Oil Carb Heat

[XL-C-100]

I am wondering if anyone has information about how to add carb heat using hot oil lines? I have a 4A084 which I setup with a more traditional carb heat using ductwork from the exhaust but I would like something more simplistic that would be less bulky.  As it is now I have a rather large carb heat box hanging off the bottom of the motor and scat tubing running to a heat collector and up to the carb. 

Maybe I should leave good enough alone....nah!

[Steve]

I am wondering if anyone has information about how to add carb heat using hot oil lines? I have a 4A084 which I setup with a more traditional carb heat using ductwork from the exhaust but I would like something more simplistic that would be less bulky.  As it is now I have a rather large carb heat box hanging off the bottom of the motor and scat tubing running to a heat collector and up to the carb.

Maybe I should leave good enough alone....nah!

If you are running a Mikuni slide carb, heat is not needed if the inlet is near the cylinder heat off-flows...
If it is a carb with a butterfly control valve then you should put an air box on the carb with heat coming from an exhaust stack muff and getting a 75 rpm drop minimum with heat on - always use carb heat when running at partial throttle...

There are plans for carb heat in the DE engine files and layouts for the heatbox & muff construction...

[XL-C-100]

Yeah that is essentially what I have setup now with the stock butterfly throttle. I was thinking about some kind on oil line wrap to warm the body of the carb a bit. has this been done successfully?

[Steve]

Yeah that is essentially what I have setup now with the stock butterfly throttle. I was thinking about some kind on oil line wrap to warm the body of the carb a bit. has this been done successfully?

Look at Scott Johnson's LE "Engelman"engine conversion - that single carb/top mounted intake has an oil driven heat exchanger...

[Dan_]

Look at Scott Johnson's LE "Engelman"engine conversion - that single carb/top mounted intake has an oil driven heat exchanger...

Scott Johnson's Legal Eagle is one of the finest examples of the breed out there for sure.


For the sake of discussion, I am want to proffer an opinion on this carb heat setup however.

It is mounted on the wrong side of the carb...

The way it is mounted will perhaps keep "frost" off the outside of the intake tubes, but that is not what is called for in a carb heat system.

The heat needs to be applied upstream of where the pressure drop occurs (venturi) if you are heating the air.

Of course if you are heating the carb body it would be possible to keep ice from forming, but the question I have is how much heat could be getting to the carb body through a rubber spigot on this setup with the heat source on the opposite side, and the incoming air blowing it away from the carburetor.

I don't know if what looks like a  piece of rubber in Scott's photo below is actually that, or a  piece of highly heat conducting aluminum billet, so stand to be corrected on how much heat this setup actually applies to the carb body...

Remember the ice you see on an intake tube is from moisture in the ambient air striking the outside of the cold tube.


What you want is to keep ice off your slide or butterfly valve that resides at the pressure drop.  If you accomplish that, the intake tubes should be fine on the inside.



The Titan folks have an electric carb body heater...  It fits a Bing carburetor you may be able to use on a 4 cylinder engine...




Carburetor icing
From Wikipedia, the free encyclopedia

Carburetor Icing, or carb icing, is an icing condition which can affect any carburetor under certain atmospheric conditions. The problem is most notable in certain realms of aviation.

Carburetor icing occurs when there is humid air, and the temperature drop in the venturi causes the water vapor to freeze. The venturi effect can drop the ambient air temperature by 30-40 degrees F, therefore carburetor icing often occurs when the outside air temperature is in the 60-70 degree F range. Unfortunately, the warm air temperature often causes pilots to overlook the possibility of carb icing. The ice will form on the surfaces of the carburetor throat, further restricting it. This may increase the Venturi effect initially, but eventually restricts airflow, perhaps even causing a complete blockage of air to the carburetor. The engine begins to run more rich as ice formation increases. Without intervention (carb heat or leaning) this can only continue until the mixture is outside of the "chemically correct" range for combustion. Icing may also cause jamming of the mechanical parts of the carburetor, such as the throttle, typically a butterfly valve.

While it applies to all carburetors, carburetor icing is of particular concern in association with piston-powered aircraft, especially small, single-engine, light aircraft. Aircraft powered by carbureted engines are equipped with carburetor heat systems to overcome the icing problem. In cars, carburetor icing can occasionally be a nuisance. The inlet manifold and parts of the carburetor often have warm water from the cooling system or exhaust gas circulating through them to combat this problem. Motorcycles can also suffer from carburetor icing, although some engine designs are more susceptible to it than others. Air-cooled engines may be more prone to icing, due to the absence of warm coolant circulating through the engine.

See also

Atmospheric icing
   Fog
    Dew point
    Carburetor heat
    Fuel injection
    Fuel system icing inhibitor