Possible Mechanisms by which Combustion-Chamber Deposits Accumulate and Influence Knock

THREE mechanisms by which combustion-chamber deposits might increase the octane requirement of an engine are discussed in this paper. These are volume, catalysis, thermal insulation.

The experiments reported here indicate that the increase in compression ratio caused by deposit volume accounts, for 20-40% of the octane requirement increase, catalysis may not be a contributing factor, and the thermal insulating effect of the deposits is one of the major causes of deposit knocking harm.