Electric controlled Carb Heat

[fusionfab 14]

Hey again just looking for input and opinions on a control for carb heat. 

I am used to a Rotax 503 where we'd just leave the carb muff attached full time running warm air. But with this soob I am currently fabbing up the plumbing and airbox for it.

Now, should I just run it directly from the heat muff full time or fab a control box to alternate between cold air and warm? 

I was pondering the idea of running a small aluminum "Y" pipe from the intake box housing and installing an exhaust cutout on the cold side to be able to close it off and just suck back warm/hot air that's connect to other part of "Y". 

Not sure what this unit weighs but I know the motor used is 0.350 lbs. That stainless pipe included would be scrapped. 

[lostman 198]

Where are you locating your radiator(s)? If you have them in the air inlet like cheek style I wouldn't even bother with carb heat. I've done a lot of research on it, including talking to guys that build up Chevy engines for larger aircraft and they never seem to get carb heat as long as you're pulling air from around the engine instead of fresh air. If the check style radiators on the Pursang it didn't carb heat and I definitely flew it at points where I would have needed it if it weren't for pulling engine air instead of direct air from outside the cowling. 

Even the big guys with the Chevy engines didn't worry about it inside the cowling. These are guys up in Montana and Wyoming that fly all the time where icing is an issue. They told me they'd never experienced with a top mounted carb like your picture shows. Obviously I'm not saying don't do it on my word, but I think if you do some digging you might come to the conclusion that you might not need it. 

[EDMO 1078]

Mine has the manual shutter on the Carb filter box for carb heat, but the guys running stock Soob intakes say they never need card heat because the manifold is always heated.  I'm not sure how much good that would do with my Holly carb.  Most carb heat air is unfiltered and you only want unfiltered air when absolutely necessary.  I am told that you can cut down a Dodge/Plymouth 6 cyl or Horizon - lost the words - thing that sits on the carb - to where it is only about 1" tall if necessary, and it has the trapdoor and filter built into it - haven't checked this out tho.  

That electric motor thingy looks neet, but a lawnmower cable is cheaper.   EDMO

Edited 12 Dec 2016 by EDMO

[fusionfab 14]

Just put a quick video together to make it easier for me to explain

Edited 13 Dec 2016 by fusionfab

[lostman 198]

Best way ever to ask a question on the forum! 

Personally I still don't think you need the head. Your carb isn't in the direct intake ducts from the cowling. Plus your aluminum intake should heat sink some heat from the heads and be warm most of the time. I'd be interested to know how warm it does get after running it for a few minutes. This is the same intake setup that one builder uses and sales up in Wyoming for the 4.3 and 5.7 Chevrolet converted engines. He assured me he never got any carb ice and all and it wasn't needed. 

Just wonder, Ed brought this up too. Do you still have coolant in your intake like the factory set up? It's hard to tell from the video. Either way I wouldn't hesitate to run it without heat IF it were mine. Since it's not, use your best judgement though. I certainly don't blame you for asking for input. 

Again, this is just my worthless opinion. 

[1avidflyer 1983]

I didn't read everything mentioned in this post so maybe this got mentioned, but I know some car engines use a piece under the carb with hot coolant running through it.   That would seem like an easy way to have carb heat, not sure if it would rob power either, cause it isn't really hot air coming into the engine.  Would raise the carb a bit though.  Just another thought occurred to me, build a box under the carb on the manifold that you could pump coolant through.  Would heat the carb, and not raise it up higher.  JImChuk

[lostman 198]

I didn't read everything mentioned in this post so maybe this got mentioned, but I know some car engines use a piece under the carb with hot coolant running through it.   That would seem like an easy way to have carb heat, not sure if it would rob power either, cause it isn't really hot air coming into the engine.  Would raise the carb a bit though.  Just another thought occurred to me, build a box under the carb on the manifold that you could pump coolant through.  Would heat the carb, and not raise it up higher.  JImChuk

Jim, by design the Soob engine does have coolant running through the intake tubes. Obviously they are a separate tube but heat the intake. Not sure if this intake does have that or not. It does rob some power for sure. The claims are wildly unsubstantiated but some claim as much as 10 horse power by blocking off the ports that supply the heated coolant. Of course one thing for sure, if it's there it would reduce the possibility of carb heat. 

Maybe I'm totally off in my thinking that this would work without heat. I've been doing some digging on the internet to see about it associated with the older Soob cars. Seems they did have the tendency to ice up, although not sure about it with a Weber type carburetor yet. 

[1avidflyer 1983]

His manifold doesn't look anything like the factory built one on my Subaru engine that came in the Kitfox 4.  I do have a manifold built by Ram performance that looks like his.  It's just a pipe with the correct fittings on the ends.  Mine doesn't have coolant going through it.  I don't think this one does either.  JImChuk

[fusionfab 14]

His manifold doesn't look anything like the factory built one on my Subaru engine that came in the Kitfox 4.  I do have a manifold built by Ram performance that looks like his.  It's just a pipe with the correct fittings on the ends.  Mine doesn't have coolant going through it.  I don't think this one does either.  JImChuk

that is exactly what I have. I located a picture online and duplicated the design using 1-3/8" aluminum and then after I finished it machine all surfaces flat and even. But the coolant lines are separate. The intake portion does sit about 7/8" off the top surface of the block. I can try running it and see what temps that manifold itself gets to at the carb and so on. 

Edited 13 Dec 2016 by fusionfab

[fusionfab 14]

Again guys EDMO, lostman, 1avidflyer and anyone else who may post in the future, thank you for the advice, input, suggestions etc. I am considering all options for best and simplest method to do the carb heat. If it's not needed then even better. 

[EDMO 1078]

fusionfab,  Anything someone posts on here can be a learning experience for someone.  Glad you posted, and let us know the final outcome.  EDMO

[fusionfab 14]

Would it matter if I did a run up today until warmed up and took some temp measurements off the manifold and carb? Today OAT is 15.8F. 

Just wondering how warm the manifold and carb base would need to be to avoid carb ice. Obviously above freezing but by how much?

[EDMO 1078]

Would it matter if I did a run up today until warmed up and took some temp measurements off the manifold and carb? Today OAT is 15.8F. 

Just wondering how warm the manifold and carb base would need to be to avoid carb ice. Obviously above freezing but by how much?

I read about using a digital temperature gauge from Radio Shack and screwing the sender into an unused port in the carb, but I have no idea of what a "no-ice" temperature would be for the carb - air coming thru the venturi would probably be colder than the carb or outside air.   EDMO

[lostman 198]

I've seen installed thermometers that would tell you if you were getting carb ice in certified aircraft. I don't remember what they are called. I'm sure if you put it just down from the venturi in the carb it would give you a good indication of how the temps are doing in there though. EDIT: after a very quick search I found this. http://www.aircraftspruce.com/catalog/inpages/umatsodcarbtempguage.php It could be pretty useful actually. 

Just did a quick search and came up with this. http://www.aircraftspruce.com/catalog/inpages/icedetect2.php  Interesting that it detects ice crystals and not temps. 

I'll have to go back and read the temp gauge and see if it tells where to install it. A radio shack type sensor would be simple to install as long as you could do it without messing up the intake. I kind of like this idea now.

[EDMO 1078]

I've seen installed thermometers that would tell you if you were getting carb ice in certified aircraft. I don't remember what they are called. I'm sure if you put it just down from the venturi in the carb it would give you a good indication of how the temps are doing in there though. EDIT: after a very quick search I found this. http://www.aircraftspruce.com/catalog/inpages/umatsodcarbtempguage.php It could be pretty useful actually. 

Just did a quick search and came up with this. http://www.aircraftspruce.com/catalog/inpages/icedetect2.php  Interesting that it detects ice crystals and not temps. 

I'll have to go back and read the temp gauge and see if it tells where to install it. A radio shack type sensor would be simple to install as long as you could do it without messing up the intake. I kind of like this idea now.

I think the Radio Shack sensor was installed in the Vacuum port in the Holly carb, since that port was no longer used to advance timing?  I see on the Spruce temperature gauge that Lostman listed the CAUTION range starts at 50F and below.   Big difference in price tho - the RShack thingy was only about $7 or $10.   EDMO

Edited 14 Dec 2016 by EDMO