TM 10-3950-672-24-2
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 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 horsepower 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.
General* Engine Test Specifications
Maintain the following limits during a chassis dynamometer test:
Intake Restriction (Maximum)
Clean Filter (light duty) ..................................................................................................254 mm H20 [10 in.H20]
(medium duty)...........................................................................................305 mm H20 [12 in. H20]
(heavy duty)..............................................................................................381 mm H20 [15 in. H20]
Dirty Filter (light duty) .................................................................................................................. 635 mm [25 in.]
(medium duty)........................................................................................................... 635 mm [25 in.]
(heavy duty).............................................................................................................. 635 mm [25 in.]
Industrial............................................................................................................................ 76 mm Hg [3.0 in. Hg]
EPA Certified.................................................................................................................... 11 4 mm Hg [4.5 in. Hg]
Blowby** (at Given Speed, 100% Load)
New (L/Min)
Worn (L/Min)
4B @ 2200
18
36
4B @ 2500
20
40
4B @ 2800
23
46
** Blowby checking tool, Part No. 3822476, has a special 5.613 mm [0.221 in.] orifice that must be used to get an
accurate reading.
Oil Pressure
Low Idle (minimum allowable)........................................................................................................69 kPa [10 psi]
Rated Speed (minimum allowable) ..............................................................................................207 kPa [30 psi]
Fuel Filter Restriction (Maximum)
Dirty Filter......................................................................................................................... 89 mm Hg [3.5 in. Hg]
Fuel Return Restriction (Maximum) ..............................................................................................................35 kPa [5 psi]
* Due to variations in ratings of different engine models, refer to the specific engine data sheet for the particular
engine model being tested.
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