Engine Tune-Up
DETROIT DIESEL
Full Load
No-Load
50 cycles 1000 rpm
52.5 cycles 1050 rpm
60 cycles 1200 rpm
62.5 cycles 1250 rpm
50 cycles 1500 rpm
52.5 cycles 1575 rpm
60 cycles 1800 rpm
62.5 cycles 1875 rpm
TABLE 1
If a full-rated load can be established on the engine and
the fuel rod, injector rack control levers and load limit
have been adjusted, the speed droop may be adjusted
as follows:
1. Start the engine and run it at approximately one-half
the rated no-load speed until the lubricating oil
temperature stabilizes.
NOTE: When the engine lubricating oil
is cold, the governor regulation may be
erratic. The regulation should become
increasingly stable as the temperature of
Fig 5 Adjusting Maximum Engine Sped
the lubricating oil increases.
Adjust the speed droop bracket in each engine governor
2. Stop the engine and remove the governor cover.
to obtain the desired variation between the engine no-
Discard the gasket.
load and full-load speeds shown in Table 1.
3. Loosen the lock nut and back off the maximum
The recommended speed droop of generator sets
speed adjusting screw (Fig. 5) approximately 5/8" .
operating in parallel is 50 rpm (2-1/2 cycles) for units
operating at 1000 and 1200 rpm and 75 rpm (2-1/2
4. Refer to Fig. 4 and loosen the droop adjusting bolt.
cycles) for units operating at 1500 rpm and 1800 rpm
Move the droop bracket so that the bolt is midway
full load. This speed droop recommendation may be
between the ends of the slot in the bracket. Tighten the
varied to suit the individual application.
bolt.
Adjust Maximum No-Load Speed
5. With the throttle in the run position, adjust the
engine speed until the engine is operating at 3% to 5%
With the speed droop properly adjusted, set the
above the recommended full-load speed.
maximum no-load speed as follows:
6. Apply the full-rated load on the engine and readjust
1. Loosen the maximum speed adjusting screw lock
the engine speed to the correct full-load speed.
nut and back out the maximum speed adjusting screw
three turns.
7. Remove the rated load and note the engine speed
after the speed stabilizes under no-load. If the speed
2. With the engine operating at no-load, adjust the
droop is correct, the engine speed will be approximately
engine speed until the engine is operating at
3% to 5% higher than the full-load speed.
approximately 8% higher than the rated full-load speed.
If the speed droop is too high, stop the engine and again
3. Turn the maximum speed adjusting screw (Fig. 5)
loosen the droop bracket retaining bolt and move the
in lightly until contact is felt with the linkage in the
droop adjusting bracket in toward the engine. Tighten
governor.
the bolt. To increase the speed droop, move the droop
adjusting bracket out, away from the engine.
4. Hold the maximum speed adjusting screw and
tighten the lock nut.
The speed droop in governors which control engines
driving generators in parallel must be identical,
5. Use a new gasket and install the governor cover.
otherwise, the electrical load will not be equally divided.
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