Chilling

page not found ... another god bites the dust!

You may have missed the tail of the link. Add the "92846.ece" to it. Dan in no doubt very proud that the president will be from his very own Chicago rather than some doddering old guy planning on more of the same til his death of old age, cancer, etc.

"Standing before a room of oil company executives in June, John McCain flip-flopped and declared support for coastal oil drilling. Now the Washington Post is reporting that, within days, oil and gas execs ponied up nearly $1 million to elect McCain."

"Give Blood, Vote Republican" "Bush. Like a Rock. Only Dumber." "Vote Republican, Suffering Builds Character"

Not long after arriving in the Senate, Mr. Obama himself briefly provoked a controversy by flying at subsidized rates on corporate airplanes, including twice on jets owned by Archer Daniels Midland, which is the nation?s largest ethanol producer and is based in his home state.

It turns out that Obama?s national campaign co-chairman, former South Dakota Senator Tom Daschle, serves on the boards of three ethanol companies and his top advisor on environmental issues, Jason Grumet, used to work for a bipartisan initiative (National Commission on Energy Policy) that strongly supports ethanol.

Obama is also very tight with Illinois agriculture giant Archer Daniels Midland, the nation?s largest ethanol producer. Incidentally, a few years ago Archer Daniels Midland became the first company to sell food directly from the U.S. to Cuba since the implementation of the decades-old embargo and, perhaps not coincidentally, Cuban communist Dictator Fidel Castro has endorsed Obama. In fact, months ago he said an Obama-Hillary Clinton ticket would be unbeatable.

Obama has even made ethanol a national security issue, saying that the nation?s security will benefit from it because America?s oil dependence makes it difficult to shape an intelligent foreign policy and pointing out that the U.S. sends billions of dollars to some of the most hostile nations on earth. Not surprisingly, he favors multibillion-dollar government subsidies that the industry has for years received.

Obama: "I'm not in this race to continue the special-interest-driven politics of the last eight years. I'm in this race to end it. I've been taking on lobbyists throughout my career in Illinois." (Sen. Barack Obama, Remarks At A Town Hall Meeting, Billings, MT, 5/19/08)

Obama: "[T]he more transparency we can bring to Washington, the less likely it is that Washington will be run by lobbyists and special interests." (Sen. Barack Obama, Remarks At A Town Hall Meeting, Billings, MT, 5/19/08)

Daveb

"DaveB" wrote

Excellent. Nothing wrong with burning ethanon. It's a fine fuel, and a fine gasoline additive.

And it's derrived from biomass.

I just wouldn't make it out of food.

Only Capitalists would be that stupid.

IIRC The MPG go down.

"Cliff" wrote

Not relevant since it's MPJoule that matters.

They sell it by the gallon.

"Cliff"

Different grades, different prices.

Same gallon no matter the Ethanol content AFAIK. Higher octane does not get better MPG either AFAIK.

The correct response to that would be, "it depends". This being a timely subject these days, I'll make a few comments. Lower combustion pressure engines (normally aspirated low compression ratio engines) that do not experience detonation with low octane gasoline will not benefit from using a higher octane fuel. This is NOT one of those cases where you will automatically get what you pay for. The octane rating of a gasoline relates to its ability to resist detonation (knock), it does not relate to its energy content OR its flame front speed. In other words, the common misconception that higher octane gasolines reduce detonation because they are "slower burning" is a myth.

BUT, and this is a BIG but; *IF* you are running a high combustion pressure engine (either a high static compression ratio OR low compression ratio with significant boost from a turbo or supercharger), which IS prone to detonation, then using a lower octane fuel that causes the engine management system to retard the spark and/or richen the mixture... you'll be running the engine inefficiently and no-doubt hurting your power AND mileage. You may never hear any pinging/knocking due to the speed of the electronic knock-sensing and retardation system, so might be led to believe that lower octane fuel is more than adequate, when it may not be.

Is it? The Octane has a higher molecular weight IIRC. This may then take longer to fully combust.

Such as a diesel?

Nobody said that lower octane was better for high compression.

Speaking of which ... think of having to use gasoline to get a diesel engine to even run a little bit when somebody is "cooling" it with "water injection" .

Cliff:

So it would appear:

==================================================================

Octane rating has no direct impact on the deflagration (burn) of the air/fuel mixture in the combustion chamber. Other properties of gasoline and engine design account for the manner at which deflagration takes place. In other words, the flame speed of a normally ignited mixture is not directly connected to octane rating. Deflagration is the type of combustion that constitutes the normal burn. Detonation is a different type of combustion and this is to be avoided in spark ignited gasoline engines. Octane rating is a measure of detonation resistance, not deflagration characteristics. ==================================================================

==================================================================

The antiknock ability is related to the "autoignition temperature" of the hydrocarbons. Antiknock ability is _not_ substantially related to:

1. The energy content of fuel, this should be obvious, as oxygenates have lower energy contents, but high octanes.

1. The flame speed of the conventionally ignited mixture, this should be evident from the similarities of the two reference hydrocarbons. Although flame speed does play a minor part, there are many other factors that are far more important. ( such as compression ratio, stoichiometry, combustion chamber shape, chemical structure of the fuel, presence of antiknock additives, number and position of spark plugs, turbulence etc.) Flame speed does not correlate with octane. ==================================================================

You seem to be confusing molecular Octane with octane ratings in modern gasoline formulations.

I was talking about gasoline engines. Diesels use a different fuel rating system called cetane number, which measures the time between injection of diesel fuel and the beginning of combustion.

Someone claimed that using a higher octane gasoline doesn't give an increase in MPG. I just showed a case in which switching to the use of a higher octane fuel, in a high combustion pressure engine, DOES give better power & MPG.

The later use ot the term "octane" relates directly to the earlier effects of octane-enriched

gasolines.

[ The octane number of a fuel is measured in a test engine, and is defined by comparison with the mixture of iso-octane and normal heptane which would have the same anti-knocking capacity as the fuel under test: the percentage, by volume, of iso-octane in that mixture is the octane number of the fuel. ]

HTH

Cliff:

Molecular weight isn't the sole determining factor of either flame front speed or knock resistance. Iso-octane has a octane (knock) rating of 100 (eight branched chain carbons), and n-heptane has an octane rating of zero (seven straight chain carbons).

Modern octane increasing gasoline additives are not generally octane or octane isomers.

=====================================================================

ADDITIVES Oxygenates e.g. alcohols or ethers These compounds work by raising the octane number of the fuel. They cause less pollution, because apart from not containing lead, they produce lower levels of carbon monoxide when they burn. The most commonly used oxygenate is MTBE (methyl tertiary butyl ether). The systematic name is 2-methoxy-2-methylpropane. Its octane rating is 118.

HIGH OCTANE COMPOUNDS Apart from the use of additives, knocking may also be prevented by using a mixture of high-octane compounds in petrol manufacture. Certain molecular features are desirable in ensuring that compounds have high-octane ratings. These are: a) A high degree of branching b) Short chain length c) The existence of rings. =====================================================================

Chemical reactions usually start on the ends of a chain. The atoms there are more exposed to reactions, probably have stronger electric fields, etc. This would include oxidation. After one Carbon is gone you have Heptane-like material left over from the Octane. Then it can start again. Hence it takes longer for Octane to fully combust than it does for Heptane, all else being equal.

Explosives may be another matter as the molecules self-destruct and the same may apply to some other (often unstable) molecular structues.

Check the heats of combustion too.

Cliff:

Replying to a post from Aug 5? Not exactly what I'd call a timely response.

What you have failed to consider in your speculative procedural hypothesis above is that the particular isomer of octane used for octane ratings (octane rating of 100) is iso-octane, a branched chain hydrocarbon. And that n-heptane (octane rating of zero) is a straight chain hydrocarbon.

The straight chain octane isomer (n-octane) has an octane rating of

-10. Which means it's MORE prone to knocking than zero octane n-heptane.

===============================================================

iso-octane 100 n-heptane 0 n-octane -10 ================================================================

================================================================

1. Effects of octane rating: Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction. Since higher octane fuels have higher activation energies, it is less likely that a given compression will cause knocking.

Octane rating has no direct impact on the deflagration (burn) of the air/fuel mixture in the combustion chamber. Other properties of gasoline and engine design account for the manner at which deflagration takes place. In other words, the flame speed of a normally ignited mixture is not directly connected to octane rating. Deflagration is the type of combustion that constitutes the normal burn. Detonation is a different type of combustion and this is to be avoided in spark ignited gasoline engines. Octane rating is a measure of detonation resistance, not deflagration characteristics. ================================================================

My original comment stands:

"Molecular weight isn't the sole determining factor of either flame front speed or knock resistance."

"Toluene can be used as an octane booster in gasoline fuels used in internal combustion engines. Toluene at 86% by volume fueled all the turbo Formula 1 teams in the 1980s."

I remember being at Circuit Gilles Villeneuve for the F1 race and thinking that it smelled like someone had burned the air.

Jon Banquer San Diego, CA

So was Benzene. Made a comment on another list about original formula Hoppe's #9. Then I looked up Benzene after a negative response.

Wes

Any links to support this?

Jon Banquer San Diego, CA