Talk:Lean burn

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Older Honda lean burn models[edit]

Since Honda's introduction into the US, they've had CVCC (lean burn) motors. And even up through the 80s right before they switched to fuel injection. I'm not sure of all the models and years, but I know for certain it was up until the later 80s when Honda finally introduced fuel injection. —Preceding unsigned comment added by (talk) 21:56, 2 May 2010 (UTC)

More NOx?[edit]

Surely one of the main advantages of lean burn engines is that the give of less NOx due to the fact that the higher ratio of Oxygen to fuel causes the engine to run cooler. This reduces the amount of NOx produced as less O2 molecules a split (which requires 800C+) which are a prerequisite for NOx (as the O radical then reacts with the N2 in a catalytic cycle). EvilGuru

It seems counter-intuitive, but I've seen enough motors with forced induction packing in extra air and stock fuel injectors not able to keep up melt pistons to know that leaner mixtures produce more heat, not less.
This is true only if you're on the rich side of peak EGT (14.7:1 mixture typically). If you go to the lean side of peak, then things cool down. This article is discussing lean burn engines that are lean of the ideal mixture, not "lean but on the rich side of peak," which does burn holes in pistons. — Preceding unsigned comment added by 2620:0:1008:1001:D267:E5FF:FEEC:F6A9 (talk) 15:52, 7 August 2012 (UTC)

LAF O2 Sensor same as wideband[edit]

Some of us know the LAF O2 sensor as a wideband O2 sensor. I believe the terms LAF and wideband are interchangeable. A typical oxygen sensor only tells us only if the mixture is rich or lean. A wideband (LAF) O2 sensor quantifies how rich or lean the mixture is.

PLohr (talk) 21:21, 24 February 2008 (UTC)

"Honda can't sell lean-burn in California"[edit]

This link seems dead. (talk) 10:57, 5 November 2008 (UTC)

Noticed that a while ago, but forgot to fix. I have the text offline, but since it's copyrighted I can't post it. I've converted it so the link's removed, but the cited source remains and can be treated as any other offline resource would be. --DeLarge (talk) 11:11, 5 November 2008 (UTC)

Rich burn vs. Lean burn emissions curve[edit]

Though I don't consider myself an expert in this area, I do use it every day to design control systems for natural gas engines. This curve is common and found many places on the Net. This particular one is from CECO discussion page on air/fuel ratio

Rich burn is the first point where the CO and NOx lines cross. Lean burn is 2nd point where CO and NOx lines cross. Exhaust temperature observations from my own experience show rich burn running around 950F and lean burn around 650F for 150hp to 1000hp industrial natural gas engines.


British English[edit]

Is there some reason this article uses the British term "petrol" but not other British spelling and syntactical conventions? At this point, flagging it pending further discussion.There can be only one...TheKurgan (talk) 03:38, 18 June 2012 (UTC)

Need to seperate discussion of NOx creation factors and NOx remediation factors[edit]

The article seems to weave together some seperate topics concerning combustion and engine emission remediation, with NOx being a pollutant thats one of the key threads in the tangle. As it is the article seems to attempt to compare various lean burning vehicle implementations. It might be helpful if the discussion of engine dynamics and combustion is seperated to a greater extent from the emission remediation strategies. This article might make more sense if it simply stated the creation as the fraction of nitrogen (N2) in the intake air converted to nitric and nitrous oxides (NOx) is a strong function of the combustion temperature and pressure at the flame front. Likewise the strategies for reducing NOx emissions are either in-engine combustion dynamics that reduce flame front peak temperature and pressure (by EGR, reducing compression, combustion dynamics, etc.) or post-combustion (catalytic converters Similarly seperating discussion of how other undesirable combustion products, (particulate, CO, HS, etc.) are created by combustion dynamics and the remediation strategies would also help. It might also help to seperate the combustion discussion to avoid intermingling the discussion of engines that directly inject fuel into compressed air (diesel style) from the engines that compress fuel air mixtures, and the breakdown further to seperate the strategies as control, swirl, stratified swirl, stratified layer, etc. rather than chronologically by manufacturer. It might also help to avoid the manufacturer's marketing names as much as possible except when meaningfully descriptive, and just use the 3 or 4 letter abbreviation as necessary to distinguish one from another. — Preceding unsigned comment added by PolychromePlatypus (talkcontribs) 14:11, 19 July 2012 (UTC)

Civic Hybrid, does it really use lean burn?[edit]

The difference in EPA MPG when comparing the 2005 Civic Hybrid (39/43) and the 2006 Civic Hybrid (40/45) (EPA 2008+ adjusted and CVT transmission on both) leads me to think that the 2005 and possibly earlier Civic Hybrids don't use lean burn, since the 2006+ ones do not, yet mileage is as good if not better. Please verify. — Preceding unsigned comment added by (talk) 20:10, 28 October 2012 (UTC)

second sentence[edit]

2. "In lean burn engines there can be 65 times as many air molecules as fuel molecules, yielding an air–fuel ratio of 65:1"

No. The air-fuel ratio is a *mass* ratio, not a ratio of molecular count. An air-fuel ratio of 65:1 means there are 65 units of air mass to 1 unit of fuel mass. Since the fuel molecules have about four times the (average) mass of the air molecules, the molecular ratio is about four times the mass ratio, about 260:1 in this example. See the first sentence of the article (talk) 11:18, 23 March 2014 (UTC)

More on the second sentence:

In one sense the author is correct in citing air fuel ratio as 65:1 as he makes it clear that he is referring to the molar ratio. However he is confused when he contrasts this ratio with the stoichiometric ratio for petrol of 14.64:1 as this figure is the mass ratio as mentioned by the previous commentator. 65:1 is very close to the molar stoichiometric ratio for octane.

This can be obtained from the equation for the burning of octane: 25O2 + 2C8H18 -> 16CO2 + 18H2O. (see article So 25 molecules of oxygen are needed for 2 of octane, i.e. a ratio of 12.5:1. As air is about 1/5 oxygen you need about 5 times as much air to provide this amount of oxygen, i.e. 12.5 * 5 = 62.5 so the molar stoichiometric ratio for octane in air is 62.5:1.

To convert this to the more usual mass ratio you need to multiply each part of this ratio by the gram molecular weights (of oxygen & octane) as follows: 12.5 mols O2 (GMW 32) = 12.5*32 = 400 grams, 1 mol Octane (GMW 114) = 1*114 = 114 grams. Dividing 400 by 114 gives a stoichiometric ratio of an oxygen fuel mixture of 3.51:1. Multiply by 4.5 to add in the weight of nitrogen in air results in 15.8 grams of dry air per gram of octane, a figure close to the commonly quoted ratio of 15:1.

Neither of the figures quoted by the author indicates how lean 'lean burn' engines are since both figures are virtually the same stoichiometric ratio represented by different conventions. — Preceding unsigned comment added by Johnrl45 (talkcontribs) 22:20, 12 May 2014 (UTC)

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