Editing Fuel injection (section)

== Direct injection systems ==
Direct injection means that the fuel is injected into the main combustion chamber of each cylinder.<ref>{{cite web |url= http://www.unep.org/transport/gfei/autotool/approaches/technology/ic_engines.asp |title=IC Engines |work=Global Fuel Economy Initiative |archive-url= https://web.archive.org/web/20121006095155/http://www.unep.org/transport/gfei/autotool/approaches/technology/ic_engines.asp#gasoline |archive-date=2012-10-06 |access-date=2014-05-01}}</ref> The air and fuel are mixed only inside the combustion chamber. Therefore, only air is sucked into the engine during the intake stroke. The injection scheme is always intermittent (either sequential or cylinder-individual).

This can be done either with a blast of air<ref name="Teichmann">Rüdiger Teichmann, Günter P. Merker (publisher)</ref> or hydraulically, with the latter method being more common in automotive engines. Typically, hydraulic direct injection systems spray fuel into the air inside the cylinder or combustion chamber. Direct injection can be achieved with a conventional helix-controlled injection pump, unit injectors, or a sophisticated common-rail injection system. The last is the most common system in modern automotive engines.

=== Direct injection for petrol engines ===
{{main|Petrol direct injection}}

During the 20th century, most petrol engines used either a [[carburettor]] or indirect fuel injection. Use of direct injection in petrol engines has become increasingly common in the 21st century.

=== Common-rail injection systems ===
{{Main|Common-rail injection}}

In a common-rail system, fuel from the fuel tank is supplied to a common header (called the [[Hydraulic accumulator|accumulator]]), and then sent through tubing to the injectors, which inject it into the combustion chambers. The accumulator has a high-pressure relief valve to maintain pressure and return the excess fuel to the fuel tank. The fuel is sprayed with the help of a nozzle that is opened and closed with a [[Solenoid valve|solenoid-operated]] [[needle valve]].<ref>Helmut Tschöke, Klaus Mollenhauer, Rudolf Maier (ed.): Handbuch Dieselmotoren, 8th edition, Springer, Wiesbaden 2018, {{ISBN|978-3-658-07696-2}}, p. 289</ref> Third-generation common-rail diesels use [[Piezoelectric motor|piezoelectric]] injectors for increased precision, with fuel pressures up to {{convert|300|MPa|psi|abbr=on|lk=on|disp=or}}.<ref>Helmut Tschöke, Klaus Mollenhauer, Rudolf Maier (ed.): Handbuch Dieselmotoren, 8th edition, Springer, Wiesbaden 2018, {{ISBN|978-3-658-07696-2}}, p. 1000</ref>

The types of common-rail systems include ''air-guided injection''<ref name="van Basshuysen_62">Richard van Basshuysen (ed.): Ottomotor mit Direkteinspritzung und Direkteinblasung: Ottokraftstoffe, Erdgas, Methan, Wasserstoff, 4th edition, Springer, Wiesbaden 2017, {{ISBN|978-3-658-12215-7}}, p. 62</ref> and ''spray-guided injection''.<ref name="van Basshuysen_62" />

=== Unit injector systems ===
{{main|Unit injector}}

Used by diesel engines, these systems include:
* Pumpe-Düse<ref name="Tschöke_295">Helmut Tschöke, Klaus Mollenhauer, Rudolf Maier (ed.): Handbuch Dieselmotoren, 8th edition, Springer, Wiesbaden 2018, {{ISBN|978-3-658-07696-2}}, p. 295</ref>
* Pump-rail-nozzle system<ref name="Tschöke_295" />

=== Helix-controlled pump systems ===
This injection method was previously used in many diesel engines. Types of systems include:
* Lanova direct injection<ref>Helmut Hütten: ''Motoren. Technik, Praxis, Geschichte''. Motorbuchverlag, Stuttgart 1982, {{ISBN|3-87943-326-7}}</ref>
* Afterchamber injection<ref name="von Fersen_131">{{cite book |editor-last1=von Fersen |editor-first1=Olaf |title=Ein Jahrhundert Automobiltechnik: Nutzfahrzeuge |date=1987 |publisher=Springer |location=Berlin, Heidelberg |isbn=978-3-662-01120-1 |page=131 |language=de}}</ref>
* G-System ([[sphere]] combustion chamber)<ref name="Droscha_429">Hellmut Droscha (ed.): Leistung und Weg – Zur Geschichte des MAN-Nutzfahrzeugbaus, Springer, Berlin/Heidelberg 1991, {{ISBN|978-3-642-93490-2}}. p. 429</ref>
* Gardner system (hemisphere combustion chamber)<ref name="Droscha_429" />
* Saurer system ([[torus]] combustion chamber)<ref name="Droscha_429" />
* Flat piston (combustion chamber between piston and head)

=== Air-blast injection systems ===
{{main|Air-blast injection}}

=== Other systems ===
The [[M-System]], used in some diesel engines from the 1960s to the 1980s, sprayed the fuel onto the walls of the combustion chamber,<ref name="Droscha_433">Hellmut Droscha (ed.): Leistung und Weg – Zur Geschichte des MAN-Nutzfahrzeugbaus, Springer, Berlin/Heidelberg 1991, {{ISBN|978-3-642-93490-2}}. p. 433</ref> as opposed to most other direct-injection systems which spray the fuel into the middle of the chamber.