Controls and Operating
3-30
Engine Exhaust Brake
There are 2 positions for the switch. Press the top of the switch to request
the engine exhaust brake. This position applies the engine exhaust brake
when service brake is applied. Press the bottom of the switch. This posi-
tion applies the engine exhaust brake when throttle pedal is not
active.The engine exhaust brake symbol illuminates on the display screen
when the engine exhaust brake is engaged.
NOTICE: For the Engine Exhaust Brake to activate -
a) the ECU must be live. Engine speed must be greater than 1000 rpm
b) the throttle pedal should be deactivated
c) the throttle pedal position must be less than 5%
The engine exhaust brake is applied automatically when throttle pedal is
released and engine speed is greater than 1000 rpm.
The engine exhaust brake also operates when ever the service brake is
applied.
Operation
Before the machine starts down the gradient fully laden, it is recom-
mended that the descent gear be preselected manually (Refer to Section
3). The manually pre-selected gear should be high enough to keep the
engine operating at governed speed. Generally the gear used to ascend a
grade, fully laden, is also correct for its descent. Please refer to the grade-
ability decal for recommended gear selection per grade specification. The
engine exhaust brake can now be selected and the accelerator released
(off gas). If the rate of descent is too slow, the transmission should be
upshifted to the next highest gear. If the rate of descent is too fast, the
service brakes should be applied and the transmission shifted into a lower
gear which will allow a safe descent and efficient engine braking. If further
braking is required, apply the service brakes.
If descending a steep gradient in a laden truck in automatic gear
shift mode, the transmission E.C.U. may automatically upshift
to prevent a machine (engine) overspeed condition. Also, if the
accelerator is re-applied when engine brake is actuated and the
truck is in automatic gear shift mode, a rapid acceleration
(increase in ground speed) and gear upshift could occur.
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