718 The Lucas EPIC electronically controlled pump

The Lucas EPIC injection system, Fig. 7.36, was conceived in the late 1970s and design and development work on it began in the 1980s. This system was first installed on a production engine in 1991.

It was designed for application to a distributor type pump to deliver at pressures of up to 1100 bar for high speed direct injection light duty engines with three, four and six cylinders up to 0.75 litres per cylinder. Maximum speeds of up to 4500 rev/min were contemplated and, subsequently, medium duty engines were catered for running at about 3500 rev/min. To cope with the pressures, a rotor with four plungers was thought desirable. This arrangement had the additional advantage that the rate of injection could be shaped by causing one pair of plungers to strike the cams before the other, but retracting all four together.

For these pumps intended for direct injection engines, a resistance sensor is available as an optional substitute for the injection needle position sensor used for timing control, as indicated in Fig. 7.37. It is a cam position sensor and is used in conjunction with a Hall effect sensor attached to the pump drive shaft. The latter detects the passage of an asymmetric vane, taking into account the precise angular position at which the pump is bolted to the shaft. This enables the ECU, in setting the injection timing, to compensate for manufacturing and assembly tolerances. It also serves as a back-up sensor in the event, admittedly unlikely, of failure of the engine speed sensor.

The EPIC and DPC pumps, Figs 7.37 and 7.19, are similar, except that the former is electronically controlled, and the transfer pump is on the drive

Engine

Boost Air inlet speed

Coolant precc temp and tdc

Crui cont

EGR cont

Engine

Boost Air inlet speed

Coolant precc temp and tdc

Crui cont

EGR cont

Lucas Epic Electronic Compensation

Fig. 7.36 Lucas EPIC electronic control system for indirect injection

Injectors

Fig. 7.36 Lucas EPIC electronic control system for indirect injection

Injectors

Lucas Epic
Fig. 7.37 The electronically controlled distributor type injection pump

shaft, where the governor is in the DPC. By virtue of the latter feature, there is plenty of space of accommodating a sensor for monitoring the axial position of the rotor.

The rotor moves axially to vary the maximum stroke of the plunger over the whole operational range, thus dispensing with the axially sliding carriage of the DPC. This movement, which is effected electrohydraulically, slides the cam follower shoes up and down an inclined surface, Fig. 7.38. Although the transfer pump, plunger arrangement and the timing advance unit are similar to those of the DPC, the last mentioned differs in detail because it too is electrohydraulically actuated.

Both the filling of and delivery from the injection pump is effected through a single short hole drilled in the distributor shaft, Fig. 7.38. Consequently, the volume of fuel between the plungers and delivery valves is small, and therefore variations in timing due to its compressibility are extremely small.

There are 25% fewer components in the electronically controlled pump as compared with those of the mechanically controlled equivalents. Consequently, it is significantly lighter, between 20 and 50%, according to which units are taken for comparison, and 28% shorter. These features partly offset the cost of the electronic control system.

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