4
XF ENGINE BRAKE
General
95
XF series
2-16
Switching on the exhaust brake
The exhaust brake consists of an engine brake
control switch fitted in the cab floor, an engine
stop valve (3), an operating cylinder (1)
connected to the fuel pump stop lever, and an
operating cylinder (2) connected to the butterfly
valve in the exhaust pipe.
If the engine brake control switch is operated, a
signal is passed to the CTE unit. This signal
activates the engine stop valve (3), causing
compressed air to flow to the operating
cylinder (1).
This operating cylinder (1) places the fuel pump
in the stop position.
At the same time, compressed air flows to
the operating cylinder (2). The latter cylinder
closes the butterfly valve in the butterfly valve
housing. The exhaust pipe is then almost
entirely closed off.
Controlled discharge of exhaust gases is still
possible through a calibrated hole in the butterfly
valve.
The engine now acts as a compressor, creating
a braking action.
The higher the engine speed, the greater the
braking action of the exhaust brake.
Switching off the exhaust brake
If the engine brake control switch is released,
the engine stop valve will bleed the two
cylinders. The springs fitted in the cylinders
force the pistons back into in their starting
position, thus re-opening the butterfly valve, and
the fuel pump starts to deliver once again.
4
©
0008