TM 5-2420-230-24-2
B3.9 and B5.9 Series Engines
Air Intake Restriction (010-031)
Section 10 - Air Intake System - Group 10
Page 10-27
Airflow restriction results in excessive smoke and low
power.
Restriction increases as the filter removes contaminants
from the intake air. Restriction airflow changes the air-to-
fuel ratio, reducing power and increasing smoke from the
engine. Verify that the air cleaner is being maintained
correctly.
Intake Air Restriction -- Checking
Replace the air cleaner element when the restriction
reaches the maximum limit at rated engine power and
speed.
Naturally Aspirated
Turbocharged
50.8 mm H2O
63.5 mm H2O
[2 in. H2O]
[2.5 in. H2O]
NOTE: The illustration shows the measurement in centi-
meters instead of millimeters.
For turbocharged engines, measure the restriction just be-
fore the turbocharger. Measure just before the intake mani-
fold for naturally aspirated engines.
Measure (010-031-010)
Manometer, Part No. ST-11113
Install a vacuum gauge or water manometer, Part No. ST-
1111-3, in the intake air piping.
The gauge adapter must be installed at a 90-degree angle
to the airflow in a straight section of pipe, one pipe diameter
before the turbocharger.
L-1151