DAF LF45, LF55 Series. Manual — part 302

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General

BE ENGINE INLET/EXHAUST SYSTEM

ΛΦ45/55 series

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2.2 SYSTEM DESCRIPTION, TURBOCHARGER WITH WASTEGATE

To make the engine more responsive at lower

engine speeds, a turbocharger is used that

produces a better charge ratio at these speeds.

Without provision having been made for this, the

boost pressure yielded by this turbocharger

would be too high at maximum engine speeds.

Use of a wastegate prevents this.

The boost pressure is measured by a diaphragm

box (1) on the delivery side of the turbocharger.

The diaphragm is pushed back against the spring

pressure by the boost pressure. The linked

control rod (2) is also pushed back. The control

rod operates a valve in the turbine housing (3).

The valve in the turbine housing is opened when

the maximum pre-set pressure has been

reached.

When the valve is opened, some of the exhaust

gases will be discharged directly to the exhaust

pipe rather than being used to propel the turbine

rotor of the turbocharger.

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General

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Inspection and adjustment

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3. INSPECTION AND ADJUSTMENT

3.1 INSPECTING TURBOCHARGER WASTEGATE

Note:

Depending on the fitting position of the

turbocharger, it may be necessary to remove the

turbocharger from the engine before this

adjustment; see "Removal and installation".

Note:

The turbocharger is calibrated in the factory and

must not be re-adjusted. The length of the control

rod on the wastegate valve lever may only be

changed when assembling a new turbocharger.

After that, only an inspection of the actuating

pressure of the wastegate may be carried out. If

the result is negative, the turbocharger must be

replaced.

1.

Remove the flexible pipe (2) from the

diaphragm box (1) of the wastegate.

2.

Connect an air-pressure reducer valve to the

diaphragm box of the wastegate. Set the

reducer valve to max. 0.2 bar gauge

pressure. Connect the reducer valve to a

compressed air installation.

3.

Set the reducer valve to exactly the same

test pressure as listed in "Technical data".

4.

Check the diaphragm in the diaphragm box

for leaks by listening carefully for a hissing

sound from the diaphragm box.

5.

Check whether the control rod of the

wastegate has moved. If it has not moved,

the control rod must be loosened from the

lever. Check again whether the control rod

has moved. If is has not moved, the

diaphragm box must be replaced. If it has

moved, the wastegate valve must be made

to move freely or, if that does not help

sufficiently, the entire compressor unit must

be replaced.

6.

Remove the flexible pipe with the reducer

valve and re-connect the flexible pipe of the

compressor pump to the wastegate

diaphragm box.

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Inspection and adjustment

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3.2 INSPECTING TURBOCHARGER AXIAL BEARING PLAY

Note:

The turbocharger axial bearing play should only

be checked when the engine is cold.

1.

Remove the exhaust pipe from the

turbocharger.

2.

Remove the charge pipes from the

turbocharger.

3.

Fit a dial gauge (1) to the charge supply

flange of the turbocharger.

4.

Push the compressor shaft away from the

dial gauge and set the gauge to zero.

5.

Push the compressor shaft to the dial gauge

and read off the axial play. Compare the

reading with the specified value; see

"Technical data". Replace the turbocharger if

necessary.

6.

Fit the charge pipes to the turbocharger.

7.

Fit the exhaust pipe to the turbocharger.

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