Carb ice in car vs. aircraft

jrh

jrh

Well-Known Member
I was talking to my good friend contactground.9 a few minutes ago and he asked me something I'd never thought about...why do old cars with carbs never get carb icing, yet it happens on a regular basis with aircraft engines?

Is it something to do with the volume of air being drawn through the venturi? Or the fuel flow, or ambient air temperature inside the engine compartment?

I have no idea, and I must admit, I know a lot more about the mechanics of an aircraft than those of a car.
 
Carbureted engines would have a thermostatically controlled heat riser valve that would draw warm air from around the exhaust manifold until the engine warmed up.

But to answer your question, I have never heard of cars getting carb ice.
 
Old VW bugs used to get carb ice when the conditions were right, although I understand it wasn't a terribly common occurrence. I believe the reason is the cooling system. Most car engines are liquid cooled and can have hot coolant piped through the carburetor to prevent ice without ill effects. The old bug engine, like an airplane, was air cooled and didn't have the luxury of a hot coolant system to keep ice away.
 
Cars have a coolant bypass that circulates warm coolant around the carb/ tbs to warm them, like full time carb heat. , hi performance carbs eliminate this, but those arnt normally on daily drivers, or are boosted, so they are less prone to issues. The large 4 barrel carbs cause less pressure differential with larger openings. To compensate for the reduced airflow velocity, they run larger jets. These are less likely to ice, because there is not as much pressure change, and larger intake areas.

All fuel injected tb's in cars have the coolant heat.
 
TUCKnTRUCK said:
Cars have a coolant bypass that circulates warm coolant around the carb/ tbs to warm them, like full time carb heat. , hi performance carbs eliminate this, but those arnt normally on daily drivers, or are boosted, so they are less prone to issues. The large 4 barrel carbs cause less pressure differential with larger openings. To compensate for the reduced airflow velocity, they run larger jets. These are less likely to ice, because there is not as much pressure change, and larger intake areas.

All fuel injected tb's in cars have the coolant heat.
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You're correct on the carb side, but actually quite a few cars do not have any coolant heating of the throttle body.

At the end of the day, this is just one more example of the archaic technology used on piston powerplants in aviation.
 
Patrick said:
You're correct on the carb side, but actually quite a few cars do not have any coolant heating of the throttle body.

At the end of the day, this is just one more example of the archaic technology used on piston powerplants in aviation.
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Remember the Porsche Mooney?
 
Consider that aircraft engines create over 80% power 90% of the time, and car engines generate over 50% power 5% of the time.
It only requires 25 horsepower for the average car to cruise at 50 mph.
 
I don't know how "old" the cars are that you guys are talking about, but I used to own a '73 Monte Carlo that often showed signs of carb ice when it initially started up.

It had a manual choke (ergo, mixture control) that you'd have to let run rich when it was cold-ish out until it warmed up.
 
My motorcycle can get carb ice. I ride an old Kawasaki, and it's European model actually has a basic system that runs some heat near the carb to prevent carb icing. I've never actually experienced it but I know it's possible.
 
Patrick said:
At the end of the day, this is just one more example of the archaic technology used on piston powerplants in aviation.
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I have often wondered why I get into a late 90's(and even after) airplane and its like starting the space shuttle then I get into a car and just fire it up.
 
OhioStatePilot said:
Old VW bugs used to get carb ice when the conditions were right, although I understand it wasn't a terribly common occurrence. I believe the reason is the cooling system. Most car engines are liquid cooled and can have hot coolant piped through the carburetor to prevent ice without ill effects. The old bug engine, like an airplane, was air cooled and didn't have the luxury of a hot coolant system to keep ice away.
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:yeahthat:
Had it happen to me a few times in my '68 vw bug. The decklid was off so carb ice was common with me in that car. If I kept it on there were no problems at all. It would basically just shut off unless you kept giving it a lil bit of gas.
 
Louie1975 said:
I have often wondered why I get into a late 90's(and even after) airplane and its like starting the space shuttle then I get into a car and just fire it up.
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One word: Regulation.

It costs BOATLOADS of money to get something through FAA certification, and there just isn't enough product moving to get the GA companies to cough up the money to make big changes.

Look at the technology in experimentals now and you'll see some real innovation.
 
My old '74 Trans Am used to carb ice up all the time. A few times it iced up so bad that is iced the throttle valve up in the open position! :eek:

(Much to my surprise when I took my foot off of the gas)
 
Roger said:
One word: Regulation.

It costs BOATLOADS of money to get something through FAA certification, and there just isn't enough product moving to get the GA companies to cough up the money to make big changes.

Look at the technology in experimentals now and you'll see some real innovation.
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Unfortunately that's exactly the case. There's a decent bit of cool stuff in the experimental market, but really, Diamond is the only certified manufacturer who is pushing the envelope as far as powerplant development.
 
Patrick said:
Unfortunately that's exactly the case. There's a decent bit of cool stuff in the experimental market, but really, Diamond is the only certified manufacturer who is pushing the envelope as far as powerplant development.
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Dry vacuum pumps? And magnetos?

I mean, even simple stuff like brake calipers. They're still aluminum with an O-ring seal, which means they leak way more often than they should. Put a steel sleeve in there and a lip seal and you'd never need to change them. Or so says one of the old geezers out at the airport. Lots of little stuff like that where there just isn't enough product moving for the manufacturers to invest in changing it.
 
Patrick said:
Unfortunately that's exactly the case. There's a decent bit of cool stuff in the experimental market, but really, Diamond is the only certified manufacturer who is pushing the envelope as far as powerplant development.
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They've tried in the past, too. With the original DA-20, they had the Rotax 912. They gave up on it, for an IO-240. I understand why, but they could have made the plane work with a Rotax.
 
Roger said:
Dry vacuum pumps? And magnetos?

I mean, even simple stuff like brake calipers. They're still aluminum with an O-ring seal, which means they leak way more often than they should. Put a steel sleeve in there and a lip seal and you'd never need to change them. Or so says one of the old geezers out at the airport. Lots of little stuff like that where there just isn't enough product moving for the manufacturers to invest in changing it.
Click to expand...


There would be motivation for change provided the process for certification wasn't such a nightmare- that still invited significant legal liability.

Call up Brembo, and give them the specs you need for a brake caliper, and they'd give you something leaps and bounds better than what's on your aircraft, for a fraction of the cost. Oh ya, you just can't do that though...
 
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