Carb heat needed?

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Theodore959

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Nov 19, 2019
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Looks similar to Bosch Jetronic

Ok as we throttle back for decent, vacuum pressure goes up, time for EGR to kick in, not to forget PCV, this adds heat yep.
I'm using as much tech as needed on VW Type 4 install, temp probe needed on carb/throttle body area
 

Dan Thomas

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Looks similar to Bosch Jetronic

Ok as we throttle back for decent, vacuum pressure goes up, time for EGR to kick in, not to forget PCV, this adds heat yep.
I'm using as much tech as needed on VW Type 4 install, temp probe needed on carb/throttle body area

Aircraft engines don't use EGR and PCV systems. The EGR was to reduce NOX emissions, and the PCV was to get good crankcase scavenging. The high manifold pressures that aircraft engines are usually running at means the manifold vacuum is so low that the PCV system wouldn't work, and terrific amounts of water and other contaminants would accumulate in the crankcase, so an ordinary large-diameter breather is used to allow free exit of those gases.

There really is no substitute for heated air. As I said before, it's easy ton underestimate the power of that little freezer we call a carb, and too many accidents have been caused by carb ice that was either unsuspected by the pilot, or the carb heat system wasn't up to the job. The certified airplanes have a legal requirement that the carb heat air be heated by a considerable amount:

Sec. 25.1093 — Induction system icing protection.
(a) Reciprocating engines. Each reciprocating engine air induction system must have means to prevent and eliminate icing. Unless this is done by other means, it must be shown that, in air free of visible moisture at a temperature of 30 F., each airplane with altitude engines using—
(1) Conventional venturi carburetors have a preheater that can provide a heat rise of 120 F. with the engine at 60 percent of maximum continuous power; or


(2) Carburetors tending to reduce the probability of ice formation has a preheater that can provide a heat rise of 100 °F. with the engine at 60 percent of maximum continuous power.
 

Dana

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Can't remember where I saw it but some have used copper tubing to circulate hot engine oil around the body of the carburetor.
Leonard Milholand has done this with Legal Eagle engines
I've seen the oil line wrapped around the intake manifold on half VW engines, I think it'd be hard to wrap it around the carb itself; too uneven a shape. But heating the manifold on those engines is to prevent the atomized fuel from condensing on a cool manifold since they have such long intake tubes. It's not a substitute for hot air coming in, a warm manifold won't keep ice from forming on the butterfly. I believe Pops built a welded oil heated "hot box" to sandwich between the carb and manifold, same idea... Dan, did you have conventional carb heat on the SSSC too?
 

Dan Thomas

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I'm wondering if bolting my carbs to an oil heated plate would do the trick?
That's basically what Lycoming does: bolt the carb to the bottom of the oil sump. It still makes ice. I've had it way too often.
 

Pops

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I've seen the oil line wrapped around the intake manifold on half VW engines, I think it'd be hard to wrap it around the carb itself; too uneven a shape. But heating the manifold on those engines is to prevent the atomized fuel from condensing on a cool manifold since they have such long intake tubes. It's not a substitute for hot air coming in, a warm manifold won't keep ice from forming on the butterfly. I believe Pops built a welded oil heated "hot box" to sandwich between the carb and manifold, same idea... Dan, did you have conventional carb heat on the SSSC too?
Yes, conventional exhaust manifold heat . At first I was getting carb ice very often. After installing the hot oil box at the base of the carb, I ever had carb ice again, but I still used the exhaust carb heat as I would flying a small Cont engine. Lyc is doing the same thing with the carb on the bottom of the oil sump. The hot oil box cools the oil 20 degs from the inlet to the outlet. Also before installing the hot oil box the engine was never smooth as it should have been, and the color of the plugs was never the same. With the long intake tubes , the mixture charge was condensing into droplets and making the mixture going into the heads lean and then rich. It ran smoother and with more power with the hot oil box. The next VW engine will have a hot oil box, but since I always make a oil slump at the bottom of the engine where the oil strainer plate is bolted and welding a longer pickup tube. Thinking about combining the two by having the carb bolted to the bottom of the oil sump with a 90 deg elbow of intake tube inside the oil sump. Eliminate the oil lines to and from the hot oil box.
 
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103

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Yes, conventional exhaust manifold heat . At first I was getting carb ice very often. After installing the hot oil box at the base of the carb, I ever had carb ice again, but I still used the exhaust carb heat as I would flying a small Cont engine. Lyc is doing the same thing with the carb on the bottom of the oil sump. The hot oil box cools the oil 20 degs from the inlet to the outlet. Also before installing the hot oil box the engine was never smooth as it should have been, and the color of the plugs was never the same. With the long intake tubes , the mixture charge was condensing into droplets and making the mixture going into the heads lean and then rich. It ran smoother and with more power with the hot oil box. The next VW engine will have a hot oil box, but since I always make a oil slump at the bottom of the engine where the oil strainer plate is bolted and welding a longer pickup tube. Thinking about combining the two by having the carb bolted to the bottom of the oil sump with a 90 deg elbow of intake tube inside the oil sump. Eliminate the oil lines to and from the hot oil box.
Always inovating I like the idea of eliminating the hoses. I believe Leonard Milholand"s 1st 1/2 vw LE routed the intake up and out the position of the unused cylinders before he switched to a carb for each cylinder.
 

Pops

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Have some drawing made, just need to get time to weld one up. Being retired is very time consuming. Don't know how I ever had time to work :)
Love to built a couple of airplanes including the BeetleMaster. Just how old can a person live ?
 

blane.c

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Have some drawing made, just need to get time to weld one up. Being retired is very time consuming. Don't know how I ever had time to work :)
Love to built a couple of airplanes including the BeetleMaster. Just how old can a person live ?
1,000 years
 

Pops

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The more I think about it , the more I understand. Must be the reason my children keep telling me to grow-up.
 
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