MIL-DTL-46796D
3.5 Performance
3.5.1 Engine break-in run. An engine break-in run shall be performed by the contractor.
The break-in run schedule shall be established by the contractor to ensure that the engine, as
offered for delivery, is suitable for immediate operation. All the required checks or tests,
complete and in sequence of performance and endurance, shall be performed with no loss in
engine life expectancy (see 4.6.10.1, 4.6.10.1.1 and 4.6.10.1.2).
3.5.2 Speed range. The engine shall operate satisfactorily under all loads and conditions
as specified herein through a speed range of 1150 to 2600 revolutions per minute (rpm)
(see 4.6.10.2).
3.5.2.1 Idle speed. The engine shall maintain a satisfactory idle speed of 550 to 600 rpm
when using diesel fuel conforming to grade 4-D of ASTM D975 (see 4.6.10.2.1).
3.5.3 Governor. The governor shall limit the engine speed as follows during vehicle
operations:
Full Load
2275 to 2325 rpm
No Load
2450 to 2500 rpm minimum
When engine is equipped with a two speed governor, speed during winching operations shall be
as follows:
Full Load
1150 rpm minimum
No Load
1350 rpm maximum
In each case, the engine speed with no load on the engine shall stabilize within 3 seconds after
full rack position is reached (see 4.6.10.3).
3.5.4 Brake horsepower (bhp). The bare engine at a full rack setting, upon the
completion of the break-in run, shall develop not less than the brake horse power shown below
at 2300 rpm using diesel fuel conforming to grade 4-D of ASTM D975 (see 4.6.10.4).
TYPE I
380 observed bhp
TYPE II
418 observed bhp
3.5.4.1 Operating conditions. The engine horsepower rating shall be corrected to the
following conditions (see 4.6.10.4).
Dry air barometer
28.33 inches (in.) of mercury (Hg)
(96 kilopascals (kPa))
90F (32.2C)
Inlet air temperature
100F (37.7C)
Fuel (specific gravity
0.853 at 60F(15.5C))
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