page_title: Unit injector
section_title: Hydraulically actuated electronic (HEUI) development and applications
hierarchical_section_title: Unit injector / Hydraulically actuated electronic (HEUI) development and applications
caption_attribution_description: English: A view of one of the Bosch electronic unit injector fitted to the Scania's R164 15.6 Litre (16L) V8 diesel engine.
context_page_description: A Unit injector is a high pressure integrated direct fuel injection system for diesel engines, combining the injector nozzle and the injection pump in a single component. The plunger pump used is usually driven by a shared camshaft. In a unit injector, the device is usually lubricated and cooled by the fuel itself.
  High pressure injection delivers power and fuel consumption benefits over earlier lower pressure fuel injection by injecting fuel as a larger number of smaller droplets, giving a much higher ratio of surface area to volume. This provides improved vaporization from the surface of the fuel droplets and so more efficient combining of atmospheric oxygen with vaporized fuel, delivering more complete and cleaner combustion.
context_section_description: In 1993, CAT and International Truck & Engine Corporation introduced "hydraulically actuated electronic unit injection" (HEUI), where the injectors are no longer camshaft-operated and could pressurize fuel independently from engine RPM.  First available on Navistar's 7.3L /444 cuin, V8 diesel engine.  HEUI uses engine oil pressure to power high-pressure fuel injection, where usual method of unit injector operation is the engine camshaft.
  HEUI applications included the Ford 7.3L and 6.0L Powerstroke used between May 1993 and 2007. International also used the HEUI system for multiple engines including the DT 466E, DT 570, T-444E, DT-466–570, MaxxForce 5, 7, 9, 10, MaxxForce DT and VT365 engines. Caterpillar incorporated HEUI systems in the 3116, 3126, 3406e, C7 ACERT, C9 ACERT among others and the Daimler-Detroit Diesel Series 40 engine supplied by International also incorporated a HEUI fuel system.
  Unit injector fuel systems are being used on wide variety of vehicles and engines; commercial vehicle from manufacturers such as Volvo, Cummins, Detroit Diesel, CAT, Navistar International and passenger vehicles from manufacturers such as Land Rover and Volkswagen Group, among others, and locomotives from Electro-Motive Diesel.
  The Volkswagen Group mainstream marques used unit injector systems (branded "Pumpe Düse", commonly abbreviated to "PD") in their Suction Diesel Injection (SDI) and Turbocharged Direct Injection (TDI) diesel engines, however this fuel injection method has been superseded by a common-rail design, such as the new 1.6 TDI.
  In North America, the Volkswagen Jetta, Golf, and New Beetle TDI 2004–2006 are Pumpe Düse (available in both the MK4 and MK5 generations, with BEW and BRM engine codes respectively, older models use timing belt driven injection pump).
  Volkswagen Group major-interest truck and diesel engine maker Scania AB also use the unit injector system, which they call "Pumpe-Düse-Einspritzung", or "PDE".
  HEUI system has been replaced by many manufacturers with common rail injection solutions newer technology to meet better economy and new emissions standards being introduced.
caption: Bosch UI on a Scania R164 V8 engine
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