THE use of ignition quality improver additives has been under active laboratory investigation since the early 1930’s, but economic and fuel availability considerations have not been such as to foster their commercial application. The Navy has, however, conducted evaluation tests of many of the additives that have been made available for testing over the past 15 years.
A large number of compounds of various types have been found to be effective in raising the cetane number of diesel fuels. Many of the additives lose their effectiveness, however, when blended with diesel fuel and stored under certain conditions.
The results of laboratory engine tests have shown that certain additives do not materially increase piston-ring wear or engine deposits outside the piston-ring belt but show a tendency to cause ring sticking. They generally decreased maximum cylinder pressure, rate of pressure rise, and ignition lag, reduced exhaust smoke to a slight degree, and improved engine startability under certain conditions. At the same time they reduced power output and increased fuel consumption slightly and, in an isolated case, may have contributed to exhaust-valve and injector-valve sticking, and corrosion of the diaphragm in a cylinder pressure pickup.