Octane question

[Bill G]

Normally I skip running the diesel when I'm going to get gas. But its mostly an over exaggerated issue. At least around here. You can't dispense anything higher then e-10 from the same hose. E-15,E-85, non-E all have separate lines.

I am not sure if we have any specific laws regulating it here. There may be some that I am unaware of. I know E-85 is definitely a separate pump. One of the craziest things was when I was at a station and the owner was telling me a woman had put gas in her diesel car. He was livid because she was blaming the owner and wanted him to pay. He was calling her every name in the book...well from what I could understand of his poor English he was. I tried explaining to him that yes she was ignorant for doing so but dammmmit buddy you have a separate pump there that is green with a green nozzle and you are selling gas through it. Yes it was marked gas but she saw a green pump and assumed it was diesel. Yes she was wrong but change your colors to avoid future confusion. To this day I think it remains.

 

[ZeroJunk]

At the station up the hill they only have regular and high test gasoline in the ground. Mid Grade is mixed in the pump itself. Diesel is a stand alone pump and kerosene is a stand alone pump. No non-ethanol though. No E-85 .

 

[bwalker]

If you consider that it often comes out of the same oil well it does. Since I'm not remotely connected to the oil refining business, you'll need to explain what you mean by "blending pool".

For the purposes of this conversation, I was using bitumen as an example of a much heavier molecular weight hydrocarbon with which to compare the flame speed with high octane fuel. In general, it is pretty easy to see that the smaller the molecule the faster it burns. Similarly, we can also see that the heavier the molecule, the more energy it releases when burned completely.

When you refine oil you always end up with some asphalt after the oil goes though the vacuum distillation unit. It typicly is then sent to a Coker at most refinery where it is made into gasoline, diesel and lighter end products. Any excess is marketed to making asphalt but the economics of this is poor these days.

In regards to your last paragraph graph. When talking about the various streams of hydro carbons used to blend gasoline all of them are within a narrow carbon range. As such they have very similar densities. Similar flame speeds as well yet vastly different octane numbers.
Inferring that iso octane burns slower than regular gas(whatever that is) from the chart you posted isn't valid because the chart parameters are not related to what happens inside a motor or at the air to fuel ratios a motor operates under.

 

[bwalker]

I don't know of any ethanol-free fuel around here. But I have stored E10 foir a year or more, using Sta-Bil, and I have had no fuel-related problems.

In what sort of containers?

 

[pdqdl]

When you refine oil you always end up with some asphalt after the oil goes though the vacuum distillation unit. It typicly is then sent to a Coker at most refinery where it is made into gasoline, diesel and lighter end products. Any excess is marketed to making asphalt but the economics of this is poor these days.

In regards to your last paragraph graph. When talking about the various streams of hydro carbons used to blend gasoline all of them are within a narrow carbon range. As such they have very similar densities. Similar flame speeds as well yet vastly different octane numbers.
Inferring that iso octane burns slower than regular gas(whatever that is) from the chart you posted isn't valid because the chart parameters are not related to what happens inside a motor or at the air to fuel ratios a motor operates under.

I find it remarkable that you will argue that different chemicals will detonate differently, but burn at the same rate. Now we all know that fuels with vastly different chemical compositions can be formulated to arrive at the same resistance to detonation (octane #), yet you persist in arguing that they all burn at the same rate regardless of both chemical composition AND octane rating. Even when they also have different BTU ratings.

I guess calling it "gasoline" is sufficient enough for you, but I don't buy into that logic. if you want me to believe you, it's going to take more than cogent arguments. I expect some data from a reputable source. I found data that directly shows my argument, you have not. Probably wisest at this point to concede that neither of is is going to change their mind.

 

[bwalker]

It shows the velocity of the combustion of various fuels across a range of air mixtures. The maximum speed of each fuel's combustion occurs at different air mixtures, and it also shows which is fastest according to the maximum velocity reached.















Notice that iso-octane is the lowest curve, exceeded only a small distance by "gasoline". So we know that the emperical standard for a grade 100 octane burns a bit slower than gasoline.















I would have liked to have seen the chart plotted against the flame velocity under variable pressures. I suspect, however, that might be a really hard thing to measure, as each fuel will produce different volumes of combustion gases.



I find it remarkable that you will argue that different chemicals will detonate differently, but burn at the same rate. Now we all know that fuels with vastly different chemical compositions can be formulated to arrive at the same resistance to detonation (octane #), yet you persist in arguing that they all burn at the same rate regardless of both chemical composition AND octane rating. Even when they also have different BTU ratings.



I guess calling it "gasoline" is sufficient enough for you, but I don't buy into that logic. if you want me to believe you, it's going to take more than cogent arguments. I expect some data from a reputable source. I found data that directly shows my argument, you have not. Probably wisest at this point to concede that neither of is is going to change their mind.

I find it remarkable that you will argue that different chemicals will detonate differently, but burn at the same rate. Now we all know that fuels with vastly different chemical compositions can be formulated to arrive at the same resistance to detonation (octane #), yet you persist in arguing that they all burn at the same rate regardless of both chemical composition AND octane rating. Even when they also have different BTU ratings.

I guess calling it "gasoline" is sufficient enough for you, but I don't buy into that logic. if you want me to believe you, it's going to take more than cogent arguments. I expect some data from a reputable source. I found data that directly shows my argument, you have not. Probably wisest at this point to concede that neither of is is going to change their mind.

To be clear I am stating that there is effectively no differance in flame speed inside a motor between regular and premium. That statement is absolutely 100% factual.
The data you found has doesn't say what you think it does and isn't applicable to a motor.
You are trying to infer stability IE resistance to detonation as measured by Octane number as density and it just doesn't work like that. Octane is more related to the hydrocarbon bond structures than density. ISO Butane and N Pentane and very similar densities with the former being slightly lighter than the latter. The Octane for the Iso Butane is 94 and N pentane is 70 going by memory. Flame speeds for either are very similar. This is just a fact.
The problem is guys equate flame speed with stability and there just isn't a direct correlation.
Also consider that by the chart you posted ethanol has a higher flame speed than iso octane and it also has higher octane number. How do you reconcile that?

 

[bwalker]

@pdqdl Two pertinent articles by tuner, racer, and holder of a physics degree from Harvard, Kevin Cameron. If he says it it's spot on.
In particular see point #8 of the second article towards the end. Sound familiar?
https://www.cycleworld.com/2015/05/...l-editor-kevin-cameron-insights-and-analysis/https://factorypipewatercraft.com/t_deto.php

 

[bwalker]

I find it remarkable that you will argue that different chemicals will detonate differently, but burn at the same rate. Now we all know that fuels with vastly different chemical compositions can be formulated to arrive at the same resistance to detonation (octane #), yet you persist in arguing that they all burn at the same rate regardless of both chemical composition AND octane rating. Even when they also have different BTU ratings.

I guess calling it "gasoline" is sufficient enough for you, but I don't buy into that logic. if you want me to believe you, it's going to take more than cogent arguments. I expect some data from a reputable source. I found data that directly shows my argument, you have not. Probably wisest at this point to concede that neither of is is going to change their mind.

And one more thing. I find it remarkable that a person with no industry knowledge, no understanding of HC chemistry and nothing to go by other than what his dad said and unrelated stuff he googled up can be so addemate.
I suppose the problem is the internet is littered with absolute crap on this subject. Including articles in enthusiast publication whose authors should know better, but clearly dont.

 

[pdqdl]

Huge assumptions, lad. Inclusive, in fact, of some very obvious errors. I have a degree in chemistry. Do you?

If not, I might even know more "hydrocarbon chemistry" than you do, petrochemical industry excepted. It kinda depends on what you have been educated on.

While it is true that we should all evaluate the source of our information, as well as the facts involved, that doesn't entitle you to cast aspersions about folks you know nothing about. I have cited to you research on hydrocarbon burn rates, and you quoted me generalizations from an automotive mechanic.

Including articles in enthusiast publication whose authors should know better, but clearly dont.

That's just precious! What you quoted to support your argument was from an enthusist publication, was it not?

Let's compete then, on who has the best and most pertinent factoids? Or maybe just drop it. It's fairly obvious you got nothing but quotes from an enthusiast magazine that should know better. And your own opinion, which doesn't seem likely to change.

 

[pdqdl]

@pdqdl Two pertinent articles by tuner, racer, and holder of a physics degree from Harvard, Kevin Cameron. If he says it it's spot on.
In particular see point #8 of the second article towards the end. Sound familiar?

Sure! I'll read.

https://www.cycleworld.com/2015/05/...l-editor-kevin-cameron-insights-and-analysis/

This is another article from an enthusiast publication. I thought you scorned such sources? I can assure you, however, that not very much of that verbiage is accurately describing the chemistry involved.

Now I'll concede that not many reactions burn faster than free radical hydrogen and oxygen. All we need to do is think of the Hindenburg, and we can see that burns real fast. All your article has stated is the obvious: "knocking" occurs when the fuel in question burns too fast. We knew that already.

https://factorypipewatercraft.com/t_deto.php, but it

That is a pretty technical article, and it describes the detonation process much better than your first article. While it does an excellent job of describing the cylinder conditions when detonation occurs, It doesn't exactly describe too well why it occurs, why exhaust temperatures decline under detonation, and why engine heat increases. The details are there, but they are obscured by techno-speak that doesn't illuminate understanding.

And it also describes exactly the problem: higher octane fuels burn more to the bottom of the stroke because they haven't detonated. Lower octane fuels (at least under detonation) burn MUCH faster under detonation. We knew that already.

Your 2nd article was informative, thank you, but it doesn't support your claim in any way. NOTHING in either article addresses the relative burn velocity of these fuels when NOT under detonation, which was your claim.

 

[bwalker]

Huge assumptions, lad. Inclusive, in fact, of some very obvious errors. I have a degree in chemistry. Do you?

If not, I might even know more "hydrocarbon chemistry" than you do, petrochemical industry excepted. It kinda depends on what you have been educated on.

While it is true that we should all evaluate the source of our information, as well as the facts involved, that doesn't entitle you to cast aspersions about folks you know nothing about. I have cited to you research on hydrocarbon burn rates, and you quoted me generalizations from an automotive mechanic.



That's just precious! What you quoted to support your argument was from an enthusist publication, was it not?

Let's compete then, on who has the best and most pertinent factoids? Or maybe just drop it. It's fairly obvious you got nothing but quotes from an enthusiast magazine that should know better. And your own opinion, which doesn't seem likely to change.

Kevin, unlike the dolt you quoted is a widely respected SME. If you have noted errors in what he has written point them out.
It's OK to admit you don't know the first thing about HC chemistry, the basics of combustion engine or the refining industry and leave it at that. My brother has a chemistry degree as well and he doesn't know the first thing about fuel chemistry either. It's a fairly obscure and dieing field these days.
And it's not my opinion. It's fact. You have opinions and I am dealing in undisputable facts.
I will give you a hint. Your conflating density with things like flame speed and stability, but your not considering the effects of molecular structure. IE straight chained molecules will have less stability IE octane regardless of there density than branched or ringed structure molecules. For instance Benzene which has a ringed structure and has a burn speed faster and octane higher than Iso octane. How do you explain this?
The real problem is you don't understand what octane is a measure of at all.

 

[bwalker]

Sure! I'll read.

This is another article from an enthusiast publication. I thought you scorned such sources? I can assure you, however, that not very much of that verbiage is accurately describing the chemistry involved.

Now I'll concede that not many reactions burn faster than free radical hydrogen and oxygen. All we need to do is think of the Hindenburg, and we can see that burns real fast. All your article has stated is the obvious: "knocking" occurs when the fuel in question burns too fast. We knew that already.



That is a pretty technical article, and it describes the detonation process much better than your first article. While it does an excellent job of describing the cylinder conditions when detonation occurs, It doesn't exactly describe too well why it occurs, why exhaust temperatures decline under detonation, and why engine heat increases. The details are there, but they are obscured by techno-speak that doesn't illuminate understanding.

And it also describes exactly the problem: higher octane fuels burn more to the bottom of the stroke because they haven't detonated. Lower octane fuels (at least under detonation) burn MUCH faster under detonation. We knew that already.

Your 2nd article was informative, thank you, but it doesn't support your claim in any way. NOTHING in either article addresses the relative burn velocity of these fuels when NOT under detonation, which was your claim.

Not only does it support my claims perfectly your take on it is the exact opposite of what it is saying in regards to the burn speed point.

 

[ZeroJunk]

The real problem is you don't understand what octane is a measure of at all.

I thought that it was pretty clear that it is a knock rating.

 

[pdqdl]

To be clear I am stating that there is effectively no differance in flame speed inside a motor between regular and premium. That statement is absolutely 100% factual.

Nothing you have presented discusses any such facts. Except for one enthusiast publication, which you have scorned as a source of information.

The data you found has doesn't say what you think it does and isn't applicable to a motor.

Quite true. You would, however, need to read that article to see the experimental conditions under which the tests were conducted.

You are trying to infer stability IE resistance to detonation as measured by Octane number as density and it just doesn't work like that.

Huh? Where did I make any such claim. Density has little to do with molecular weight of hydrocarbons, to which I have indeed referred. ONLY A NON-CHEMIST WOULD MAKE THAT MISTAKE. And I don't think I ever made any references to "stability"

Octane is more related to the hydrocarbon bond structures than density. ISO Butane and N Pentane and very similar densities with the former being slightly lighter than the latter. The Octane for the Iso Butane is 94 and N pentane is 70 going by memory. Flame speeds for either are very similar. This is just a fact.

Fluff and nonsense. Again, I wasn't discussing "density". Why again are we talking about lighter hydrocarbons?

The problem is guys equate flame speed with stability and there just isn't a direct correlation.

Your concept of "stability" is a misnomer. What all your physics nerds are describing is the conditions that lead to a flame speed that is accelerated beyond the speed of sound by the reaction rate and the higher pressures under cylinder compression. There is no "stability" issue. The chemical reactions are the exact same as when there is no detonation. The only difference is the speed at which the reaction occurs. Like almost all chemical reactions, it happens faster at higher temperatures and pressure. Each fuel is a chemical, and each chemical will have it's own specific reaction rates for each temperature and pressure involved.

Also consider that by the chart you posted ethanol has a higher flame speed than iso octane and it also has higher octane number. How do you reconcile that?

Well for starters, ethanol isn't generally considered "a hydrocarbon", it is an alcohol. As such, it is less energetically inclined to combine with oxygen, since it is already attached to one oxygen molecule.

I did find this: "The octane rating of pure ethanol is 100. What's interesting is that when ethanol is blended with gasoline, it performs as if its octane rating is 112, making ethanol a very effective octane booster when used in gasoline."

What you should also understand is that because it might burn faster than iso-octane, it does not produce as many gas metabolites after burning. Which will have the net effect of not increasing the pressure inside the cylinder as much as other fuels, and it will consequently have a greater resistance to detonation under identical physical conditions as gasoline.

Something to think about:
As you have already pointed out, gasoline is composed of a lot of different chemicals. Lets mix in some water!
Water would have a flame speed of 0, at least until it were dissociated into hydrogen and oxygen. Then it becomes the best rocket fuel known, with a monumentally fast flame speed. And we all know how well water prevents detonation when we add it to the gas tank, so I'd guess it has a pretty damned high octane number as well. Until you "dissociate" that highly stabile water molecule into rocket fuel. I'll bet the octane number of liquid oxygen & hydrogen is in the negative thousands.

Allow me to suggest that much like water, comparing alcohol to other hydrocarbon fuels isn't probably a valid comparison.

 

[pdqdl]

Not only does it support my claims perfectly your take on it is the exact opposite of what it is saying in regards to the burn speed point.

I can't help it if you have formed that opinion. My thoughts are different. Let's just let the other readers decide for themselves.

I can tell, however, that you are very unlikely to have that degree in chemistry. So what is your college education about, eh? I'm only questioning you on that because you told me I was unqualified, yet we are talking about physics and chemistry. We disagree on the content of your article, and you have made several statements that reveal a lack of understanding.

 

[bwalker]

Your opinion are what they are...wrong. what I have stated is absolutely a fact.
My degree is in Environmental Science and I completed course work in organic chemistry. I also am a fee credits short of a BA as well
and yes you are not qualified and your thought process bares this out.

 

[Section VIII]

I like fried chicken and fish too much to not eat it...

Guess I'll have health complications and die.

 

[lone wolf]

I like fried chicken and fish too much to not eat it...

Guess I'll have health complications and die.

So fry them in Olive oil not processed vegetable oil its nasty stuff.

 

[bwalker]

Nothing you have presented discusses any such facts. Except for one enthusiast publication, which you have scorned as a source of information.


Quite true. You would, however, need to read that article to see the experimental conditions under which the tests were conducted.


Huh? Where did I make any such claim. Density has little to do with molecular weight of hydrocarbons, to which I have indeed referred. ONLY A NON-CHEMIST WOULD MAKE THAT MISTAKE. And I don't think I ever made any references to "stability"


Fluff and nonsense. Again, I wasn't discussing "density". Why again are we talking about lighter hydrocarbons?


Your concept of "stability" is a misnomer. What all your physics nerds are describing is the conditions that lead to a flame speed that is accelerated beyond the speed of sound by the reaction rate and the higher pressures under cylinder compression. There is no "stability" issue. The chemical reactions are the exact same as when there is no detonation. The only difference is the speed at which the reaction occurs. Like almost all chemical reactions, it happens faster at higher temperatures and pressure. Each fuel is a chemical, and each chemical will have it's own specific reaction rates for each temperature and pressure involved.




Well for starters, ethanol isn't generally considered "a hydrocarbon", it is an alcohol. As such, it is less energetically inclined to combine with oxygen, since it is already attached to one oxygen molecule.

I did find this: "The octane rating of pure ethanol is 100. What's interesting is that when ethanol is blended with gasoline, it performs as if its octane rating is 112, making ethanol a very effective octane booster when used in gasoline."

What you should also understand is that because it might burn faster than iso-octane, it does not produce as many gas metabolites after burning. Which will have the net effect of not increasing the pressure inside the cylinder as much as other fuels, and it will consequently have a greater resistance to detonation under identical physical conditions as gasoline.

Something to think about:
As you have already pointed out, gasoline is composed of a lot of different chemicals. Lets mix in some water!
Water would have a flame speed of 0, at least until it were dissociated into hydrogen and oxygen. Then it becomes the best rocket fuel known, with a monumentally fast flame speed. And we all know how well water prevents detonation when we add it to the gas tank, so I'd guess it has a pretty damned high octane number as well. Until you "dissociate" that highly stabile water molecule into rocket fuel. I'll bet the octane number of liquid oxygen & hydrogen is in the negative thousands.

Allow me to suggest that much like water, comparing alcohol to other hydrocarbon fuels isn't probably a valid comparison.

Nothing you have presented discusses any such facts. Except for one enthusiast publication, which you have scorned as a source of information.


Quite true. You would, however, need to read that article to see the experimental conditions under which the tests were conducted.


Huh? Where did I make any such claim. Density has little to do with molecular weight of hydrocarbons, to which I have indeed referred. ONLY A NON-CHEMIST WOULD MAKE THAT MISTAKE. And I don't think I ever made any references to "stability"


Fluff and nonsense. Again, I wasn't discussing "density". Why again are we talking about lighter hydrocarbons?


Your concept of "stability" is a misnomer. What all your physics nerds are describing is the conditions that lead to a flame speed that is accelerated beyond the speed of sound by the reaction rate and the higher pressures under cylinder compression. There is no "stability" issue. The chemical reactions are the exact same as when there is no detonation. The only difference is the speed at which the reaction occurs. Like almost all chemical reactions, it happens faster at higher temperatures and pressure. Each fuel is a chemical, and each chemical will have it's own specific reaction rates for each temperature and pressure involved.




Well for starters, ethanol isn't generally considered "a hydrocarbon", it is an alcohol. As such, it is less energetically inclined to combine with oxygen, since it is already attached to one oxygen molecule.

I did find this: "The octane rating of pure ethanol is 100. What's interesting is that when ethanol is blended with gasoline, it performs as if its octane rating is 112, making ethanol a very effective octane booster when used in gasoline."

What you should also understand is that because it might burn faster than iso-octane, it does not produce as many gas metabolites after burning. Which will have the net effect of not increasing the pressure inside the cylinder as much as other fuels, and it will consequently have a greater resistance to detonation under identical physical conditions as gasoline.

Something to think about:
As you have already pointed out, gasoline is composed of a lot of different chemicals. Lets mix in some water!
Water would have a flame speed of 0, at least until it were dissociated into hydrogen and oxygen. Then it becomes the best rocket fuel known, with a monumentally fast flame speed. And we all know how well water prevents detonation when we add it to the gas tank, so I'd guess it has a pretty damned high octane number as well. Until you "dissociate" that highly stabile water molecule into rocket fuel. I'll bet the octane number of liquid oxygen & hydrogen is in the negative thousands.

Allow me to suggest that much like water, comparing alcohol to other hydrocarbon fuels isn't probably a valid comparison.

I will respond to this tommorow when I have time, but needless to say your off in most regards.

 

[bwalker]

So fry them in Olive oil not processed vegetable oil its nasty stuff.

Olive oil isn't great for frying.
Better to forgo fried crap altogether.. although that's hard if you live in the south.