="Mau_1984_50" /> Roots-type superchargers were used for ship engines until the mid-1950s, however since 1955 they have been widely replaced by turbochargers.<ref name="Mau_1984_23" /> Usually, a two-stroke ship diesel engine has a single-stage turbocharger with a turbine that has an axial inflow and a radial outflow.<ref name="Mau_1984_pp53" />

==== Scavenging in two-stroke engines====
In general, there are three types of scavenging possible:
* Uniflow scavenging
* Crossflow scavenging
* [[Schnuerle porting|Reverse flow scavenging]]

Crossflow scavenging is incomplete and limits the stroke, yet some manufacturers used it.<ref name="Mau_1984_148" /> Reverse flow scavenging is a very simple way of scavenging, and it was popular amongst manufacturers until the early 1980s. Uniflow scavenging is more complicated to make but allows the highest fuel efficiency; since the early 1980s, manufacturers such as MAN and Sulzer have switched to this system.<ref name="Mau_1984_16" /> It is standard for modern marine two-stroke diesel engines.<ref name="Grote_2018_P93" />