Carb Icing - again still
in 912 / 914 Technical Questions
10 years ago
I have several questions concerning carb icing. My Cessna had carb heat via a muff heater, which caused significant loss of power but prevented engine stoppage due to ice. I’ve read everything I could find on Rotax 912/Bing carb icing and concluded that there are strong opinions that it doesn’t occur and strong opinions that it does occur, and others that maybe it can, the whole range. Rotax and Bing are remiss for not addressing this directly. But I understand, it is like saying “do not drink the contents of the cooling system” (legal worries) - if they say carb icing doesn’t happen and someone says it did, then there is a lawsuit. So I’ve decided to install carb heat.
I like the hot airbox/muff heater style best, but am thinking about something less expensive and easier. There are two popular systems, the coolant AFTER downstream of where ice would form, presumably conducing heat through the carb body and heating up the ice formation point to where it does not happen. The second one uses electricity to heat the carb body directly by bolting to the unused, untapped holes at the point of ice formation in the venturi. Well, ok, there is a third model that heats air with electricity inside the air filter, but I doubt this tiny heat source would do much of anything given the volumes of air that flows here.
Looking at the second type, the one using the untapped holes in the side of the carb, I am thinking of routing a 3/8” coolant line through a copper pipe heat sinked and connected to the side of the carb at this very point. This would be very easy to fabricate and install. If I do this I will post pictures. But this brings me to my questions.
Could too much heat cause vapor lock with the horrible corn gas (ethanol)many of us are foced to use? Or could the heat cause other issues inside the carb? I could make the heat sink to carb mount less effective in an attempt to regulate how hot it might get. But then it might not prevent icing. Keep in mind that the coolant might approach 250 degrees, but hopefully be down around 200. These temps are not what the carb body would see by the time the heat reaches it, just something to keep in mind.
Any thoughts?
Thanks,
Dennis Urban
717-349-7756
I like the hot airbox/muff heater style best, but am thinking about something less expensive and easier. There are two popular systems, the coolant AFTER downstream of where ice would form, presumably conducing heat through the carb body and heating up the ice formation point to where it does not happen. The second one uses electricity to heat the carb body directly by bolting to the unused, untapped holes at the point of ice formation in the venturi. Well, ok, there is a third model that heats air with electricity inside the air filter, but I doubt this tiny heat source would do much of anything given the volumes of air that flows here.
Looking at the second type, the one using the untapped holes in the side of the carb, I am thinking of routing a 3/8” coolant line through a copper pipe heat sinked and connected to the side of the carb at this very point. This would be very easy to fabricate and install. If I do this I will post pictures. But this brings me to my questions.
Could too much heat cause vapor lock with the horrible corn gas (ethanol)many of us are foced to use? Or could the heat cause other issues inside the carb? I could make the heat sink to carb mount less effective in an attempt to regulate how hot it might get. But then it might not prevent icing. Keep in mind that the coolant might approach 250 degrees, but hopefully be down around 200. These temps are not what the carb body would see by the time the heat reaches it, just something to keep in mind.
Any thoughts?
Thanks,
Dennis Urban
717-349-7756
