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Diesel Engine BACS (Boost and Altitude Compensator System)

admin — Mon, 26 Jul 2010 06:49:00 +0000

1. Description
The BACS is a device that provides both the functions of the turbocharger boost compensator and the HAC. The HAC valve maintains the constant pressure in the constant pressure chamber located below the diaphragm and thus has the function of the HAC.
2. Construction
The basic construction is the same as that of the turbochargerboost compensator.
3. Operation
(1) Low-altitude drivingThe air is introduced into the constant pressure chamber from the filter. Then, a vacuum is applied by the vacuum pump to make the pressure lower than normal atmospheric pressure at all times.
(2) High-altitude drivingThe atmospheric pressure, of the air which is introduced into the constant pressure chamber, is lower at high altitude. When the atmospheric pressure is low, the bellows expand to make the vacuum passage from the vacuum pump narrow. As a result, the vacuum pressure, which is applied to the constant pressure chamber, decreases. Thus, the pressure inside the constant pressure chamber stays the same at both the low-altitude and high-altitude driving. The HAC functions to maintain the pressure in the constant pressure chamber by moving the push rod in accordance with the change in atmospheric pressure on the top part of the diaphragm.
Diesel Engine PCS (Power Control System)
The PCS is a device that reduces the maximum injection volume when the vehicle is driven under a certain conditions such as 1st or reverse gear. Normally, the VSV is off and a vacuum from the vacuum pump is applied to the power control valve. Accordingly, the power control lever rotates clockwise causing the governor tension lever to separate. When the VSV is on, the air is let into the power control valve causing the power control lever to rotate counterclockwise. Thus, the power control lever causes the tension lever to rotate clockwise and this reduces the maximum fuel injection volume.

Turbocharger Boost Compensator

admin — Sun, 25 Jul 2010 06:46:06 +0000

1. Description When the intake air volume (boost pressure) is increased by the turbocharger, the boost compensator increases the maximum fuel injection volume in accordance with the increased intake air volume, in order to maintain optimal combustion conditions and increase the engine output at all times.

2. Construction The boost compensator is installed above the governor of the injection pump. The diaphragm and push rod move up and down by the boost pressure. The push rod has a tapered construction, by which, the control arm is rotated via the connecting pin. This amount of movement becomes tension lever movement distance, and the spill ring movement distance (injection volume).

3. Operation

(1) When the boost pressure is low: The spring pushes the diaphragm upward. The injection volume does not increase because the connecting pin is in contact with the tapered bottom portion of the push rod.

(2) When the boost pressure is high: The diaphragm is pushed by the boost pressure to move the push rod downward. The tension lever is pulled by the control spring. Therefore, the connecting pin moves to the right toward the tapered portion of the push rod, and the control arm also rotates clockwise. The tension lever and control lever rotate counter-clockwise around fulcrum A and move the spill ring to increase the maximum fuel injection volume. (3) When the boost pressure is too high: Normally it is controlled at the area C and D. If the boost pressure rises above the intercept point on the graph, the connecting pin is pushed back to the left by tapered portion B of the push rod, reducing the maximum fuel injection volume. This prevents the boost pressure from rising too high in the case of a failure.

Diesel Engine High-Altitude Compensator (HAC)

admin — Sat, 24 Jul 2010 05:03:21 +0000

1. Description
At high altitudes, the air density decreases with the decrease in the atmospheric pressure. For this reason, if the fuel is injected under the same conditions as at low altitudes, the air-fuel mixture becomes too rich, making the engine susceptible to generating black smoke. Therefore, the HAC automatically reduces the maximum fuel injection volume in accordance with the vehicle’s present altitude.
2. Construction
The HAC, which is installed above the pump governor, consists of vacuum bellows, a push rod, connecting pin and control arm.
3. Operation
(1) Low altitude
As the bellows are contracted when the atmospheric pressure is high, the push rod is pulled upward by the spring. The spill ring is kept at the normal position.
(2) High altitude
When the atmospheric pressure is low, the bellows expand to push the push rod downward. This movement is transmitted via the connecting pin, the control arm and the tension lever, and serves to move the spill ring to the left. In this way, the maximum fuel injection volume is decreased.

VE Pump Options ACSD (Automatically-controlled Cold Starting Device)

admin — Fri, 23 Jul 2010 04:32:16 +0000

1. Description
The ACSD uses the contractive and expansive properties of thermo wax and the tension of a spring to automatically advance the injection timing in response to the coolant temperature, causing the engine to idle-up (fast idle). This improves the startability at low temperatures and the stability of idling.
2. Operation
(1) Cold engine
The thermo wax contracts and pulls the plunger. Lever A rotates clockwise by the spring tension. This causes lever B to push the adjusting lever toward the idle-up position, resulting in a faster idle speed. At the same time, the roller ring is rotated, advancing the injection timing.
(2) Warm engine
As the coolant temperature rises, the thermo wax gradually expands to push the plunger out. Lever A causes the plunger to rotate counter-clockwise, gradually decreasing the advance angle of the injection timing and lowering the idle speed. When the coolant temperature reaches about 5C (12F), both injection timing and idle speed return to normal.
HINT
The adjusting method is different between the engine with the ACSD and without the ACSD.

TCV (Timing Control Valve) of Fuel Injection

admin — Fri, 23 Jul 2010 04:30:59 +0000

The TCV renders the LST inactive if the vehicle is operated with a cold engine (coolant temperature below 6C (14F)) or at high altitudes (where the atmospheric pressure is below 93 kPa (70mmHg)). The purpose of providing a TCV is to prevent misfiring. If the injection timing is allowed to keep advancing at conditions where misfiring occurs easily (cold engine or high altitude), misfiring is prevented. Then, white smoke is also prevented. The emission control ECU determines the conditions of the engine using signals from the water temperature sensor and the atmospheric pressure sensor.

Then, the emission control ECU outputs signals that cause the TCV to close the fuel passage of the LST, thus rendering the LST inactive. TCV on Before the engine has warmed up (coolant temperature below 6C (14F)) or when the vehicle is driven at high altitudes (where the atmospheric pressure is below 93 kPa (700mmHg)), the emission control ECU outputs signals that cause the TCV to turn on and close the fuel passage. Therefore, even if the accelerator pedal is released and the engine load decreases, the LST becomes inactivated and does not retard the injection timing.

LST (Load-Sensing Timer) of Fuel Injection

admin — Thu, 22 Jul 2010 04:29:11 +0000

The LST changes the fuel injection timing in accordance with the engine load, and obtain the characteristic of advancing. The fuel is released from the orifice on the governor sleeve via the governor shaft passage to the inlet side of the feed pump. Therefore, the pressure inside the pump housing is lowered to retard the injection timing. When the load on the engine increases (increased injection volume), the flyweights remain closed. The pressure inside the pump housing is not lowered because the orifice on the governor sleeve and the governor shaft passage are not aligned. On the contrary, when the load on the engine decreases (decreased injection volume), the flyweights open. The orifice on the governor sleeve and the governor shaft passage are aligned causing the pressure inside the pump housing to be reduced and the timing to be retarded.

M-M (Minimum-Maximum) Speed Governor ofDiesel Engine injection pump

admin — Wed, 21 Jul 2010 04:19:59 +0000

The M-M speed governor controls the injection volume in accordance with the engine speed at minimum and maximum speeds. At other speed ranges, the fuel volume in accordance with the level of depression of the accelerator pedal is injected. (Except for the control spring, the construction of the all-speed governor and M-M speed governor are basically the same.)
Adjusting Screws
The injection pump has the following adjusting screws:
1. Maximum speed adjusting screwControls the maximum engine speed.
2. Idle speed adjusting screwAdjusts the engine speed during idling.
3. Full-load setting screwAdjusts the maximum fuel injection volume.
HINT:
As the maximum speed adjusting screw and full-load setting screw are adjusted to the proper position and sealed, normally they are not adjusted. However, if due to changes with the passing of time, adjustment becomes necessary, break the seal and perform an adjustment. After an adjustment, the maximum speed adjusting screw and full-load setting screw must be sealed.

Fuel Injection All-speed Governor

admin — Tue, 20 Jul 2010 04:17:49 +0000

The all-speed governor controls the fuel injection volume at all engine speed ranges. The spill ring is moved by the governor, changing the effective stroke, resulting in an adjustment of the injection volume.
1. Starting
When the accelerator pedal is depressed and the adjusting lever is moved in full-load direction at the time of starting, the control spring pulls the tension lever until it contacts the stopper. Because the pump speed is low at starting and the centrifugal force of the flyweights is extremely small, even the start spring (a plate spring), which has a small tension, is able to push the control lever against the governor sleeve, thus causing the flyweights to close completely. At this time, the control lever rotates counter-clockwise around fulcrum A and moves the spill ring to the start position (maximum injection volume) in order provide the fuel injection volume that necessary during starting.
2. Idling
After the engine is started and the accelerator pedal is released, the adjusting lever returns to the idle position. Because the tension of the control spring at this time is practically zero, the flyweights can expand outward despite the low speed. As a result, the governor sleeve compresses the idle spring. At this time, the control lever rotates clockwise around fulcrum A, to move the spill ring to the idle position. In this manner, a smooth idling speed can be realized when the centrifugal force of the flyweights and the tension of the idle spring are balanced.
3. Full-load (accelerator pedal fully depressed)
When the accelerator pedal is fully depressed, the adjusting lever moves to the full-load position and the tension lever comes in contact with the stopper, similar to the starting. In this situation, the control spring has a high tension and the damper spring is completely compressed and inactive. Unlike the starting, a strong centrifugal force acts on the flyweights, and the governor sleeve pushes the control lever to the right. Then the control lever rotates clockwise around fulcrum A, until fulcrum B comes in contact with the tension lever, thus moving the spill ring to the full-load position. Consequently, the injection volume at this time will be less than during starting.
4. Maximum speed (accelerator pedal fully depressed)
When the engine speed becomes greater than the specified speed, the centrifugal force of the flyweights becomes greater, which causing the force that is applied to the governor sleeve to become greater than the tension in the control spring. Then the control lever and the tension lever move in unison, rotating clockwise around fulcrum A, in order to move the spill ring in the direction that decreases injection volume. By restricting the maximum speed in this manner, the engine is prevented from overrunning.
5. Partial load (medium speed) (accelerator pedal depressed halfway)
When the adjusting lever is in the intermediate position between fullload and idling, the control spring has a weak tension, allowing the spill ring to move in the direction that decreases the injection volume at a lower speed than during the maximum speed control. As a result, the engine speed is controlled in accordance with the level of depression of the accelerator pedal. The characteristic of the injection volume in this situation is the same as during the full-load when the engine speed is low (before the spill ring is moved in the direction for decreasing the injection volume). As the speed increases thereafter, the injection volume decreases in order to control the speed.

VE Pump Mechanical Governor (Fuel Injection)

admin — Mon, 19 Jul 2010 03:59:17 +0000

It is necessary to control the fuel injection volume in accordance with the effort that the accelerator pedal is depressed and engine load as the output of the diesel engine is controlled by the fuel injection volume. Because the injection volume is determined by the spill ring position, it is necessary for the governor to control the spill ring position so that the engine can operate stably.
1. Control according to accelerator depression
Depressed:
The fuel injection volume is increased. (The engine speed is increased.)
Released:
The fuel injection volume is decreased. (The engine speed is decreased.)
2. Control with constant accelerator position and fluctuating engine load
Load increases:
The fuel injection volume is increased.
Load decreases:
The fuel injection volume is decreased. The governor also plays these rolesPrevents the engine from overrunning by controlling the maximum engine speed, and prevents engine stalling by stabilizing the engine speed at low speeds.
Construction and Function
For the mechanical governor, the flyweights, which rotate with the drive shaft of the injection pump, expand outward due to centrifugal force in accordance with the increase of shaft speed. This movement is transmitted to the spill ring through the governor sleeve and control lever to adjust the fuel injection volume.
There are two types of governors:
All-speed governor
M-M (Minimum-Maximum) speed governor

Diesel Engine Automatic Timer (Injection Timing Control)

admin — Sun, 18 Jul 2010 03:45:09 +0000

As in the case of gasoline engine ignition timing, diesel engine injection timing must be advanced (or retarded) in accordance with the engine speed in order to obtain optimum performance. Advancing or retarding is controlled by the automatic timer in response to the engine speed.

Construction and operation

Fuel injection timing is controlled by changing the position of the roller, which touches the face cam. When the injection pump is not rotating, the roller is in the maximum retarding position. When the injection pump starts rotating and speed is increased, the timer piston moves to the left pushing the timer spring, as the fuel pressure inside the pump housing also increases. The slide pin connected to the piston converts the piston movement into the rotational movement of the roller ring. When the roller ring rotates in the opposite direction of the drive shaft, the injection timing advances. When the roller ring rotates in the same direction, the injection timing retards.