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Carb Heat
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LarryM

Joined: 27 Nov 2007
Posts: 63
Location: Genoa, IL

Posted: Fri Nov 30, 2007 2:35 pm Post subject: Carb Heat

Thought this might be helpful.  Now that winter is upon us, carb ice is less likely, however...



Carb Heater

I can’t remember my whole thought process, but it evolved from a fellow listee who used a 15w tail light bulb taped to his carb to successfully defeat carb ice.  Trying to improve from there, I had figured that 20w would provide approximately a maximum of 100F heat to the carb body which would be warm enough without being too hot.  I used NiCrA-30DGL at 30 awg, which is a glass-insulated wire.  I had calculated that 18” of wire would yield 9.8 ohm >20w >1.42amps (per carb).  I initially wanted to wrap the wire around the carb intake, but after concern for the rubber air filter mount and discovering that the aluminum carb conducts the heat so fast, that it did not matter where it was wrapped.  I then wrapped it around the easiest place, in the Bing’s case, around the slide housing.  I used high temperature silicon around the housing, and simply wrapped the wire into it.  I choose to connect it DC on a switch.  It can also be wired AC directly.  I use it as an “ANTI - ice” system, turning it on at engine start whenever conditions are conducive for icing.  It does not create enough heat to wait until ice is present before using it.  This is my personal untried opinion.  It does not degrade engine performance, as the air going in is just as cold, but the water cannot turn to ice because the carb body temp stays above freezing.  If I were to do it again, I would wire it directly to AC and have it always on.  (I keep mine on all of the time anyway)   Having not been plaque by carb ice, I did not do anymore testing.  Though I fly in conditions that the “carb ice chart” will show as being prone, I do not fly in mist, fog, etc.  This conversation does prompt me to further investigate the effectiveness of the heater, but in 2yrs, I haven’t a problem.  I would like to see what my carb body temp is with the heater on while actually flying in cold damp air. More heat requires more wattage/amps and less wire.  

   I bought the wire from www.wiretronics.com  (209-296-8460).   They have a downloadable calculator that is real good to check (in my case to teach) things out.  They had a 20’ min order; you only need 18” per carb.  Perhaps someone wants to ‘group order’.  I gave my excess to guys around here who didn’t have any heat system.  You can also use it to make warm gloves, sock, etc.  I think it was about $40.00 total with shipping?



Hope this helps,

Larry

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Fri Nov 30, 2007 5:16 pm Post subject: Re: Carb Heat

What's the advantage of this over conventional carb heat based on hot air? Also, I might be paranoid but the idea of a light bulb in the vicinity of a carburetor sounds risky to me. 



What motor are you using? I've read that carb heat isn't really necessary on the Rotax 912. Anyone have thoughts on that?

 	  Quote: 	
		   can’t remember my whole thought process, but it evolved from a fellow listee who used a 15w tail light bulb taped to his carb to successfully defeat carb ice.

_________________
Luis Rodriguez
Model IV 1200
Rotax 912UL
Flying Weekly
Laurens, SC (34A)

john(at)leptron.com
Guest

Posted: Fri Nov 30, 2007 6:17 pm Post subject: Carb Heat

Carb heat is necessary on a 912, I have had ice, and it was not fun.



John Oakley

Speedster 4

912ul and cap



--

LarryM

Joined: 27 Nov 2007
Posts: 63
Location: Genoa, IL

Posted: Sat Dec 01, 2007 8:21 am Post subject: Re: Carb Heat

Wingnunt,



  I didn't want to go through the hassle of making a carb heat muff, box, control etc.  This is A kind of do it and for get about it.  I always leave it on as there is no performance loss.  It's designed to keep the carb above freezing even when considering the evaporation due the venturi. After a few years, I have had no icing problems.  The 15W light bulb taped to the side of the carb work real good too. 



  I don't think that any carb is immune from carb ice.  I had a car that always iced up on me. (British no less - I can imagine how it performed over there with all those days of good carb ice weather)   I had to build a heat muff directed on the carb.  The throttle body on my injected VW van would ice up as well.  The throttle body manufacture had made a system to allow hot water to circulate around it.  No body knew it at the time what it was for.  I finally figured it out after a few times of getting stuck due to ice. It was an imported VW engine from South Africa made for their market and had no use for the anti - ice system, therefor the instructions ignored it and the barbs where plugged)

darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Sat Dec 01, 2007 9:03 am Post subject: Re: Carb Heat

John,



I never had any problems with ice on my 912 but would never rule it out.  I have read many posts from 912 owners that think that ice is a non-issue as the air intakes are higher in the cowl and should have adequate heat to prevent icing, but I am not so sure.  With my 914, the setup is different, there is a single intake and it is located in the radiator scoop on the bottom of the cowl so I will be getting cold, moist air straight to my carbs.  As you know, here in Utah we have a pretty dry climate but there are a few days a year that are conducive to carb ice.  What are you using for carb heat?

_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Sat Dec 01, 2007 9:19 am Post subject: Carb Heat

I wouldn't be quick to dismiss you idea, on the other hand I doubt if it 

makes much difference. First the carb body is not aluminum as far as I know. 

I believe it's a zinc type pot metal alloy. The second issue is that in a 

very breezy environment I don't think that your wire would effectively 

transfer much heat unless there is a lot of surface contact. It might be 

worth getting a carb temp guage and seeing how effective your setup is.



I live right where the US gov't comes to test their aircraft in icing 

conditions, and I know a couple of guys who are using 912's without carb 

heat. That might be a bad idea, I just don't know. I'd like the option of 

heat if it was me, but I think the carb heaters that bolt right into the 

body might be a better idea.



Dave Goddard- Mod IV 1050/582

do not archive

---

john(at)leptron.com
Guest

Posted: Sat Dec 01, 2007 9:29 am Post subject: Carb Heat

Darin,

I have the carb box that was a stock system on the model 4. I have had ice

twice, both times in a bad place. I have several friends that fly rans and

they have had ice also. On the 914 you get the air after the turbo if I

remember right and it will take care of any problems. 



john



--

Sbennett3(at)aol.com
Guest

Posted: Sat Dec 01, 2007 10:03 am Post subject: Carb Heat

I have a 1994 built kitfox 4 with a 912. No carb  heat, and it has almost 800 hrs on it.  I live in NC. Steve  Bennett



Check out AOL Money & Finance's list of the hottest products and top money wasters of 2007.

  [quote][b]

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Sat Dec 01, 2007 11:35 am Post subject: Re: Carb Heat

Did you ever have a problem with icing on your 912 before adding the light bulb?



 	  Quote: 	
		  I didn't want to go through the hassle of making a carb heat muff, box, control etc. This is A kind of do it and for get about it. I always leave it on as there is no performance loss. It's designed to keep the carb above freezing even when considering the evaporation due the venturi. After a few years, I have had no icing problems. The 15W light bulb taped to the side of the carb work real good too.

_________________
Luis Rodriguez
Model IV 1200
Rotax 912UL
Flying Weekly
Laurens, SC (34A)

av8rps(at)tznet.com
Guest

Posted: Sat Dec 01, 2007 1:47 pm Post subject: Carb Heat

Luis,



I have a 912ul in a Model IV Kitfox that I've put about 300 hours on thus 

far and not ever have I experienced carb ice problems.  But a friend of mine 

with a very similar kitfox two hangars down from me has experienced it a few 

times already in less than 50 hours of flying.  (Wisconsin has great weather 

for carb ice fwiw)  So why would he have the problem when I don't?



Here's my idea;



If you installed the standard Kitfox carb heat kit you are forcing cold air 

from the front of the engine compartment down the scat tubing directly into 

the carburetor venturis.  So you have nothing but nice ice cold air coming 

into your carbs.  And being that it is speeded up as it goes through the 

venturi opening on the carb, if the conditions are right, you are going to 

get ice in your carbs.



If you DIDN'T install the carb heat kit you will have air filters attached 

to the back of the carburetors resting nearly against the firewall, rather 

than scat tubing from the front of the cowl. And because the carbs sit 

directly above the exhaust pipes, plus the muffler is nearby along with all 

the other heat that gets blown back toward the firewall coming off the 

engine, the air going into the carbs is going to be relatively warm.  So 

that makes carb icing pretty unlikely.  However, I did say unlikely, not 

impossible.



So long story short, Kitfoxes with the carb heat kits are the ones that will 

ice up (ironic isn't it?).  BUT, all the pilot needs to do when that happens 

is to pull the knob to engage manifold heat to the carbs and they will be 

able to fix the problem.  My friend has since adopted a carb heat on policy 

whenever flying in conditions that look good for carb icing.  He says he 

doesn't even notice a performance loss.  Thus far, that is working good for 

him.



So if you have carb heat installed, you'll get ice.  But you can fix the 

problem by applying heat with the carb heat knob.



If you don't have carb heat installed, and you get carb ice, you are 

probably going to be making an unplanned landing....



Paul Seehafer

Central Wisconsin

Model IV 1200 912ul amphib

---

Vic Baker

Joined: 11 Jan 2006
Posts: 71
Location: Carson City, Nevada

Posted: Sat Dec 01, 2007 3:13 pm Post subject: Carb Heat

Ok guys,

I've got a Model 7 here about ready to go,  got the induction plenum 

installed behind the carbs with the feed being cold air from the lower cowl 

intake scoop which directs air across the radiator.  There is an alternate 

air intake on the plenum which the instructions call for safety wiring 

closed.  Seems like an ideal setup for carb icing.  Any suggestions out 

there?

Vic



Vic Baker

S7 912S Warp 95%

Carson City, Nv

---

_________________
Vic Baker
Series 7
Carson City, Nevada

lcfitt(at)sbcglobal.net
Guest

Posted: Sat Dec 01, 2007 3:19 pm Post subject: Carb Heat

Paul's experience is what has been the mantra since I started building in 

1993.  With the exception of the first Alaska trip reporting hiccups of the 

912s that they attributed to carb ice, the only reports of carb ice in the 

nearly fifteen years I have been monitoring the list is in carb heat box 

equipped Kitfoxes.  Paul, regarding your friends no loss of power with carb 

heat on - the overall reports seem to indicate that the assembly with SCAT 

tubing will degrade performance a bit due to induction resistance whether 

the carb heat is on or off.  As I recall, this was the most compelling 

reason most opted to remove the system.  My now desceased Model IV did not 

have carb heat nor did any of the other six  guys I regularly flew with and 

the bunch all had hours approaching 1000 or more.  I had 909 when Kay and I 

went down.  None have reported anything approaching carb ice.



Lowell



---

LarryM

Joined: 27 Nov 2007
Posts: 63
Location: Genoa, IL

Posted: Sat Dec 01, 2007 4:04 pm Post subject: Re: Carb Heat

Dave,



  When I was testing the unit before deciding how hot to make it, at 20F, with the carb left to cold soak overnight, within minutes of plugging it in - it was hot to touch.  It is estimated than 100f is hot to the touch.  The way I use it as an "anti ice" is having the carb body warm all the time, therefore the condensation can't freeze.



  I concur with the others who say carb ice is rare, but at our strip, I'm the only one without an unscheduled landing due to carb ice.  OH No, what did I just do to my self!!!!???



larry

dgolden(at)golden-consult
Guest

Posted: Sat Dec 01, 2007 4:40 pm Post subject: Carb Heat

Lowell Fitt wrote:

 	  Quote: 	
		   

 

 Paul's experience is what has been the mantra since I started building

 in 1993.  With the exception of the first Alaska trip reporting hiccups

 of the 912s that they attributed to carb ice, the only reports of carb

 ice in the nearly fifteen years I have been monitoring the list is in

 carb heat box equipped Kitfoxes.  Paul, regarding your friends no loss

 of power with carb heat on - the overall reports seem to indicate that

 the assembly with SCAT tubing will degrade performance a bit due to

 induction resistance whether the carb heat is on or off.  As I recall,

 this was the most compelling reason most opted to remove the system.  My

 now desceased Model IV did not have carb heat nor did any of the other

 six  guys I regularly flew with and the bunch all had hours approaching

 1000 or more.  I had 909 when Kay and I went down.  None have reported

 anything approaching carb ice.

 

 Lowell


	


I don't know if there is room to install carb heaters in the Kitfox

installation, but if you're worried you might want to check this out:

http://www.ultralightnews.ca/bing/carbheater.html



Dennis

-- 

Dennis Golden

Golden Consulting Services, Inc.

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Sat Dec 01, 2007 4:44 pm Post subject: Re: Carb Heat

Paul,



Didn't you answered your own question with the rest of your post? ie: Your friend has experienced carb ice because he has carb heat box. You've not experience carb ice but how do you know that it isn't just because you don't have the same setup? So is it true as Lowel suggested that no one on this list that does not have a carb heat box has ever experience carb ice? That would be kind of compelling. 



 	  Quote: 	
		  I have a 912ul in a Model IV Kitfox that I've put about 300 hours on thus far and not ever have I experienced carb ice problems. But a friend of mine with a very similar kitfox two hangars down from me has experienced it a few times already in less than 50 hours of flying. (Wisconsin has great weather for carb ice fwiw) So why would he have the problem when I don't?

_________________
Luis Rodriguez
Model IV 1200
Rotax 912UL
Flying Weekly
Laurens, SC (34A)

darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Sat Dec 01, 2007 7:31 pm Post subject: Re: Carb Heat

John,



Yes, you are right.  I got looking at it and the air from the turbo will take care of any ice I may have.  In fact, I am going to install an intercooler in the induction line to cool the air a bit...don't know what I was thinking when I made the previous post.  According to the Europa flyers, the intercooler increases the power of the engine slightly and is better on the engine.

_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

av8rps(at)tznet.com
Guest

Posted: Sat Dec 01, 2007 8:13 pm Post subject: Carb Heat

Luis,



Yes, I know I answered my own question.  Sorry for causing you some 

confusion.



And Lowell is also right about losing some power with the carb heat on.  I 

agree you should lose power when turning on carb heat.  I'm guessing my 

friend is either too new to his airplane to really notice it, or he is so 

tickled pink with all the power his Kitfox has that he doesn't miss a few 

hundred rpms when flying.  Whatever the case, I know he has plenty of power 

with the carb heat on, so he's most likely going to keep flying it that way 

on days when carb ice is likely.



Like Lowell also said, most that have removed their carb heat kit (or choose 

not to add one) do so because they want full power from the engine.  I was 

one of those that chose to remove mine in favor of more power/rpms.  Given 

my druthers I'd have carb heat I could turn if ever needed.  But I didn't 

like the setup that came with my airplane.  So in the meantime I will 

continue to fly without carb heat.   But I will definitely keep my eyes and 

ears open for a better solution should one come along.



Paul Seehafer

Model IV-1200 912ul amphib



---

john(at)leptron.com
Guest

Posted: Sat Dec 01, 2007 8:52 pm Post subject: Carb Heat

Darin,

Adding an intercooler would be a bunch of work but would increase the life

of the 914. Another thing you can do for comfort is to install a radiator

and oil cooler louver control system made by one of our listers. I am going

to order one set this week for my fox. I am hoping he is still making them.



--

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Dec 02, 2007 5:48 am Post subject: Carb Heat

Dave, exactly where are you?  



As you know, two things are required to make ice, cold temperatures and

water.  If you remove either one then ice cannot form.  Venturi effect will

automatically produce some refrigeration effect in the throat of the

carburettor.  The throat temps can be surprisingly low, given the right

conditions even at temperatures well above freezing.  All this is covered in

everyone's flight training.



What I'm getting at is if you are high up in the mountains than you probably

also have a very dry climate and you may not get ice especially on the

coldest days.  Where I live, a few hundred miles away from the world's

biggest fog factory, The Grand Banks, ice is always a consideration.

Temperatures may not be as low as yours but 90+% moisture can more than make

up for that on days where the temperature is anything below 60F.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Dec 02, 2007 6:10 am Post subject: Carb Heat

If you are using a turbo charger then the possibility of  ice is extremely

low.  The turbo removes the low pressure area that normally ices up.

However you should be aware of impact ice.  This is ice that can form on the

air screen in the front of the cowling and cut off air to the engine.  That

is of course an IMC.  If you are flying into IMC then an alternate intake

port which is not filtered and only opens when the main air feed is blocked,

would be a good idea.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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