Paccar PX 8, Operator'S Manual

Page: 34 / 94

Operating Instructions
– 28 –
Y53-1030A 12/09 PACCAR
PACCAR engines are designed to operate successfully at
full throttle under transient conditions down to peak torque
engine speed. This is consistent with recommended
operating practices.
CAUTION: Operating the engine beyond the
maximum engine speed can cause severe
engine damage. Do not operate the engine
beyond the maximum engine speed. Use proper
operating techniques for the vehicle to prevent
engine overspeed. The maximum engine speed
specification is listed in the “
General Engine
Specifications ” on page 55.
Engine Braking System
Variable Geometry Turbo (VGT) Brake System Gen-
eral Information
T h i s e n g i n e i s e q u i p p e d w i t h a va r i a bl e g e o m e t r y
turbocharger (VGT) with an exhaust brake feature. This
feature allows the variable geometry turbocharger to act as
an exhaust brake by retarding the speed of the engine to
provide additional vehicle braking power and extend the life
of the vehicle service brakes. The on/off function is controlled
by a switch located on the dash of the vehicle. The engine
(VGT) exhaust brake works by retarding engine speed by
creating high exhaust back pressure. This back pressure is
obtained by restricting airflow through the turbine housing of
the turbocharger. This restriction through the turbine housing
of the turbocharger is created through positioning of the
sliding nozzle (1) located internally to the variable geometry
turbocharger (VGT). the position of the sliding nozzle is
controlled by the engine electronic control module (ECM).