DAF CF65, CF75, CF85 Series . Manual — part 482

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2-3

General

XE ENGINE, ENGINE BRAKE

CF65/75/85 series

4

10

1.

Solenoid valve

2.

Control valve

3.

Operating piston

4.

Main piston

5.

Spring plate

6.

Set screw

XE ENGINE, ENGINE BRAKE

2-4

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General

10

CF65/75/85 series

4

2.3 LOCATION OF EXHAUST BRAKE COMPONENTS

1.

Operating cylinder, exhaust brake

2.

Exhaust brake valve

3.

Supply pressure

4.

Butterfly valve

I400533

3

2

4

1

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2-5

General

XE ENGINE, ENGINE BRAKE

CF65/75/85 series

4

10

2.4 SYSTEM DESCRIPTION, ENGINE BRAKE, GENERAL

The collective designation 'engine brake' includes

the engine brake (butterfly valve) and the DAF

Engine Brake (DEB).

With the introduction of the DAF 12.6 litre engine,

a new type of engine brake was introduced for

DAF, which could also be applied to XE engines.

This is the DAF Engine Brake or DEB for short.

Every XE engine has a factory-fitted exhaust

brake.

At the request of the customer, the DEB can be

fitted at the factory or at a later date.

If the driver activates the engine brake by means

of the engine brake control switch on the cab

floor, both the exhaust brake and the DEB are

engaged. Therefore, the DEB always works in

conjunction with the exhaust brake.

As the UPEC electronic unit checks the activation

of the engine brake, it will disengage the engine

brake below a certain engine speed (see UPEC

system manual).

2.5 SYSTEM DESCRIPTION, DEB

The DEB consists of two different housings, each

cylinder head having its own DEB housing.

Each housing contains various valves, pistons,

and a solenoid valve.

When the DEB is activated, fuel ceases to be

injected and one exhaust valve will be opened

hydraulically at the end of the compression

stroke. This means that the compressed air can

escape to the exhaust system, so that during the

working stroke this pressure does not help the

piston to fall.

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XE ENGINE, ENGINE BRAKE

2-6

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General

10

CF65/75/85 series

4

Position A: Induction stroke
The piston moves down and the cylinder is filled

with clean air.

Position B: Compression stroke
The piston moves up and compresses the air in

the cylinder, creating a braking force.

At the end of this stroke, one exhaust valve is

opened briefly. The compressed air can now

escape to the exhaust system. Otherwise this

compressed air would press the piston down

faster.

If the DEB has been activated, no fuel is injected

and hence no combustion takes place.

Position C: Power stroke
The piston moves down and the exhaust valve is

closed.

Position D: Exhaust stroke
The piston moves up, as during a normal exhaust

stroke.

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A

B

C

D