purpose of choke

MetalHead · 02-22-2002, 04:08 AM

Ok,

once and for all i would like a definitive explanation about what a choke on a carburetor does. I have not had a choke on my carb for almost 9 months and today my friend and I installed an electric choke on the carb and we didn't notice any difference. but when i test drove the car i did notice a difference in performance. someone please explain the purpose of this little device.

72grande · 02-22-2002, 04:39 AM

And if anyone post's a link explaing how a lawn mower choke works I'll scream.

PKRWUD · 02-22-2002, 09:15 AM

Iron Skull-
Another pretty easy one. When an engine is cold, the air and fuel don't mix very well because the gas stays in a liquid form, and it's harder for the engine to start. The solution for this is to reduce the amount of air let in, so that the mixture is richer. This will get the engine going, and after a few minutes of running, the engine temp warms up enough to vaporize the fuel/air mixture, thus burning better, with less need for gas. After 5 minutes, the engine is normal, and the regular air fuel mixtrure presented by the carb idle circuit is fine. So, the question the engineers had was "How do we reduce the amount of air going into the engine for the first 5 minutes?". The answer was a choke. A manual choke is one that the driver operates by hand. When the engine is cold, you close the choke. This reduces the air going in, and richens the mixture. As it warms up, you let the choke out. After 5 minutes, the choke should be completely open.

It has nothing at all to do with performance. It is used to "choke" the air supply to the engine in order to warm it up.

Take care,
-Chris

MetalHead · 02-22-2002, 02:54 PM

thank you that makes perfect sense. the only problem i had installing the electric choke was that it needed a 12v ignition activated energy source. at the moment it is simply connected straight to my battery, and we were going to run it to my fuse box, and simply stick it in between one of the fuses. do you know a better way?

PKRWUD · 02-23-2002, 09:19 AM

Okay, what you did basically makes the choke inactive. It needs to be attached to the ignition switch, or a lead that is only energized when the ignition is turned on. Going to a fuse in the fuse box that only gets power when the key is turned on would be the smartest way to wire it. The way an electric choke works is when you apply voltage to it, a heating element warms up, and causes a spring to react, opening the choke. The down side to an electric choke is that everytime you turn off the key, the choke resets, so that the next time you turn it on, the choke closes, and goes through it's routine again. This will lead to rich restarts when they aren't necessary, like after getting gas, or stopping at McDonalds, or running into the 7-Eleven, etc. Also, if the engine is not started right away after turning the key on, when cold, it won't work. See, when you turn the key on, it starts working, so if the engine isn't started, by the time you do, the choke will already be open, and won't do it's job. For example, let's say it's a cold, icy morning, and you want to see how much gas you have before leaving for work, so you'll know if you need to stop and get some. You climb in the car, turn the key on, and watch the gas gauge for a minute. You decide you are okay, and don't need to stop for fuel, so you try and start it, only it won't start. It coughs and acts like it's out of gas. What has happened is you used up the time that the choke was working watching the gas gauge. By the time you tried to start it, the choke was already open. Turning off the ignition for a couple minutes, and then restarting, would solve the problem.

Take care,
-Chris

02-22-2002, 04:08 AM	#1
MetalHead Registered Member Join Date: Feb 2002 Location: Monterey, CA Posts: 76	purpose of choke Ok, once and for all i would like a definitive explanation about what a choke on a carburetor does. I have not had a choke on my carb for almost 9 months and today my friend and I installed an electric choke on the carb and we didn't notice any difference. but when i test drove the car i did notice a difference in performance. someone please explain the purpose of this little device.

02-22-2002, 09:15 AM	#3
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Iron Skull- Another pretty easy one. When an engine is cold, the air and fuel don't mix very well because the gas stays in a liquid form, and it's harder for the engine to start. The solution for this is to reduce the amount of air let in, so that the mixture is richer. This will get the engine going, and after a few minutes of running, the engine temp warms up enough to vaporize the fuel/air mixture, thus burning better, with less need for gas. After 5 minutes, the engine is normal, and the regular air fuel mixtrure presented by the carb idle circuit is fine. So, the question the engineers had was "How do we reduce the amount of air going into the engine for the first 5 minutes?". The answer was a choke. A manual choke is one that the driver operates by hand. When the engine is cold, you close the choke. This reduces the air going in, and richens the mixture. As it warms up, you let the choke out. After 5 minutes, the choke should be completely open. It has nothing at all to do with performance. It is used to "choke" the air supply to the engine in order to warm it up. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

02-23-2002, 09:19 AM	#5
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Okay, what you did basically makes the choke inactive. It needs to be attached to the ignition switch, or a lead that is only energized when the ignition is turned on. Going to a fuse in the fuse box that only gets power when the key is turned on would be the smartest way to wire it. The way an electric choke works is when you apply voltage to it, a heating element warms up, and causes a spring to react, opening the choke. The down side to an electric choke is that everytime you turn off the key, the choke resets, so that the next time you turn it on, the choke closes, and goes through it's routine again. This will lead to rich restarts when they aren't necessary, like after getting gas, or stopping at McDonalds, or running into the 7-Eleven, etc. Also, if the engine is not started right away after turning the key on, when cold, it won't work. See, when you turn the key on, it starts working, so if the engine isn't started, by the time you do, the choke will already be open, and won't do it's job. For example, let's say it's a cold, icy morning, and you want to see how much gas you have before leaving for work, so you'll know if you need to stop and get some. You climb in the car, turn the key on, and watch the gas gauge for a minute. You decide you are okay, and don't need to stop for fuel, so you try and start it, only it won't start. It coughs and acts like it's out of gas. What has happened is you used up the time that the choke was working watching the gas gauge. By the time you tried to start it, the choke was already open. Turning off the ignition for a couple minutes, and then restarting, would solve the problem. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

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02-22-2002, 04:39 AM	#2
72grande Registered Member Join Date: Feb 2002 Location: Monterey Posts: 33	And if anyone post's a link explaing how a lawn mower choke works I'll scream.

02-22-2002, 02:54 PM	#4
MetalHead Registered Member Join Date: Feb 2002 Location: Monterey, CA Posts: 76	thank you that makes perfect sense. the only problem i had installing the electric choke was that it needed a 12v ignition activated energy source. at the moment it is simply connected straight to my battery, and we were going to run it to my fuse box, and simply stick it in between one of the fuses. do you know a better way?