The igniton behavior of the primary reference fuel isooctane was studied behind reflected shockwaves in a shock tube using high-speed, 4-D imaging. Mixtures of 0.1%C8H18/5.94%Air/Ar were used to study the ignition behavior of the fuel. For the majority of experiments conducted in this study, a mild ignition of iso-octane was observed, characterized by ignition first occurring outside of the visible test section and then by local reaction centers that gradually develop in the test region as time progresses. If the energy within the system is increased sufficiently, a strong ignition behavior characterized by ignition occurring at the end wall surface can be observed. This phenomenon was observed for temperatures >
1500K.