Detroit Diesel — Adjust Governor Speed Droop (Internal Droop Adjustment)
Adjustments
From a Detroit Diesel service manual — check it applies to your exact model before use.
Before you start
- Governors controlling engines driving generators in parallel must have identical speed droop, otherwise electrical load will not be equally divided.
Procedure
- Start engine and run at approximately one-half rated no-load speed until lubricating oil temperature stabilizes.
- Stop engine and remove governor cover.
- Loosen lock nut and back off maximum speed adjusting screw approximately 5/8 in.
- Loosen the droop adjusting screw and move droop bracket so screw is midway between ends of the slot in the bracket; tighten screw.
- With throttle in RUN position, adjust engine speed to 3% to 5% above recommended full-load speed.
- Apply full rated load and readjust engine speed to correct full-load speed.
- Remove load and note engine speed; if droop correct, speed is approximately 3% to 5% higher than full-load speed.
- To reduce droop, move adjusting bracket IN toward governor center; to increase droop, move bracket OUT.
Tools required
- Accurate tachometer Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 3% to 5% speed droop
- 50 rpm (2-1/2 cycles) recommended droop at 1000 and 1200 rpm
- 75 rpm (2-1/2 cycles) recommended droop at 1500 and 1800 rpm
Source: Detroit Diesel service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.