text: Of course, the engine airflow is a function of 
  RPM for two reasons. A higher engine speed 
  increases the pumping rate and the volume flow 
  the engine 
  through the engine. Also, with 
  driven supercharger or impeller, an increase in 
  engine speed increases the supercharger pres- 
  sure ratio. With the exception of near closed 
  throttle position, an increase in engine speed 
  will produce an increase in manifold pressure. 
  The many variables affecting the character 
  ,.F the romL.,*r;nn 
  “1 L..,, c YYU”Cl”Y process a:e an I.n~“Lrant 
  subject of 
  reciprocating engine operation. 
  Uniform mixtures of fuel and air will support 
  combustion between fuel-air ratios of approxi- 
  mately 0.04 and 0.20. The chemically correct 
  proportions of air and hydrocarbon fuel would 
  be 15 lbs. of air for each lb. of fuel, or a fuel- 
  air ratio of 0.067. This chemically correct, or 
  fuel-air ratio would provide 
  “stoichiometric,” 
  the proportions of fuel and air 
  to produce 
  maximum release of heat during combustion of 
  the fuel-air 
  a grven weight of mixture. 
  ratio were leaner than stoichiometric, the ex- 
  cess of air and deficiency of fuel would produce 
  lower combustion temperatures and reduced 
  If 
  heat release for a given weight of charge. 
  the fuel-air ratio were richer than stoichio- 
  metric, the excess of fuel and deficiency of air 
  would produce lower combustion temperatures 
  and reduced heat release for a given weight of 
  charge. 