Regarding stoiciometery, I thought I would try and reply to this, although I am not sure exactly where this came from.
1bolt, you said:
"Oh yeah and before I lose it, Mike the EPA did not invent stoichiometry
stoichiometric combustion is *
the theoretical ideal air fuel ratio at which the most complete combustion is made* (this is not necessarilly the most miles per gallon) that's what stoichiometric means; it has absolutely dick all to do with the EPA. Now please stop reading whatever wacko web site you got that EPA lunacy from."
Quote:
Originally Posted by
FordGuy
I have seen so many people think they can figure out a better way to increase fuel economy, they never work, they will tell you it helped, but they are kidding themselves. Gas engines are most effect with a fuel ratio of 14:7 to 1, and that is what a electronically controlled vehicle accomplishes. so if your vehicle is operating as designed, why do so many people waste there money? Wishful thinking!
Previously posted by Ecomike:
"14.7:1 was not selected to optimize fuel efficiency, it was selected by EPA to minimize air pollution and waste just enough fuel to supply the needs of the catalytic converters. The cat converters need fuel to burn, in order for them to get hot enough to convert trace, excess CO to CO2, etc......
Also, from what I have read the exhaust valves and timing are set to open early enough to leak just enough O2 and fuel into the exhaust to supply the thermal needs of the Cat converters. That early opening slows and delays the completion of the combustion process."
My reply:
For gasoline engines, A/F ratio stoichiometery is somewhat of an oxymoron, since the moles of oxygen needed to oxidize a "mole of gasoline" (another oxymoron as there is no such thing as a mole of gasoline), have no precise meaning since the gasolines we all buy and use have variable quantities, and a variety of different hydrocarbons with different mass densitities and different molecular structures.
The EPA regulation driven / O2 sensor target A/F ratio is 14.7:1
and they (EPA) specifically define Stoichiometric as:
"Term most often used to describe the ideal air/fuel mixture entering the intake. The point at which the production of emissions is at a minimum and catalyst conversion of emissions is most efficient. The stoichiometric air/fuel ratio is 14.7 to 1, measured in parts by weight."
Taken from:
http://www.epa.gov/otaq/epg/keyterm.htm#stoichio
It says nothing about true scientific "Stoichiometry"
EPA loves to redefine scientific terms to meet their own needs. If you don't believe me read CFR 40 on the definition of a "Solid Waste". EPA redifines the word solid, specifically it is: "Any liquid, solid, or containerized gaseous material.....
Here ares some very interesting links on some of this!
The stoichiometry of
automotive fuels can vary from as low as 6/1 A/F (
air fuel ratio) to as high as 15/1 A/F (
air fuel ratio). Because of this variation
...Many pump gases have varying amounts of Ethanol added and therefore varying Stoichiometry. Ethanol has a stoichiometry of 9 to 1. If you mix 10% ethanol (8.9/1) with 90% gasoline (14.7/1) you get fuel that has a stoichiometry of about 14.1 to 1...... When you run fuel with 10% ethanol and you do not enrichen the A/F ratio your motor will be leaner compared to fuel without Ethanol. The difference from 14.1/1 to 12.6/1 is lean enough to cause motor damage over a period time....Ethanol, in pump gas, can vary from 0%-15%). To determine the amount of Ethanol or alcohols in the gas a water test can be performed.
Quoted from:
www.scca-enterprises.com/updates/FSCCATechnicalbullitinfuels.doc
For gasoline, the stoichiometric
ratio is about
14.7:1, meaning that for each pound of gasoline, 14.7 pounds of
air will be burned. The
fuel mixture
...
auto.howstuffworks.com/catalytic-converter1.htm
"
- Reducing emissions: Keeping the air-fuel mixture near the stoichometric ratio of 14.7:1 (for gasoline engines) allows the catalytic converter to operate at maximum efficiency.
- Fuel economy: An air-fuel mixture leaner than the stoichometric ratio will result in near optimum fuel mileage, costing less per mile traveled and producing the least amount of CO2 emissions.
- However, from the factory, cars are designed to operate at the stoichometric ratio (rather than as lean as possible while remaining driveable) in order to maximize the efficiency and life of the catalytic converter. While it may be possible to run smoothly at mixtures leaner than the stoichimetric ratio, manufacturers must focus on emissions and especially catalytic converter life (which must now be 100,000 miles on new vehicles) {fact} as a higher priority due to U.S. EPA regulations."
Quoted From:
http://en.wikipedia.org/wiki/Air_fuel_ratio_meter
Now, I think I see another area where you and I differ(ed) on this stoichiometric issue. The true scientific meaning of stoichiometric is a balanced amount of 2 reactants that when they react completely, they leave no excess of either reactant.
It says up above that running at a higher ratio than 14/7:1 will lower the CO2 emmisions, this tells me that it is consuming less fuel when run leaner, and therefore 14.7:1 is not a true stoicimetric ratio in the true scientific meaning of the word. But, keep in mind that the cat converter also consumes fuel. So if all the fuel is not consumed in the engine first, then the cat converter is completing that task, with no incease in power or mileage. Also keep in mind that the O2 sensor must sense some excess, unused oxygen across the range from rich to lean, meaning there is still unused oxygen even under rich fuel conditions.
Conclusion? The version of the word Stoichiometric that we use in the automotive industry is not the same as the scientific definition. In fact it seems to be a rather nebulous use of the word.
In other words, I think the word stoichiometric in this case has become somewhat distorted in its use in the automotive and EPA circles. Therefore 14.7:1 is not a real, true stochiometric ratio, but some average value arrived at by EPA and automotive engineers over the last 40 years.
Personally, at this point I think it is a
targeted mass (in lbs) ratio of the two (air to gasoline) that has been determined over the years to be the best ratio
compromise for the varying demands, including EPA emissions, and Cat Converter requirements, put on automotive engines.
arty:
. Frankly I don't think I am being obtuse at all, in fact I think I was being quite "transparent" (LOL). Don't know where you got the idea that it scares me, the only thing that scares me is G. Bush and the Patriot act :us:, but that's getting off topic. 
:eyes:
