ON THE KNOCKING CHARACTERISTICS OF AIR-COLLED ENGINES.

The temperature level of the walls of the combustion chamber of the engine within the limits of change of from 135 to 260 C shows substantial influence on its tendency to knock. With a change in the average temperature of 10, the required octane number of the fuel for the engine MeM3-966 goes up on the average by one point on the octane scale. Turbulation of the charge by means of setting in the combustion chamber of displacers is accompanied by a lowering of the tendency of the engine to knocking. The setting in of a displacer with the area of 24 in the combustion chamber leads to a lowering of the required octane number of the fuel with t sub head.average 200 C by 3.5 points, while increase of the area of the displacer to 36 is accompanied by further lowering of the requirements for the octane number of the fuel by 1.5 points. The means of lessening the tendency to knock in the engine consisting in the lowering of its temperature level, and also in the reducing of the power by means of setting in delay angles of advance of ignition, prove to be more effective with the presence in the combustion chamber of displacers. The change in the degree of compression from 6.5 value set up for the series engine MeMe-966 to 8 is accompanied by a rise in the required octane number of the fuel by 10 points. Author