THIS paper constitutes a progress report on work undertaken with the object of ascertaining the order of magnitude of the errors likely to be introduced in knock testing by variations in atmospheric conditions.
The atmospheric factors studied were barometric pressure, air temperature and humidity. The latter two were controlled, the effect of barometric pressure being studied as opportunity arose. The effects of these factors on both absolute and relative detonation of fuels were studied, ratings being obtained in terms of benzol and of tetraethyl lead in straight-run Pennsylvania-base gasoline and in terms of iso-octane in normal heptane in some cases.
The results show that normally the effects of humidity and barometric pressure are small and that air temperature should be maintained reasonably constant.
