By raising the compression (increased heat = increased efficiency) you would increase the engines thermodynamic effeciency, but no where near enough to offset the difference in BTU's (a 63% increase in TE would have to occure just to break even with gasoline).

Currently, cast iron, normally aspirated internal combustion engines run at around 20-30% TE (gas & diesel). CI and aluminum engines will never overcome this because of component expantion generated from the higher heat needed to run at the increase efficiency level.

Now if you could build an IC engine out of ceramic, you could run in the neighborhood of 60-80% TE and see a 3 to 4 times an increase in efficiency.
However, the automotive world is an unfriendly one with a wide range of temperatures to operate under. Say you hit a pothole on a cold winters morning with your brittle ceramic engine, it could grenade!

 

Mark, I am going to disagree with your numbers and assumptions here for a minute. I think Rusty has the right idea here with compression ratios. Yes most gasoline engines operate at about 25% termal efficeincy. But the diesels, which you also mentioned, are at 35-40%, thats why diesels get better mileage. Its their high compression that does it, not the fact that diesel has more BTUs per gallon ( which I'll admit it does ).And there is more to it that BTUs- we ain't boiling water on the stove, we are pushing the pistons around. There is also flame speed and temperature to consider, because alcohol burns faster but colder than gasoline, there is more of the effort available to move the pistons, rather than going out the tailpipe as heat. Ethanol also has a latent heat of vaporization about 3 times that of gasoline. Have you ever watched an engine running full throttle on a dyno ? The gasoline engines have the headers glowing cherry red. Alky engines don't even get the pipes to glow dull red. That cherry red is all the excess heat going out into the air, instead doing usefull work moving the pistons. So if we have using the previous numbers 126000 x 25 TE, we get 31500 BTUS of actual work done, in a 9 to 1 gasser. Now lets run our ethanol engine at 86000 fed into it at 13 to compression suppose a TE of 40%- then we have 34400 btus of actual work done. 13 to 1 is very do-able on ethanol, but it isn't going to happen on normal gasoline. So alcohol wins the mileage game, if the engine is set up for alky. If you have a low compression engine set up for gasoline, the gas wins. It is as simple as what the engine is setup to use most effectively. The reasons that we have a petroleum based transportation system have NOTHING to do petro be superior to alky. It isn't. It was all about marketing and squashing the competition, with lots of help from the government ( can you say prohibition ? ). Alcohol fuels and gasoline were tested and compared exhaustively in the late 1800s and early 1900s. Alcohols win every time. Gasoline was foisted upon us by the rockefeller family and the Standard oil trust, with plenty of collusion by GM, and sometimes help ( although unwitting ) from our own government. Currently, the American Petroleum Institute has a near total lock on selling transportation fuels, and they won't give it up without a fight. These are wealthy and powerful people, and they are intersted their own pocket books, not what works best,or is good for our nation, or what might be best for the enviroment, or for you ( remember tetraethyl lead ? ). DF

 

I have to disagree that ethanol burns cold. Ethanol burns hot and dry. Also I question the compression theriories. I have a 1987 Thunderbird Turbo coupe. When I run gas with 10% ethanol I lose 4-6 mpg depending on how hard I drive. The more boost the faster it burns, in that case I should get better mpg because under boost my compression is being increased dramatically. I have been advised by more than one experienced tech not to use ethanol in more than 10% blend due to damage to valves from the higher heat and dry burn.

 

99, ethanol does in fact have a colder burn than gasoline, by a couple of hundred degrees. Ask a chemist or a physicist or combustion engineer. I'll agree with the 'dry' description, however. Most unleaded fuels are 'dry' as far as the valves see things. But the valves can take it. alky could be tough on the valve seats in an older engine with soft seats. Your 87 'bird has hard seats. And i have a theory about why your mileage suffers so much when you run 10% ethanol. Because ethanol has 2/3rds of the btus of gasoline, but there is only 10% of it in there,your only losing 1/3 of 10% of the possible btus. Thats not enough to cause the 4-6 mpg loss. My guess is that the ethanol gives enough extra cooling ( latent heat of vaporization ) and some octane boost, so You have your foot in it more ! Could that be ? DF, @ his Dad's

 

Interesting, I would like to do more research on this topic.

Can any one tell me what the MFG's are doing to the cars that are set up to run E85? Is it just computer mods, though i doubt it? They must be making changes to the engine parts themselves. Why is it that Ford and others say in the owners man. do not run E85 while towing if it burns so cold?

I am all for running E85 if they would price it right. Most cars will lose 6 or more mpg and here in SD the price cut is only $.20 per gal. not near enough to break even.
Still full of questions.
Dan

 

99Dan, the cars that GM, Ford, & Chrysler all sell as new 'FFV's, flexible fuel vehicles, have a reprogrammed computer, a wider than normal band O2 sensor, slightly bigger injectors, and more stainless fuel lines. There is also a sesor in the fuel tank that measures specific gravity of the fuel, and the computer adjusts the injector spray accordingly- ethanol is heavier than staight gasoline. Why they would not recommend towing with ethanol I don't know, but I will try and ask around. I would have thought ethanol would THE recommended tow fuel. The higher ( 3 x that of gasoline ) latent heat of vaporization would prevent knocking very well, I would think. The Mother Earth News set up a ford pickup to run ethanol in the early 80s ( '81 300 6 cyl ). They raised compression quite a bit and were able to get 16% better mileage towing on ethanol than unmodified on gas. They pulled their still around on a trailer, and the ATF followed tham around. Honestly, the fact that ethanol is also dinking liquor has been its biggest problem. The MEN's truck did get 12% less MPG empty, however. I don't know if that is an ethanol trait in general, or if MEN weren't very good mechanics. I am looking for some old reprints of their articles. I think the FFVs are setup with a gasoline friendly compression, but I believe higher compression, and 15% or less gasoline is the way to go. DF

 

http://www.ethanol.org/pdfs/e30_report.pdf take a look at the linked file, it is a study done in MN at the University of Mankato. Not very conclusive with the exception that you lose fuel economy up to 15% going from E10 to E30. They also point out that most of the tested cars took over 100 miles for the computer to adjust to the higher blend.
I cannot find any reason why they don't skip the E85 and go 100% ethanol.
Dan

 

99Dan, I'll see if I can read that report after supper ( venison stew ). I think there are a couple of reasons for the 15% gasoline. 1st, it makes the stuff undrinkable. Oh, I suppose you could drink it, then get very drunk, then die. The 15% petro is enough to discourage that. Also ethanol is tougher to vaporize when it is cold outside. Winter starting is easier with some esay evaporating petro in the mix. 3rd, how do you get the petro monopoly to let you sell it at their stations ? Even an idependantly owned station would feel some pressure from petro suppliers to not sell ethanol, I would imagine. Keeping 15% petro in the mix lets the oil trust make a few pennies, and so maybe they will tolerate ethanol sales. DF

 

Lots of good information in here (along with a few road apples). A couple of minor points:

1. Those who cite the stoichiometric ratios of fuels as the primary determinant of fuel economy are correct. Lost in this, though, is that a higher stoichiometric ratio means more fuel in the cylinder, which can mean much more power under the right circumstances. I don't know if they still do, but dragsters used to run a methanol mix for just this reason...their injectors must have looked like lawn sprinklers.

2. Probably the biggest reason that E85 isn't E90 or E100 is that ethanol becomes a little "funny" above 85% purity. It tends to exhibit a high affinity for water, manifested by sucking moisture out of the air, which brings it back toward 85% or so.

3. There's a list of factory-ready FFVs here:

http://www.e85fuel.com/information/ford.htm

It's (sadly) hard to imagine E85 gaining widespread acceptance any time soon. One non-trivial drawback is that stoichiometric ratio discussed above...it makes E85 a lot more expensive to distribute per BTU than is gasoline. Factor in the lower heat content (meaning you need more for the same mileage), meaning that it would have to sell for about 60% of the price of gas on a volume basis, and it just doesn't look too viable. For right now. I look forward to technology marching on and making this situation a little more viable.

 

Mzimmers, how, exactly, does ethanol get 'funny' above 85% purity ? Yes, alcohol is hydroscopic, but the problem is not so bad that it prevents usage above 85%. And the thinking that because of the lower heat content you need more of it is simply not correct. Yes, alcohol is far more efficient on a btu per mile basis. But if the compression ratio is increased to an ethanol friendly 12 to 1 or more, ethanol can also compete with gasoline on a miles per gallon basis. The idea that you need more of it is an oil industry myth. The technology for ethanol was figured out over 100 years ago. There are no tech issues to tackle anymore, it is simply a matter of marketing. With a barrel of oil going for $51.15 ( feb22 05, 1800hrs ), I think we will see a bunch of ethanol marketing emerging, sooner rather than later. DF

 

Which is pretty much consistent with what I was saying. The question that was asked was why the fuelmakers stopped at E85, instead of going for E100. The answer was (partly) due to the reasons I mentioned.

In the first place, upping the compression will NOT overcome the lower BTU content entirely, or even mostly. Secondly, upping the compression of an engine is a pretty big undertaking...you'll have to do a lot of driving before you break even on the engine rebuild investment. Finally, a rebuilt engine is going to be able to accept gas from a much smaller number of stations.

No it isn't. It's a matter of determining how much power you want from your engine. The lower BTU content may be overcome by the higher stoichiometric ratio, but...that's going to give you an engine goes through fuel MUCH faster than it did in gas form...unless you dramatically decrease the displacement (another non-trivial modification that renders the vehicle unsuitable for regular gas).

Converting a gas engine to E85 is pretty simple, IF you're willing to accept the engine as is when you're done. Unfortunately, you might find yourself with an overpowered engine (admittedly a problem many of us would like to have) with a considerably shortened cruising range. If this is OK, then you're in good shape. But don't think that you're going to magically have some new technology with no significant downsides.

I'd like to believe that's true, but I think it's going to be a long time before E85 enjoys any popularity outside of corn country. And to make a big difference in US fuel prices, it's going to have to catch on in the big markets like CA, where the lack of raw resources for production, and the higher cost of distribution, is going to keep E85 pretty pricey, for awhile at least.

DF

 

Zimmers, buddy, where are you getting so much mis-information ? Any technical problems running alcohol really have been figured out long ago. 1st, fuelmakers stopped at 85% to make it impossible, or at least nearly so, to separate the ethanol from the gasoline. There are still many people who are afraid of folks trying to drink it. The 15% gasoline in the mix makes that very unlikely, with the added benefit of easier starting in sub zero weather. Is 100% ethanol a usable fuel, sure it is. In Brazil, they have been driving around on E100 since the early 1930s. 2ndly, yes upping the compression IS more than enough. It is the high compression that makes diesels so efficient. Normal gasoline gets really unhappy when you try more than 9 to 1, but ethanol ( and E85 ) can do 12 to 1 without trouble. Which brings us to range-3rd. The higher compression helps a bunch, and because alky burns differantly than gasoline ( faster flame speed ) the thermal efficiency is better. Much better. 'Gasoline only' engines struggle to get above 25% TE. Dedicated ethanol engines have no trouble hitting 40% TE. Fourty percent of the 2/3rds BTU content is going to be over what the 25% of the original was. 4th overpowered !?! There is no such thing as overpowered. Yes, alcohol will make more power usually something like 15%. While I can't imagine this being a problem, there is no reason you have to have your foot on the firewall all of the time. I haven't noticed any downsides yet.....but you did mention exspense. I'll give you that one, and the bit about you'll have far fewer filling staions to choose from. Hers how I see it- I have more than 1 truck, lots of us hear on the board do. If you are going to rebuild anyway, building for 12 to 1 is not much more exspensive than 9 to 1, if at all. Because of the lack of ethanol filling stations, I bought a 150 gallon tank and mounted it sideways in the bed of the truck. I have another 150 tank on a cradle- so I can fill up with E85 150gallons at a time, drive home and drain it into the tank on the cradle. Then I always have some, but don't have to carry 150 gallons around in the bed everyday. One of my trucks is ready for a rebuild now, and the other can stay gasoline only. Should ethanol beome more popular like I think it will, I'll be ready. I really do think it is just a matter of marketing. Our own government ( not that I beleive or trust them currently ) tested alcohol as a fuel in 1906-1908. I'm hoping that they were less corrupt and dishonest then, but anyway, the USDA tested alky in farm machinery, the navy tested it in submarines, there were 100s of tests. If the engines were built with the proper compression for the fuel used, fuel usage ( what we would call MPG) was the same. But gasoline isn't the same now as 100 yrs ago, one might say. And they would be right. From '97 through 2003 the ethanol producers have run an 'ethanol challenge'. Several colleges have participated. Those who won the competition were always able to get more MPG on ethanol than the unmodified engine on gasoline. The goal was to create an automobile that the customer would not notice any differance in. I believe the challenges are no longer run because it is considered all figured out, there are no more tech issues to be solved. It really is just a maketing issue now. That, and lots of propaganda and lies coming out of the American Petroleum Institute. The APIs members are making profits beyond obsenity, and they won't give up without a heck of a fight. But thats okay, some of us like to fight. DinosaurFan

 

1. I didn't say 100% ethanol was unusable; I said that it was very difficult to keep alcohol that pure. Above about 85% its affinity for water will draw moisture from the atmosphere. If you disbelieve this, find some E100 and let it stand in a beaker overnight. Weigh it before and after. You'll be surprised at what you see. I don't know about Brazil, but that's a weird place anyway...don't their toilets run backwards? Anyway, this isn't a point worth debating further IMO.

2. WRT compression ratio: the law of diminishing returns kicks in around 9:1. Going to 12:1 does help (if you have the rest of the engine tuned for it), but much less so than going from 6:0 to 9:0 did. Diesels derive improved efficiency from MUCH higher compression ratios (I think around 20:1 or so). I've yet to hear someone claim that they *gained* gas mileage by going to a higher compression engine and switching to E85. I'd find such a claim to be highly dubious, too.

3. I don't disagree that "it is just a matter of marketing" but you say it like it's a minor thing. Marketing is the name of the game in this economy. And part of marketing is distribution. That's a big reason why I don't see it coming to CA anytime soon; it's too expensive to transport for the reasons I gave above.

Believe me, I'd love to be wrong about this...I'm no fan of paying the oil companies what I have to. But, conspiracy rumors aside, if E85 were truly that viable nationwide, someone would be bringing it to us.

 

100% Alcohol would be much safer in an accident. Not explosive like gasoline.

 

DinosaurFan: do you have copies of any of the studies you mentio? If so I would like to read them.

Mzimmers: Distribution is E85's biggest problem right now. It has to be trucked and that is very expensive, if they were to put it in the existing pipelines it would eat up all the gunk in the pipes. That would contaminate the fuel and could cause the pipeline to leak.