directinjected

Direct injection is a method of delivering a substance directly to its target, bypassing intermediary conduits. In automotive engineering, fuel direct injection injects fuel directly into the combustion chamber, rather than into the intake port.

Implementation relies on high-pressure fuel pumps, precise injectors, and an electronic control unit that times and meters the injections with the engine cycle. The injector sprays into the combustion chamber through its closed intake/compression stage, allowing fine control over the air-fuel mixture.

Two principal automotive forms are gasoline direct injection (GDI) and diesel direct injection (DI). In GDI engines, fuel is injected directly into the combustion chamber at high pressure, allowing tighter control of the air-fuel ratio and the possibility of lean burn in some operating regions. In diesel engines, fuel is injected directly into the hot compressed air, enabling auto-ignition and efficient combustion.

Benefits include increased thermal efficiency, higher power output for a given engine size, and reduced pumping losses. It also enables engine downsizing and turbocharging.

Drawbacks include higher complexity and cost, more stringent strength requirements for fuel-system components, potential carbon buildup on intake valves in engines that use a mixed strategy, and emissions challenges such as NOx and particulate matter requiring after-treatment.

In other fields, direct injection refers to delivering a substance directly into a target area, such as injectable medicines directly into tissue or bloodstream, bypassing other routes.