Electronically controlled unit injector
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An electronically controlled unit injector (EUI) is a unit injector (UI) with electronic control. It performs the same function as a conventional unit injector in an
internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
, such as in an on-road or off-road vehicle or a
diesel-electric locomotive A diesel locomotive is a type of railway locomotive in which the prime mover (locomotive), prime mover is a diesel engine. Several types of diesel locomotives have been developed, differing mainly in the means by which mechanical power is conv ...
. The pressurized delivery of fuel is
camshaft A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...
-driven, but the timing of the injector's internal operations are controlled by the
engine control unit An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by re ...
so as to achieve certain advantages.


Advantages

* Maximum horsepower, within the applicable emissions tier * Minimum emissions, possibly at the expense of slightly increased fuel consumption * Minimum fuel consumption, possibly at the expense of slightly increased emissions * Optimum vehicle performance


Construction

Central to the EUI is the built-in
plunger pump A plunger pump is a type of positive displacement pump where the high-pressure seal is stationary and a smooth cylindrical plunger slides through the seal. This makes them different from piston pumps and allows them to be used at higher pressures. ...
, which, just as in a UI, allows for low-pressure fuel delivery and return to all injectors, yet provides exceptionally high pressure and concomitant injection and atomization of the fuel to a cylinder during the engine's power cycles. As in a UI, the injector is connected to common banks of fuel supply and fuel return. Fuel is always circulating within the EUI as two of its functions, other than injection for combustion, are injector lubrication and injector cooling. Connections on UIs are by formed steel tubes. Connections on EUIs are by stainless steel-reinforced hoses. The controlled part of the injector is a solenoid-operated spill valve. Normally, it is open, allowing the fuel to return to the supply line when the pump plunger descends. When the solenoid is energized, the spill valve closes, and the fuel is forced through the spray tip into the cylinder. The four phases of EUI operation are: ; Fill phase: As the pump plunger retracts, fuel is drawn into the pump chamber from the fuel supply line. ; Spill phase: The pump plunger begins descending, but the spill valve is open, and fuel recirculates back to the return line. ; Injection phase: Partway through the pump stroke, the solenoid is energized, which closes the spill valve. The fuel is forced into the cylinder through the spray tip. ; Pressure reduction phase: Toward the end of the pump stroke, the spill valve is re-opened, allowing the fuel to recirculate again and ending the injection phase. Thus, although the mechanical plunger pump has a fixed stroke, electronic control can select any part of that stroke to deliver to the cylinder, thereby controlling the volume and timing of fuel delivery.


Users

This system is employed primarily on
Electro-Motive Diesel Progress Rail Locomotives, doing business as Electro-Motive Diesel (EMD), is an American manufacturer of diesel-electric locomotives, locomotive products and diesel engines for the rail industry. The company is owned by Caterpillar through its sub ...
(EMD) locomotive, marine and stationary engines, and primarily on the
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family of diesel engines.


Locomotive use

When implemented in a locomotive, the ECU may also be incorporated into the Locomotive Control Unit (LCU), which performs a variety of functions, such as wheel-slip control, "phone home" for incident reporting and scheduling of delivery of service parts, etc. EMD's LCU is often
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-assisted, and maintenance personnel can effectively monitor the performance of perhaps thousands of locomotives at all times. EMD has released updated LCU software, and EIUs which complement that software, which allows mixing Tier-1 and Tier-0 injectors within the same engine, and yet meets the applicable emissions tier for that engine. A specific benefit is reduced inventory of injectors. A significant feature of the new EUIs is reduced "smoke". Also improved fuel economy. Indeed, the new "Tier 1/Tier 0" injectorsEMD Part Number 40112933 (new); 40112941 (remanufactured) are also applicable to locomotives which are not certified to any Tier, and the same "smoke" reduction and fuel economy benefits apply thereto.


References

{{Reflist Diesel engine components