E-3 injector. The E-3 is a huge improvement from the N-3 injector that it replaced, the N-

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1 E-3 injector The twin or dual actuator electronic unit injector was developed By Delphi in Volvo has been using it on their D12D engine since then. From 2002 to 2007 it has been introduced by various manufacturers and all North American OEMs have been using it in their EUI fueled engines since 2007 The E-3 is a huge improvement from the N-3 injector that it replaced, the N- 3 had reduced the size of the typical unit injector by incorporating the control solenoid within the body of the injector, this got rid of the bulky external control solenoid and allowed more room in the cylinder head allowing more space for the valve actuating systems increasing engine breathing efficiencies. Moving the solenoid inside the body of the injector also forced the solenoid to become smaller using smaller actuating coils allows faster operating times because coil saturation time is less. The N-3 single actuator injector spill valve is inside the barrel assembly The N3 injector at right has only one actuator the spill valve which control injection quantity and duration by its on time

2 The E-3 has two control solenoids, the first solenoid controls the injector spill valve and it is called many different names by different OEM s however it s function is to control the pressure rise in the injector because it traps the fuel in the plunger and barrel when the ECM energizes it s control solenoid. This in turn causes an increase in pressure in the barrel the ECM controls the time available for injection by controlling the spill valve on time. However the E-3 is also equipped with an electro-hydraulic nozzle controlled by the nozzle control valve, in order for an injection pulse to occur both valves must be energized. The electro-hydraulic nozzle controls NOP with both spring pressure and hydraulic pressure caused by the plunger and barrel assembly. This hydraulic pressure is directly or indirectly pushing against the nozzle needle. The second solenoid controls the opening and closing of the electro-hydraulic nozzle valve by draining the hydraulic pressure that is holding the valve shut. Having control of the nozzle valve allows the ECM a sort of soft control over nozzle opening pressure that is that the ECM can delay nozzle opening after the injector control valve solenoid is actuated.

3 12. Header 7. Lower Insulating Sl Figure 1. Electronic Fuel Injector Spill valve control solenoid coil Electro-hydraulic control Nozzle valve coil Electro-hydraulic nozzle

4 The process of injection of fuel is as follows the injector plunger is pushed down as the cam lobe ramps towards outer base circle while it is moving down fuel below the plunger is being displaced through the open spill control valve, sometimes called simply the control valve. When desired the ECM will actuate the control valve solenoid or spill control valve during the stroke of the injector plunger. Energizing this solenoid seals of the exit pathway for the fuel trapped below the plunger and pressure starts to increase very rapidly. The pressure building below the plunger is directed towards the nozzle needle pressure chamber to open it but it is also directed through a small orifice to the top of the needle valve to hold it closed. The ECM, using extensive algorithms, delays the opening of the nozzle by controlling the electro-hydraulic nozzle solenoid until the pressure rises to a desired level. The amount of pressure increase is based on how far in terms of crank angle degrees the ECM allows the pressure rise to increase before it actuates the nozzle control solenoid. This means that the actual pressure is a calculation not a measured value. This does however allow some control over opening pressure which allows some rate shape control. When injection is desired the ECM will energize the nozzle control solenoid this action drains the pressure on top of the needle through an orifice that is sized to allow the pressure to drop faster than the pressure leaking can rise. Removing the pressure allows the pressure already present at the needle pressure chamber so the needle will open at the pressure that is under the plunger. The ECM also has control of nozzle closing pressure by deactivating the nozzle control solenoid during the downward stroke of the plunger then the injection pressure is used to close and hold the nozzle shut. This capability eliminates one of the inherent shortcomings of traditional EUI systems and that is larger droplet sizing at the beginning and ending of the injection cycle because opening and closing of the nozzle is no longer limited by the pressure setting of the nozzle spring. It also gives the ECM some control over injection rate. This means more complete combustion, better emission characteristics, especially where particulates are concerned. The electronic control of the nozzle also allows multi-shot injection meaning that the injection pulse can be broken into as many as five separate injections, (at present), one or two pilot injections, two main injection pulses and a post injection event.

5 The ECM having some control over the injection rate, (the amount of fuel injected per crank angle degree), leads to much more efficient control of the pressures inside the combustion chamber which can optimize engine performance and fuel economy while reducing emissions. The injection strategies are sometimes described as lean, for fuel economy, mean for maximum performance or green, (clean), for superior emissions control. Newer models of these injectors may be equipped with piezo-electric actuators which operate at much faster speeds and may allow even more rate shaping and increased number of injection events. The manufacturers of engines using this technology have defended the use of these injectors because up until now they were the only system capable of the higher injection pressures required to atomize the fuel properly to meet emission standards, these pressures are currently in excess of 35,000 PSI however fuel amplified common rail, (FACR), systems are now at equal pressures and have the potential for higher pressures up to 60,000 PSI in the future. The jury is still out on which of these systems will survive into the next decade but the reduced cost and easier adaption FACR system seem to give them the edge.