Carb icing on the 0-320?

[BritishCubBloke]

Because the air intake passes through the sump and the air gets heated, I am told this makes carb icing relatively unlikely on the 0-320. In my limited experience I have never detected any when flying in ideal carb icing conditions, but is this true? Is carb icing unlikely with the 0-320 for this reason?

BCB

 

[klm_ak]

I don't have much experience with other engines except the two I've had in my PA-12, but my 0-320 builds carb ice at least as well as my old O-290D2, in fact it seems worse. The pressure drop is in and near the venturi, so it seems likely heating the intakes wouldn't completely solve the problem.

 

[S2D]

Carb ice is formed in the carburetor before the air ever gets to the sump. All the Super Cubs I've ever flown in icing favorable conditions formed lots of carb ice. I think it would be more of how the air was routed before it got to the carburetor,and how warm that area is inside the cowling. Obviously it must not be too warm in a Super Cub before it gets to the carb.

 

[BritishCubBloke]

Bang goes that rather cosy theory then!

BCB

 

[Ken Grindlay]

BCB
I had a cherokee 140 with an O-320 for years. It never developed carb ice, not once. I now have an SC with O-320 that ices rather easily. Go figure.
Ken

 

[PA12driver]

My O320/160 in my PA12 develops ice real good in the right conditions! As was said a lot has to do with the temp of the air between the intake air opening and the venturi? I fly in the NW and we get a lot of "winter" weather that is a perfect Ice maker! It keeps you on your toes! When I was in Alaska I could putz around at low rpm 2200 and seldom develop Ice, Down here I run the rpm up on high humidity 32-45 derree days, seems to help. I still watch the tach closely and occasionally test for RPM/carb heat function. (I have considered adding a carb air temp guage)

Tim

 

[Cubus Maximus]

The O-320 A2B I had in my old Cub had ice maybe twice in 9 years. It spent almost all its time in MN. The carb will be somewhat warmer in the O-320 than in say a C-90 due to the location on the engine.

My friend Jim in his Husky (bad word I know put in an ice detector gauge/warning. It lights up red and beeps when ice starts building in the carb. It also will do this on occasion when you get a lot of fuel in the carb. The sensor says to itself, ah ha - ice!

 

[BritishCubBloke]

Interesting responses, gents. Thanks. It would also be interesting to hear how people manage carb ice. Round here, it's almost always 30s to 60s and high humidity -- ideal conditions. I pull the carb heat for about 30 secs every five minutes. Do others wait for ice indications, e.g. through a falling tach?

BCB

 

[PA12driver]

I do check mine on regular basis when I am poking around slow! I have been caught before, (especially do to the fact that my trottle tends to creep back anyway) I have it on my to-do list to tighten the frictions washers! Others might be advised to make sure that their throttle stays put where you put it! especially if they are in icing conditions alot?

Tim

 

[Ken Grindlay]

BCB
The first indication of carb ice on my sc shows up as a drop in EGT (no, I don't know why). I apply carb heat till EGT is normal again, but its gotta be either full on or full off.
Ken

 

[klm_ak]

BCB,

When operating above 2000 rpm, I don't generally pull carb heat unless I see the RPMs drop or run through a patch of "visible moisture". I found a good patch of air over Bering Land Bridge this summer that required carb heat at about 1 minute intervals after each application. Happily it only lasted about 20 miles, but it felt like all day.

Tim, as for applying carb heat when flying around slow, if I followed that rule I'd never turn it off ;-)

KL

 

[PA12driver]

KL, That is a relative term, as I often fly around (airspeed slow higher RPM) my point is if you putz around at less then 2450rpm in Icing potential weather, I have experienced the 0320 building carb ice quickly.

You are right about one thing--As for me and my cub we are always slow (just the way I like it)

My goal is to get the sucker to fly even slower!!

Tim

 

[FlipFlop]

I just got home from shooting 11 full stops in 1.1 hours in the Grasshopper... Slow?, yes... Fun?, you bet!...

 

[PA12driver]

Doesn't get better than that! I'll post pictures of our little flying fun today when I can take the time to compress the photos
Tim

 

[supercub]

This past summer on climb out, I saw 1.2mph on the GPS, actually I think I was backing up, GPS doesn't know which way you're going concerning speed, now that's slowwwwwwwwwwwwwwww.
Brian

 

[PA12driver]

Supercub! That is obvious by the speed of that "slow train" in your Avatar photo!

"Cub drivers do it slow"

 

[supercub]

Ya, but you'll notice the cub is a nose ahead of that steamer

 

[Bob Heinrichs]

Carb Icing

I Fly a PA 18 on floats in Canada. Lots of icing in lake countryup here. The best investment I may have ever made is a carb heat temp guage. Its small, inexpensive and can save your life.

 

[PA12driver]

supercub! I know those supercubs are fast (especially compared to my PA12 but I studied that photo real close and you are converging on the train, obviously either you went in front of him or your brakes really work too??

Tim

 

[Gary Reeves]

Carb Ice

I have noticed that you can get quite a lot of carb ice late in the season when the water is warmer than air and you are taxiing at low RPM on floats. It can give you quite a thrill on applying full power unless you have done a carb heat runup. Under the worst conditions I taxi with the carb heat on and wait to turn it of at mag check.

The strange weather demanded using floats late in Lake Clark since we had no ice and with the high water - no beach either. The warm water and cool air certainly were some of the worse ice generators I have seen.

Gary

 

[Trapper]

carb ice

I would agree with Gary, keep carb heat on when taxiing on floats. I also usually remove the air filter element when flying on floats later in the season (after the bugs have died down) and have definitely noticed a higher tendency for carb ice without the filter element (also bit higher RPM which is the reason for removing.)