All Products RevFlow Injector Carburetor Technical Study (continued)

Under certain moist atmospheric conditions with air temps ranging anywhere from 20 to 90 degrees F it is possible for ice to form in the induction system. The rapid cooling in an induction system using a float type carburetor is caused by the absorption of heat from the air during vaporization of fuel and, also due in part to the high air velocity, causing a low pressure area through the carburetor venturi. As a result of the latter two influences, the temperature in the mixing chamber may drop as much as 79 degrees F below the temp of incoming air. If this air contains a large amount of moisture, the cooling process can cause precipitation in the form of ice, generally in the vicinity of the butterfly which may build up to such an extent as to cause engine stoppage. In a float type carb, the fuel jet is ahead of, or just below, the venturi and throttle butterfly which means that the fuel is being impinged directly in the worst possible place for icing...the carb venturi. Since the RevFlow injector carburetor does not contain a venturi, nor a butterfly valve, the fuel and air is mixed further downstream, beyond the float type venturi refrigeration chamber. The absence of these parts accounts for the decreased likelihood for ice in this type of system.

If ice were to form, it would most likely collect in the intake manifold T area, however, tightly cowled engines with internal exhaust systems would retard or preent this from happening. The alternate air source/ram air cut off valve also assists in this matter. When the ram air is cut off, the engine will digest warm air through the alternate air filter. The exhaust system we usually have in the KR air frame is a four into one, whereas the #4 exhaust pipe runs parallel to the intake manifold. This exhaust heat keeps the intake system above freezing.

The higher the pressure drop in the intake tract, the more likely the system could ice. At higher power settings the pressure drop is lower and less prone to icing. At lower power settings, the pressure drop is much higher and more prone to icing. Auto fuel vaporizes more completely in the same time as 100LL. Thus, a lower air temp will result. This will create a lower threshold for icing. This should be considered when switching over to auto fuel.