Two-cycle oil Formulations

[lilspenny]

Many customers many models over 26 years

Mostly Stihl and Husky stuff for me

Thanks. I've run 64:1 and it has done well. I'm running all 4-mix equipment except my chainsaw. There's just something about 100:1 that makes me nervous.

 

[Pablo]

Thanks. I've run 64:1 and it has done well. I'm running all 4-mix equipment except my chainsaw. There's just something about 100:1 that makes me nervous.

Wise imho

 

[Bwalker]

We have to keep the big picture in mind: This is a "once-through" lubrication system. No oil sump, no oil cooling, only a thin film of lubricant passing through with approximately the same viscosity as gasoline, about 0.6 cSt@100C.

The viscosity of the the oil once inside the motor is the viscosity of the oil prior to mixing with gasoline minus the effect of any solvents added for miscability. On other words fairly thick.
The reason for this is once the fuel/air charge enters a two cycle motor at operating temps the solvent in the oil and the gasoline changes phase from liquid droplets to vapors and thus deposits the two cycle oil component of the pre mixed fuel on the rotating assembly. As you noted the viscosity of premixed fuel is very low and in additional has very little lubricating ability. If not for this phase change and the resulting deposition of oil the engine wouldn't last long.

 

[MolaKule]

The viscosity of the the oil once inside the motor is the viscosity of the oil prior to mixing with gasoline minus the effect of any solvents added for miscability. On other words fairly thick.

Gasoline has an average viscosity of 0.75 cSt at 40C, 2-cycle oils average about 46 cSt at 40C (about a 20 grade).

At a 40:1 ratio there is no way the final 2-cycle oil/gas mix is going to still be a 20 grade oil going into the engine.

The reason for this is once the fuel/air charge enters a two cycle motor at operating temps...

The fuel mix enters the engine at a bit less than atmospheric pressure and at about atmospheric temperature. The carb atomizes (breaks fuel into small particles), it emulsifies (mixes fuel with air), and then vaporizes (changes into a rarefied form). The carburetor is what creates the phase change from liquid to vapor.

the solvent in the oil and the gasoline changes phase from liquid droplets to vapors and thus deposits the two cycle oil of the pre mixed fuel on the rotating assembly. As you noted the viscosity of premixed fuel is very low and in additional has very little lubricating ability. If not for this phase change and the resulting deposition of oil the engine wouldn't last long.

A combination of the oil's base mix and the additives lubricates the rotating and reciprocating components.

 

[Bwalker]

Gasoline has an average viscosity of 0.75 cSt at 40C, 2-cycle oils average about 46 cSt at 40C (about a 20 grade).

At a 40:1 ratio there is no way the final 2-cycle oil/gas mix is going to still be a 20 grade oil going into the engine.

The fuel mix enters the engine at a bit less than atmospheric pressure and at about atmospheric temperature. The carb atomizes (breaks fuel into small particles), it emulsifies (mixes fuel with air), and then vaporizes (changes into a rarefied form). The carburetor is what creates the phase change from liquid to vapor.


A combination of the oil's base mix and the additives lubricates the rotating and reciprocating components.

In the first place thats not what I said. Go re read.
The fuel mixture in liquid droplet form enters the crankcase as liquid droplets. If it didnt the motor would run very hot as a two cycle gets much of its cooling from evaporation of fuel entering the crank case.
Have you ever wondered why a properly tuned two cycle smokes when its cold but not when it's warm? It smokes because fuel is entering the combustion chamber as a liquid due to the motor not being warm enough turn the liquid fuel droplets into vapor. Vapor is the only thing the spark plug can ignite, so a choke is also used in a effort to flood the motor with enough fuel so that enough vapors exist that they can be lit off. All of this liquid premix in the combustion chamber is why they smoke when cold. When at operating temp the fuel is evaporated INSIDE the crankcase depositing oil on the rotating assembly and cooling the piston and cylinder.
This is basic two cycle theory.

 

[MolaKule]

In the first place thats not what I said. Go re read.
The fuel mixture in liquid droplet form enters the crankcase as liquid droplets. If it didnt the motor would run very hot as a two cycle gets much of its cooling from evaporation of fuel entering the crank case.

So what is the purpose of the carb?

Have you ever wondered why a properly tuned two cycle smokes when its cold but not when it's warm?

It's because what is in there when cold is an overly rich mixture.

One hits the squirter bulb which pumps in raw fuel. The carb lever is moved to choke. Pull the cord then move choke lever to partially open or fully open. As soon as the air/fuel mixture gets close to stoiciometry, then the mixture will ignite but since the mixture is still rich, you will have exhaust smoke until the rich mixture is depleted.

 

[Opelman]

Found this the other day in a dark corner of an unused building at work. I might open one up and see what color it is.

 

[Bwalker]

So what is the purpose of the cab?

It's because what is in there when cold is an overly rich mixture.

One hits the squirter bulb which pumps in raw fuel. The carb lever is moved to choke. Pull the cord then move choke lever to partially open or fully open. As soon as the air/fuel mixture gets close to stoiciometry, then the mixture will ignite but since the mixture is still rich, you will have exhaust smoke until the rich mixture is depleted.

The purpose of the carb is to meter the fuel entering the engine in order to achieve the correct air to fuel ratio.
An overly rich mixture is required for a cold start for the reasons I noted. IE you have to throw enough fuel at the motor with the hope it generates enough vapor to start combustion. This is also why Reid Vapor Pressure of gasoline is adjusted during the winter to allow for the fuel to be more volatile or put another way the fuels distillation curve on the low end is set lower.
You start sequence does not consider the state of the fuel. IE it must be a vapor for ignition to happen. In a cold two stroke you have already poured the fuel to it with the hope you generate enough vapor to light off. When it does light off its still not up to temp and as a result much unburnt fuel and oil goes straight out the exhaust. When the engine is warm the majority of the fuel changes to vapor in the crank case from liquid droplet form, depositing the oil on the rotating assembly when it does so and then enters the combustion chamber via the transfer ports. The spark plug fires and the vapor mixtures combusts with little to no smoke.
Again this is very basic two stroke theory.

 

[Bwalker]

So what is the purpose of the carb?

It's because what is in there when cold is an overly rich mixture.

One hits the squirter bulb which pumps in raw fuel. The carb lever is moved to choke. Pull the cord then move choke lever to partially open or fully open. As soon as the air/fuel mixture gets close to stoiciometry, then the mixture will ignite but since the mixture is still rich, you will have exhaust smoke until the rich mixture is depleted.

You might read this article by Kevin Cameron. Kevin is a two cycle tuner, racing enthusiast and member of the motorsports hall of fame. He also holds an applied physics degree from Harvard.
https://www.cycleworld.com/story/bikes/kevin-cameron-explains-how-to-tune-carburetors/

 

[MolaKule]

@Bwalker

Let's keep our discussion here and not make posts in other threads to avoid confusion. Your comments are italicized.

This thread was started to explain the tribological basis of 2-cycle oils. Another Forum was established to discuss the analysis of 2-cycle oils.

In post #64 I quoted your wording exactly which showed you had a personal misunderstanding of the fuel/2-cycle oil mix viscosity.

You start sequence does not consider the state of the fuel. IE it must be a vapor for ignition to happen.

In post #66 and #64 I correctly stated the thermodynamic and hydrodynamic state of the fuel. "The fuel mix enters the engine at a bit less than atmospheric pressure and at about atmospheric temperature. The carb atomizes (breaks fuel into small particles), it emulsifies (mixes fuel with air), and then vaporizes (changes into a rarefied form). The carburetor is what creates the phase change from liquid to vapor."

The carburetor at the molecular level creates a "vapor" which is a "diffused" mixture of fuel and air.

In another thread you commented about the combustion improvers. When speaking of burn times we're talking about a burn time increase in the microsecond time frames so any increased heating should be minimal.. Secondly, these CI's have been incorporated in both 2-cycle and 4-cycle formulations as explained earlier in this thread. An SDS is not a disclosure of the "formulation."

 

[Bwalker]

@Bwalker

Let's keep our discussion here and not make posts in other threads to avoid confusion. Your comments are italicized.

This thread was started to explain the tribological basis of 2-cycle oils. Another Forum was established to discuss the analysis of 2-cycle oils.

In post #64 I quoted your wording exactly which showed you had a personal misunderstanding of the fuel/2-cycle oil mix viscosity.

You start sequence does not consider the state of the fuel. IE it must be a vapor for ignition to happen.

In post #66 and #64 I correctly stated the thermodynamic and hydrodynamic state of the fuel. "The fuel mix enters the engine at a bit less than atmospheric pressure and at about atmospheric temperature. The carb atomizes (breaks fuel into small particles), it emulsifies (mixes fuel with air), and then vaporizes (changes into a rarefied form). The carburetor is what creates the phase change from liquid to vapor."

The carburetor at the molecular level creates a "vapor" which is a "diffused" mixture of fuel and air.

In another thread you commented about the combustion improvers. When speaking of burn times we're talking about a burn time increase in the microsecond time frames so any increased heating should be minimal.. Secondly, these CI's have been incorporated in both 2-cycle and 4-cycle formulations as explained earlier in this thread. An SDS is not a disclosure of the "formulation."

In the first place you incorrectly alluded to the viscosity of two cycle oil inside the motor being the same as pre mixed gasoline. Its not and no motor would last long running at full load while being lubricated by a mixture of gasoline and oil. Such a low viscosity mixture would have virtually no lubricating ability. Phase change takes place inside the crankcase and oil is deposited on the rotating assembly.

The carb does not vaporize the fuel, period. You can actually look into the bore of a carb with the engine running and see liquid fuel going into a two cycle motor. This isnt theory as I have seen it, but two cycle theory agrees with me too. A two cycle is actually cooled in large part by this fuel changing phase inside the crankcase. Does the carb help this process by atomizing the fuel into fine droplets? Of course it does, but it's the heat of the motor which vaporized it. Its for this reason that the distillation curves of racing gasoline are optimized for intake runer length, and engine state of tune. Heat from the motor is key in the phase change from a liquid to a vapor in a two cycle or 4 cycle engine for that matter.
I suggest you read the article I posted as you seem to be confused on how this all works.
In the other thread I asked you if you were aware of a formulation in widespread usage that contained such improvers. I got crickets. I am well aware an MSDS isnt an ingredient list and said as much in my post.
I appreciate the civil tone btw.

 

[MolaKule]

The carb does not vaporize the fuel, period. You can actually look into the bore of a carb with the engine running and see liquid fuel going into a two cycle motor. This isnt theory as I have seen it, but two cycle theory agrees with me too.
In the other thread I asked you if you were aware of a formulation in widespread usage that contained such improvers. I got crickets. I am will aware an MSDS isnt an credit list and said as much in my post.

I answered your question from the other thread in the above post #70 with the comments:

"Let's keep our discussion here and not make posts in other threads to avoid confusion. Your comments are italicized.

This thread was started to explain the tribological basis of 2-cycle oils. Another Forum was established to discuss the analysis of 2-cycle oils.

In another thread you commented about the combustion improvers. When speaking of burn times we're talking about a burn time increase in the microsecond time frames so any increased heating should be minimal.. Secondly, these CI's have been incorporated in both 2-cycle and 4-cycle formulations as explained earlier in this thread. An SDS is not a disclosure of the "formulation."

You can actually look into the bore of a carb with the engine running and see liquid fuel going into a two cycle motor.

The liquid fuel droplets along with the mixed air constitutes the definition of a "vapor."

"It is the vapor cloud above the liquid that will burn if the vapor's concentration is between the lower flammable limit (LFL) and upper flammable limit (UFL), of the flammable liquid." Ferguson, Lon H.; Janicak, Christopher A. (2005-09-01). Fundamentals of Fire Protection for the Safety Professional. Government Institutes. ISBN 9781591919605.

From a chemical dictionary: "a substance diffused or suspended in the air."

From the Biological dictionary

https://biologyinsights.com/what-are-vapors-the-science-of-phase-change/

"Distinguishing Vapors from Gases and Aerosols​

The terms vapor, gas, and aerosol are often used interchangeably, but they describe distinct physical states. A true gas exists at a temperature above its critical temperature, meaning its molecules have so much kinetic energy that pressure alone cannot force them back into the liquid state. Nitrogen and oxygen in the air are examples of true gases at room temperature.

A vapor, in contrast, is the gaseous state of a substance that is below its critical temperature. This distinction is based entirely on the thermal condition. If the substance can be compressed back into a liquid at its current temperature, it is a vapor; if not, it is a gas.

An aerosol is physically different from both a vapor and a gas because it is not a homogenous gaseous phase. An aerosol is a suspension of tiny solid particles or liquid droplets dispersed within a gas. Mist, fog, and smoke are common examples. They are visible because the suspended particles are large enough to scatter light, whereas a true vapor, such as pure steam, is invisible because its individual molecules are too small to scatter light."

I hope this helps in your understanding of vapor.

 

[Bwalker]

I answered your question from the other thread in the above post #70 with the comments:

"Let's keep our discussion here and not make posts in other threads to avoid confusion. Your comments are italicized.

This thread was started to explain the tribological basis of 2-cycle oils. Another Forum was established to discuss the analysis of 2-cycle oils.

In another thread you commented about the combustion improvers. When speaking of burn times we're talking about a burn time increase in the microsecond time frames so any increased heating should be minimal.. Secondly, these CI's have been incorporated in both 2-cycle and 4-cycle formulations as explained earlier in this thread. An SDS is not a disclosure of the "formulation."

You can actually look into the bore of a carb with the engine running and see liquid fuel going into a two cycle motor.

The liquid fuel droplets along with the mixed air constitutes the definition of a "vapor."

"It is the vapor cloud above the liquid that will burn if the vapor's concentration is between the lower flammable limit (LFL) and upper flammable limit (UFL), of the flammable liquid." Ferguson, Lon H.; Janicak, Christopher A. (2005-09-01). Fundamentals of Fire Protection for the Safety Professional. Government Institutes. ISBN 9781591919605.

From a chemical dictionary: "a substance diffused or suspended in the air."

From the Biological dictionary

https://biologyinsights.com/what-are-vapors-the-science-of-phase-change/

"Distinguishing Vapors from Gases and Aerosols​

The terms vapor, gas, and aerosol are often used interchangeably, but they describe distinct physical states. A true gas exists at a temperature above its critical temperature, meaning its molecules have so much kinetic energy that pressure alone cannot force them back into the liquid state. Nitrogen and oxygen in the air are examples of true gases at room temperature.

A vapor, in contrast, is the gaseous state of a substance that is below its critical temperature. This distinction is based entirely on the thermal condition. If the substance can be compressed back into a liquid at its current temperature, it is a vapor; if not, it is a gas.

An aerosol is physically different from both a vapor and a gas because it is not a homogenous gaseous phase. An aerosol is a suspension of tiny solid particles or liquid droplets dispersed within a gas. Mist, fog, and smoke are common examples. They are visible because the suspended particles are large enough to scatter light, whereas a true vapor, such as pure steam, is invisible because its individual molecules are too small to scatter light."

I hope this helps in your understanding of vapor.

I hope you understand what I am referring to is the phase change of a liquid to a gas. I am being facetious because I know fell well you knew what I was saying. This phase change happens inside the crank case and not in the carb. I hope this helps your understanding of what is happening in a two cycle motor.

 

[MolaKule]

I hope you understand what I am referring to is the phase change of a liquid to a gas.

Thanks, I am very well versed in phase changes.

I am being facetious because I know fell well you knew what I was saying.

No need to be facetious and argumentative if you state your comments clearly.

This phase change happens inside the crank case and not in the carb.

In post #72 I fully explained vapors, gases, and aerosols because you seemed to be confused in the differences between the three.

I hope this helps your understanding of what is happening in a two cycle motor.

I am very familiar with the design, operation, and lubrication requirements of 2-cycle engines.

A good read on the design and simulation of two-cycle engines which will benefit interested members is:

https://www.normsplash.com/Samples/SAE/117997259/R-161-en.pdf

 

[greaseguy15]

Thanks, I am very well versed in phase changes.



No need to be facetious and argumentative if you state your comments clearly.

In post #72 I fully explained vapors, gases, and aerosols because you seemed to be confused in the differences between the three.



I am very familiar with the design, operation, and lubrication requirements of 2-cycle engines.

A good read on the design and simulation of two-cycle engines which will benefit interested members is:

https://www.normsplash.com/Samples/SAE/117997259/R-161-en.pdf

Ahh man now I have to find my SAE student login to read this paper!

 

[Bwalker]

Thanks, I am very well versed in phase changes.



No need to be facetious and argumentative if you state your comments clearly.

In post #72 I fully explained vapors, gases, and aerosols because you seemed to be confused in the differences between the three.



I am very familiar with the design, operation, and lubrication requirements of 2-cycle engines.

A good read on the design and simulation of two-cycle engines which will benefit interested members is:

https://www.normsplash.com/Samples/SAE/117997259/R-161-en.pdf

Dr.Blair is indeed a legend, but tgat does not change tge fact that you appear to have a very rudimentary knowledge of this subject. That you think a two cycle motor is lubricated by gasoline and oil mix is telling. And most certainly I am not confusing anything. Liquid gasoline changes phase from a liquid to a gas inside the crankcase. Thus us what deposits oil on tge rotating assembly and this is what provides for a large part of the two stroke motors cooling.

 

[Mechanician]

Thus us what deposits oil on tge rotating assembly and this is what provides for a large part of the two stroke motors cooling.

Could you elaborate on this please, what percentage of the total is this large part?
It seems that the volume of liquid evaporating wouldn't be enough to constitute a large part.

 

[MolaKule]

Dr.Blair is indeed a legend, but tgat does not change tge fact that you appear to have a very rudimentary knowledge of this subject.

That you think a two cycle motor is lubricated by gasoline and oil mix is telling.

What I am telling you is, air is not a lubricator so the base oil and additives from the fuel mix is the only thing left to lubricate.

And most certainly I am not confusing anything. Liquid gasoline changes phase from a liquid to a gas inside the crankcase. Thus us what deposits oil on tge rotating assembly and

The fuel/air mix enters the bottom part of the crankcase as a vapor (see my comprehensive explanation above). As this point the fuel-oil droplets deposits on the various components, lubricating them. A short time later, the piston moves down to compress the vapor below it; the combination of compression and residual crankcase heat results in a phase change converting most, but not all, of the residual vapor to a gas. As the piston moves up the gas below the piston is allowed to enter the "combustion chamber" for ignition, the power stroke.

this is what provides for a large part of the two stroke motors cooling.

Now you're discussing the thermodynamics of the 2-stroke engine. Heat is removed from the head by air passing over the cooling fins. Thermal energy (heat) is conducted to the fins and air removes heat by convection.

Another measure of cooling is accomplished by what is called the, "Latent Heat of Vaporization" to which you may be referring, but you never identified the cooling process.

The amount of energy absorbed or released during a phase change is called, "Latent Heat." The
"Latent Heat of Vaporization" is highly dependent on the temperature and pressure at which the phase change occurs.

See for example, Fundamentals of Thermal-Fluid Science, by Yunus Cengel, et. al.,, page 71.

 

[MolaKule]

For a good, basic explanation of the two-cycle engine:

https://science.howstuffworks.com/transport/engines-equipment/two-stroke1.htm

 

[#18FAN]

Dr.Blair is indeed a legend, but tgat does not change tge fact that you appear to have a very rudimentary knowledge of this subject. That you think a two cycle motor is lubricated by gasoline and oil mix is telling. And most certainly I am not confusing anything. Liquid gasoline changes phase from a liquid to a gas inside the crankcase. Thus us what deposits oil on tge rotating assembly and this is what provides for a large part of the two stroke motors cooling.

How many 2T oils have you developed out of curiosity