Cold Air Intake on 418?

[mattd860 161]

The intake on my 418-8 can be turned to suck cold air or warm air from the exhaust manifold.

What is the advantage of turning the intake to suck warm air during the winter? I thought sucking cold air was always the best hence all those 'cold air intake' kits made for cars and trucks.

I just assume to let it suck cold air year round unless you all disagree.

[Kelly 1,028]

In the winter if the incoming air is to cold you can freeze up the carb, so yes put to the warm side in the winter.

[mattd860 161]

In the winter if the incoming air is to cold you can freeze up the carb, so yes put to the warm side in the winter.

Probably a good reason

Is freezing the carb during winter a common problem though? There are many tractors that don't have this feature like the K-series that doesn't have the exhaust near it.

[Kelly 1,028]

I've seen them all do it some, but the twins seem to ice up more, not sure why more don't have that feature.

[Kelly 1,028]

And cheap grades of gas will ice up faster, or like around here we have summer gas and winter gas, they put additives in it so it will not freeze up as soon.

[btrrg1969 11]

Hmm , I didnt know gas could freeze or atleast til it gets down to -97 degrees fht as far as the blends I thought that had something to do with emissions

[Kelly 1,028]

Lots of gas stations have small amounts of water in there tanks, that's why up north they sell dry gas just for the purpose of stopping gas line freeze, and some of the blends are for emissions, but in the cold climates they use additives in the winter for gas line freeze.

[btrrg1969 11]

Kelly

Please educate me , what is dry gas ? I work for a oil company and I never heard of that . I work on the environmental side , I really dont deal with the blends , mainly I make sure the stores arent leaking product . Ethanol is the biggest problem in gas , the alcohols will absorb water and keep it suspended in the gas and thats how you get gas with water. Gas that is ethanol free will not blend , the only way you get water in your gas then is if the operators ignore the water lever in the bottom of the thank and it gets high enough for the pump to pick it up.

[HorseFixer 2,012]

In the winter if the incoming air is to cold you can freeze up the carb, so yes put to the warm side in the winter.

Probably a good reason

Is freezing the carb during winter a common problem though? There are many tractors that don't have this feature like the K-series that doesn't have the exhaust near it.

That all depends on dew point and ralative humidity & air tempature. Many small fixed wing aircraft had a knob you could pull to add carb heat. As they could experiance Carb Icing Alot of this depends on what you are doing with the tractor also. For example many Toro snowthrowers had a Tecumseh Snow King Engines, altho I am not a fan of Tecumseh Engines they do make a Fantastic Snow Blower Engine and one of the reasons their Engines work well is the intake is on the same side as the Exhaust which warms the Carburator and where they have the intake. Carb Heat does have its advantages durring these times where fine snow paticles are swirling and snow could get packed or block the intake and linkages around the carb! :ychain:

[Shuboxlover 474]

This is what happened to mine when I was sucking in cold air, I built a little heater box out of aluminum tape and it worked great!!!

Attached Image (Click thumbnail to expand)

[wallfish 15,960]

It looks like you had a carburator diaphragm in there.

[HorseFixer 2,012]

Kelly

Please educate me , what is dry gas ? I work for a oil company and I never heard of that .

Brandon what Kelly is referring to is products like Heat, Snap, aka (gas line antifreeze). Us older guys grew up calling it "Dry Gas" when in all actuality it was an additive.

How Do These Products work?

They contains special additives and methanol. When added to the gas tank, it sinks to the bottom and mixes with any water. Since both the additives and water are heavier than gasoline, they go to the bottom of the gas tank. The additives absorbs water and keeps it from freezing, and blocking the flow of gasoline through the gas line and fuel pump. When the vehicle is started, the additives, methanol, water, and gasoline are consumed during combustion inside the engine.

[boovuc 1,090]

My KT17 NEEDS the warm air intake to run below 25 degrees F. If it sucks cold air, the manifold freezes up on the outside and it misses, sputters and backfires.

Most any alcohol will mix and displace water. Isopropanol, (IPA), does it best in my opinion. Rubbing alcohol is 70% alcohol and 30% water.

I can still get plain old gasoline without the ethanol and it still frosts the manifold if it isn't sucking the warm air. I believe the cooling effect is magnfied as you pull air through a narrow opening at high speed. The more narrow and the more volume, the more cooling occurs. The physics of it escapes me. Come to think of it, there is always a gas passing through a narrow opening on me. I think it comes with age!

BooVuc

Mill Hall, PA

[Butch 194]

If you don't keep your gas tank full you can also get a build up of moisture in your gas tank. That's why I like to keep a full tank in our vehicles in the winter. If you get enough water in your system you will get problems on the coldest of days. I've had my system freeze up in the teens 3 times. All 3 times were pure hell. Breaking down when it's 15 degrees outside can be the worse automotive problems I've ever had. Just remember that a frozen fuel system ONLY happens during the lousiest of cold weather. Dry gas can be a saviour if you have it when you need it! Many of us used dry gas as a precaution during winter months.

[puddlejumper 67]

A week or so ago I had fired up the crane to warm up (WAUKESHA) I let it set and Idle while doing some work on the ground. It had been running for awhile and I could here it starting to act up. Got to looking for promblem and the carb was frosted up like a big snowball. Gradually was able to increase rpm on machine enough that warmth from the engine thawed it so it would run. It struck me funny because I had started it to warm it up and actually I froze it up.

[rickv1957 70]

A week or so ago I had fired up the crane to warm up (WAUKESHA) I let it set and Idle while doing some work on the ground. It had been running for awhile and I could here it starting to act up. Got to looking for promblem and the carb was frosted up like a big snowball. Gradually was able to increase rpm on machine enough that warmth from the engine thawed it so it would run. It struck me funny because I had started it to warm it up and actually I froze it up.

That it the reason for the warm air intake,Rick

[btrrg1969 11]

Kelly

Please educate me , what is dry gas ? I work for a oil company and I never heard of that .

Brandon what Kelly is referring to is products like Heat, Snap, aka (gas line antifreeze). Us older guys grew up calling it "Dry Gas" when in all actuality it was an additive.

How Do These Products work?

They contains special additives and methanol. When added to the gas tank, it sinks to the bottom and mixes with any water. Since both the additives and water are heavier than gasoline, they go to the bottom of the gas tank. The additives absorbs water and keeps it from freezing, and blocking the flow of gasoline through the gas line and fuel pump. When the vehicle is started, the additives, methanol, water, and gasoline are consumed during combustion inside the engine.

OK thanks for the education. I was a diesel mechanic for 12 years and the winters can be a real devil with gelled fuel .Of coarse we use additives as well however for some reason we would get caught with our pants down . I have never seen carburetor freeze though , what you say about the air mix etc makes since . Back to the diesel , when it got real cold here , I have been outside all day thawing out trucks and getting them started , I always wondered how you all up north did it

Thanks Brandon

[TT-(Moderator) 1,128]

Behold the power of Google: CLICK THIS

Carb icing is more common on twin cylinder engines because the carb sits on a long intake manifold in the cooler area between the cylinders.

@Brandon:

The guys up north who operate trucks and other diesel equipment usually have specially-treated "winter" blends of fuel by now. Most of the (big) trucks I drove also had electric fuel heaters, and I tried to keep the tanks topped off as much as possible -- and I drained the water "traps" as often as I could remember.

When I had the diesel pick-up, I would add some kerosene to the tanks during winter months.

[linen beige 14]

You guys are getting close, but not exactly right. Aside from moisture in the fuel supply, there are factors that, when combined, can cause a carburetor to ice up. It is not limited to winter temperatures either, as I have seen several late '70s/early '80s Chrysler 318 engines with iced over single barrel carbs in temps of 60 degrees or even higher.

Air temperature decreases as it's speed increases. As air enters a carb and is forced through the venturi it's speed increases and it's temp decreases.

Cooler air will hold less moisture than warm air. As air's temperature decreases some of the moisture that is vaporized in it will condense. That moisture will adhere to the carb's interior surfaces and, if cold enough will freeze.

As moisture begins to freeze on the inside of the carb it further restricts the incoming airflow. In order to maintain the volume of needed air through a smaller space the air's speed increases even more compounding the cooling/condensation effect, speeding up the rate at which ice builds up.

More likely than moisture coming from inside the fuel system causing ice is the probability that the ice was formed by moisture condensing out of the intake air supply and freezing. As mentioned above, it is common for aircraft to have carb heaters to avoid freeze ups. Air at higher altitudes is generally much cooler than air near ground level and usually has a higher relative humidity. The moisture in that air will still cool and condense as it goes through the carb's venturi, but by heating it sufficiently it will be pulled on through and not allowed to freeze on the carb's insides.

The old style gas drying additives didn't really remove the moisture from the fuel. They lowered the freezing point of that moisture to a point below the internal temp of the carb. That accomplished the same end as heating the intake air.

[linen beige 14]

:D Dammit TT!

As I was typing all that stuff from Jr. High science class you post that Google thing. :ychain:

[TT-(Moderator) 1,128]

Even the #1 poster gets lazy occasionally. :ychain:

[JimD 3,345]

:ychain:

[W9JAB 156]

In the "old days" airplanes had carbonator heaters

just for the stated reasons.

As far as water in fuel I just installed a fuel/water

separator on my tractor.

[mattd860 161]

wow - didn't realise all the science behind it! Figured I just asked a simple question that needed a quick response.

Moved the intake to suck warm air from exhaust last night....

[btrrg1969 11]

wow - didn't realise all the science behind it! .

I learned from it :ychain: