• If you see ads here, log in and they will disappear. If you need help logging in or getting registered, send request to: webmaster@southernairboat.com

Carb heater/warm intake air solutions?

C

Canuk

Well-known member
Had a chance to give the 180hp Lycoming a good run in cooler temps (approx 28 degrees) and noticed the intake manifold iced up pretty good on the outside and the idle was greatly effected.

Having no experience with these units I have read almost everything written about carb icing on the internet and have concluded I need to try and address the problem.

I live on an island in northern Ontario and plan to use the craft to get back and forth to the mainland. ....smiling from ear to ear all the way.

As the temps get colder can I expect the icing problem to get worse? Is it possible to ice up so much that it will shut me down?

Would anyone happen to have any suggestions on how to go about fabricating a warm air intake from the exhaust, or is there a solution available on the market?

Appreciate your thoughts
 
Geez I hope some of the Lycoming guys can answer that one: Seems that you should be able to duct hot air from the exhaust manafold(s) or possibly thru the oil sump.
The previous owner of my boat used it on the St. Lawrence River in the winter: he had an air cleaner from a car motor and ducted air from a header to the intake, since that' been eliminated I'm thinking of bending a sheet of metal to fit on top of the carb, under the airfilter that will draft rising air from the cylinders around the carb....Difrence is my engine is a down-drafted Continental and yours is an up-draft Lycoming.
Sux to be running WOT and let off and it doesn't :shock:
 
Canuk, you should have no problem with icing on the Lycoming. Notice that the intake tubes are run through the warm oil in the sump. Also, usually in the winter the air is very dry. Carburetor icing is normally a problem with very humid air. The cold air will just give you more dense air which will add a bit more power.
 
Des Moines Boater":kel42xbm said:
Canuk, you should have no problem with icing on the Lycoming. Notice that the intake tubes are run through the warm oil in the sump. Also, usually in the winter the air is very dry. Carburetor icing is normally a problem with very humid air. The cold air will just give you more dense air which will add a bit more power.
Click to expand...
Canuk posted in another thread about his engine that it's got a Holly carb, presumably in a down-draft fashion, so drawing air thru the oil sump might prove difficult.
My old Ford P/U was notorious for iceing the carb on long highway trips when there was a lot of shushy snow.
 
I've had the linkage on my old 0290 freeze up at wide open
on lake winder in east central Florida, I think it was in the
high twenties. Scared the stuffin out of me.
But it seems like any one at a muffler shop could make a
heat exchanger, mounted like a duct in front of your
carb. maybe out of 5'' truck exhaust pipe with two tubes
run through it the same size as your header outlet then let
your flex pipe cris cross through it and run out on the opposite side. and maybe make a cap to fit over the inlet
during warmer weather. Well maybe a muffler shop guy
with some imagination
 
Thanks all for your input. I should be able to fab up a duct with a little help from a muffler shop.
Do you think I would be able to get more warm air by sucking air past the cylinder heads vs the headers?
Based on the advise I was thinking of adding a duct to top of the carb to make sure all the air ingested is heated but I have read that this might reduce power by as much as 15%, do you think this will have such an effect in below zero temps.

I'm thinking the potential power loss might be a necessary compromise to ensure reliability.
Have been told by the past owner that it can go a scary 75mph on glare ice so I don't mind losing some power if that happens and sure don't want to be stuck wide open.

I have also been trying to figure out all the model numbers you folks refer to, is my 180 Lycoming called a model 0290?


Thanks again, what a great site this is for learning about the mystery of aircraft engine technology. The more questions you folks answer the more I have.
Once I feel I have enough knowledge to ask intelligent questions I'd be thrilled to speak with you folks that have already been where I'm about to go.

Regards Neil
 
Canuk, if you can post a picture of your engine we might be able to help identify the model. A picture of the front of the crankshaft without a prop on it would help.

For aircraft we have an airbox with a flapper that lets in ram air for normal operation and hot air to prevent icing. The hot air is ducted from heat from the exhaust and not the cylinders. The heat muff is usually a couple of pieces of aluminum that surround a portion of the exhaust piping with scat hosing run from the heat muff to the carburetor air box.

I think I may have a heat muff I could give you to get you started. If you don't have an aircraft carb you may have to make your own airbox. You will lose a little power with the hotter air. PM me your address and I'll send the heat muff to you.
 
Thanks for the offer Des Moines Boater, my unit has been converted to a holly carb so I guess I will need to start working on a homemade solution.

I'm not familiar with the scat hosing you referred to, is it like a flexible metal duct product?
 
Post pics.I'd like to see how they put a holley carb on a 180.I don't think you have a lycoming 180.Are you sure its a lycoming and not a Continental,or is it even a holley carb?
 
I'm trying to get a couple of pics uploaded, it would be a lot easier if one could use a wrench to make these PC's work.

I'm sure it is a holly carb on a Lycoming engine (per stampings on the carb & valve covers).The intake manifold is stamped with "For Air Boats Only".
Once the pics are posted you folks can better help me identify the set up.



I'll try to get the pics loaded today.
Thanks
 
As a suggestion, maby someone could bend a sheetmetal "box" with a 5" cut out.
Make the box large enough to fit over the carb, leaving the aircleaner exposed...Someone who installs metal heating/air conditioning ducts could make one in minutes and a pair of tin-snips to make little cuts or slots to fit it better is easy. If you can keep the outside above freezing, then the linkage won't freeze up, and while it's possible to ice up the venturi's inide, the warmth from the carb body sould prevent it.
If you can e-mail pictures, send them to me and I'll post them for you. 8)
 
Airboatforposting010.jpg
 
It looks like a sump from a helicopter engine.
with the carb being up in front of the engine
it tends to change my line of thinking.
how bowt you roll a sheet of aluminum
maybe 16'' x 16'' ( like 1/2 of a 5 gal. bucket )
to keep the wind off
it, then maybe a 12v. 50wt. bulb under it to be
turned off and on as needed. You would need to
seal up the bottom as good as you could, to
keep the cold air out leaving the top open
to the rear for air intake while keeping
as much warm air under the carb as possible.
or maybe rather than a light bulb, you could
still run your exhaust through the 1/2 cylinder
shaped cover for heat.
I'm sorry if this sounds like rambling, but
I know you'll work it out Airboaters always do!
Good luck.
 
What a nice old "glass-slipper" :headbang:
Well the carb set up is beyond anything I could have imagined! Now it's easy to see the problem, so maby someone will come up with a novel solution.
 
So it sounds like I might have something a little different here.
Based on another pic I saw I am assuming the folks at Air Cat were the ones that came up with the carb/manifold combination when they buit it.
Is there anyone on the forum from Air Cat/ or that erra that may have some background on the design?

I had it out again yesterday in approx 26 degree temps, it didn't seem to ice up nearly as bad as the the last time, probably due to lower humidity levels. It took a good half hour to get her heat soaked and up to operating temp, it never did warm the oil above 140. After an hour running it didn't seem to have any ill effects from the iced up manifold, it would even idle properly?

Based on most everyones opinions it seems keeping the carb body warm is more important than warming the ingested air, that is probably easier to do than ducting warm air intake.
It seems to me that it will still take quite a bit of heat to effect the amount of cold air that will flow past the carb ......and it isn't even cold yet.

Trail and error, I will start making up a heated intake box to house the carb.

BTW, were these engines actually used in helicopters, or just the manifold?

I sure appreciate everyones opinions.
 
It doesn't take much heat to warm the carburetor. However, I don't think you need to bother building a carb heat box. Carb icing shouldn't be a problem with the Lycoming since the intake tubes are run through the sump. The warm oil will help prevent any icing. You also need the temperature and dew point to be close together to get icing. In the winter the air is very dry and very dense. In other words, no humidity, no icing. If it does ice up, it will not leave you stranded. The engine heat will thaw any ice in the venturi in a few minutes and you can be on your way again.

I think AirCat is out of business. A guy by the name of Combee was part of that company and made other boats on his own. I'm not sure of the history but I had one of the little AirCat boats a few years ago. A picture is in my gallery.

What were your cylinder temps when the oil temp was at 140?
 
I don't have a cyl head temp gauge yet, it is on the list the next time I go to the city. I do know it got very hot during the warm summer days.

I'd like to see your pics so off I go to try and figure out how to find them.
 
The best place I found to get one is Aircraft Spruce. They cost a little over $50 and around $12.00 for the spark plug style sensor. Be sure to use aircraft spark plug washers even if you use auto plugs. Auto plugs have a little taper.
 
You must log in or register to reply here.
Back
Top