It is not, but the discussion is not about running 85% ethanol in a corvette, it is about running regular 94 octane gasoline that has a certain percentage of Ethanol, MUCH LOWER than 85%, added to it.
85% ethanol would be well over 100 octane.

 

So according to you every vehicle sold is a FlexFuel vehicle, even if it's not labeled so. I can't believe the Big 3 missed that advertising opportunity

E85 vehicles have a completely different fuel supply system than non-E85 vehicles. They also have a PCM algorithm to detect a E85 refueling event and adjust the fuel trims accordingly. Using E85 in a non-E85 vehicle will throw the fuel trims way off. Maybe not enough to set a DTC though.

 

 

Please re-read my post. I was very specific:

"The only fuels you will EVER find in a gas station that will not run your Corvette, or any other gasoline only car for that matter, are diesel and ethanol."

E85 = Ethanol.

E85 is NOT oxygenated gasoline, which is what the original poster was asking about.

Trust me, I understand what is involved in running a car on ethanol very well. Where I am from (Brazil), over 50% of all vehicles sold run on pure (100%) ethanol, and a good portion of the remainder are dual fuel.
You might find it interesting that the same vehicle with the same motor available in either Gasoline or Ethanol burning trim will make more power in Ethanol. A crappy Golf 1.0L will make 48hp on gas, but will make 56hp on ethanol. They are both fantastically slow though

 

only if tuned for it.

the ethanol engine requires more compression (which would detonate the gasoline engine to pieces), modified fuel trims, timing, etc. etc. ...

a gasoline engine that has not been tuned for ethanol (E100) will produce more power using gasoline than it will with ethanol.

ethanol is a very close cousin to alcohol, pouring a bottle of jack into the tank ain't gonna give you more power.

 

Trying to run 100% ethanol in a passenger car which has to be started in any climate where temperatures are below 50F or so is a losing proposition. Ask anyone who has alcohol (ethanol or methanol) fueled race car about starting when the weather is cold. Most use some kind of gasoline primer to get started and even then they preheat both the oil and the water (if the engine is using a cooling system).

Some think ethanol would be wonderful because of it's higher octane rating. Those thinking that should look into how octane rating is measured to see why the numbers come up higher. If octane rating is what you are after use methanol which is what racers who aren't sponsored by the ethanol lobby use. The same physical property, latent heat of vaporization, which gives rise to a higher octane rating of ethanol over gasoline, is higher for methanol than for ethanol which is why racers having a choice choose methanol. The hype given to running ethanol in the Indy Car racing series doesn't mention the reason they switched is the ethanol lobby paid them to do so.

With respect to using a much higher compression ratio with ethanol to get back some of the energy losses of ethanol vs gasoline, this is not a cost free design change. High compression engines in the region you need to run to make the gains are hard to crank and hard to start. This results in having to carry along a bigger starter and bigger battery.

 

You may be surprized with how the times have changed. Ethanol has come a LONG ways from the days of carburatted cars that refuse to start. As I mentioned before, over 50% of the motor fleet in Brazil runs on 100% ethanol. These are cars that will start in any weather and make more horsepower than their gasoline counterparts. The disadvantage of course is that given the lower energy density of Ethanol they will attain a lower fuel mileage. This is well offset by the much lower price of Ethanol, however, and, being a renewable resource, the sugar cane that is grown to produce the Ethanol absorbs a good fraction of the CO2 released in burning it and its use as a fuel reduces ou dependance on Arab nations (we won't even go there).
This is, of course, well off topic for this thread though. But I just wanted to point out that Ethanol IS a viable fuel, and has been in other countries for decades. It isn't in the US yet because labor and land are more expensive here, and also because big petrol companies don't want it to be.
Just wait untill gasoline hits 5, maybe 6 bucks a gallon... Ethanol will start to sound like a WONDERFUL idea That's what Brazil did; the first big petrol crisis sent gas prices through the roof and stimulated the growth of the ethanol industry.

 

i recall the '70's and gasahol? ethanol and leaded didn't work too well, however, ethanol alone works better but it requires an industry retooling before it becomes viable.

remember,... all octane does is slow the burn/ignition process.

 

While this line of reasoning (the Net Energy Debate) sounds good on the surface, it's flawed. There is a report by Professor Bruce Dale at Michigan State University, which explains, in excellent detail, how the above quote and subsequent line of reasoning may not be totally correct.

I found it to be an interesting read.

Here's the link, for those who may be interested in learning more about the topic.

http://www.consumerwatchdog.org/reso...ergyDebate.pdf

 

The octane rating of any fuel has absolutely nothing to do with the flame speed of the fuel. Octane is a measure of a fuel's resistance to detonation and that is ALL.

Check out this link:
http://www.faqs.org/faqs/autos/gasol.../preamble.html
The last line of paragraph 6.3: "Flame speed does not correlate with octane."

More good reading:
http://www.faqs.org/faqs/autos/gasol...section-1.html

Also, as flame speed decreases, the mixture is more susceptible to detonation since the end gases have more time for pre-flame reactions to occur which is counter to what you want with higher octane fuels. Remember, combustion is just a chemical reaction that releases heat.

 

... and more reading.

OCTANE - A rating scale used to grade gasoline as to its antiknock properties. Also any of several isometric liquid paraffin hydrocarbons, C8H18. Normal octane is a colorless liquid found in petroleum boiling at 124.6 degrees Celsius.

OCTANE RATING - A measure of a gasoline's resistance to exploding too early in the engine cycle, which causes knocking. The higher the rating, the lower the chance of premature ignition.

http://www.consumerenergycenter.org/glossary/o.html

isn't detonation premature ignition?

an ignition point (the point at which the flame begins) too low will cause detonation or very low cylinder compression, depending upon the valve and ignition events.

octane is used for it's resistance to detonation. (kinda like lead in the old days?)

 

Detonation and preignition (I assume that's what you meant with "premature ignition") are two different things. Preignition is when the mixture is ignited before the spark occurs while detonation is when the mixture burns all at once (explodes) after the spark plug has initiated a normal flame front. However, detonation can lead to preignition. The vibrating pressure waves created by detonation "scrub" the walls of the combustion chamber and the "boundary layer" that typically insulates the combustion chamber surface is crossed causing a spike in the surface temperatures of the combustion chamber which can lead to preignition.

I think you may be confused about "octane". It's not added to fuel as a way of increasing the "octane rating" or resistance to detonation. Actually, the octane rating of "pure" octane (referred to as n-octane) is -17...kind of a paradox isn't it.

As noted in your link above, the Parrafin family (also called alkanes) have open-chain chemical structures with the general formula C(n)H(2n+2).
(Ignore the dots, it was the only way I could make everything line up. The vertical lines link the H atoms to the C atoms.)
...H
....l
H-C-H would be Methane CH4
....l
...H


...H..H.H..H.H..H.H.H
....l...l..l...l..l...l...l..l
H-C-C-C-C-C-C-C-C-H would be Octane C8H18
....l...l..l...l..l...l...l..l
...H..H.H..H.H..H.H.H

These normal members of the parrafin family are identified by the prefix "n": n-octane. Isomers of each normal member of the family have the same chemical formula as the normal member but with different molecular structure and properties. Isomers have the suffix "yl" added. For example, the name 2,2,4 trimethyl pentane is one specific isomer of octane. Tri means three and methyl means the radical CH3. So three methyl groups are attached to the pentane base (5 carbon atoms) at carbon atoms 2, 2, and 4 (numbered left to right) giving:


........CH3....CH3
....H....l...H....l...H
.....l....l....l....l....l
H--C--C--C--C--C--H
.....l....l....l....l....l
....H....l...H...H...H
........CH3
This is the structural formula for 2,2,4 trimethyl pentane or isooctane. These terms are used synonymously since this particular isomer of octane is of importance in combustion engine work as you'll see below.

The critical compression ratio of the parrifin family for audible knock in a spark ignition (SI) engine decreases rapidly as the length of the chain of the normal members is increased. The normal parrafins in the volatility range of gasoline are poor SI fuels due to very low octane ratings...remember n-octane has an octane rating of -17. Catalytically cracked fuels have branched parrafins (like above) making the carbon chain shorter resulting in higher critical compression ratios.

Finally, the octane rating is a reference scale to measure SI knock and has been estabilished by arbitrarily selecting two primary reference fuels. They are isooctane (2,2,4 trimethyl pentane) which has been arbitrarily assigned an "octane rating" of 100 and n-heptane which has been arbitrarily assigned an "octane rating" of 0. The "octane rating" of a fuel is found by comparing its' knock intensity with various mixtures of n-heptane and isooctane. So an octane rating of 93 means a fuel has the same knock intensity in a standard CFR engine (google "astm CFR engine", you can vary compression ratio while it's running ) and at standard conditions is equivalent to a mixture of 93 parts isooctane and 7 parts n-heptane (by volume).

Lead in the old days delayed the preflame reactions to increase detonation resistance and get octane ratings higher than 100. Adding the fuel n-octane would have the opposite effect. Sorry this got so long.

A longer but more in depth version of the above:
http://www.faqs.org/faqs/autos/gasoline-faq/part1/

 

Actually you were not specific at all. You never even mentioned E85 in your first post.

E85 does not equal ethanol, it equals 85% ethanol and 15% gasoline. Corvette is NOT an E85 vehicle, no matter what they do in Brazil.

 

most excellent.

i have read paffafin additives can provide remarkable results. i've also heard about naphthalene (which is currently found in gasoline) but not much about naphthalene vapours indroducted into the intake air.

 

No I wouldn't be surprised since I see people at the races every spring and fall having a tough time starting their cars be it ethanol or methanol.

In Brazil the ethanol is not made from corn, it is made from sugar cane if I remember correctly. Brazil has cut down vast sections of the forest to clear land to grow crops to make ethanol. It is an environmental and social disaster. Since the rain forest is in general poor soil they get a few crops and then have to move on to more land.

Ethanol has been around since the beginning of the gasoline industry. The statement that it hasn't caught on because the oil companies have suppressed it is pure environmental wacko baloney. The only reason the US has committed vast resources to the production of ethanol is the corn lobby in congress. The government, composed mostly of scientifically illiterate people, has done some dumb things in the past. Pushing ethanol as a substitute for gasoline is right at the top of the stupid list.

Alcohol has some advantages for race cars which I have posted in the past. It has none for passenger cars. This is not idle speculation. I have been running alcohol in my dragster for over ten years, both
methanol and ethanol. I use methanol now exclusively as it is a better race fuel due to it's higher heat of vaporization. I tried ethanol when I was given a few race supply for free. The long and short of the story is it made slightly less power and offered no advantages over methanol.

BTW the energy content of a fuel has little to do with the ultimate power output. What dominates is the air fuel ratio needed to get efficient combustion. As an example nitromethane has less BTU per unit volume than gasoline, ethanol, methanol or diesel. It is used in all out drag engines because it's air fuel ratio is around 2 to 1 which means you can burn a lot of fuel even though each unit volume is somewhat lower in BTU potential.

 

Sandyc01Great thread. You didn't start a war, but have opened up a cornucopia (sorry, I just had to use that word) of responses.

I have learned even more about gasoline, gasohol, ethanol and methanol, than I ever thought possible, but the overwhelmingly saddening suggestion that someone might even put Jack Daniels in a tank, had me running to my liquor cabinet for a hit or two of my favorite blend - JD and diet coke. I'm all better now, thanks

Serioulsy, this is a good read. Good input and information guys.

 

I never said the Corvette was an E85 vehicle

Reading comprehension > You. Seriously

I said it would run on oxygenated gas. I said E85 was not oxygenated gas. Please show me a quote where I said a corvette will run on E85.
E85 is predominantly Ethanol, making it an ethanol based fuel, NOT a gasoline Gasolines can contain low percentages of Ethanol, 85% is not a low percentage. Argh. please READ before posting, it saves unecessary typing on everyone's part.

 

You are comparing apples an oranges here. Drag cars have a hard time starting wether they run on ethanol, methanol, nitromethane or Gasoline. I have *NEVER* seen a commercially available passenger vehicle have a hard time starting on ethanol.
Mass produced vehicles have a LOT more time and money into cold start and ecu programming for easy start and smooth idle than you could ever dream of putting into a drag car, thus they have none of the issues you mentioned.
And I never said energy density had anything to do with power. I just said it netted a lower range.

 

My understanding is that the reason to increase the octane of the fuel is to SLOW the flame front travel, which would DECREASE the chances of detonation.

As the flame front travels, it creates a pressure gradient in the unburned air-fuel mixture. Since pressure is directly related to temp (PV = nRT ideal gas equation of state), the temperature can rise to a point where detonation can occur before the flame front.

The purpose of adding octane, which would slow the flame front travel, is to reduce the chances of this happening.

I distinctly remembering asking the instructor this in a class I took on high speed engines last year. Am I missing something?

 

Autoinition temperature comes to mind. You can have a high flame propagation velocity, but if the autoignition temperature is also high, pressure can be allowed to rise without causing detonation. Look at Hydrogen for example; extremely high flame propagation velocity (supersonic under certain conditions), but also FANTASTICALLY high octane rating: 130R+M/2
Why? Autoignition temperature = 1085 ºF. Gasoline? 490ºF

Very high octane ratings aren't the sole realm of non hydrocarbon fuels too.. Look at Methane; R+M/2 = 125... Autoignition temp for methane ins 999F