Continental A65 carburetion question

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Al FR-153
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Continental A65 carburetion question

Post by Al FR-153 »

The Continental A65 engine in the Cub quite apparently does not have a choke (mixture control), which I have no doubt, is modeled correctly. My question is: How did Continental pull this off with a normally aspirated updraft carburetor? Engines of this vintage, even at ground level (especially automobiles) had to have a choke to control the mixture during various weather conditions, cold engine starts (even on a warm day) etc. Is there a real-life A&E around that can explain this: How do you get an A65 to several thousand feet, and not 'mess' with the mixture? I don't recall automatic chokes being considered reliable much before the mid-fifties for cars, let alone aircraft. How did they do that :?:
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CodyValkyrie
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Re: Continental A65 carburetion question

Post by CodyValkyrie »

While I am not certified to say so, my understanding is that the mixture on a Cub is not in flight adjustable and was factory made to have the best performance, including mixture at sea level. If you wanted to climb to a significantly higher altitude, naturally it posed problems. I am not sure however if the cub has an adjustable mixture from a maintenance standpoint, like many cars do.

That's about as good an answer as I have. Nothing automatic about the A65 choke to my knowledge.
I don't recall automatic chokes being considered reliable much before the mid-fifties for cars, let alone aircraft. How did they do that
Not necessarily true. Most military aircraft of the period had automatically controlled mixture. The Germans especially had a great handle on this.

As to the why or how of all this stuff.... let's just say my father was a mechanic and I took NO interest in it growing up.
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skunker
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Re: Continental A65 carburetion question

Post by skunker »

Some J3 Cubs do have mixture knobs. I don't believe they ever came from the factory this way, though.

Another thing is that the J3 cub rarely flies higher than 500 - 3k feet :mrgreen:

Also, Cubs have a primer..so sometimes people use that.

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Al FR-153
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Re: Continental A65 carburetion question

Post by Al FR-153 »

CodyValkyrie wrote: my understanding is that the mixture on a Cub is not in flight adjustable and was factory made to have the best performance, including mixture at sea level.
Thanks Cody. I know they flew them in northern climates in the winter as well as close to the equator during the summer, and probably still do, but found it unusual that at least on this model, there was no mixture control (choke). Yes, the German's (Dimler and Diesel for two) were very instrumental in how carburetion was accomplished. I tried to search the net to find out when the automatic choke was invented and by whom, and had no luck. Had a 1956 Chevy that didn't like the mountains in PA (home of Piper). That was what brought the question to mind to start with. Knowing that old Chev., flying a Cub up there could be interesting.
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Al FR-153
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Re: Continental A65 carburetion question

Post by Al FR-153 »

skunker wrote:Some J3 Cubs do have mixture knobs. I don't believe they ever came from the factory this way, though.
Maybe one to many Cub owners had the same question I do. :lol:

Another thing is that the J3 cub rarely flies higher than 500 - 3k feet :mrgreen:
That's all and good in San Antonio and even Chicago, but flying around Denver ..... you would start out at almost 5300 feet. I guess if you tuned the carb to your base elevation it might not be as severe, and although power robbing (and improper usage) the carburetor heat might help some, at higher, thin air, altitudes.
Also, Cubs have a primer..so sometimes people use that.
That would be okay for cranking, as it is injecting raw fuel into the carb, but don't know that that would be a good idea at altitude. That is what makes me curious.... How did they do that?

Giving away my age some, we used to have to put raw gas in our carburetor if the car sat around a couple days without being started. You would also pump the gas pedal several times as you were cranking. The fuel pumps were vacuum operated in those days, unlike the electric of today, and the fuel system was not nearly as tight as they are today. Basically, until you got the engine running, you didn't have a fuel pump. I can also remember carrying a can of spray either with us in the winter, just in case we needed that extra shot to get started. More than one guy lost his eyebrows and hair line doing that too. :o

When I saw the primer on the Cub, it brought about instant flashbacks. :wink:
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thunderstreak
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Re: Continental A65 carburetion question

Post by thunderstreak »

I might be able to shed a little light on some of this.
The carb has no outside mixture control but the main jet can be change to suit where you are based ie; different temperature ranges and airport altitudes.
I think you would find a J-3 pretty sluggish if you managed to get it to 10,000 feet.
A Continental A65 would be closer to 30hp up there, even if it did have a mixture control.

If you see a J-3 with mixture control that usually means the engine has been changed to a Continental C85-8 or C85-12.
The carb on a C85 has a very basic mixture control.
The external appearance of all those engines are almost identical.
The -12 engine can also have a starter and generator or alternator.

Hope this helps.
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N1684T
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Re: Continental A65 carburetion question

Post by N1684T »

Hello,Thunderstreak
I can remember the aircraft owner of the one I flew had jet adjustment screws on his C-65. In Texas he had notches for the settings between summer and winter. Texas weather got too love it. :roll:

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Re: Continental A65 carburetion question

Post by thunderstreak »

N1684T, you are correct. I should have explained myself a little better.
I meant mixture adjustment from the cockpit!
I think they all have a mixture screw on the carb itself.

My bad :(
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Re: Continental A65 carburetion question

Post by N1684T »

Hello,Thunderstreak
I understood what you were saying I think you explained it very well. I was just making alittle humor about the about the notches on the adjustment screws with the CUB I flew. I wonder when Piper changed too a Manuel Mixture control inside the cockpit or did owners install this on their on with the the - 12 series?
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Al FR-153
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Re: Continental A65 carburetion question

Post by Al FR-153 »

Oh yes.... Almost forgot about the old needle valves. That would make sense, I remember having to do that on an old Chevy, winter / summer and from lower elevations to higher mountainous elevations, now that you mention it. We had indoor plumbing (choke knob on the dash) but would still have to adjust the carb. The comment about notching the jet screw brought back several memories. I guess that would also explain the insistence on the engine being warmed up (to operating temp) prior to making a take off run too. Warming the oil was vital, but suspect that getting the carb warmed up was necessary as well; not so much for engine icing, but, to insure that all the metal carburetor parts were up to temp as well.

Thanks for the info gents. Just thought that some form of tweeking the carb would have been standard before it was.
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