ENGINE DIAGNOSTIC TOOLS
Section 4
CALIBRATING THE PRESSURE TEST KIT
(SE-2239) USING THE DWYER
SLACK TUBE® MANOMETER (Continued)
4.
Read manometer as follows: (Continued)
Use the conversion factor one inch of mercury
equals 0.4912 psi to determine the actual
pressure in pounds per square inch.
15.15 x 0.4912 = 7.44 psi
Read the gauge pressure again to determine if
any air leakage has reduced the gauge pressure
from six psi. If the gauge pressure still reads 6
psi, we have determined that the gauge reads
1.44 psi lower than the actual pressure.
Record the gauge pressure, corresponding
mercury manometer reading, and convert the
manometer reading to psi for each gauge psi
from 6 to 22 psi. Repeat the calibration test from
6 psi to 22 psi to double check for air leaks and
accuracy of gauge and manometer readings.
Gauge
PSI
Inches
Actual
Reading
of Mercury
Conversion
PSI
6
7.65+ 7.50=
15.15x0.4912= 7.44
15.15
7
8.65+ 8.45=
17.10x0.4912= 8.39
17.10
8
9.70 + 9.45 =
19.15 x 0.4912 = 9.40
19.15
9
10.80+ 10.40 =
21.20 x 0.4912 = 10.41
21.20
From the above information, make up a correction chart
for the gauge and place it on the gauge panel.
Gauge PSI Reading
Actual PSI
6
7.4
7
8.4
8
9.4
9
10.4
Guideline intake manifold pressures for each engine
horse power rating are printed on the "PERFORMANCE
DATA GUIDELINE" pages at the rear of
each Engine Section. Each pressure has a +1.5 psi
range. For example, the DTI-466B rated at 210 HP at
2600 RPM pressure of 125 + 10 kPa (18 + 1.5 psi) at
2600 RPM. An engine operating with 117-138 kPa (17-
20 psi) pressure will produce the rated horsepower at the
flywheel. Using this calibration procedure to test the
accuracy of the 0-30 psi gauge before measuring engine
pressure
will
assist
you
in
evaluating
engine
performance. Using an accurately calibrated boost
gauge along with the diagnostic procedures in this
manual, will allow you to determine if the engine is
producing rated horsepower and eliminate unnecessary
engine component changes.
ROBERT BOSCH SMOKE SAMPLING KIT
(SE-2580)
DESCRIPTION
The smoke sampling kit (Figure 14) is used for reading
smoke density at the exhaust stack at rated load and
speed only to determine acceptability of smoke emission.
Figure 14. Smoke Sampling Kit
OPERATION
In the smokemeter, a sampling pump draws off a certain
amount of exhaust gas from the exhaust pipe of the
respective engine and then sucks it through a filter paper
disk. The filter paper disk,
CGES-240-4
Printed in United States of America
Page 20
