Operators Manual

Table Of Contents
With the engine at normal idle, transmission in neutral and service brakes on, press
the SPD CNTL Switch, and use the RSM/ACC Switch. The engine rpm should
increase to a pre-defined speed. The engine rpm can be raised or lowered from this
point using the SET/CST and RSM/ACC switches.
Engine Brake and Cruise Control
Your engine is equipped with both Cruise Control and an engine brake; the engine
brake can operate automatically while you are in Cruise Control. If the Cruise
Control/Engine Brake function is turned ON in the DDEC system programming,
the engine brake will come on low when your set road speed increases a few mph
(kph) above your cruise set speed. If your speed continues to increase, the DDEC
system will increase the engine brake's braking power progressively. When the
vehicle returns to the set cruise speed the engine brake will turn off until you need
them.
For safety reasons, don't use Cruise Control when it is not possible to keep the
vehicle at constant speed due to:
Winding roads
Heavy traffic
Slippery pavement
Descending grades calling for engine brake assistance
For an explanation of the engine brake system and recommendations for proper
operation, "Engine Brake System" in this manual.
DD Platform Shifting
Depending on your transmission model, the gear split may vary from 400 to 500
rpm. The electronic governor provides almost no overrun capability; and, if the
transmission is downshifted too early, you will experience a temporary loss of
pulling power until the engine speed falls below rated speed.
In general, when using a 7- or 9-speed transmission, you should always downshift
between 1150 and 1250 rpm for the DD13 and between 1000 and 1100 rpm for the
DD15 and DD16. This is true even on steep grades with heavy loads. When using
an 18-, 15-, or 13-speed transmission, you will need to downshift at an rpm that
allows "less than rated" rpm before throttle application in the next gear down. You
may want to limit engine speed to 1900 rpm in all gears. DD Platform engines
provide horsepower through 2100 rpm, but fuel economy is not as efficient above
1800 rpm.
If you decide to drive at a lower rpm for improved fuel economy, don’t let different
engine noises throw you off guard. The engine sounds quiet at 1400 rpm, almost as
if it had quit pulling. Depending on the air intake arrangement, you may also
experience a "chuffing" sound as the engine starts to pull hard at lower rpm. This is
DD Heavy Duty Platform Operators Manual
All information subject to change without notice. 75
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