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Detroit Diesel — Speed Droop Adjustment

A Detroit Diesel service procedure — check it applies to your exact model before use.

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Before you start

  • When the engine lubricating oil is cold, the governor regulation may be erratic. Regulation will become increasingly stable as the temperature of the oil increases.
  • The speed droop in governors which control engines driving generators in parallel must be identical, otherwise the electrical load will not be equally divided.

Procedure

  1. Start the engine and run it at approximately one-half the rated no-load speed until the lubricating oil temperature stabilizes.
  2. Stop the engine and remove the governor cover.
  3. Loosen the lock nut and back off the maximum speed adjusting screw approximately 5/8".
  4. Loosen the droop adjusting screw. Move the droop bracket so that the screw is midway between the ends of the slot in the bracket. Tighten the screw (Fig. 8).
  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 readjust 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, loosen the droop adjusting screw and move the adjusting bracket IN toward the center of the governor. Tighten the screw. To increase the speed droop, move the bracket OUT, away from the center of the governor.

Tools required

  • Accurate tachometer

Specs & torque values

  • 50 cycles 1000 rpm full-load, 1050 rpm no-load
  • 60 cycles 1200 rpm full-load, 1250 rpm no-load
  • 50 cycles 1500 rpm full-load, 1575 rpm no-load
  • 60 cycles 1800 rpm full-load, 1875 rpm no-load
  • 3% to 5% speed droop

Source: manual:part 2.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.