TM 5-2420-230-24-2
B3.9 and B5.9 Series Engines
Engine Testing - General Information
Section 14 - Engine Testing - Group 14
Page 14-3
Engine Testing - General Information
The engine test is a combination of an engine run-in and a performance check. The engine run-in procedure provides
an operating period that allows the engine parts to achieve a final finish and fit. The performance check provides an
opportunity to perform final adjustments needed to optimize the engine's performance.
An engine test can be performed using either an engine dynamometer or a chassis dynamometer. If a dynamometer
is not available, an engine test must be performed in a manner that simulates a dynamometer test.
Check the dynamometer before beginning the test. The dynamometer must have the capability to test the performance
of the engine when the engine is operating at the maximum rpm and horspower range (full power).
The engine crankcase pressure, often referred to as engine blowby, is an important factor that indicates when the piston
rings have achieved the correct finish and fit. Rapid changes of blowby or values that exceed specifications more than
50 percent indicate that something is wrong. The engine test must be discontinued until the cause has been determined
and corrected.
Specifications
Engine Testing
Maintain the following limits (see note) during a chassis dynamometer test:
Intake Restriction (maximum)
Clean Filter:
Light-Duty .............................................................................................................. 254 mm H2O [10 in H2O]
Medium-Duty ......................................................................................................... 305 mm H2O [12 in H2O]
Heavy-Duty ............................................................................................................ 381 mm H2O [15 in H2O]
Dirty Filter:
Light-Duty ............................................................................................................................. 635 mm [25 in]
Medium-Duty ........................................................................................................................ 635 mm [25 in]
Heavy-Duty .......................................................................................................................... 635 mm [25 in]
Exhaust Back Pressure (maximum) Nonautomotive ............................................................ 76 mm Hg [3.0 in Hg]
Exhaust Back Pressure (maximum) Automotive with Catalyst
.. 152 mm Hg [6.0 in Hg] to 127 mm Hg [5.0 in Hg]
Back Pressure (maximum) Automotive without Catalyst ............. 114 mm Hg [4.5 in Hg] to 102 mm Hg [4.0 in Hg]
Oil Pressure:
Low Idle (minimum allowable) ................................................................................................... 69 kPa [10 psi]
Rated Speed (minimum allowable) ......................................................................................... 207 kPa [30 psi]
Fuel Inlet Restriction (maximum) ......................................................................................... 100 mm Hg [4 in Hg]
Fuel Return Restriction (maximum)
................................................................................ 518 mm Hg [20.4 in Hg]
NOTE: Due to variations in ratings of different engine models, refer to the specific engine data sheet for the particular
engine model being tested.
L-1301