MBE 900 ENGINE 2007 OPERATOR'S GUIDE
ENGINE BRAKE SYSTEM
Certain MBE 900 vehicle engines
are equipped with engine brakes,
commonly referred to as
retarders
.
Before operating the vehicle, you
must
familiarize yourself with the
retarder system to obtain optimum
bene
fi
t from it. Engine brake control
systems may vary slightly, depending
on the engine brake con
fi
guration and
cab design. However, basic operator
controls are similar for all models.
Exhaust
Brake/Constant-Throttle
Valves, Optional
To increase braking performance,
the engine can be equipped with an
exhaust brake on the turbocharger
in conjunction with constant-throttle
valves in the cylinder head. See Figure
24.
Figure 24 Constant — Throttle
Activation
The two systems operate
independently of each other and
in combination.
Exhaust back pressure is used by the
exhaust brake to increase braking
performance. The constant-throttle
valves use the air that escapes through
them on the compression stroke to
provide braking force.
The constant-throttles valves are
small valves which are built into the
cylinder head and positioned opposite
the exhaust valve. When open, a link
is created between the combustion
chamber and the exhaust port.
When the engine brake is switched
on, the constant-throttle valves are put
under pressure, which in turn opens
the valves.
The constant-throttle valves are
activated by engine oil pressure.
The engine brake is activated by the
CPC and can be activated only at
engine speeds up to 2600 rpm.
Below 900 rpm, the engine brake
is always turned off to prevent the
engine from stalling. Also, the engine
brake is automatically turned off when
the accelerator pedal is pressed.
NOTE:
When in emergency running mode
(constant rpm), the engine brake can
All information subject to change without notice.
(Rev. 04/08)
55
DDC-SVC-MAN-0040 0704
Copyright © 2008 DETROIT DIESEL CORPORATION
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