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Author Topic: BTU's are 35% less for Ethanol but we are not heating water... Back to Topics
JonnyEnergyE85

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Message Posted: Apr 11, 2012 9:28:07 AM

The minimal difference in mileage is not a matter of BTU. A British Thermal Unit is a measurement of how long it takes a particular fuel to heat one pound of water one degree. It is a heat measurement, and if we were all concerned about only BTU for our engines we would be running them on candle wax, dynamite or any other number of high BTU content fuels. The problems with running candle wax or dynamite should be obvious. Lets say that there are other more important issues with a liquid fuel than just the very simple and blunt BTU, shall we? I see BTU content as more of a red herring, something to bitch about and a chip to use with less than knowledgeable people who dont understand the inner workings of engines and the relationship they have with differing fuels.

If all we wanted to do was heat water, then sure gasoline is better than ethanol. The thing is we want to do work, in an internal combustion engine, that has to suck its air in, squeeze it pretty hard, ignite it, then expel the burned gasses. The fact of the matter is, ethanol does that work more efficiently than does gasoline. Outlaw was being overly generous with gasoline engines and thermal efficiency, they are usually around 20%, and rarely if ever above 25%, because the vast majority of the BTUs in gasoline go to waste heat, that needs to be shed through the radiator to the air, or it will cause all the parts in the engine to expand, break down the oil film protecting the surfaces, and destroy the engine due to friction.

So we want to do work, you know, twist the crankshaft which turns the transmission, which turns the diveshaft and then the wheels. Work, moving something that would be otherwise stationary. Work over time is horsepower, a simple measurement of work is Torque, or twisting force measured in ftlbs or Nm.We want torque, its what moves things. Engines with pistons, connecting rods, and crankshafts all respond similarly to increases in compression and airflow as to how much work they can do. It affects the engines capability because it changes the amount of torque the engine produces. Cam timing can move the torque range around a bit, but it is still based on air and fuel going in, then exploding thus shoving the piston back down the cylinder to move the crankshaft.

Higher compression results in higher torque for a given displacement. Just raising the static compression ratio (SCR) will have an effect on the torque produced even if nothing else in the engine is changed. An engine with an 8:1 scr will produce less torque than a same sized engine with 14:1, quite a bit less actually. Timing also has an effect on the torque output, and preignition and other problems can arise with gasoline that simply arent there with ethanol. To a certain extent advancing the timting from top dead center will increase power, retarding it from TDC will reduce power, generally speaking

(Thanks Thumpin)
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Banjoe
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Message Posted: May 19, 2014 8:51:09 AM

My hat's off to anyone up the challenge of farming. That's a life of dedication and I admire those folks.
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prkuehn
Champion Author Arkansas

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Message Posted: May 15, 2014 12:36:04 AM

I bet you grow corn for a living.
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jrfan6767
All-Star Author Kansas

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Message Posted: May 14, 2014 4:11:58 PM

ok sounds good
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Banjoe
Champion Author Winnipeg

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Message Posted: May 14, 2014 8:27:30 AM

Wonder if they experience any explosions in the hot summer sun?

Maybe popping popcorn could be a source of energy. There's certainly a lot of force in those little kernels.
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SilverStreaker
Champion Author Twin Cities

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Message Posted: May 13, 2014 10:52:57 AM

Banjoe, I've been to the Corn Palace.
I got hungry.
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Banjoe
Champion Author Winnipeg

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Message Posted: May 13, 2014 8:21:04 AM

Why limit ourselves indeed; corn is also for palaces:

http://www.cornpalace.org/Information/corn-palace-history.php
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vaporlock13
Champion Author Pittsburgh

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Message Posted: May 13, 2014 6:51:09 AM

For vehicles driven by individuals,(driving habits have a LARGE effect on MPG) the MPG with no ethanol vs the MPG with 10% or greater ethanol content should be determined through actual miles/fuel consumption. Then the results will tell you what fuel you should be using. I just wish I could find some local gasoline without ethanol to run this test!!!!

[Edited by: vaporlock13 at 5/13/2014 6:53:13 AM EST]
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SoylentGrain
Champion Author Illinois

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Message Posted: May 12, 2014 3:23:14 PM

"Corn is for drink and food. "

Why limit yourself?
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thuathienhue
Champion Author Michigan

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Message Posted: May 12, 2014 2:37:07 PM

Corn is for drink and food.
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Shockjock1961
Champion Author Illinois

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Message Posted: May 12, 2014 2:34:08 PM

What's there to comprehend? You burn a fuel with lower heat content (such as ethanol) in an engine designed and tuned for gasoline and you are going to get worse gas mileage.

You see that clearly with the FFV's...
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SilverStreaker
Champion Author Twin Cities

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Message Posted: May 12, 2014 10:13:19 AM

ZR1S10 says "There's more to it then BTUs"
Exactly. Something Shocky can't comprehend.
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Shockjock1961
Champion Author Illinois

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Message Posted: May 12, 2014 8:44:40 AM

"Begs the question - can diesel fuel be burned in a regular gasoline engine?"

Nope, but you can fill your tank up with it and try if you don't believe it...
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Banjoe
Champion Author Winnipeg

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Message Posted: May 12, 2014 8:04:55 AM

Begs the question - can diesel fuel be burned in a regular gasoline engine?
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ZR1S10
Rookie Author Chicago

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Message Posted: May 12, 2014 4:36:00 AM

The higher MPG in a diesel engine comes from the design of the engine. Having a 18:1 compression ratio or higher, a turbo putting out 30psi of boost and a compression igntion that happens all at once vs. a spark flame front. As well as having no throttle body to reduce pumping losses. Diesel engine also tend to have 30% less displacment then their gasoline rivals. You can't really compare a diesel engine vs a gasoline engine based solely on their fuels. Just like you can't compare gasoline to ethanol without comparing engines made and tuned for each. There's more to it then BTUs.
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Shockjock1961
Champion Author Illinois

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Message Posted: May 11, 2014 6:07:11 PM

"Only in a steam engine."

This coming from an individual who thinks you can use diesel in a gasoline engine...
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SoylentGrain
Champion Author Illinois

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Message Posted: May 11, 2014 5:44:19 PM

"
The higher mileage is directly related to the higher energy content. "

Show us the science, Einstein.
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SilverStreaker
Champion Author Twin Cities

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Message Posted: May 11, 2014 4:47:35 PM

"The higher mileage is directly related to the higher energy content."
Only in a steam engine.
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Shockjock1961
Champion Author Illinois

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Message Posted: May 11, 2014 11:08:28 AM

"If diesel fuel has higher energy content than our local gasoline/ethanol fuel, does high mileage directly relate to higher energy?"

The higher mileage is directly related to the higher energy content.
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Banjoe
Champion Author Winnipeg

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Message Posted: May 11, 2014 8:27:40 AM

My little diesel gives me exceptional mileage compared to our Honda.

If diesel fuel has higher energy content than our local gasoline/ethanol fuel, does high mileage directly relate to higher energy? Or is the difference just because of the engine design?
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SoylentGrain
Champion Author Illinois

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Message Posted: May 11, 2014 8:25:50 AM

"Banjoe asks "Oh wait, maybe energy content is actually why engines run?""

Actually, energy content is not why engines run. It's the expansion of combustion gasses that drive the piston down. The dynamics if this action is reflected in the equation pv=nrt. p=pressure, v=volume, n=moles of combustion product, r=ideal gas constant, t= temperature. There aint no btu per gallon in this equation.

Both fuels produce a similar amount of combustion gas per pound of fuel. Ethanol can and is burned at a higher temperature. How hot each fuel is burned is limited. Neither is burned anywhere close to their full potential. If they were, instead of a relatively slow heating and expansion of gas, you would hear an explosion, commonly referred to as engine knock.

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Shockjock1961
Champion Author Illinois

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Message Posted: May 11, 2014 8:22:33 AM

"Shocklogic at its finest"

No worse then your logic on trying to use diesel in a gasoline engine...
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PrototypeDevil
Champion Author Los Angeles

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Message Posted: May 11, 2014 3:17:42 AM

k
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SilverStreaker
Champion Author Twin Cities

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Message Posted: May 10, 2014 8:28:32 PM

Shocklogic at its finest.
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Shockjock1961
Champion Author Illinois

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Message Posted: May 10, 2014 8:19:12 PM

"Diesel fuel has a much higher energy content than ethanol, but which will give you better mpg in a gasoline engine?"

If diesel will not run correctly in a gasoline engine, why would you expect ethanol to?

Time to get rid of the federal minimum usage mandate and give back the citizenry the right to choose not to use ethanol....
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SilverStreaker
Champion Author Twin Cities

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Message Posted: May 10, 2014 5:08:37 PM

Banjoe asks "Oh wait, maybe energy content is actually why engines run?"
True, but consider how the "energy content" is measured and how that measured value relates to the application you are using it in. Diesel fuel has a much higher energy content than ethanol, but which will give you better mpg in a gasoline engine?
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stickyvalves
Champion Author Iowa

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Message Posted: May 10, 2014 7:24:43 AM

I expect my mileage to improve just because of increased air temperature. Maybe I will achieve a double mileage increase.
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Banjoe
Champion Author Winnipeg

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Message Posted: May 10, 2014 7:20:27 AM

"Winter gas contains more butane and the fuel diluted with ethanol and/or butane typically lowers fuel economy by 1 to 3% due to lower energy content. Gasoline sold in warmer months has a higher energy content which results in better gas mileage,” DeHaan noted.
Read more at http://blog.gasbuddy.com/posts/Summer-gas-is-here-cleaner-air-better-fuel-economy/1715-571412-2435.aspx#F68VRFzDwSrQ1JLP.99

Don't these people understand the theory of heat engines and realize that energy content has no effect on mileage?

Oh wait, maybe energy content is actually why engines run? This is so confusing.
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krzysiek_ck
Champion Author Illinois

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Message Posted: May 1, 2014 9:07:25 AM

BobD2009 wrote: "It's at the expense of the driving public and taxpayers who pay the subsidy."

Please list at least one federal Ethanol subsidy. Maybe you will learn something why searching for it. While at it, how many federal subsidies does Big Oil receive?

[Edited by: krzysiek_ck at 5/1/2014 9:08:27 AM EST]
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WVUtailgater
Champion Author Cleveland

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Message Posted: May 1, 2014 7:49:47 AM

this is good
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Banjoe
Champion Author Winnipeg

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Message Posted: May 1, 2014 7:28:09 AM

All true statements. Ethanol also reduces the demand for oil.

This is a mixed bag of good and bad points - kind of like people. Not you folks, of course. Just the regular people.
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BobD2009
Champion Author Long Island

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Message Posted: May 1, 2014 6:37:58 AM

Face it, ethanol is a government scam to make money for political insiders. It's at the expense of the driving public and taxpayers who pay the subsidy.
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ThunderBird89
Champion Author Columbus

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Message Posted: May 1, 2014 3:03:04 AM

ethanol will produce more power, if tuned properly, but it takes more ethanol volume to make the same power as an equal volume of gasoline.
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cutter1330
Champion Author Oklahoma

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Message Posted: May 1, 2014 12:46:59 AM

Still don't ethanol in my gasoline.
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Banjoe
Champion Author Winnipeg

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Message Posted: Apr 12, 2014 8:17:39 AM

Being classified as somewhat of an Einstein gives me a vague understanding of relativity and the relationship between energy content and available power.

Your question does provide its own answer.

My diesel does produce much more power per unit of fuel than does our gasoline engines. Conversely, burning ethanol mixtures does result in less mileage (you can read that as available work) than more energy dense fuels.

I think you're starting to catch the glimmer of what is really going on when various energy sources are converted to useful work.

Now excuse me while I get back to this string theory I've been working on.
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SilverStreaker
Champion Author Twin Cities

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Message Posted: Apr 11, 2014 10:54:28 AM

Banjoe says "Ethanol has less energy content than gasoline"
If you are talking about the BTU value, consider how that is measured. Diesel fuel has a much higher BTU value than gasoline, but will you get more MPG using it in a gasoline engine compared to gasoline or ethanol?
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SoylentGrain
Champion Author Illinois

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Message Posted: Apr 11, 2014 9:52:24 AM

"More energy in equals more energy out unless there's some serious fractures to thermodynamics going on."

Bingo, Einstein. One of the only things with an ounce of validity you have ever posted on this site. A gasoline engine is highly inefficient. Only a small portion of the heat energy going into the system is converted to work. While ethanol contains less energy per gallon, it does burn more efficiently. So, a higher percentage of it's btu content is transferred to work.

The fact remains, the energy developed by a fuel is more dependent on how much combustion product is produced per pound and the temperature that volume of gaseous material can be heated to. The reality is methane, methanol, ethanol, gasoline, nitromethane all produce a similar amount of hourse power per pound of fuel. It's just that some of these fuels can be delivered at a higher rate than gasoline and, therefore, produce more horsepower.

BTU content per gallon is, for the most part, meaningless.
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Banjoe
Champion Author Winnipeg

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Message Posted: Apr 11, 2014 8:46:57 AM

I'm not sure where this hot air engine keeps coming back from but it certainly has legs. And I do appreciate and respect the enthusiasm to explore and explain the concepts.

Ethanol has less energy content than gasoline and, in spite of the volumetric power society beliefs, that's what provides power for our engines.

To get the same power out requires the same energy in (all things being equal) and the air/fuel mixtures need to be set to allow proper combustion with each fuel.

The thin linkage to hot air engines is valid to the point that hot air is needed. What is being missed is that we are dealing with hot air. That heat comes from the input energy contained in the selected fuel laid on top of the incoming air stream. More energy in equals more energy out unless there's some serious fractures to thermodynamics going on.
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SoylentGrain
Champion Author Illinois

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Message Posted: Apr 11, 2014 8:26:05 AM

"The lower ethanol ratio means more more fuel is needed to burn correctly. You must match the stoichiometric air fuel ratio to burn all the fuel with the available air in the engine cylinder."

Doesn't work that way. The air fuel ratio simply means less air is required to OPTIMALLY burn a pound of fuel. A pound of ethanol and a pound of gasoline produce about the same amount of work. That's because a pound of gasoline and a pound of ethanol produce a similar volume of combustion product.

PV=nrt is the gas law that your engine follows. There aint no BTU per gallon in that equation. While t refers to temperature, btu per gallon has no relationship, in this case. Temperature is controlled by amount of oxygen present and pressure. In your engine, those parameters are controlled by the throttle, timing, and octane of the fuel. All of those affect absolute compression.

Yes, more fuel can be used with ethanol. But, that is by turning the engine faster to generate more horsepower. Both fuels generating the same hp will be consumed at a similar rate, assuming the fuels are burned optimally.
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CrazyComputers
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Message Posted: Apr 1, 2014 11:37:13 PM

The forum doesn't seem to allow for URL's in the post.
I tried to edit the URL's but it didn't work.

sorry about that.

I only got one edit so I posted this note.

Just copy and Google the partial URL to get the whole thing.

[Edited by: CrazyComputers at 4/1/2014 11:38:14 PM EST]
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CrazyComputers
Rookie Author Michigan

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Message Posted: Apr 1, 2014 11:27:37 PM

There is more than the 35% less energy of the ethanol fuel that affects the mileage.

The stoichiometric air fuel ratio also is necessary to see what the fuel usage will be.

The stoichiometric air fuel ratio for gasoline is 14.7:1

The stoichiometric air fuel ratio for ethanol is 9:1

en. /wiki/Stoichiometry (Grab your math books, folks)
www. /machine-design/15235-the-stoichiometric-air-fuel-ratio/

The lower ethanol ratio means more more fuel is needed to burn correctly. You must match the stoichiometric air fuel ratio to burn all the fuel with the available air in the engine cylinder.

Automobile racers use this fact to get a lot of horsepower out. (Think Indy cars.)

By raising the compression ratio to 14:1 and dumping in lots of fuel and the engine just screams. Not good for fuel mileage though.

E85 fuel needs the air fuel percentage changed to do the same thing in the engine. The ECU is programmed to do this when switched for flex fuel, and dumps in more fuel into the engine. You might get more horsepower out, but it will burn more fuel doing it too.

Read this about Indy Car rules, it's interesting.
www. /en/News/2013/02/2-12-Fuel-options-for-teams


[Edited by: CrazyComputers at 4/1/2014 11:32:57 PM EST]
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Chazzer
Champion Author Nevada

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Message Posted: Mar 30, 2014 2:01:33 PM

You've got that right!
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Banjoe
Champion Author Winnipeg

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Message Posted: Feb 15, 2014 8:05:27 AM

Now things are getting interesting again.

Bring on some science about oxygenation so we can all learn something new.
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krzysiek_ck
Champion Author Illinois

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Message Posted: Feb 14, 2014 9:48:57 PM

GrumpyCat wrote: "Thats what oxygenation is/was all about, the richer mixture burns cleaner."

Wrong. Oxygenated fuel will cause the lean mixture not rich. Also, complete burn requires air. Rich mixture lacks the necessary air to fully burn fuel.
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Banjoe
Champion Author Winnipeg

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Message Posted: Feb 14, 2014 6:23:37 PM

Thanks GrumpyCat.
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GrumpyCat
Champion Author Alabama

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Message Posted: Feb 14, 2014 4:09:31 PM

""EPA forces manufacturers to run engines rich for less emissions. Thats what oxygenation with ethanol is all about, fooling the O2 sensor into running richer, which in the early 1980's the EPA found burned cleaner."

That's nonsense."

Its fact. Thats what oxygenation is/was all about, the richer mixture burns cleaner.

All research quoted by EPA to support reformulation and oxygenation used early 1980's vehicles and is still quoted as current fact.

Fact: big American engines suddenly started getting spectacular MPG in the 1990's. Fact: The EPA had a fit when they found software was being used to bypass the O2 sensor during relatively clean periods in the EPA test cycle where the manufacturer tuned for MPG. Manufactures were meeting the specified emissions while bypassing the EPA's editing by reformulating fuels. In early O2 sensor engines the O2 sensor was directly connected to the carburetor or injector. In later generations the O2 sensor was connected to the ECU.
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krzysiek_ck
Champion Author Illinois

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Message Posted: Feb 14, 2014 3:20:14 PM

CiVX wrote: "It would be better to compare net BTU's of the two fuels and cost, performance and maintenance."

Not so fast. Assumptions like this is a reason why OP created this post in the first place.
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nighthawk91
Sophomore Author South Dakota

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Message Posted: Feb 14, 2014 12:28:28 AM

You need to look at things as mile per $. Not miles per gallon.

If it cost less, it cost less. It doesn't make a difference how my BTU's it has.
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CiVX
Champion Author Oakland

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Message Posted: Feb 13, 2014 9:30:43 PM

I don't know why they compare them that way because gasoline is just more energy dense per unit volume. It would be better to compare net BTU's of the two fuels and cost, performance and maintenance.
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SilverStreaker
Champion Author Twin Cities

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Message Posted: Feb 13, 2014 9:52:51 AM

I've used ethanol blends in two non-FFVs and haven't seen any significant change in mileage at any blend. The only substantial difference that I have seen is between summer and winter. I haven't determined if that's because of the different fuels or the outside temperature difference.
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HotRod10
Champion Author Wyoming

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Message Posted: Dec 18, 2013 12:44:09 AM

"SilverStreaker - thanks for the study link. I'm reading that as resulting in lower mileage with ethanol blends right across the board."

That's what I got from it too - significantly lower mileage using E85. That's after they optimized the programming of the ECM for E85, which the vast majority of people would have to pay someone to do; then you'd probably get worse mileage if you went back to E10 than you were before the reprogramming.
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