text: flame propagation speed, fuel distribution, 
  temperature variation, etc., 
  the maximum 
  power obtained with a fixed airflow occurs at 
  fuel-air ratios of approximately 0.07 to 0.08. 
  The first graph of figure 2.16 shows the varia- 
  tion of output power with 
  fuel-air ratio for a 
  a constant engine airflow, i.e., constant RPM, 
  MAP, and CAT (carburetor air temperature); 
  Combustion can be supported by fuel-air ratios 
  just greater than .0.04 but the energy released 
  is insufficient to overcome pumping losses and 
  engine mechanical friction. 
  Essentially, the 
  same result is obtained for the rich fuel-air 
  just below 0.20. Fuel-air ratios be- 
  ratios 
  tween these limits produce varying amounts of 
  output power and the maximum power output 
  generally occurs at fuel-air ratios of approxi- 
  mately 0.07 to 0.08. Thus, this range of fuel- 
  air ratios which produces maximum power for 
  a given airflow 
  is termed ,the “best power” 
  range. At jo,me lower range of f-ue;-air rariop, 
  a maximum of power per fuel-air ratio is ob- 
  tained and this the “best economy” 
  range. 
  The best economy range generally occurs be- 
  tween fuel-air ratios of 0.05 and 0.07. When 
  maximum engine power is required for take- 
  off, fuel-air ratios greater than 0.08 are neces- 
  sary to suppress detonation. Hence, fuel-air 
  ratios of 0.09 to 0.11 are typical during this 
  operation. 