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Carb Temp variations in Pponk'd C180s

sj

Staff member
Northwest Arkansas
I have an EI carb temp gauge in my 55 c180 and pretty much ALWAYS winter or summer, have to have at least a little carb heat on to keep it out of the "ice zone". It has proven at night over Pennsylvania that it can make ice like a Manitowoc ice machine - in fact, enough that it won't clear all the way even with full car heat.

The other day I flew in a gorgeous 59 c180 with a PPonk and asked the owner about his carb temps. 135 degrees and he never uses carb heat, never had ice, etc. It was about 30 degrees out that day.

I have the "small" crossover tube on my engine which is what is prescribed to help with this problem.

The cowling intakes are different on these two planes.

Any ideas?

sj
 
For the majority of the years I've owned my 180 it had a carb temp gauge in the panel. It pretty much always ran in the yellow zone. My plane doesn't make ice so I never paid attention to it and I never ran with partial carb heat. When I replaced the old panel and installed an EDM711 I added the carb temp probe so I could experiment with partial carb heat to help normalize cylinder temps, something I'd read about for years. That experiment lasted about 5 minutes and I've never looked at carb temp since. And I still don't use partial carb heat. Some 180s make ice. Some don't.

If your friend's carb temp was 135* he's getting heat from somewhere.

It sounds like you ought to re-plumb your carb heat source!
 
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Great Subject. The "early" pre-1956 Cessna 180's with the large intake probably flow differently than the smaller intake 1959 model or even SB's late model.

Speculation as to how and why induction icing would be more acute on the early models would be welcome.

My 1953 requires attention to the carb temp. I have a JPI EDM 900 engine instrument cluster. I love that thing
 
It isn't a matter of what year. Some J models make lots of ice. Mine doesn't. It's a mystery that modern science should be able to solve.
 
Steve, you mentioned "135 degrees". Can you clarify what that is about?

He was using the same EI carb temp probe that I do, and his reads 135 degrees of intake air and he has never had carb icing. Never uses in landing, etc. While he lives in Texas, he flys in plenty of conditions where I would need near full carb heat.

sj
 
Great Subject. The "early" pre-1956 Cessna 180's with the large intake probably flow differently than the smaller intake 1959 model or even SB's late model.

Speculation as to how and why induction icing would be more acute on the early models would be welcome.

My 1953 requires attention to the carb temp. I have a JPI EDM 900 engine instrument cluster. I love that thing

I was curious if the larger intake scoop on the earlier models had an effect.
 
I wonder if carb intake air pressure has some role. If my plane was an ice maker I'd make a temporary flange around the intake perimeter to make a little ram air collector to see if that helps. With the history of carb ice accidents in aviation I don't understand why more hasn't been done to study it.
 
I haven't had many carb ice issues in my 54 Pponk. Several years ago (when i still had a J engine) I was flying with another 54 (also with a J engine). His was running so rough, he thought he was going to have to put it in a field. Mine had no issues. Not sure what could have been different between the 2 planes. I don't have a carb temp gauge...seems like it would just give me something to worry about.
 
I haven't had many carb ice issues in my 54 Pponk. Several years ago (when i still had a J engine) I was flying with another 54 (also with a J engine). His was running so rough, he thought he was going to have to put it in a field. Mine had no issues. Not sure what could have been different between the 2 planes. I don't have a carb temp gauge...seems like it would just give me something to worry about.

One possible culprit that could explain that behavior is if your airplane has an insulated induction crossover tube at the front of the engine and the other plane didn't.

A lot of 180s won't run for beans in cold unless that crossover tube is wrapped with some pipe insulation. Without that insulation, they exhibit exactly the symptoms you describe.

MTV
 
One possible culprit that could explain that behavior is if your airplane has an insulated induction crossover tube at the front of the engine and the other plane didn't.

A lot of 180s won't run for beans in cold unless that crossover tube is wrapped with some pipe insulation. Without that insulation, they exhibit exactly the symptoms you describe.

MTV

Interesting. I don't understand why that crossover makes such a big difference.

sj
 
I haven't had many carb ice issues in my 54 Pponk. Several years ago (when i still had a J engine) I was flying with another 54 (also with a J engine). His was running so rough, he thought he was going to have to put it in a field. Mine had no issues. Not sure what could have been different between the 2 planes. I don't have a carb temp gauge...seems like it would just give me something to worry about.

It's obvious that the carb temp probe causes carb ice ;-)

Glenn
 
Fuel condenses in the foward induction area. That has nothing to do with carb ice.

Stewart

Correct, but it could be precisely what the difference was between the two planes he described. It's possible this was carb ice related, but I'll guarantee that a lot of 180s will run really rough and almost seem like they're going to die in cold weather without that balance tube insulated.

MTV
 
except on the buddy of SJ's 180 and also SB's 180

To add to this, plenty of SuperCubs i have flown didnt make ice and a few of em really did!??

Exactly. I put quite a few hours on a SC in Kodiak, where icing is common. Never made much ice till the engine was swapped for new. I don't know what else was. changed, but that plane REALLY made carb ice after the new engine. I figured the air box or ??? was rebuilt during the engine change.....maybe.

MTV
 
Stewart

Correct, but it could be precisely what the difference was between the two planes he described. It's possible this was carb ice related, but I'll guarantee that a lot of 180s will run really rough and almost seem like they're going to die in cold weather without that balance tube insulated.

MTV

My comment was in reply to SJ. I remember my 180 with an uninsulated balance tube. The front cylinders don't run well with condensed fuel making them excessively rich. It does feel a bit like carb ice except carb heat doesn't fix it. Hmm, a little heat from the get-go might reduce it, though. Perhaps that is what SJ is describing?
 
In my experience, carb heat doesn't help an uninsulated balance tube much, but it really depends on how cold it is I reckon.

MTV
 
...A lot of 180s won't run for beans in cold unless that crossover tube is wrapped with some pipe insulation. Without that insulation, they exhibit exactly the symptoms you describe. MTV

It was cold around here (Puget Sound) last week-- nothing like what some of you guys experience, but lows in the low-to-mid 20's & highs ranging from 31 to 36 or so. I was flying home on one of the colder days, after leaving my airplane to sit on a cold ramp for a couple hours, and I pulled the carb heat on briefly (as is my habit) a few minutes after takeoff. Only this time the engine ran like crap, just like when you have carb ice and the engine ingests a bunch of water after carb heat melts it off.
But it didn't clear up after a few seconds, just kept running like crap. Ran OK without carb heat, cruise power mag check was fine.
Is this something that might be crossover tube related? I have a 53 180 with a K engine, not sure what size crossover tube it has but it's not insulated.
 
It was cold around here (Puget Sound) last week-- nothing like what some of you guys experience, but lows in the low-to-mid 20's & highs ranging from 31 to 36 or so. I was flying home on one of the colder days, after leaving my airplane to sit on a cold ramp for a couple hours, and I pulled the carb heat on briefly (as is my habit) a few minutes after takeoff. Only this time the engine ran like crap, just like when you have carb ice and the engine ingests a bunch of water after carb heat melts it off.
But it didn't clear up after a few seconds, just kept running like crap. Ran OK without carb heat, cruise power mag check was fine.
Is this something that might be crossover tube related? I have a 53 180 with a K engine, not sure what size crossover tube it has but it's not insulated.

Could there have been any ice in the scat tubes? IF water gets into your scat tube and freezes, the carb will be flooded with moisture with carb heat on.

Keeping induction air warm would easily effect the ability of the air to bring atomized fuel into the cylinders. Maybe many of the issues experienced in the past is more of a fuel atomizing issue, not a carb ice issue.

Consider once carb heat is on you warm the carb, with warm air which will also warm the entire induction system. Carb heat goes off and you again get cold air, which after a few minutes will cool the induction system.

If the temps needed to keep fuel atomized are not sustained, the plane will begin dropping out fuel in the inductions, and running rough.


Any thoughts?
 
It was cold around here (Puget Sound) last week-- nothing like what some of you guys experience, but lows in the low-to-mid 20's & highs ranging from 31 to 36 or so. I was flying home on one of the colder days, after leaving my airplane to sit on a cold ramp for a couple hours, and I pulled the carb heat on briefly (as is my habit) a few minutes after takeoff. Only this time the engine ran like crap, just like when you have carb ice and the engine ingests a bunch of water after carb heat melts it off.
But it didn't clear up after a few seconds, just kept running like crap. Ran OK without carb heat, cruise power mag check was fine.
Is this something that might be crossover tube related? I have a 53 180 with a K engine, not sure what size crossover tube it has but it's not insulated.

I kind of doubt it. That said, no down side to installing some foam pipe insulation (the split stuff) and zip tying it in place.

How long did you leave the carb heat on when applied? May not have had time to comepletely remove all the ice?

MTV
 
I kind of doubt it. That said, no down side to installing some foam pipe insulation (the split stuff) and zip tying it in place.

How long did you leave the carb heat on when applied? May not have had time to comepletely remove all the ice?

MTV

But that would necessitate SJ to remove the cowling, he hates that task.
 
It was cold around here (Puget Sound) last week-- nothing like what some of you guys experience, but lows in the low-to-mid 20's & highs ranging from 31 to 36 or so. I was flying home on one of the colder days, after leaving my airplane to sit on a cold ramp for a couple hours, and I pulled the carb heat on briefly (as is my habit) a few minutes after takeoff. Only this time the engine ran like crap, just like when you have carb ice and the engine ingests a bunch of water after carb heat melts it off.
But it didn't clear up after a few seconds, just kept running like crap. Ran OK without carb heat, cruise power mag check was fine.
Is this something that might be crossover tube related? I have a 53 180 with a K engine, not sure what size crossover tube it has but it's not insulated.

Did you lean the mixture to smooth it out? If you're cruising rich of peak and pull carb heat it should run like crap until you make adjustments. And yes, the balance tube may play a role in it.
 
Did you lean the mixture to smooth it out? If you're cruising rich of peak and pull carb heat it should run like crap until you make adjustments. And yes, the balance tube may play a role in it.

No, didn't mess with the mixture.
Yes (to an earlier question), left the carb heat on long enough to melt any ice--
the temperature / dewpoint spread was wide enough where I shouldn't have had any icing anyway.

FWIW I flew the airplane again two days ago, after the cold snap was over,
and it ran just fine-- including with carb heat pulled.
Just one of those things I guess.
 
With a seaplane exhaust extension the bottom cowl won't easily fall off with gravity and is much easier to install solo.
 
Maybe I am wrong, but I always either had full carb heat or no carb heat never partial, just cause temp gauge says its cold enough for ice means very little in my opinion
 
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