The efficiency of an engine can be checked by making a comparison of the pressure in the inlet manifold with the information given in the TMI (Technical Marketing Information) or Fuel Setting And Related Information Fiche. This test is used when there is a decrease of horsepower from the engine, yet there is no real sign of a problem with the engine.
The correct pressure for the inlet manifold is given in the TMI (Technical Marketing Information) or Fuel Setting And Related Information Fiche. Development of this information is done with these conditions:
a. 747 mm (29.4 inches of mercury) barometric pressure.
b. 29°C (85°F) outside air temperature.
c. 35 API rated fuel.
Any change from these conditions can change the pressure in the inlet manifold. Outside air that has higher temperature and lower barometric pressure than given above will cause a lower horsepower and a lower inlet manifold pressure measurement than given in the TMI (Technical Marketing Information) or Fuel Setting And Related Information Fiche. Outside air that has a lower temperature and a higher barometric pressure will cause higher horsepower and a higher inlet manifold pressure measurement.
A difference in fuel rating will also change horsepower and the pressure in the inlet manifold. If the fuel is rated above 35 API, pressure in the inlet manifold can be less than given in the TMI (Technical Marketing Information) or Fuel Setting And Related Information Fiche. If the fuel is rated below 35 API, the pressure in the inlet manifold can be more than given in the TMI (Technical Marketing Information) or Fuel Setting And Related Information Fiche. Be Sure That The Air Inlet And Exhaust Do Not Have A Restriction When Making A Check Of Pressure In The Inlet Manifold.
Use the 1U5470 Engine Pressure Group to check the pressure in the inlet manifold.
1U5470 Engine Pressure Group
This group has a gauge to read pressure in the inlet manifold. Special Instruction, SEHS8907 is with the tool group and gives information for its use.
Location For Pressure Test
(A) Remove fitting and install test fitting.
Location For Pressure Test
(A) Remove fitting and install test fitting.