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Show F1IS1P01M " iff MOTOR COOLING Drives Air Back Over the Motor, Not Through Radiator. Fresh air plays a part in reducing the high temperatures of hydro-carbon combustion com-bustion that there is a common temptation tempta-tion to underestimate. In truth, it is a factor of nearly equal importance to water in keeping the thermal condition of the motor at the point of greatest efficiency, says the latest technical bulletin bul-letin issued by the Haynes Automobile ' company. 0 The temperature of an automobile cylinder at the time of explosion is approximately ap-proximately 3000 degrees, and the heat of the exterior metal coverings of the water manifold is sometimes well toward to-ward the boiling point. A Btoppage of air cooling, particularly in traveling through desert regions, where the atmospheric at-mospheric temperature is noticeably high, means immediate expansion of the motallic parts to the extent of stuck pistons or scored cylinders. The hood of practically every motor car is marked by a row of louvres, or slits, cut along the lower edge of the bonnet; in the Haynes "light six" and "light twelve" the number is seventeen. seven-teen. The presence of these air passages pas-sages eliminates the back pressure of warmed air on the fan and guarantees a stream of cool air even over the heated water manifolds. Contrary to the idea many motorists have, the radiator fan does nbt drive air through the meshes of the radiator. Instead, In-stead, the fresh air that has already penetrated the interstices of the radiator radia-tor core is impelled back over the heated heat-ed manifolds of the motor. The revolutions of the fan tend to create a partial vacuum in the space between the fan and the radiator. When the motor is running and the car standing stand-ing still, the unwarmed air continually flows through the radiator apertures to equalize atmospheric pressure. If the motor car is moving only at a low speed the impact of air against the radiator surface is sufficient to greatly increase the amount of unwarmed "air that reaches the motor and with its load of wasted hoat units finds it way out through the louvres. |