Fuel Octane
#21
12-17-2008, 11:41 PM
RE: Fuel Octane
ORIGINAL: SpecterGT260
i typically dont read for my opinions on these things..... 4 years of study in chemistry and thermodynamics do wonders on these subjects
i typically dont read for my opinions on these things..... 4 years of study in chemistry and thermodynamics do wonders on these subjects
And ultimatly your studies must have been from some kind of written word that took some reading..... or books on tape.
#22
12-17-2008, 11:58 PM
Join Date: Oct 2007
Location: The 'Burbs of Chicago
Posts: 18,306
RE: Fuel Octane
That's exactly what I was thinking Mike.
Why is it that reading and studying from a few years ago becomes "knowledge", but reading present info is only considered "research" and supposedly doesn't carry as much weight?
Why is it that reading and studying from a few years ago becomes "knowledge", but reading present info is only considered "research" and supposedly doesn't carry as much weight?
#23
12-18-2008, 12:10 AM
RE: Fuel Octane
Its all them Uthamisms (sp).
I don't need to read, I studied.
Its not a used car, its pre-owned.
I went to replace my mattress the other day and found they did not sell them any more, They only had sleep systems.
I don't need to read, I studied.
Its not a used car, its pre-owned.
I went to replace my mattress the other day and found they did not sell them any more, They only had sleep systems.
#24
12-19-2008, 06:40 AM
RE: Fuel Octane
ORIGINAL: SpecterGT260
really? the turbonator has been advertising "complete fuel burn" for several years now 
. "complete burn" has NEVER been a real issue, its just that misinformed consumers see it as an issue so we these god aweful products that prey on these misconceptions. You ought to know better...... you act like people in the communications industry have a scientific cell in their body.... and most fuels over 96 octanes are leaded, and therefore designated "off road only". these fuels have a distinct smell to them
How do you relate this to the chemical formulation of gasoline that is formulated for burning cleaner? And yes reformulated gasolines do burn cleaner partly due to the oxygenated content.
weve had a dozen threads over the last couple months about miracle fuel savers, and EVERY SINGLE ONE says something about atomization or mixing to increase % fuel burn even when the underlying principles are counterintuitive or completely unrelated.
the octane rating, in the simplest sense, relates only to the activation energy of the combustion reaction. lower octanes have a lower AE, therefore it takes less energy to get them to react. heat=energy. which is why many people experience more knock with a hot engine. the rating, as a resistance to detonation, has nothing to do with the kinetics. if it WAS kinetically hindered, you would expect knock to go AWAY with increasing rpm as the "reaction chamber", the cylinder, is left alone to react for shorter periods of time. this isnt the case. detonation increases with rpm due to the increased heat.
I dont believe this is true because there is less time for the detonation to occur it decreases with RPM
you NEVER want complete fuel burn. that right there completely negates your 76 argument as complete hoo-ha. if you want to see proof of this look at the AFR (14.7) measured in the exhaust manifold. unburnt fuel is NECESSARY to the operation of the engine. combusting fuel releases more heat than it absorbs, liquid fuel, however, absorbs heat without detonating, and this AFR is a measure of how much is left. it acts as a heat quencher, therefore if you add too much fuel, you get too much heat quenching and eventually can get to the point where the heat from the reaction is consumed and the reaction stopped. too little and the engine gets too hot and you start to get detonation or you just melt engine components.
ORIGINAL: MadMikeZ28
I read in a hot rod magazine about higher octane fuel being slower burning and how unburned fuel could make it out the exhaust. It was explained better than I could do it. Not only that but about 4 or 5 years ago 76 advertised "92 octane now with complete burn technology". Now why would they advertise that if it was never an issue.
The clean burn technology probably relates more to environmental issues they add oxygenators like MTBE or Ethanol to get the fuel to burn more completly reducing emmisions.
Oh and when we are riding and go to the motorcycle races at Sears point and fill up with 100 octane. When you are behind some one with that high an octane you can smelldamn near raw gasreal well.
I read in a hot rod magazine about higher octane fuel being slower burning and how unburned fuel could make it out the exhaust. It was explained better than I could do it. Not only that but about 4 or 5 years ago 76 advertised "92 octane now with complete burn technology". Now why would they advertise that if it was never an issue.
The clean burn technology probably relates more to environmental issues they add oxygenators like MTBE or Ethanol to get the fuel to burn more completly reducing emmisions.
Oh and when we are riding and go to the motorcycle races at Sears point and fill up with 100 octane. When you are behind some one with that high an octane you can smelldamn near raw gasreal well.
. "complete burn" has NEVER been a real issue, its just that misinformed consumers see it as an issue so we these god aweful products that prey on these misconceptions. You ought to know better...... you act like people in the communications industry have a scientific cell in their body.... and most fuels over 96 octanes are leaded, and therefore designated "off road only". these fuels have a distinct smell to them How do you relate this to the chemical formulation of gasoline that is formulated for burning cleaner? And yes reformulated gasolines do burn cleaner partly due to the oxygenated content.
weve had a dozen threads over the last couple months about miracle fuel savers, and EVERY SINGLE ONE says something about atomization or mixing to increase % fuel burn even when the underlying principles are counterintuitive or completely unrelated.
the octane rating, in the simplest sense, relates only to the activation energy of the combustion reaction. lower octanes have a lower AE, therefore it takes less energy to get them to react. heat=energy. which is why many people experience more knock with a hot engine. the rating, as a resistance to detonation, has nothing to do with the kinetics. if it WAS kinetically hindered, you would expect knock to go AWAY with increasing rpm as the "reaction chamber", the cylinder, is left alone to react for shorter periods of time. this isnt the case. detonation increases with rpm due to the increased heat.
I dont believe this is true because there is less time for the detonation to occur it decreases with RPM
you NEVER want complete fuel burn. that right there completely negates your 76 argument as complete hoo-ha. if you want to see proof of this look at the AFR (14.7) measured in the exhaust manifold. unburnt fuel is NECESSARY to the operation of the engine. combusting fuel releases more heat than it absorbs, liquid fuel, however, absorbs heat without detonating, and this AFR is a measure of how much is left. it acts as a heat quencher, therefore if you add too much fuel, you get too much heat quenching and eventually can get to the point where the heat from the reaction is consumed and the reaction stopped. too little and the engine gets too hot and you start to get detonation or you just melt engine components.
#25
12-19-2008, 08:16 AM
RE: Fuel Octane
you speaking on behalf of the gasoline companies is hearsay. you dont know why they advertise "complete burn technology". and mike embodies my point: people think that a "complete" burn is what is ideal and somehow relates to fuel economy. So you made an unsupported claim in the inner quote box, and then used it as your main point to dispute my later statements . If they meant "clean burn" they would have said "clean burn" instead of "complete burn"..
I relate the two because both systems attempt to get the consumer to believe in a fallacy - that a complete burn is what the consumer wants. we have a number of other systems (the electrolysis devices that are showing up on youtube for example are also commenting on "atomization" and "a more complete burn", 'better air/fuel mixing" even though the science behind it doesnt have anything to do with these properties. fancy words to make people believe in the system)
knock DOES increase with rpm.
Did you realize that i had just covered that when you posted your reasoning? Do you have some proof that the TIME is the deciding factor?
because I have never read nor studied gasoline. I am currently working on my bachelor of science in chemistry, which emphasizes thermodynamics and quantum systems. thats why I can speak with some level of authority on this.I have seen no valid counter point. when mike says "i know what I have read" he points to a 76 commercial and some anecdote about bike rallies. that is the learn-ed reasoning we turn to as absolute truth? please..... you dont have to believe me or change your own thoughts, but that doesnt change the fact that your own reasoning is in fact incorrect.
and mike, it may now be appropriate to tell you that other mods have mentioned you in the mod room as being overly sarcastic and generally unhelpful when it comes to the tech sections, choosing to belittle posters rather than aid them. somebody validates their credentials by saying they have focused their undergrad studies on these very principles and you ask him if he wants a pat on the pooper? How exactly do you justify such a comment towards someone who undeniably knows more on the subject than you do? maybe I will modify my previous statement:
I dont read hotrod magazine for my opinions on these things. 4 years of study at a certified institution into chemistry and thermodynamics do wonders for these subjects
. If they meant "clean burn" they would have said "clean burn" instead of "complete burn"..I relate the two because both systems attempt to get the consumer to believe in a fallacy - that a complete burn is what the consumer wants. we have a number of other systems (the electrolysis devices that are showing up on youtube for example are also commenting on "atomization" and "a more complete burn", 'better air/fuel mixing" even though the science behind it doesnt have anything to do with these properties. fancy words to make people believe in the system)
knock DOES increase with rpm.
if it WAS kinetically hindered, you would expect knock to go AWAY with increasing rpm as the "reaction chamber", the cylinder, is left alone to react for shorter periods of time. this isnt the case. detonation increases with rpm due to the increased heat.
I dont believe this is true because there is less time for the detonation to occur it decreases with RPM
I dont believe this is true because there is less time for the detonation to occur it decreases with RPM
That's exactly what I was thinking Mike.
Why is it that reading and studying from a few years ago becomes "knowledge", but reading present info is only considered "research" and supposedly doesn't carry as much weight?
Why is it that reading and studying from a few years ago becomes "knowledge", but reading present info is only considered "research" and supposedly doesn't carry as much weight?
and mike, it may now be appropriate to tell you that other mods have mentioned you in the mod room as being overly sarcastic and generally unhelpful when it comes to the tech sections, choosing to belittle posters rather than aid them. somebody validates their credentials by saying they have focused their undergrad studies on these very principles and you ask him if he wants a pat on the pooper? How exactly do you justify such a comment towards someone who undeniably knows more on the subject than you do? maybe I will modify my previous statement:
I dont read hotrod magazine for my opinions on these things. 4 years of study at a certified institution into chemistry and thermodynamics do wonders for these subjects
#26
12-19-2008, 12:42 PM
RE: Fuel Octane
[sm=admin.gif]
Seriously though, you guys should listen to Spec on this. The difference between reading something and taking it as fact and studying the subject in depth is this: reading makes you take something at face value, you say "ok, this must be how it is." Studying something gives you the tools to be able to analyze what is going on and allows you to further question and analyze problems.
Here's my $0.02 for whatever it's worth (no, I don't have a bachelors in Chemistry, but I do have a strong science background...):
I think we can all agree that the spark plug is what ignites the gasoline. Most people see this as "spark make fire." To be more technical about this, we have to get over the activation energy (that is the energy required to begin the combustion reaction) and the spark is what provides us with this energy. I think we can also all agree that predetonation is the fuel igniting before spark is supplied. If we think logically about this we have to conclude that something is getting us over that activation energy hump. This equates to cylinder temperature. Another point about this, as we increase compression we have a higher tendency to have predet. because we increase the temperature of the cylinder when we compress the air more. This should be enough to say that the heat of the cylinder is what causes predet., thus the reason the LT1 has a reverse cooling system to keep the heads cooler for high compression. If this isn't enough for you let's have a look at spark plugs. We all know that when you have a car that's running rich, when you remove the plug it has a carbon buildup on it due to the cylinder not burning hot enough to burn off all the carbon. When you're running lean the tip of the plug has discoloration, this is due to oxidation because the motor is running hot (i.e. lean). What do you do to get the motor to run at the correct temperature such that you don't have carbon buildup nor a hot condition, you vary the amount of fuel you add. This alone should tell us that the amount of fuel is the main determining factor in how hot a cylinder burns. When you have the perfect oxygen to fuel ratio in a combustion reaction the reaction take place extremely fast (read: instantly) and extremely hot, when there's too much fuel to oxygen the reaction takes place at a similar speed, but it is not a complete reaction and it leaves extra carbon deposits as well as unburnt fuel. This would tell us why a rich condition leaves extra carbon on our plugs and why a more lean condition will result in a hotter cylinder temp. If we truly had a "complete burn" of the gasoline we would be running extremely lean in automotive terms because we would want the hottest possible cylinder temperature. If we only vary the fuel content as well as the fuel octane to stop predet. than this means that a higher octane must have a higher activation energy such that a higher cylinder temperature does not ignite the fuel and that more fuel will bring the cylinder temperature down. If predetonation was dependant on time a motor running at 14000 rpm could have a ridiculously high compression ratio just because of the fact that there is less time involved. It would also be true that a stroker with a low rpm wouldn't be able to have a high compression ratio because it would ping all the time. Most cars are capable of running a higher octane, it just doesn't help fuel economy or power after a certain point, but it for sure isn't because you're not burning all the fuel and you think you should be, it's because you can only advance the timing to a certain point.
Seriously though, you guys should listen to Spec on this. The difference between reading something and taking it as fact and studying the subject in depth is this: reading makes you take something at face value, you say "ok, this must be how it is." Studying something gives you the tools to be able to analyze what is going on and allows you to further question and analyze problems.
Here's my $0.02 for whatever it's worth (no, I don't have a bachelors in Chemistry, but I do have a strong science background...):
I think we can all agree that the spark plug is what ignites the gasoline. Most people see this as "spark make fire." To be more technical about this, we have to get over the activation energy (that is the energy required to begin the combustion reaction) and the spark is what provides us with this energy. I think we can also all agree that predetonation is the fuel igniting before spark is supplied. If we think logically about this we have to conclude that something is getting us over that activation energy hump. This equates to cylinder temperature. Another point about this, as we increase compression we have a higher tendency to have predet. because we increase the temperature of the cylinder when we compress the air more. This should be enough to say that the heat of the cylinder is what causes predet., thus the reason the LT1 has a reverse cooling system to keep the heads cooler for high compression. If this isn't enough for you let's have a look at spark plugs. We all know that when you have a car that's running rich, when you remove the plug it has a carbon buildup on it due to the cylinder not burning hot enough to burn off all the carbon. When you're running lean the tip of the plug has discoloration, this is due to oxidation because the motor is running hot (i.e. lean). What do you do to get the motor to run at the correct temperature such that you don't have carbon buildup nor a hot condition, you vary the amount of fuel you add. This alone should tell us that the amount of fuel is the main determining factor in how hot a cylinder burns. When you have the perfect oxygen to fuel ratio in a combustion reaction the reaction take place extremely fast (read: instantly) and extremely hot, when there's too much fuel to oxygen the reaction takes place at a similar speed, but it is not a complete reaction and it leaves extra carbon deposits as well as unburnt fuel. This would tell us why a rich condition leaves extra carbon on our plugs and why a more lean condition will result in a hotter cylinder temp. If we truly had a "complete burn" of the gasoline we would be running extremely lean in automotive terms because we would want the hottest possible cylinder temperature. If we only vary the fuel content as well as the fuel octane to stop predet. than this means that a higher octane must have a higher activation energy such that a higher cylinder temperature does not ignite the fuel and that more fuel will bring the cylinder temperature down. If predetonation was dependant on time a motor running at 14000 rpm could have a ridiculously high compression ratio just because of the fact that there is less time involved. It would also be true that a stroker with a low rpm wouldn't be able to have a high compression ratio because it would ping all the time. Most cars are capable of running a higher octane, it just doesn't help fuel economy or power after a certain point, but it for sure isn't because you're not burning all the fuel and you think you should be, it's because you can only advance the timing to a certain point.
#27
12-19-2008, 01:13 PM
Join Date: Oct 2007
Location: The 'Burbs of Chicago
Posts: 18,306
RE: Fuel Octane
As long as "pats on the poopers" are being handed out, would you like one too slvr? Shhhh..don't tell Spec I said that!!!
Seriously though, I think kyleag89's "octane knock" problem has really gotten dissected beyond recognition here!
I still don't think that the octane rating of his gas is the true problem. I see it more as using a higher octane is masking the "symptom", not curing the illness. My "guess" is he may have a good amount of carbon buildup on the pistons and heads, affecting his compression and creating hot-spots and pre-detonation.
But back to my earlier point. With a knock sensor equipped engine, the computer should be retarding the timing before an "octane knock" becomes audible.
And to answer Spec's query about what an "old school" octane knock sounds like. Imagine if you dropped some marbles into the spark plug hole and started the engine back up. You would swear that's what you have flying around inside.
Seriously though, I think kyleag89's "octane knock" problem has really gotten dissected beyond recognition here!
I still don't think that the octane rating of his gas is the true problem. I see it more as using a higher octane is masking the "symptom", not curing the illness. My "guess" is he may have a good amount of carbon buildup on the pistons and heads, affecting his compression and creating hot-spots and pre-detonation.
But back to my earlier point. With a knock sensor equipped engine, the computer should be retarding the timing before an "octane knock" becomes audible.
And to answer Spec's query about what an "old school" octane knock sounds like. Imagine if you dropped some marbles into the spark plug hole and started the engine back up. You would swear that's what you have flying around inside.
#28
12-19-2008, 01:29 PM
RE: Fuel Octane
Camaro 69, I'm not asking for handouts, but if you're offering
Well what compression and timing is he running? I agree that just increasing the octane rating of his fuel could be masking the problem (you have to excuse my lack of knowledge on the more "old school" motors, I don't have a massive store of info in my head about them), but I think we're more disagreeing with Mike's statement about running too high of octane is going to cause problems.
Well what compression and timing is he running? I agree that just increasing the octane rating of his fuel could be masking the problem (you have to excuse my lack of knowledge on the more "old school" motors, I don't have a massive store of info in my head about them), but I think we're more disagreeing with Mike's statement about running too high of octane is going to cause problems.
#29
12-19-2008, 02:01 PM
RE: Fuel Octane
Spec you read what you want between the lines but you may not be coming up with what is correct. Pat on the pooper was a joke. Thats why this was there. I once had a problem taking a joke when I was 7 years old.
What I read is not a 76 commercial or a bike ralley. Again you come too the wrong conclusion. What I do read has to do with the subject, not science or chemestry in general, and is written by people who have studied and tested on the very subject. People do studies on things and write on it for others to read.
As for overly sarcastic. I like to joke and make others laugh. We all have a different view and sense of humor. I have been around here long enough to also have seen I am no where near the only one with some sarcasm. But I am sure many will agree I am nothing like the one person that comes around here for a short time once a month or so who is condescending and belittling to others.
I am unhelpful. I get thanks in PM and emails from others. I take the time to walk away from my computer to grab one of my books I read, or study from, to look up answers for posters. But if you wonderful group of mods don't think so that is fine by me.
With the exception of a few....
*
*
*
*
Y
O
U
A
L
L
!
I'll spend my time elsewhere
was there. I once had a problem taking a joke when I was 7 years old. What I read is not a 76 commercial or a bike ralley. Again you come too the wrong conclusion. What I do read has to do with the subject, not science or chemestry in general, and is written by people who have studied and tested on the very subject. People do studies on things and write on it for others to read.
As for overly sarcastic. I like to joke and make others laugh. We all have a different view and sense of humor. I have been around here long enough to also have seen I am no where near the only one with some sarcasm. But I am sure many will agree I am nothing like the one person that comes around here for a short time once a month or so who is condescending and belittling to others.
I am unhelpful. I get thanks in PM and emails from others. I take the time to walk away from my computer to grab one of my books I read, or study from, to look up answers for posters. But if you wonderful group of mods don't think so that is fine by me.
With the exception of a few....
*
*
*
*
Y
O
U
A
L
L
!
I'll spend my time elsewhere
#30
12-19-2008, 02:29 PM
RE: Fuel Octane
Mike, the issue isn't that you're sarcastic sometimes, it comes from the fact that often times you will post a response that is sarcastic and demeaning to others and then you don't follow it up with any helpful info. I would say this happens to all of us on occasion, but I have seen it multiple times and I would be willing to say that we don't have very much interaction, which leads me to believe it happens more times than I have seen. The F-you is great, thanks for that, it really makes you look like a mature, considerate, stand-up guy and really reinforces your point about you being helpful and tolerant. What Spec and I are disputing is the fact that the info you're posting about a "complete burn" appears to come from a fuel company advertisement in order to persuade you to purchase their fuel or product. To state it simply, we're stating that a true complete burn is blatantly not good for your motor. If you have access to post up whatever you got that info from I would love to read it so I can see exactly what it says, until then, I say it's garbage.