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Old 09-15-2020, 03:53 PM   #21
ericr
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Default Re: Wisdom of Stopping Engine by Choking It Out

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Originally Posted by BRENT in 10-uh-C View Post

Just to muddy up the waters here a bit. Ponder these thoughts for a bit;


.. ~ If gasoline typically evaporates when exposed to heat, what happens when a teaspoon, --or maybe two drips into a gallon of hot oil? Does it evaporate or does it dilute the oil?

.. ~ If it does dilute the oil, how much does it dilute it, -how long does the dilution last, -and what are the effects of this amount of dilution??

.. ~ If it does not evaporate before the engine cools, does it evaporate the next time the engine is at operating temperature? Did it evaporate in one or more cylinders due to a hot piston, or cylinder wall, -or a combustion chamber roof giving off heat just as the engine stopped running?

.. ~ If the gasoline finds its way past the first ring gap, and goes to the second ring gap, -is there enough liquid gasoline left to actually dilute any residual oil on the cylinder walls? If it does dilute the oil as the fuel drips, does it dilute the entire 360 circumference of the cylinder bore, or maybe one small little area?

.. ~ When an engine stops operating due to the ignition source stopping, what happens to the gasoline/air mixture left unburned in each cylinder?

.. ~ When a running engine is stopped, how long does it take before rust starts forming on the cylinder walls and piston rings. What happens to that rust when the engine is restarted?



I guess I view much of this question as we have always been told not to do this because it sounds believable that it would harm something, ...but in the grande scheme of things, I truly believe there is little, -if any, noticeable damage done using the choke to stop an engine from running.



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well there would still be some cylinder and valve rotation as the engine conked out, wouldn't some gas get expelled through the exhaust valves?
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Old 09-15-2020, 04:03 PM   #22
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Default Re: Wisdom of Stopping Engine by Choking It Out

Lots of armchair opinions within, and yet these cars have managed to survive 90 years with all sorts of abuse and neglect.

Choking the engine to kill it will do absolutely no harm to the engine, maybe the plugs overtime. We're talking about such a minimal amount of fuel that is transmitted in a near vapor form. And from maybe 800 rpm to 0 in a matter of seconds.

If you were so concerned, you wouldn't choke the engine to start it, and you'd kill the fuel, to stop the engine. Turning off the ignition just takes away the spark, it still allows fuel into the cylinders without burning.
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Old 09-15-2020, 05:07 PM   #23
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Default Re: Wisdom of Stopping Engine by Choking It Out

Quote:
Originally Posted by BRENT in 10-uh-C View Post

Just to muddy up the waters here a bit. Ponder these thoughts for a bit;


.. ~ If gasoline typically evaporates when exposed to heat, what happens when a teaspoon, --or maybe two drips into a gallon of hot oil? Does it evaporate or does it dilute the oil?

.. ~ If it does dilute the oil, how much does it dilute it, -how long does the dilution last, -and what are the effects of this amount of dilution??

.. ~ If it does not evaporate before the engine cools, does it evaporate the next time the engine is at operating temperature? Did it evaporate in one or more cylinders due to a hot piston, or cylinder wall, -or a combustion chamber roof giving off heat just as the engine stopped running?

.. ~ If the gasoline finds its way past the first ring gap, and goes to the second ring gap, -is there enough liquid gasoline left to actually dilute any residual oil on the cylinder walls? If it does dilute the oil as the fuel drips, does it dilute the entire 360 circumference of the cylinder bore, or maybe one small little area?

.. ~ When an engine stops operating due to the ignition source stopping, what happens to the gasoline/air mixture left unburned in each cylinder?

.. ~ When a running engine is stopped, how long does it take before rust starts forming on the cylinder walls and piston rings. What happens to that rust when the engine is restarted?



I guess I view much of this question as we have always been told not to do this because it sounds believable that it would harm something, ...but in the grande scheme of things, I truly believe there is little, -if any, noticeable damage done using the choke to stop an engine from running.
OK look at the other side. If that gas were to evaporate, how is the going to help the engine on re-start?

I never mentioned rust, my concern was dry cylinders. And where is the gas going to evaporate to in a cylinder with the valves closed?

i think I will continue to let the carburetor run dry.
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Old 09-15-2020, 08:33 PM   #24
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Default Re: Wisdom of Stopping Engine by Choking It Out

If you choke it, you are cutting off its air supply.
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Old 09-16-2020, 08:46 AM   #25
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Default Re: Wisdom of Stopping Engine by Choking It Out

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Originally Posted by Ruth View Post
OK look at the other side. If that gas were to evaporate, how is the going to help the engine on re-start?

I never mentioned rust, my concern was dry cylinders. And where is the gas going to evaporate to in a cylinder with the valves closed?

i think I will continue to let the carburetor run dry.

I am not necessarily disputing or disagreeing with you on the 'restart' assistance.

I agree you never mentioned rust however I have looked at many cylinders doing inspections and they tend to rust, -even when the valve appear to be seated. This would tend to indicate there is a lack of oil there anyway. The skirts when cold have not expanded enough to create friction like they would when the engine is running. By the time an A engine has started, the rods have splashed enough oil where it is no longer an issue for the lower cylinder walls.

As far as where the evaporated fuel goes, my theory is it goes to the same place as where the compression goes when an engine is stopped. It slowly escapes past the ring gaps.
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Old 09-16-2020, 10:52 AM   #26
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Default Re: Wisdom of Stopping Engine by Choking It Out

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Quote:
Originally Posted by BRENT in 10-uh-C View Post
As far as where the evaporated fuel goes, my theory is it goes to the same place as where the compression goes when an engine is stopped. It slowly escapes past the ring gaps.
Exactly.
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Old 09-17-2020, 09:34 AM   #27
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Default Re: Wisdom of Stopping Engine by Choking It Out - speaking of KICKING TIRES

delete

Last edited by Benson; 09-17-2020 at 09:46 AM.
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Old 09-17-2020, 10:09 AM   #28
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Default Re: Wisdom of Stopping Engine by Choking It Out

Another point to ponder: In the days of carburetors it was common to find excessive cylinder wall wear at the top, to the extent that a ridge reamer was standard equipment in every mechanic's toolbox. This ridge was often in evidence before 100,000 miles. Now you will see the factory hone crosshatch clear to the top of the cylinders after 300,000 miles-no ridge! I think fuel injection has a lot to do with this. With a carburetor, a choke was needed for cold starts, resulting in a lot of raw gas (liquid fuel does not burn) washing down the cylinders, causing excess wear. With electronic injection, fuel is atomized at approx. 50 psi. The computer richens the mixture, but the air is not choked off so the cylinders are not washed down.
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Old 09-17-2020, 10:58 AM   #29
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Default Re: Wisdom of Stopping Engine by Choking It Out

Methinks that a lot of the longevity of modern engines is in the use of superior metals in the construction.
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Old 09-17-2020, 05:16 PM   #30
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Default Re: Wisdom of Stopping Engine by Choking It Out

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Methinks that a lot of the longevity of modern engines is in the use of superior metals in the construction.
Yes very true about superior metals and machining, -and add synthetic oils to the reason for better longevity too, ...not so much on the fuel injection.
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Old 09-17-2020, 11:33 PM   #31
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Default Re: Wisdom of Stopping Engine by Choking It Out

Right or wrong I turn off the gas cock and let it burn up the fuel.
Keeps the fumes down a bit in the garage.
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Old 09-18-2020, 10:13 AM   #32
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Default Re: Wisdom of Stopping Engine by Choking It Out

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Originally Posted by Aarongriffey View Post
I remember back in the day seeing folks rev up their engine real fast and shuting the ignition off. Especially in the winter time.
I remember a guy shutting is tractor off at full throttle when it was belted to a silo filler.
It kept turning over a long time with the silo filler acting as a flywheel.

Yup, my father used to do the same thing. He felt it made it easier to restart with a charge of gas in the cylinders. But he stopped doing that when they started putting smog crap on the engines in the early '70s. They were prone to dieseling after switching off the ignition, and goosing it before shutting it off just made it worse.
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Old 09-18-2020, 10:27 AM   #33
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Default Re: Wisdom of Stopping Engine by Choking It Out

I don't have much of an issue with shutting down by choking, but, I have to ask why.

That doesn't make sense to me. On a cold start the choke is pulled anyway, so why pull it twice. To shut the engine down I give a twist to the key, its easier.
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