Correlation of Engine Noises With Combustion Phenomena

A BETTER knowledge of the nature and causes of preignition and of its frequency during normal engine operation has been obtained by instrumenting a 9/1-compression-ratio engine on a test stand and an engine in an automobile with rate of change of pressure pickups.

Photographic records of the oscilloscope traces produced by this instrumentation have enabled the determination of:

1. 1.
   The relative tendency for preignition or postignition to occur and the relation of these phenomena to engine or car operating conditions.
2. 2.
   The physical causes of the noises accompanying the several types of preignition.
3. 3.
   The effect of retarded spark timing on deposit-induced preignition.
4. 4.
   The significance of the “key-off” method of fuel rating.