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Starbucket
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Joined: April 30, 2007
Posts: 4025
Location: WA
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 Posted: Sun Jan 23, 2022 4:11 pm Post subject: Re: Octane question |
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| viiking wrote: |
Sorry there is so much misinformation here.
The facts:
1. The original measure of octane rating the Raw Octane Number or RON is the proportion of octane versus heptane in a fuel. Octane is an eight carbon molecule straight chain hydrocarbon. Heptane only has 7 carbon atoms. Other straight chain similar molecules include propane (3 carbons) and butane (4 carbons). As a generalisation the more carbon atoms in the straight chain the more bang in the engine. Indeed many cars in the world run and continue to run successfully on propane or butane with limited engine modification!
So the RON was determined by running a "standardised" engine of known capacity, temperature and compression ratio. The engine was started at 100% octane, and heptane (a lower powerful fuel) was slowly added. When the engine started to "ping" under load conditions the proportion of octane to heptane was measured. Let's say this was a generally normal fuel of say 87 Octane i.e. 87% Octane and 13% Heptane.
This measure gave the Octane rating and fuels which contained all sorts of other additives were given an octane rating based on a comparison to the octane/heptane ratio in the standardised engine.
2. Ethanol is NOT a straight chain molecule like octane. It is NOT less energy dense. It has an octane rating of 113. Any proportion of ethanol added will increase the octane rating and hence the potential performance of the engine. The reason that ethanol is used in fuel is that there are only 2 carbon atoms in ethanol for a fuel with higher performance than standard fuel hence there are only 2 carbon dioxide molecules produced in the exhaust (read climate change) versus normal fuels which contain many more carbon atoms.
Yes ethanol does serve a purpose. It reduces pollution. Oil based fuels are an exhaustable resource. Ethanol is not. There is an incentive for the big oil companies to continue to push their product.
Another chemical that some people have heard of is methanol used in drag cars. These produce a lot of energy as well. Methanol is identical to ethanol except it only has ONE carbon atom.
3, Yes ethanol is HYGROSCOPIC not hydroscopic. It is like brake fluid. Only in the worst case and over extended period of times will free water exist. In fact in the "old days" a bottle of denatured alcohol (ethanol) was added into a fuel tank if there was any thought of water being in the tank. The ethanol would absorb the water and burn through over the tankful of gas.
4. Ethanol fuels can degrade some rubber parts. We are dealing with cars that are over 50 years old. Technology has moved on from there. Move to modern rubber parts.
5. Ethanol based fuels are not "thicker" than normal fuel. The viscosity difference is so insignificant that it is unlikely that there is any real difference in how they pull through the jets. Temperature and atmospheric pressure has a much larger impact.
6. Fuels are different from different suppliers.
Fuels are different in different parts of the country.
Fuels used in cold winter climates are blended to make starting easier.
Fuels used in hot climates are purposely made "heavier" to prevent vapor locking.
Storing fuels from one season to the next is problematic as the mixture may be different which actually exacerbates the problem.
Fuels contain all sorts of garbage in them so long as they can meet the specifications, specific gravity and octane rating. The more crap and unsaleable byproducts that a producer can add into their fuel, the more there profit level goes up.
7. Fuel properties change with altitude and temperature. Tuning at one elevation or temperature will affect the performance if the cars are used in another environment. Fuel injected cars take all of this into account but not our 90 year old carburettor technology.
8. A car can be made to run successfully on any sort of fuel (within reason). 100% ethanol cars are available. Cars used to run on town gas during WW2 in countries that had little spare fuel. Cars currently run on LPG and NG. The problem is that the average VW owner does not have the skills to make them do so.
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mukluk
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Joined: October 18, 2012
Posts: 7028
Location: Clyde, TX
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| Posted: Sun Jan 23, 2022 5:04 pm Post subject: Re: Octane question |
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| viiking wrote: |
...
2. Ethanol is NOT a straight chain molecule like octane. It is NOT less energy dense. It has an octane rating of 113. Any proportion of ethanol added will increase the octane rating and hence the potential performance of the engine. The reason that ethanol is used in fuel is that there are only 2 carbon atoms in ethanol for a fuel with higher performance than standard fuel hence there are only 2 carbon dioxide molecules produced in the exhaust (read climate change) versus normal fuels which contain many more carbon atoms.
Yes ethanol does serve a purpose. It reduces pollution. Oil based fuels are an exhaustable resource. Ethanol is not. There is an incentive for the big oil companies to continue to push their product.
Another chemical that some people have heard of is methanol used in drag cars. These produce a lot of energy as well. Methanol is identical to ethanol except it only has ONE carbon atom.
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Gasoline with ethanol (E10) has roughly the same energy as ethanol-free gasoline (97-100%, depending on formulation), but ethanol by itself (E100) contains only about two thirds the amount of energy by volume. Methanol actually has only half the engergy per gallon versus gasoline. (Dept of Energy source here)
To clarify the higher power potential from using ethanol statement for those that may not understand, ethanol's higher octane rating means that it will resist preignition better than gasoline, thus more ignition advance and/or higher compression can be used without negative effect. If one doesn't build an engine with higher compression or spend the time required to tune it to take advantage of the higher octane, then there is no performance advantage. This is also only applicable when discussing the use of fuel with a much higher than normal ethanol content such as E85. The mere presence of ethanol in a fuel doesn't mean there is a higher power potential available, it is solely due to the higher octane rating of the fuel overall that makes this possible -- an 87 octane E10 ethanol blend fuel will experience preignition just as readily as an 87 octane ethanol free fuel if that octane rating is too low for the compression ratio or state of tune required on a particular engine.
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viiking
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Location: Sydney Australia
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| Posted: Sun Jan 23, 2022 5:58 pm Post subject: Re: Octane question |
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Mukluk, you are absolutely right!
Octane of 87, being straight gasoline or blended with ethanol or added biofuels or adding aromatic products, vodka, or any other combination will give the same physical effects e.g. power and as you say pre-ignition propensity for the same octane rating.
Too many people just jump to the conclusion that there is a problem with using ethanol based fuels where the real reason may be something else.
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Q-Dog
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Location: Sunset, Louisiana
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| Posted: Sun Jan 23, 2022 6:22 pm Post subject: Re: Octane question |
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I miss the days of water in my gas!
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No I don't. Before we got ethanol added to our gas it was common for us in humid south louisiana to have to regularly drain water out of fuel tanks. Or add a bottle of alcohol to the tank to absorb the water. I haven't had to do that in over 30 years.
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adventurebob
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Joined: August 06, 2020
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Location: Colorado
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| Posted: Sun Jan 23, 2022 7:35 pm Post subject: Re: Octane question |
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| Why would you add alcohol to gas with alcohol in it? Alcohol, whether that’s methyl or ethyl, are hydrophilic meaning the bond to water. If you had so much water in your gas that it was coming out of phase, that’s a whole different problem. |
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mukluk
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Location: Clyde, TX
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| Posted: Sun Jan 23, 2022 8:14 pm Post subject: Re: Octane question |
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I used to dislike ethanol blended fuel until I had no choice but to use it due to non-ethanol being completely unavailable for over a decade where I live. Now I like it, or at least tolerate it rather well. 
I believe older blends had problems back in the day, but the current stuff has proven to me that it's perfectly fine for use now. Despite ethanol free quite recently once again becoming available from one station in the next town over, I still use common E10 in all of my vehicles and lawn mowers -- the Bug likes it, hell, my sixteen year old mower runs it like a champ year after year even though I don't drain it all out or flush the system before winter storage. My experience has been that the fuel system seems to stay cleaner and I don't see much of any rust forming in gas tanks or fuel cans. An added bonus is I haven't had to buy a bottle of HEET in years -- I used to buy that stuff by the case in North Dakota and Ohio.
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Q-Dog
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Location: Sunset, Louisiana
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| Posted: Mon Jan 24, 2022 7:09 am Post subject: Re: Octane question |
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| adventurebob wrote: |
| Why would you add alcohol to gas with alcohol in it? Alcohol, whether that’s methyl or ethyl, are hydrophilic meaning the bond to water. If you had so much water in your gas that it was coming out of phase, that’s a whole different problem. |
Go back and read it again. "Before we got ethanol added to gasoline ..."
Gas and water don't blend, but alcohol and water do. Easier to add alcohol than to drain gas tanks.
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Igpoe
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| Posted: Mon Jan 24, 2022 7:37 am Post subject: Re: Octane question |
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I googled the processes for making ethanol only to discover that ethanol is the same alcohol type used in our beer and liquor! Also the production of ethanol only helps the producer of the biomass, (corn).
[Quote]Although biofuels are in theory carbon neutral, this does not take into account the carbon dioxide emissions associated with growing, harvesting and transporting the crops, or producing the ethanol from them. Therefore, overall, more carbon dioxide is emitted than is absorbed, which means that it contributes to global warming.
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Maddel
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Joined: February 12, 2013
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| Posted: Mon Jan 24, 2022 8:03 am Post subject: Re: Octane question |
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May be off topic...
https://en.wikipedia.org/wiki/Volkswagen_Bras%C3%ADlia
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Volkswagen Brasília
At its debut, the Brasília had a flat-four-cylinder, air-cooled boxer engine with single carburetor.
The rear-engine, rear-wheel drive had a gearbox with four speeds.
In the 1980s, Volkswagen also offered an ethanol-powered engine option, with 1300 cc and 49 hp. |
Back in the day over here in Germany we loved these ethanol cylinder heads.
Perfect for beefing up our gasoline engines. |
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Zundfolge1432 
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Joined: June 13, 2004
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| Posted: Mon Jan 24, 2022 8:53 am Post subject: Re: Octane question |
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| How are they different? |
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sb001
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Posts: 10406
Location: NW Arkansas
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| Posted: Mon Jan 24, 2022 9:31 am Post subject: Re: Octane question |
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| Zundfolge1432 wrote: |
| How are they different? |
They're made of corn. So when you put the wrong gas in and your engine blows and leaves you stranded in the middle of nowhere, you can eat them and drink the ethanol in your fuel lines to survive.
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Maddel
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| Posted: Mon Jan 24, 2022 11:55 am Post subject: Re: Octane question |
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| Zundfolge1432 wrote: |
| How are they different? |
IIRC compression ratio 11:1 and valve seats suitable for unleaded fuel
Not sure about the valve size... I think the exhaust valve was larger.
'84 1.6 Fusca. |
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beanlover
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Posts: 370
Location: PA
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| Posted: Mon Jan 24, 2022 12:03 pm Post subject: Re: Octane question |
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| viiking wrote: |
| Sorry there is so much misinformation here. |
Thanks viiking!!  great information! |
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Multi69s
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Posts: 5364
Location: Lefty, CA
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| Posted: Mon Jan 24, 2022 12:41 pm Post subject: Re: Octane question |
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As far as Ethanol and its issues. I have seen the worst problems in my dirt bikes. I have been riding dirt bikes for over 20 years, so before the ethanol in the fuel. For my family, I have 5 dirt bikes, with owning some of them longer then we have had ethanol in the fuel. The problem that ethanol had affected on each bike is the fuel petcock (shutoff). Even with fuel stabilizer in the tank, the rubber seals on each bike would deteriorate in a couple of years, forcing either a rebuild or replacement. I finally stopped this from happening by making my own seals out of Viton.
So from my experience, ethanol will attack the rubber component in a fuel system, if it is allowed to sit in it, even with fuel stabilizer. However, I have not had a problem in vehicles that have been regularly used.
You really shouldn't store fuel for a long period in a vented fuel system (gas tank) anyway. The aromatic hydrocarbons start to evaporate off when you approach one month of storage. This will change the structure of the gas in a bad way.
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viiking
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Posts: 2668
Location: Sydney Australia
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| Posted: Mon Jan 24, 2022 1:33 pm Post subject: Re: Octane question |
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[quote="Igpoe"]I googled the processes for making ethanol only to discover that ethanol is the same alcohol type used in our beer and liquor! Also the production of ethanol only helps the producer of the biomass, (corn).
| Quote: |
| Although biofuels are in theory carbon neutral, this does not take into account the carbon dioxide emissions associated with growing, harvesting and transporting the crops, or producing the ethanol from them. Therefore, overall, more carbon dioxide is emitted than is absorbed, which means that it contributes to global warming. |
There is no doubt that ethanol production is also energy intensive and people do not take into consideration the whole energy balance of fuel production. However ethanol IS less polluting where it is used and IS renewable. It’s the same story with electric cars. There are huge environmental costs in mining Lithium for the batteries so whilst non polluting at the tailpipe there is an efficiency cost at the electricity generation plant where in the case of coal fired plants the electrical efficiency is only about 30% meaning pollution at the plant not in the suburbs.
Hydrogen fuelled cars are also a potential problem. Some hydrogen is being made from “water gas shift” reaction by reacting natural gas from non renewable sources again with no tailpipe pollution but energy and environmental consequences at the plants.
But the real TRAGEDY is this!
Brazil as you know runs cars on mostly ethanol. It comes from renewable resources through agricultural fermentation of crops. That’s great for the environment isn’t it?
Humour me (no pun intended) and go to Google Earth. Go and look at the Amazon basin from a distance. Slowly zoom in.
Do you see some parallel and perpendicular zebra like stripes? Zoom in closer.
What you see is tens of thousands of tracts of Amazon bush and rainforest being systematically bulldozed to produce pasture for animals and to grow more crops to make food and probably ethanol.
We all need to educate ourselves in the real costs of doing things and not just look at the superficial cost or what is reported as being good for you!
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1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
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Floating VW
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| Posted: Mon Jan 24, 2022 4:28 pm Post subject: Re: Octane question |
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| viiking wrote: |
Sorry there is so much misinformation here.
The facts. . . |
Sorry man, most of what you said was spot on, but I'm going to have to disagree with some of your "facts".
Ethanol is very much so less energy dense than gasoline, by just over half, in fact. (27 MJ/kg for ethanol vs 46 MJ/kg for gasoline).
Ethanol is also twice as viscous as gasoline (0.12 Pascal seconds for ethanol vs 0.06 Pascal seconds for gasoline).
I'm not sure why you said that these things are not true.
Adding ethanol to the gasoline used in an engine that was designed to run on pure gasoline WILL cause a decrease in performance, unless, as mentioned above, changes in timing, jetting and compression are made to compensate for the ethanol.
Will adding 10% ethanol to the gasoline have a noticeable effect on engine performance? Maybe, maybe not. I would say it depends on the state of tune of the engine. But certainly, the higher the percentage of ethanol, the more you're going to notice it (unless, of course, you make the necessary changes to the engine).
Also, while using alcohol as fuel does, in fact, produce less of certain types of pollution, it is not really 100% accurate to say that burning alcohol "reduces pollution". What you said about Brasil is a good example of what some might call "pollution". You're absolutely right about that, by the way. I lived in Brasil for about 15 years. They are bulldozing the Amazon at a truly alarming rate! They sell a lot of "flex fuel" cars down there, but most people I knew bought the gasoline only ones. They're cheaper.
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nbvolks
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Posts: 344
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| Posted: Mon Jan 24, 2022 7:05 pm Post subject: Re: Octane question |
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| Floating VW wrote: |
Adding ethanol to the gasoline used in an engine that was designed to run on pure gasoline WILL cause a decrease in performance, unless, as mentioned above, changes in timing, jetting and compression are made to compensate for the ethanol.
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Only if the fuel has a significantly different octane rating. All other things being equal, if it's just a matter of being E10, but an octane rating of 91AKI, then that's the same as pure gas at 91AKI.
It's like trying to say that 1 gallon of E10 is somehow not quite the same as a gallon of pure gas. |
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viiking
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Location: Sydney Australia
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| Posted: Tue Jan 25, 2022 4:45 am Post subject: Re: Octane question |
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| Floating VW wrote: |
| viiking wrote: |
Sorry there is so much misinformation here.
The facts. . . |
Sorry man, most of what you said was spot on, but I'm going to have to disagree with some of your "facts".
Ethanol is very much so less energy dense than gasoline, by just over half, in fact. (27 MJ/kg for ethanol vs 46 MJ/kg for gasoline).
Ethanol is also twice as viscous as gasoline (0.12 Pascal seconds for ethanol vs 0.06 Pascal seconds for gasoline).
I'm not sure why you said that these things are not true.
Adding ethanol to the gasoline used in an engine that was designed to run on pure gasoline WILL cause a decrease in performance, unless, as mentioned above, changes in timing, jetting and compression are made to compensate for the ethanol.
Will adding 10% ethanol to the gasoline have a noticeable effect on engine performance? Maybe, maybe not. I would say it depends on the state of tune of the engine. But certainly, the higher the percentage of ethanol, the more you're going to notice it (unless, of course, you make the necessary changes to the engine).
Also, while using alcohol as fuel does, in fact, produce less of certain types of pollution, it is not really 100% accurate to say that burning alcohol "reduces pollution". What you said about Brasil is a good example of what some might call "pollution". You're absolutely right about that, by the way. I lived in Brasil for about 15 years. They are bulldozing the Amazon at a truly alarming rate! They sell a lot of "flex fuel" cars down there, but most people I knew bought the gasoline only ones. They're cheaper. |
I don’t want to get into a pissing contest about “facts”! My comments were to attempt to debunk some of the hysteria surrounding ethanol containing fuels.
The viscosity of water is approx 1mPas. When we talk about the difference between 0.06 and 0.12 mPas it is so insignificant in the scheme of things. Hence my comment.
You cannot just take energy density in layman’s terms as being the energy output of certain fuels. There are other considerations other than just the heat of combustion but also the latent heat and specific heat.
The other thing to consider is that mixtures do not always behave as an average of the two main raw materials I.e. fuel and ethanol.
A recent study of E85 showed a 20% increase in power for a Koenigsegg sports car (one of the most powerful production cars in the world) when running on E85 compared to gasoline. How can this be when people claim that ethanol reduces the performance of their vehicle.
I agree to disagree. People should do some research from reputable sources and not rely on urban myths and hyperbole spread by oil companies who seek to maximise their profits by selling as much fossil fuel as possible.
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Jimbug57
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| Posted: Tue Jan 25, 2022 6:15 am Post subject: Re: Octane question |
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Interesting and informative viewpoints. Seeing as how I have zero real knowledge of the subject, I tend to agree with those who support my opinions.
Having said that, when it comes to fuel I am faced with a "reality of choices". I don't manufacture fuel, I have to choose from what's available to me. To choose ethanol free fuel I have to drive 30 miles round trip in cross town traffic. That doesn't work for me. Hmmm so many brands... I use the 2 that are closest to me, Mobile and Marathon. Oh, three octanes. I choose premium. I like the way it runs. I could care less if it costs more. I also choose to add Sta-Bil 360 to every tank. I believe it helps mitigate rust in the tank, and keeps my carb clean if nothing else. It's cheap insurance, and makes me feel good. So why not?
I did, however, purchase some 1/4" Gates fuel hose. I'm going to have the tank out to replace my U-joint shaft and I'll replace all the cloth braid fuel lines with the modern stuff then. Hopefully 1/4" works.
I don't think being more knowledgeable about fuel chemistry expands my choices, but knowing the overall effect my choices have on the environment has changed my viewpoint. In the future we'll probably have to buy synthetic fuel in 1 gallon cans at Walmart for 10 bucks a gallon.
I am now more focused on how my choices effect the planet.
Just my 2 cents.
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Igpoe
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Location: South Boston, VA
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| Posted: Tue Jan 25, 2022 8:58 am Post subject: Re: Octane question |
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Coal-fired generating plants have smokestacks between 200 and 300 ft. tall. They only pollute within a few miles when the wind at the height of the stack is ZERO. The ash left over from burning this coal is mostly landfilled in close proximity to the generating plant. It contains many "trace" elements that are lethal if found in large quantities, say twenty pounds per million. The average plant would take two days to bury that much ash. The trace elements leach into the soil and then into the underground aquifers and my source of drinking water.
NOT TO MENTION THE TONS OF SULPHUR DIOXIDE GOING OUT THE SMOKESTACK EACH WEEK! As I said it's only widely dispersed if the wind blows.
I live within an hour's drive of 4 such plants. People need electricity, yes. None of these four plants serve the people of Virginia or North Carolina. The owners, (Duke Energy) sell the Gigawatts in New Jersey, New York, Boston,etc. How do I know these things? I hauled the usable, processed, high carbon ash to concrete plants for filler for 22 years. Try as they might, they cannot hide the truth. Their own hazmat papers disclose it to the carefull reader. Cancer is "prolific" in this region
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