C3.3B – Fuel System

Fuel System Overview

These engines utilize the Center Direct Injection System (E-CDIS). The injection nozzle is positioned upright at the center of the cylinder. This system injects fuel directly at the center of the cylinder. With this system the fuel that is injected mixes more uniformly with the inlet air, which produces a more stable, higher combustion performance. This fuel system includes the following improvements: Cleaner emissions, Higher power output, Lower fuel consumption, lower operating noise and Easier starting.

Governor Operation Overview

This engine utilizes a separated fuel injection pump in combination with a multifunction mechanical governor. This governor also utilizes a torque limiting mechanism to control the maximum peak torque. This mechanism maintains a constant level under varying loads, and provides stable idling and regulates maximum engine speed

This engine uses a mechanical governor that controls the fuel injection rate at all engine speed ranges. A balance between the centrifugal force of the flyweights and spring tension is used in order to control the fuel injection rate at all rpm.

The governor shaft that monitors engine speed is independent of the injection pump shaft and rotates at twice the speed of conventional types. This provides better response to load variance and delivering greater engine output.

Governor Operation At Engine Start-Up

Illustration 1g02893498

(1) Start spring

(2) Flyweights

The stop solenoid is powered in order to release the stop lever. Low tension of start spring (1) permits the control rack to move to the starting position, which supplies the proper amount of fuel that is required to start the engine.

Governor Operation At Idle

Illustration 2g02893657

(1) Start spring

(2) Flyweights

(3) Second fork lever

(4) Speed control lever

(5) Spring pin

(6) First fork lever

(7) Governor spring

When the speed control lever (4) is rotated in the clockwise direction, the increased tension of the governor spring (7) pulls second fork lever (3) . Second fork lever (3) is pulled the torque lever pin and first fork lever (6) are moved in direction toward the front of the fuel pump in order to restrain the flyweight.

Governor Operation At Rated Speed with Full Load and Overload

Illustration 3g02878757

(8) No-load maximum rotation

(9) Output limiting bolt

(10) Torque limiting bolt

As the speed control lever is changed from the middle speed range to the high speed range, the governor spring tension increases in order to compress the torque spring. This moves the first fork lever in the direction toward the front of the fuel pump.

The second fork lever moves until the lever reaches the output limiting bolt (9) to keep rated rotation and rated output.

When the engine is overloaded, the engine rotating speed decreases and the centrifugal force of the flyweight decreases. This moves the first fork lever in the direction toward the front of the fuel pump.

The control rack moves in the direction that increases the fuel supply in order to increase output. The control rack is balanced with the centrifugal force of the flyweights to produce low-speed output.

Governor Operation At Engine Stop

Illustration 4g02894136

(11) Solenoid

(12) Stop lever shaft

Stop solenoid (11) is switched to the off position, the spring tension of the solenoid is released. This causes the rod to extrude, and stop lever (12) moves the control rack in direction toward the front of the fuel pump, which stops the engine.

Two-Stage Fuel Injector

Illustration 5g03331936

(13) Edge filter

(14) Nozzle body holder

(15) First stage injection pressure adjusting shim

(16) First spring

(17) Pressure pin

(18) Spring seat

(19) Second stage injection pressure adjusting shim

(20) Second spring

(21) Pre-lift adjusting spring seat

(22) Chip packing

(23) Maximum lift adjusting washer

(24) Retaining nut

(25) Nozzle

The two-spring holder limits needle valve lift at initial valve opening in order to throttle the injection quantity. Main injection occurs when the in-line pressure has increased sufficiently to move the needle valve through the full life of the injector cycle. The new two stage fuel injectors include the following improvements:

  • Improved engine stability at low and intermediate speeds

  • Decreased engine hunting and surging

  • Decreased noise at idle

  • Decreased idling speed due to improved engine stability

  • Stabilized fuel injection characteristics from the fuel injection pump and nozzle

First Opening Pressure

The force of the high-pressure fuel that is delivered by the injection pump forces the needle valve in the upward direction. The force overcomes the set force of the first spring. The needle valve of the nozzle forces the pushrod up and the needle valve opens.

Second Opening Pressure

After the pushrod is lifted through the pre-lift position the second pushrod is contacted. The set force of the second spring acts on the second pushrod. The combined forces of the first and second spring acts on the needle valve. The needle valve will not lift until the forces are overcome.

When the high-pressure fuel overcomes the combined spring force, the needle valve is again lifted, and main injection can begin.

Injection Pump with Fine Spill Port (FSP) Mechanism

Illustration 6g03331938

View of FSP mechanism

(A) FSP stroke

(26) Barrel

(27) Plunger chamber

(28) Plunger

(29) Main port

(30) Fine spill port

The fuel injection pump with FSP. The speed timer function delays the injection timing at low idle in order to reduce NOx and operating noise. The injection rate control function decreases the initial injection rate and increase the later injection rate, which reduces NOx and Particulate Matter.

Constant Pressure Valve (CPV) Delivery Valve

Illustration 7g03331941

(31) Delivery valve

(32) Delivery valve seat

(33) Orifice

(34) Steel ball

(35) Snapper valve

(36) Snapper valve spring

(37) Snapper valve seat

The CPV is a valve that maintains uniform residual pressure in the high-pressure pipe. The CPV also stabilizes overall fuel delivery quantity characteristics at low speed.

At high fuel pressure the delivery valve (31) , steel ball (34) , and snapper valve (35) move in the upward direction together. The delivery valve seat surface opens when the fuel pressure becomes greater that the delivery valve set pressure. After injection the delivery valve (31) , steel ball (34) , and snapper valve (35) move in the downward position, and the delivery valve seat surface closes. The steel ball closes when the fuel pressure is less than the snapper valve set pressure.

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