Engine Tune-Up
DETROIT DIESEL
Full Load
No-Load
52.5 cycles 1050 rpm
50 cycles 1000 rpm
62.5 cycles 1250 rpm
60 cycles 1200 rpm
52.5 cycles 1575 rpm
50 cycles 1500 rpm
62.5 cycles 1875 rpm
60 cycles 1800 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 the lubricating oil increases.
2. Stop the engine and remove the governor cover. Discard the gasket.
3. Loosen the lock nut and back off the maximum speed adjusting screw (Fig. 5) approximately 5/8"
4. Refer to Fig. 4 and loosen' the droop adjusting bolt. Move the droop bracket so that the bolt is midway between the
ends of the slot in the bracket. Tighten the bolt.
5. With the throttle in the run position, adjust the engine speed until the engine is operating at 3% to 5% above the
recommended full-load speed.
6. Apply the full-rated load on the engine and re- adjust the engine speed to the correct full-load speed.
7. Remove the rated load and note the engine speed after the speed stabilizes under no-load. If the speed droop is
correct, the engine speed will be approximately 3% to 5% higher than the full-load speed. If the speed droop is too high,
stop the engine and again loosen the droop bracket retaining bolt and move the droop adjusting bracket in toward the
engine. Tighten the bolt. To increase the speed droop, move the droop adjusting bracket out, away from the engine.
The speed droop in governors which control engines driving generators in parallel must be identical, otherwise, the
electrical load will not be equally divided.
Fig. 5 - Adjusting Maximum Engine Speed
Adjust the speed droop bracket in each engine governor to obtain the desired variation between the engine no-load and
full-load speeds shown in Table 1. The recommended speed droop of generator sets operating in parallel is 50 rpm (2-1/2
cycles) for units operating at 1000 and 1200 rpm and 75 rpm (2-i12 cycles) for units operating at 1500 rpm and 1800 rpm
full load. This speed droop recommendation may be varied to suit the individual application.
Adjust Maximum No-Load Speed
With the speed droop properly adjusted, set the maximum no-load speed as follows:
1. Loosen the maximum speed adjusting screw lock nut and back out the maximum speed adjusting screw three turns.
2. With the engine operating at no-load, adjust the engine speed until the engine is operating at approximately 8%
higher than the rated full-load speed.
3. Turn the maximum speed adjusting screw (Fig. 5) in lightly until contact is felt with the linkage in the governor.
4. Hold the maximum speed adjusting screw and tighten the lock nut.
5. Use a new gasket and install the governor cover.
Page 110
