text: Detonation is not necessarily confined to. a 
  period after the beginning of normal flame front 
  propagation. With extremely low grades of 
  fuel, detonation can occur before normal igni- 
  tion. 
  In addition, the high temperatures and 
  pressure caused by preignition will mean that 
  detonation is usually a corollary of preigniticn. 
  Detonation results from a sudden, unstable de- 
  composition of fuel at some critical combina- 
  tion of high temperature and pressure. Thus, 
  detonation is most likely 
  to occur at any op 
  erating condition which produces high com- 
  bustion pressures and temperatures. Gener- 
  ally, high engine airflow and fuel-air ratios for 
  maximum heat release will produce the critical 
  conditions. High engine airflow 
  is common 
  to high MAP and RPM and the engine is most 
  sensitive to CAT and fuel-air ratio 
  this 
  region. 
  
  in 