freightliner CENTURY CLASS S Driver Manual page 103

what rpm is needed to make upshifts under vari-
ous conditions. This progressive shifting tech-
nique will lower fuel costs because the engine
will be operating at the lowest rpm needed to pull
the load.
Caterpillar electronic engines can be pro-
grammed to limit engine rpm while the vehicle is
operated in the lower and higher gears. This fea-
ture assists the driver in following progressive
shifting techniques.
5.
On uphill grades, begin downshifting when the
engine speed falls to 1200 rpm for C–10, C–12,
C–15, C–16, and 3406E electronic engines. Fuel
economy will be best if you let the engine lug
back to around this speed before you downshift.
Downshift until a gear is reached in which the
engine will pull the load. Let the engine lug down
if you can make it to the top of a hill without
downshifting.
IMPORTANT: Do not let C–10, C–12, C–15,
C–16, and 3406E electronic engines exceed
2300 rpm (2100 rpm if equipped with an ex-
haust brake).
6. On a downhill grade, do not coast or put the
transmission in neutral. Select the correct gear
that does not allow the engine to exceed its
maximum speed. Use the brakes to limit the ve-
hicle speed.
A simple rule to follow is to select the same gear
(or one gear lower) than would be needed to go
up the grade.
7.
As with any engine, prolonged idling of Caterpil-
lar engines is not recommended. An idling en-
gine wastes fuel and if left unattended, is also
unsafe.
Caterpillar engines can be programmed to shut
off automatically after a specified idling time. The
vehicle transmission must be in neutral and the
parking brake must be set for the automatic shut-
off option to work.
BrakeSaver, Optional
The BrakeSaver (optional on 3406E engines) permits
the operator to control the speed reduction of the
vehicle on grades, curves, or anytime speed reduc-
tion is necessary but long applications of the service
brakes are not desired.
Engines and Clutches
During downhill operation, the crankshaft is turned by
the rear wheels (through the drivetrain). To reduce
the speed of the vehicle, an application of braking
force can be made to the crankshaft. The Brake-
Saver does this by converting rotation energy into
heat, which is removed by the engine cooling sys-
tem. The BrakeSaver is controlled by the driver, as
necessary, by operating a lever on the instrument
panel. Braking force increases as the lever is moved
toward the ON position. An air pressure gauge pro-
vides a relative indication of the braking force. An oil
temperature gauge indicates the heat in the Brake-
Saver during its operation. If the temperature gauge
indicates HOT, the BrakeSaver control lever must be
moved to the OFF position. The oil temperature will
decrease rapidly with the BrakeSaver off. When the
temperature reaches normal, the BrakeSaver can be
used.
CAUTION
Do not engage the BrakeSaver and control the
wheel speed with the accelerator. The design of
the cooling system is for the control of the tem-
perature of the oil at full engine power or full
BrakeSaver capacity, but not both at the same
time.
Cummins
Follow the directions in this manual and the Cum-
mins Operation and Maintenance Manual for trouble-
free, economical vehicle engine operation.
1. Cummins diesel engines produce high horse-
power and peak torque characteristics at lower
rpm. Because of this, it is not necessary to keep
the engine "wound up" to deliver the required
horsepower at the wheels. These characteristics
may also result in less shifting and make shifting
at lower rpm (toward peak torque) more practi-
cal.
2.
Depending on the vehicle gearing, the posted
speed limit can sometimes allow operation in ei-
ther of the top two gears; however, for improved
operating efficiency (fuel economy and engine
life), operate in the top gear at reduced rpm
rather than in the next lower gear at the maxi-
mum rpm.
3.
Drive at partial throttle whenever road conditions
and speed requirements permit. This driving
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