Talk:Air–fuel ratio

message: Thanks, but surely the lower fuel consumed would generate more CO2 if it is burning that much better? I can understand that one can reduce CO2 emission from changes in vehicle weight, drive system etc. but improving combustion just means increasing co2 from a given amount of fuel burnt. Or is it that vehicles do not have close to 100% combustion efficiency but maybe closer to 97-98% combustion efficiency and so need to burn extra fuel to compensate and the unburnt and partially burnt portions of the fuel including HCx, aldehydes, particulates, smoke etc. is released in to the atmosphere eventually to form Co2 and so any combustion efficiency improvement would increase CO2 per litre of fuel burnt but would also reduce the total amount of fuel burnt hence the Co2 reduction claim. The increase and decrease not being linear. Would appreciate your thoughts on this.  —Preceding unsigned comment added by 81.153.23.27 (talk) 11:24, 30 March 2009 (UTC)
replies: text: It is probably just that lower fuel consumption causes lower CO2 productions.  For example, if fuel consumption is reduced by 1% then clearly CO2 production will be reduced by 1%, O2consumption will be reduced by 1%, and so on.  If so, this is an obvious outcome and does not really justify fuel refiners boasting about reducing CO2 emissions.  Dolphin51 (talk) 06:25, 28 March 2009 (UTC)
thread_title: [Untitled]

message: AFR is measured in volume not weight. For every cubic feet of gasoline that enters into the combustion chamber as vapor or mist (as near as possible)approxamatly 14.7 cubic feet of air is needed to obtain  a Stiochimetric mixture. This is measured. in CFM (cubic feet per minute).  —Preceding unsigned comment added by 134.134.136.3 (talk) 17:51, 5 August 2008 (UTC)
replies: text: No. The stoichiometric mixture depends on MASS. You can measure air flow in volume and work back to mass if you wish but the air fuel ratio is very definitely dependant upon the ratio in mass. As density of air varies significantly with changes in pressure and temperature it is not possible to define the mixture by reference to volume alone. At the top of Pike's Peak for instance, a cubic feet of air contains only 2/3 as much oxygen by mass as it would at Daytona, but it's still a cubic foot of air. Beck daross (talk) 11:35, 10 February 2012 (UTC)
thread_title:  AFR

message: Someone might want to look into stoichiometric AF ratio a little more.  I understand it to be 14.6 and not 14.7, as per Heywood
marine  engine air fuel ratio on large container vessels - probable 
design faults attributable to  stochiometric air requirement caused extensive damages like scuffiing , sudden severe wear and assosciated commercial losses to due to its effect on ship's schedule is becoming more and more common.
According to "Automotive Technology,  A systems approach. 6th edition" by Jack Erjavec and Rob Thompson
"the ideal air-fuel or stoichiometric ratio for a gasoline engine is approximately 14.7 pounds of air mixed with 1 pound of gas. This provides a ratio of 14.7:1. Different fuels have different stoichiometric ratios. Because air is so much lighter than gasoline, it takes nearly 10,000 gallons of air mixed with 1 gallon of gasoline to achieve this air-fuel ratio. Lean ratios of 15 to 16:1 provide the best fuel economy. Rich mixtures have a ratio below 14.7:1 and provide more power from the engine but greater fuel consumption."
P.808 Chapter 28 Gasoline, Diesel, and other fuels. Djcookiii (talk) 20:44, 10 May 2016 (UTC)
thread_title:  Stoichiometric Ratio 

message: It’s been added to Wikipedia:Proposed mergers to gain a little more attention and help it merge faster. AeroKnight 18:18, 24 September 2006 (UTC)
thread_title:  Proposed Merger 

message: How prevelant is the "stoich" abbreviation for Air-fuel ratio?  I've always known "stoich" as a shortened versio of stoichiometry.  Google seems to agree, if you search for "stoich", it brings up "See results for: stoichiometry".  If no one has any reasonable objections, I will change the redirect in a few days.  Brien Clark 07:41, 3 January 2007 (UTC)
thread_title: Stoich Redirect?

message: 198.176.208.75 (talk) 17:49, 7 October 2008 (UTC)
thread_title: non-rocket scientist, D in chemistry viewpoint

message: Update the equivalence ratio section by making the oxidizer to be more specific, in this case air. The article should be talking about air and fuel mixtures, but equivalence ratio is a more broader concept, since it does not restrict the oxidizer definition to air or oxygen. It would be better to have a separate article for it. -- Myth  (Talk)  20:01, 4 July 2007 (UTC)
thread_title: Equivalence ratio section

message: Most of the article assumes that the fuel is a hydrocarbon. While this maybe true for most applications, I believe the definition does not have anything to do with it. It would be better if the article also reflects this where ever possible be more general in the definition of the fuel. -- Myth  (Talk)  20:01, 4 July 2007 (UTC)
thread_title: Fuels

message: Should AFR be again mentioned here? -- Myth  (Talk)  20:01, 4 July 2007 (UTC)
thread_title: Other terms used section

message: I suggest adding info or a link to info about the AFR for a typical grade of coal, or perhaps if there are significant differences, various grades of coal, coke, etc. GilesW (talk) 13:41, 10 March 2008 (UTC)
thread_title: AFR for solid fuels

message: This statement
"Vehicle manufacturers do not provide a means of altering predefined fuel maps making such alterations impossible without replacing the stock ECU with a customizable system."
is incorrect. I'm just deleting it for now.
Vehicles at least back into the 80's (Ford and GM included) have ECU's that can be remapped with a chip. Many more modern vehicles can be flashed through the OBD-II port or by other means.
--167.102.224.45 (talk) 13:08, 18 March 2008 (UTC)
thread_title: stock ECU information incorrect

message: The article describes a parameter called lambda, after the Greek letter \lambda.  I don't doubt that there is a parameter that matches the description given here, and I'm sure the parameter is abbreviated \lambda, but what is the name of the parameter?  Lambda is simply the Greek letter used as an abbreviation. Citing a source for this information would be a good move. Dolphin51 (talk) 11:59, 18 January 2009 (UTC)
replies: text: I now believe lambda, \lambda\;, is the stoichiometric ratio.  This is not to be confused with the stoichiometric air-fuel ratio (or chemically-correct air-fuel ratio) which is about 14.7:1 for gasoline.  When an air-fuel mixture is chemically correct it is said to be at a stoichiometric ratio, \lambda\;, of unity (1.0).  Unfortunately, I don't yet have a citation for this.  Dolphin51 (talk) 01:24, 27 March 2009 (UTC)
thread_title:  Lambda? 

message: In the article, it says:
"For gasoline fuel, the stoichiometric air–fuel mixture is approximately 14.7; i.e. for every one molecule of fuel, 14.7 molecules of O2 are required"
This is incorrect as the ratio is weight of air to to fuel, not the mole ratio.   
The article then goes on to correctly discuss the combustion of octane with 12.5 moles of O2.
If gasoline were composed of octane, then the stoichiometric ratio would be about 15.1 based on mass of air consumed per unit mass of octane.  (Air is about 21% oxygen by volume/mole fraction, 78% nitrogen (N2), 0.93% argon, and 0.039%CO2)
It would require a fuel of composition of about C8H15.3 to have an ideal 14.7 ratio.   Apparently the ideal ratio is based upon empirical testing, since gasoline is a complex mixture of many hydrocarbons.
Lambda (the Greek letter) is used in the automotive industry to represent the ratio of the actual air/fuel ratio to the stoichiometric air/fuel ratio.   
Article needs to be corrected, but not sure how to handle the octane combustion example with the 14.7 "standard" stoichiometric ratio, and I can find no references.
`Wwwaller (talk)  —Preceding undated comment added 21:27, 7 July 2012 (UTC)
replies: text: I agree. I have changed "molecule" to "gram". I also changed "oxygen" to "air" because air-fuel ratio is all about the mass of air, not of oxygen. Dolphin (t) 07:55, 8 July 2012 (UTC)
thread_title:  Definition of Stoichiometric Wrong in Article 

message: "Because the composition of common fuels varies seasonally, and because many modern vehicles can handle different fuels, when tuning, it makes more sense to talk about lambda values rather than AFR."
This statement contradicts itself.
Because no one actualy knows the ACTUAL stoich for most fules i would have to dissagree with the above.  Since lambda is calculated from AFR using a constant that must be accuratly known for the fule.  Slightly different blends of gas will not have the same stoich ratio (summer/winter)and therefore the lambda value will be in-accurate.  AFR is directly measured and the optimum value can be found for that fule.  — Preceding unsigned comment added by 65.51.205.194 (talk) 12:59, 5 September 2012 (UTC)
thread_title: Can't agree with this one

message: Perhaps I can clear up some of the confusion here about the relationship to the highest possible adiabatic flame temperature and the air/fuel ratio.  First, it is common to calculate an adiabatic flame temperature based on the combustion products reaching the equilibrium position.  However, in an internal combustion engine, or even in an industrial boiler, the time to reach equilibrium is longer than the residence time of the flame in the combustion chamber.  Also, there is some heat loss to the surroundings as the fuel-air mixture is burning, so the situation is not truly adiabatic.  So given a short residence time, the maximum attainable combustion temperature depends on the reaction mechanism and the kinetics.  In some cases, the maximum attainable combustion temperature could be on the slightly excess air side of perfect stoichiometry, while in other conditions or situations, Tmax could be reached with a slight excess of fuel.
Second, for combustion temperatures above about 1800 K, and near stoichiometric, there are small (but significant) amounts of minor species present at the equilibrium position, such as O, OH, N, H, and of course NO if there is a slight excess of air.  These species have a heat of formation and contain both O and fuel elements, and so they affect the heat of combustion.
Third, the system pressure affects the equilibrium position of the combustion products.  So combustion of a fuel at a specified air/fuel ratio in a constant volume device will yield a different temperature than in a constant pressure device, and the composition of the combustion gas will also be different, even for the same air/fuel ratio.   
For these and other reasons, the calculated adiabatic flame temperature obtained by assumption of equilibrium conditions will not be met in practice.  The AFT, or some version of it, must be obtained by appropriate measurements at the conditions of fuel consumption. 
Finally, the article is strongly oriented towards the internal combustion engine, with some added reference to industrial furnace combustion.   I suggest either calling the article "Air-Fuel ratio for internal combustion engines"; if so, why not move this article to the article on the internal combustion engine.  Or, if this is to be a general article on air-fuel ratio for any kind of combustion process, make it more general, and include coverage of industrial furnaces, where the air/fuel ratio is controlled for a different purpose than for the internal combustion engine.  Thermbal (talk) 05:07, 30 June 2013 (UTC)
thread_title:  Combustion stoichiometry 

message: This appeared on the article page. I'm shifting it here instead.  Stepho  talk  04:09, 12 December 2013 (UTC)
thread_title:  Question regarding this Text vs. Air-Fuel Gauges. 

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message: I don't think this paragraph makes any sense.  Could someone look at it, please?
:In the typical air to natural gas combustion burner, a double cross limit strategy is employed to ensure ratio control. (This method was used in World War II).[citation needed] The strategy involves adding the opposite flow feedback into the limiting control of the respective gas (air or fuel). This assures ratio control within an acceptable margin.
Longinus876 (talk) 12:56, 4 November 2019 (UTC)
thread_title:  Other types of engines