Editing Diesel engine (section)

=== Direct injection ===
[[File:Têtes de piston.svg|thumb|Different types of piston bowls]]
{{main|Direct fuel injection}}
Most direct injection diesel engines have a combustion cup in the top of the piston where the fuel is sprayed. Many different methods of injection can be used. Usually, an engine with helix-controlled mechanic direct injection has either an inline or a distributor injection pump.<ref name=buckman/> For each engine cylinder, the corresponding plunger in the fuel pump measures out the correct amount of fuel and determines the timing of each injection. These engines use [[fuel injection|injectors]] that are very precise spring-loaded valves that open and close at a specific fuel pressure. Separate high-pressure fuel lines connect the fuel pump with each cylinder. Fuel volume for each single combustion is controlled by a slanted [[Groove (engineering)|groove]] in the plunger which rotates only a few degrees releasing the pressure and is controlled by a mechanical governor, consisting of weights rotating at engine speed constrained by springs and a lever. The injectors are held open by the fuel pressure. On high-speed engines the plunger pumps are together in one unit.<ref name="Firstdiesel_2009" /> The length of fuel lines from the pump to each injector is normally the same for each cylinder in order to obtain the same pressure delay. Direct injected diesel engines usually use orifice-type fuel injectors.<ref name="Reif_2014_140" />

Electronic control of the fuel injection transformed the direct injection engine by allowing much greater control over the combustion.<ref name="Dieselpower_2007" />

; Common rail
[[Common rail]] (CR) direct injection systems do not have the fuel metering, pressure-raising and delivery functions in a single unit, as in the case of a Bosch distributor-type pump, for example. A high-pressure pump supplies the CR. The requirements of each cylinder injector are supplied from this common high pressure reservoir of fuel. An Electronic Diesel Control (EDC) controls both rail pressure and injections depending on engine operating conditions. The injectors of older CR systems have [[solenoid]]-driven plungers for lifting the injection needle, whilst newer CR injectors use plungers driven by [[piezoelectricity|piezoelectric]] actuators that have less moving mass and therefore allow even more injections in a very short period of time.<ref name="Reif_2014_70" />  Early common rail system were controlled by mechanical means.

The injection pressure of modern CR systems ranges from 140&nbsp;MPa to 270&nbsp;MPa.<ref name="Tschöke_2018_310" />