Flame Photographs of Light-Load Combustion Point the Way To Reduction of Hydrocarbons in Exhaust Gas

AN investigation to determine why the hydrocarbon content of automobile exhaust gas increases abruptly during deceleration and how this can be prevented is described in this paper.

High-speed motion pictures of the flame, taken through a quartz-window cylinder head, show that residual-gas dilution is the major cause of incomplete combustion under these conditions.

The concentration of hydrocarbons in the exhaust can be reduced either by admitting extra air and fuel to the intake manifold to limit vacuum attained during deceleration or by shutting off the fuel during deceleration.