Dual Carb Setups

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LJS1993

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LJ Savala
Okay gentlemen a totally odd thought came to mind. Since aviation has used superchargers, turbos, carbs, and fuel injection, it got me thinking the following question. Have dual carb setups ever been used in avation? Would a dual carb setup have any type of advantage in an aircraft?
 
Rotax 912 and 914 seres were all dual carb engines up until the 912SI fuel injected came out. They did a good job of keeping the manifolds short and fairly low profile. Balancing them is an extra task but fairly easy.
 
The Rotax series of 4strokes and several makers of 2 strokes will have multiple carburation. No significant advantage or disadvantage really that aren't situational.
 
Well look, the main advantage of multiple carburetors is even flow to the cylinders and form factor, you don't have to have a massive intake header. The disadvantage is they have to be synced, and you have a carburetor failure factor multiplied by two.

If one of the carbs fail, your engine is dead. This is different than having two engines, if you have two, the probability of having a failure is twice as much. But you can live on a single engine most of the time. The probability of having both fail at once is much less.
 
Sac Arrow said:
Well look, the main advantage of multiple carburetors is even flow to the cylinders and form factor, you don't have to have a massive intake header. The disadvantage is they have to be synced, and you have a carburetor failure factor multiplied by two.

If one of the carbs fail, your engine is dead. This is different than having two engines, if you have two, the probability of having a failure is twice as much. But you can live on a single engine most of the time. The probability of having both fail at once is much less.
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If you lose one carb on a carb split system, you'll shut down anyway before you shake the mount apart.
 
Henning said:
If you lose one carb on a carb split system, you'll shut down anyway before you shake the mount apart.
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Dunno that you need to shut down - you may not want to attemp to get full power out of the remaining side, but you can still make some power to help you drag it in to that field.
 
I've only come across it on the 912 series. Had to balance them once, wasn't bad at all
 
Right on guys. I am quite familiar with them in the auto industry but never knew there were somewhat common in aviation. I would love to see one of those setups sometime.
 
One can also build in a x-over or balance tube between sides to help control flow, and to provide a modest backup in case of single carb failure.

I've always thought that intake geometry on our engines didn't need to be very efficient due to the low speed operation. Recently, I've come to see that maybe two carbs would be useful, however there is also a modest weight penalty involved.
 
docmirror said:
One can also build in a x-over or balance tube between sides to help control flow, and to provide a modest backup in case of single carb failure.

I've always thought that intake geometry on our engines didn't need to be very efficient due to the low speed operation. Recently, I've come to see that maybe two carbs would be useful, however there is also a modest weight penalty involved.
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The weight penalty of multiple carburetors is typically offset by a simplified induction system. Most carbureted inline motorcycle engines have a dedicated carburetor for each cylinder for space reasons - no room to put in a balanced intake header.
 
Sac Arrow said:
The weight penalty of multiple carburetors is typically offset by a simplified induction system. Most carbureted inline motorcycle engines have a dedicated carburetor for each cylinder for space reasons - no room to put in a balanced intake header.
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Two air cleaner housings, two intake plenums, two hot air ducts, two throttle linkages, two mixture linkages or a crossbar. I did say 'modest' after-all.
 
docmirror said:
Two air cleaner housings, two intake plenums, two hot air ducts, two throttle linkages, two mixture linkages or a crossbar. I did say 'modest' after-all.
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Or three or four, going to a common air cleaner/intake plenum, mounted directly to the heads and lined up with a common throttle linkage. Certainly mechanically goofy compared to a single carb but still compact.

Few bikes these days are carbureted anyway. What were carburetors are now throttle bodies each holding an injector, plumbed in to a common filter housing. Once set they really don't need to be balanced again unless the throttle bodies are split.
 
LJS1993 said:
Now that would be dependable and efficient. Why more aircraft are not using fuel injection is really amazing. Also, why not conversion kits for older planes like your 310?
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Just as clarification, you probably mean electronic fuel injection. Many aircraft engines use mechanical fuel injection.
 
LJS1993 said:
Now that would be dependable and efficient. Why more aircraft are not using fuel injection is really amazing. Also, why not conversion kits for older planes like your 310?
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The option is there actually. Continental has a full range of full FADEC engines ready to go to replace any engine they made. My engines are next to new though so I will operate those until the 350hp Diesel comes out and then will change over when I can.

The main reasoning though is cost, pilots are cheap and upgrades are expensive. Luckily the Chinese bought Continental and they really want the Diesels due to 100LL cost and availability issues.
 
docmirror said:
One can also build in a x-over or balance tube between sides to help control flow, and to provide a modest backup in case of single carb failure.
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The 912s have them, I'm not sure about others.
 
Henning said:
The option is there actually. Continental has a full range of full FADEC engines ready to go to replace any engine they made. My engines are next to new though so I will operate those until the 350hp Diesel comes out and then will change over when I can.

The main reasoning though is cost, pilots are cheap and upgrades are expensive. Luckily the Chinese bought Continental and they really want the Diesels due to 100LL cost and availability issues.
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How about all the upgrades in terms of electronic control? I know in cars that can be a complex setup in addition with modifications to fuel tank. Is this modification something a regular aviation mechanic can perform? As for your plane that would be an awesome upgrade.
 
LJS1993 said:
How about all the upgrades in terms of electronic control? I know in cars that can be a complex setup in addition with modifications to fuel tank. Is this modification something a regular aviation mechanic can perform? As for your plane that would be an awesome upgrade.
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One might think that all the electronic functions would make an 'awesome' or vast improvement. However, much of time operating the engines are at steady state, and an appropriate use of the mixture control will get very good BSFC numbers. LOP ops with the mixture control can yield great economy at very low initial cost.
 
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