<div class="section abstract"><div class="htmlview paragraph">USING a high-speed motion picture camera, flame photographs were taken of the combustion process associated with the starting of hot gasoline engines.</div><div class="htmlview paragraph">Compression ignition at isolated points followed by normal combustion caused peak cylinder pressures to occur prior to top dead-center under some low-speed engine conditions.</div><div class="htmlview paragraph">In addition, an abnormal combustion phenomenon was observed in the last part of the charge to burn. The reaction rate was appreciably faster than normal for the engine speed and much slower than is usually observed in knocking combustion at normal engine speeds.</div></div>