Detroit Diesel 60 Operator's Manual page 50

DDEC V ENGINE DRIVING TIPS
In general, when using a 7- or 9-speed
transmission, you should always
downshift between 1250 and 1300
rpm. 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.
The Series 60 provides horsepower
through 2100 rpm, but fuel economy
is not as efficient above 1800 rpm.
Low rpm operation should feel greatly
enhanced due to the characteristics
of the variable nozzle turbocharger.
Engine response should be almost
instantaneous below peak torque
engine speeds. This should encourage
progressive shifting especially during
slow vehicle speed operation.
If you decide to drive at lower rpm's
for improved fuel economy, don't let
different engine noises throw you
off guard. The Series 60 sounds
quiet at 1400 rpm, almost as if it
had quit pulling. Don't believe it!
If you had a boost gage to look at
while driving, you would notice
the turbocharger maintaining steady
intake manifold pressure, even as
rpm's fall. Depending on the air
intake arrangement, you may also
experience a "chuffing" sound as the
engine starts to pull hard at lower
rpm's. This is caused by the velocity
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DDC-SVC-MAN-0039
changes of the air flow within the air
intake plumbing. Electronic engines
can actually deliver more fuel at lower
engine speeds than at rated speed.
One difference you may notice
with the EGR equipped engine is
underhood noise. The gear train
has been redesigned for quieter
operation, and the EGR gas flow may
be noticeable to the tuned attentive
ear. The turbocharger operates at
higher boost pressure forcing EGR
gas flow through the EGR plumbing
which is a noticeable change from
non-EGR equipped engines. In some
situations the driver may believe
he/she has experienced a charge air
cooler system leak. Even connecting
trailer light and air hoses, the driver
may hear a different tone (exhaust and
underhood with the engine idling.) If
equipped with a turbo boost gage, the
driver may occasionally note intake
manifold pressure exceeds 35 psi.
All information subject to change without notice.
Copyright © 2009 DETROIT DIESEL CORPORATION