Measuring Inlet Manifold Pressure
The performance of an engine can be checked. Determine the boost pressure in the inlet manifold during a load test. Compare this pressure with the specifications that are given in the Fuel Setting and Related Information in the Technical Marketing Information (TMI). This test is used when there is an increase in exhaust temperature to the turbocharger on the engine, yet there is no real sign of a problem with the engine.
The performance and correct pressure for the inlet manifold is given in the Fuel Setting and Related Information in the TMI. Development of this information is done with these conditions:
The dry barometric pressure measures 96 kPa (28.8 inches Hg).
25 °C (77 °F) outside air temperature
35 API rated fuel
Any change from these conditions can change the pressure in the inlet manifold. The outside air may have a higher temperature and a lower barometric pressure than the values that are given above. This will cause a lower inlet manifold pressure measurement than the pressure that is given in the TMI. Outside air that has a lower temperature and a higher barometric pressure will cause a higher inlet manifold pressure measurement.
A difference in fuel density will change horsepower and boost. If the fuel is rated above 35 API, the pressure in the inlet manifold can be less than the pressure that is given in the TMI. If the fuel is rated below 35 API, the pressure in the inlet manifold can be more than the pressure that is given in the TMI.
Be sure that the air inlet or the exhaust does not have a restriction when you are making a check of the pressure.
Note: The electronic service tool may be used to check the pressure in the inlet manifold.