TM 5-3895-346-14
ENGINE OVERHAUL
RUN-IN INSTRUCTIONS
as a Taylor valve or equivalent, the engine should be tested without thermostats.
The Basic Engine Run-In Schedule is shown in the following table. The horsepower shown is at SAE
conditions: dry air density .0705 lb/cu. ft. (1.129 Kg/cu.m) air temperature of 85 (29.4 ) and 500 ft.
F
C
elevation.
DYNAMOMETER TEST AND RUN-IN PROCEDURES
The Basic Engine
The great number of engine applications make any attempt to establish comparisons for each individual model
impractical. For this reason, each model has a basic engine rating for comparison purposes.
A basic engine includes only those items actually required to run the engine. The addition of any engine driven
accessories will result in a brake horsepower figure less than the values shown in the Basic Engine Run-In
Schedule. The following items are included on the basic engine: blower, fuel pump, water pump, and governor.
The fan and battery-charging alternator typify accessories not considered on the basic engine.
In situations where other than basic engine equipment is used during the test, proper record of this fact should
be made on the Engine Test Report. The effects of this additional equipment on engine performance should
then be considered when evaluating test results.
Dynamometer
The function of the dynamometer is to absorb and measure the engine output. Its basic components are a
frame, engine mounts, the absorption unit, a heat exchanger, and a torque loading and measuring device.
The engine is connected through a universal coupling to the absorption unit. The load on the engine may be
varied from zero to maximum by decreasing or increasing the resistance in the unit. The amount of power
absorbed in a water brake type dynamometer, as an example, is governed by the volume of fluid within the
working system. The fluid offers resistance to a rotating motion. By controlling the volume of water in the
absorption unit, the load may be increased or decreased as required.
The power absorbed is generally measured in torque (lb ft or Nm) on a suitable scale. This value for a given
engine speed will show the brake horsepower developed in the engine by the following formula:
BHP
=
(T x RPM)/5250
Where
BHP
=
brake horsepower
T
=
torque in lb ft or Nm
RPM
=
revolutions per minute
Some dynamometers indicate direct brake horsepower readings. Therefore, the use of the formula is not
required when using these units.
During the actual operation, all data taken should be recorded immediately on an Engine Test Report (see
sample on page x).
Certain instrumentation is necessary so that data required to complete the Engine Test Report may be
obtained. The following list contains both the minimum amount of instruments and the proper location of the
fittings on the engine so that the readings represent a true evaluation of engine conditions.
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