text: This equation relates that, for a given BMEP, 
  the BHP is determined by the product of en- 
  In a 
  gine RPM, N, and displacement, D. 
  sense, the reciprocating engine could be con- 
  sidered primarily as an air pump with 
  the 
  pump capacity directly affecting the power 
  output. Thus, any engine instrumems which 
  relate factors affecting airflow can provide some 
  indirect reflection of engine power. The pres- 
  sure and temperature of the fuel-air mixture 
  decide the density of the mixture entering the 
  cylinder. The carburetor air temperature will 
  provide the temperature of the inlet air at the 
  this carburetor inlet air 
  carburetor. While 
  is not the same temperature as the air in the 
  cylinder inlet manifold, 
  the carburetor inlet 
  temperature provides a stable indication inde- 
  pendent of fuel flow and can be used as a stand- 
  ard of performance. Cylinder inlet manifold 
  temperature is difficult to determine with 
  the 
  same degree of accuracy because of the normal 
  variation of fuel-air mixture strength. The 
  inlet manifold pressure provides an additional 
  indication of the density of airflow entering the 
  combustion chamber. The manifold absolute 
  is affected by the carburetor 
  pressure, MAP, 