CUMMINS N14 - Intake Manifold Boost Pressure Correction Factors

Intake Manifold Boost Pressure
Correction Factors (8-03)
Boost pressure measured in the intake manifold is di-
rectly related to the ambient temperature, the tempera-
ture rise across the air cleaner and turbocharger, and the
pressure drop across the charge air cooler. Typically
when the ambient temperature rises, the boost pressure
measured in the intake manifold decreases. Conversely,
higher boost pressure measured in the intake manifold
can be obtained with falling ambient temperature.
Refer to the following procedure and boost pressure cor-
rection factor charts to aid in the determination of engine
performance output. The charts define power output by
modifying boost pressure as a function of intake manifold
air temperature.
To use charts, first determine which chart is appropriate
for your engine. Select the proper chart based on the
local area altitude and the engine horsepower stamped
on the dataplate. With the engine running at full load and
full throttle at maximum horsepower RPM, the following
data must be taken.
Two pressure measurements are required:
1. Measure the turbocharger compressor outlet pres-
sure (boost) between the turbocharger and the charge
air cooler using a calibrated pressure gauge.
2. Measure the intake manifold pressure at the 1/8 inch
NPT tap in the intake manifold connection with the air
horn using a calibrated pressure gauge.
NOTE: The most accurate and reliable readings are ob-
tained using the same pressure gauge to measure both the
turbocharger compressor outlet pressure and the intake
manifold pressure.
Two temperature measurements are required:
1. Measure the turbocharger compressor inlet temper-
ature by inserting a Fluke digital thermometer, Part
No. 3822666, and thermocouple wire kit, Part No.
3822988, underneath the intake air inlet elbow which
is between the air cleaner and the turbocharger.
Engine Testing Intake Manifold Boost Pressure Correction Factors (8-03)
N14 Page 8-23