Talk:Exhaust gas recirculation

Negative section needed and the History section has no information
Where is the Negative paragraph. This EGR system causes SLUDGE in cars. This is a huge cost to vehicle owners. EGR should be reconsidered. The EPA should not have control of vehicle manufacturing. Who pushed for EGR? Who invented it? No one knows. --2605:6000:1A0D:1C0:0:94F:F47E:FDD1 (talk) 07:17, 8 August 2018 (UTC)
 * Do you have WP:RELIABLESOURCES to back up that "sludge" claim? Andy Dingley (talk) 08:49, 8 August 2018 (UTC)
 * The EPA does not "have control of vehicle manufacturing". The EPA mandates vehicle/engine emission standards, and manufacturers make their own decisions about how to make their vehicles comply with those standards.  Joe Frickin Friday (talk) 14:13, 20 August 2018 (UTC)
 * I can back up that sludge claim. Take a look at the intake manifold I just removed from my car! And from every intake manifold I have ever removed operated with an intact EGR. It creates a mess.
 * Indeed, I was very surprised to find an honest article on Wikipedia, that discussed some of the negative aspects of environmental lunacy imposed on us. Quick! Someone call in the clean-up crew to remove offensive, anti-green information, or people might make their own, independent judgements!
 * Yes, excessive combustion temperatures need to be controlled to prevent formation of NOx, but there are better ways to do it. Give the manufacturers a target, then let them experiment and come up with their own solutions that may be better than the one mandated by an out-of-control regulatory agency. 2600:8801:8E0A:CF00:88C1:995B:6956:9360 (talk) 16:56, 27 September 2023 (UTC)

neutrality
The neutrality of the section is being disputed due to environmental claims lacking citations as well as on going reverts, in order to prevent an edit war this section of the talk page has be created to improve the article. Wikipedia requires reliable resource to be valid. Kateweb (talk) 14:30, 29 July 2010 (UTC) Identifying reliable sources Kateweb (talk) 14:48, 29 July 2010 (UTC)


 * The neutrality of the entire page is disputed. The possibility of faulty engineering is something most people don't contemplate. --Dana60Cummins (talk) 17:30, 30 July 2010 (UTC)


 * I'm still keeping the neutrality issue by the Diesel EGR deletion as well, being that diesel EGR deletion in diesels is a totally different ballgame than gas deletion.--Dana60Cummins (talk) 17:33, 30 July 2010 (UTC)


 * Dana60Cummins. I have reverted your application of the "neutrality disputed" template to Exhaust gas recirculation, because it was improper and unwarranted. That template is for POV disputes that remain intractable despite discussion on the article's talk page. Going by your edit summary, you seem to feel the article lacks a section elucidating disadvantages of EGR. The appropriate thing to do is not to slap on an inapplicable template or otherwise complain about what you feel is missing, but rather to go ahead and add the section and info you feel is missing, supporting your assertions with reliable sources. It's conceivable some other editor will take issue with the material you add or the sources you use to support it, and both s/he and you will be intransigent and stubborn, and a tendentious POV dispute will develop, and that is when the "neutrality disputed" template would be appropriate to add to the article. But that's neither a goal to shoot for nor a foregone conclusion, so let's not jump the gun or provoke needless squabbles with neutrality-disputed template. —Scheinwerfermann T&middot;C 20:20, 5 February 2011 (UTC)


 * Alright retired Wiki person. Hang around.  I'm assuming you have this on your watchlist and will be checking in frequently.--Dana60Cummins (talk) 21:24, 5 February 2011 (UTC)

That's a good start you made. I've put your addition into encyclopædic format—paragraphs rather than a bullet-point list—and consolidated your three referrals to the one reference. Also I've changed the arcane term "end gas" to the accessible one "exhaust". —Scheinwerfermann T·C 02:49, 6 February 2011 (UTC)
 * I was living in the LA area in the 1970's, when a brown (visibly brown!) cloud would form over downtown, and then during the day blow over nearby cities. When you could feel the air (and ozone and NO2) going into your lungs. It is (mostly) not like that now. Even so, the article has to get it right. Gah4 (talk) 17:31, 6 August 2020 (UTC)
 * I was living in the LA area in the 1970's, when a brown (visibly brown!) cloud would form over downtown, and then during the day blow over nearby cities. When you could feel the air (and ozone and NO2) going into your lungs. It is (mostly) not like that now. Even so, the article has to get it right. Gah4 (talk) 17:31, 6 August 2020 (UTC)

Fundamentally Incorrect Information
With the amount of editing that goes into Jessica Simpson's Wikipedia page and the flurry of "citation needed" tags that abound on most pages this 'article' is dismal, almost everything on the page has been written by few people who do not understand modern combustion kinetics and the rationale for emissions equipment! The article needs to be rewritten from a NPV by someone who understands how automotive emissions equipment works. . . —Preceding unsigned comment added by 72.33.133.175 (talk) 00:03, 27 July 2010 (UTC)

Agreed. This statement alone makes no sense: 'This means the heat of combustion is less, and the combustion generates the same pressure against the piston at a lower temperature.' If exhaust gases are displacing either air or fuel, then at least the second part of that statement cannot be true since it cannot generate the same pressure. I don't think whomever wrote this article really knows what he/she is talking about. —Preceding unsigned comment added by Jatkins679 (talk • contribs) 21:58, 21 November 2010 (UTC)


 * Then do something about it!--Dana60Cummins (talk) 17:16, 22 November 2010 (UTC)

The statement "Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke" is partially correct. The "Heat reduction" part is correct, but it does not lead to "leaving more available for conversion to mechanical work during the expansion stroke". If you have less energy (heat) and consequent less temperature on the combustion chamber, it will lead to less heat energy being converted to "mechanical" energy. The highest the temperature on the combustion chamber (through normal combustion, I am not talkin about detonation), the highest will be the engine efficiency... This is thermodynamics 101. — Preceding unsigned comment added by Alecesa (talk • contribs) 04:09, 17 December 2010 (UTC)


 * Change it. Edit it. --Dana60Cummins (talk) 18:49, 17 December 2010 (UTC)

Your understanding of Thermodynamics 101 is flawed. The temperature at which heat addition occurs (for the Otto cycle, this is the peak combustion temperature) is not the only factor affecting efficiency; The heat rejection temperature (exhaust temp) also matters. In the absence of heat loss to the combustion chamber surfaces, the ratio between these two temperatures is determined entirely by the compression ratio (see Otto cycle, Equation #6). In the absence of any heat loss to the combustion chamber surfaces, lowering the peak temperature at TDC does not reduce efficiency; this is because lowering the peak temperature also reduces the exhaust temperature When heat loss to the combustion chamber surfaces is factored in, lowering the peak combustion chamber actually increases efficiency (by reducing that heat loss). This is one of the major reasons why diesel engines have great part-load efficiency (the excess air acts as a diluent that helps keep peak temperatures down, reducing heat loss to the walls). Joe Frickin Friday (talk) 20:57, 25 February 2016 (UTC) the part where it says almost all modern engines need EGR, what the heck i don't think so. — Preceding unsigned comment added by 64.135.212.67 (talk) 00:54, 8 January 2014 (UTC)
 * Otto cycle thermodynamics is complicated. As for displacement, except at wide-open throttle you can add EGR and still have the same fuel and air amounts. I suspect that the throttle can be designed to let enough in wide open. Ideally, the pressure should be more or less constant during the power stroke. A peak at the beginning is not optimal. But also, getting the right burn rate for all engine speeds isn't so obvious. Lower peak means slower burning, not less burning. (For those from the days of Covid-19, flatten the curve will make sense.) Gah4 (talk) 17:43, 6 August 2020 (UTC)
 * Otto cycle thermodynamics is complicated. As for displacement, except at wide-open throttle you can add EGR and still have the same fuel and air amounts. I suspect that the throttle can be designed to let enough in wide open. Ideally, the pressure should be more or less constant during the power stroke. A peak at the beginning is not optimal. But also, getting the right burn rate for all engine speeds isn't so obvious. Lower peak means slower burning, not less burning. (For those from the days of Covid-19, flatten the curve will make sense.) Gah4 (talk) 17:43, 6 August 2020 (UTC)

Needs rephrasing
"environmental impact of EGR outweighs the NOx emission" in the last paragraph does not make sense. NOx emission is an environmental impact. —Preceding unsigned comment added by 69.224.45.140 (talk) 16:52, 15 March 2009 (UTC)
 * I was also looking at that, NOx is also a greenhouse gas that takes more than 100 years to break up fall out of the atmosphere. Found a source here: http://www.umich.edu/~gs265/society/greenhouse.htm  —Preceding unsigned comment added by Waterppk (talk • contribs) 14:17, 29 July 2010 (UTC)

NOx is not a greenhouse gas. Nitrous oxide (N2O) is a greenhouse gas. NOx is a mixture of NO and NO2.

Is it really 'polution' or is this a mis-spelt 'pollution'? -- SGBailey 23:36 Dec 16, 2002 (UTC)

Changed the EGR composition to include the most significant component: nitrogen!129.55.200.20 (talk) 15:36, 26 August 2016 (UTC)

EGR: SI vs. CI effects
In an SI engine, the inert EGR is *added* to an existing mixture. The addition of inert exhaust gas, with its high specific heat, results in a rather large reduction in peak temperature (and corresponding reduction in NOx production)

In a CI engine, the inert EGR *substitutes* for a portion of the atmospheric air entering the cylinder. The *substitution* (rather than addition) of exhaust gas, with its high specific heat, results in a smaller reduction in peak temperature (and therefore a smaller reduction in NOx) than is observed in SI engines.

short version of EGR effects:

SI - same energy, larger total in-cylinder mass, larger specific heat ---> much lower temperature/NOx

CI - same energy, SAME total in-cylinder mass, larger specific heat ---> modest reduction in temperature/NOx

Joe Frickin Friday 15:47, 21 March 2006 (UTC)


 * The benefits of EGR in SI engines shine compared to "benefits" of EGR in CI engines. With EGR deletion in CI engines a long time rule of thumb has been a increase of fuel economy around 25%.  However newer engines have proved this to be a extremely conservative estimate.  Owners of the 6.4 Navistar VT engine that have deleted the EGR have reported increases of 50%.  10MPG to 20MPG isn't uncommon for owners to claim.   EGR is why Caterpillar Inc. stopped making on-road engines.  Reduced Carbon dioxide turns EGR deletion into a argument that Environmentally friendly people will stand behind, for obvious reasons.--Dana60Cummins (talk) 06:57, 29 July 2010 (UTC)


 * In my second source the key points of why EGR deletion is not popular are the following (word for word):

*Putting end gas back into the engine cylinder in place of fresh filtered air adds wear-inducing contaminants and increases engine oil acidity, both of which reduce engine longevity.

*EGR reduces engine power.

*EGR badly affects fuel economy.

This is a Domino effect. When longevity is effected, efficiency goes with it. When efficiency goes down, so does power and fuel economy. The acidity in the crankcase of EGR diesel engines is going to be worse than that of gasoline engines. (There is a elementary reason why this is, but I can't source it, so it doesn't matter on wiki.)--Dana60Cummins (talk) 16:46, 29 July 2010 (UTC)
 * Reaction kinetics are complicated. It all depends on which molecules (or parts of molecules) come together, with which energy, and when. It is not just inert, but which exact gases are there. Without EGR, combustion starts with no CO2, and it steadily increases. With EGR, it starts with a fair amount around, so the relative increase is smaller. Also, the specific heat of CO2 increases a lot with temperature, and besides the molar mass is higher, compared to nitrogen. Gah4 (talk) 18:00, 6 August 2020 (UTC)
 * Reaction kinetics are complicated. It all depends on which molecules (or parts of molecules) come together, with which energy, and when. It is not just inert, but which exact gases are there. Without EGR, combustion starts with no CO2, and it steadily increases. With EGR, it starts with a fair amount around, so the relative increase is smaller. Also, the specific heat of CO2 increases a lot with temperature, and besides the molar mass is higher, compared to nitrogen. Gah4 (talk) 18:00, 6 August 2020 (UTC)

EGR: other benefical effects
It's my understanding that the addition of exhaust gas also increases the mass of gas in the cylinder at part throttle during the compression/power strokes. This increases the compression ratio at part throttle. This increased pressure improves the thermodynamic efficiency. (Warning, I'm not a physicist, just a motorsickle sumbitch). I think this effect in not trivial.

Also, the heat rejection bit could be elaborated. Because the peak temperature of the combustion gasses is lower, the entire engine runs cooler. Usually, the manufacturer/designer uses an engine thermostat that's a little higher temperature to ensure the engine stays warm enough to keep the fuel vaporized, keep water vaporized, and further improves heat rejection by reducing the temperature differential between the exhaust gas and the cylinder head.

Finally, it might be helpful to dispel the idea that EGR is an attempt to 'reburn' unburnt exhaust gasses. This is the most common misperception about EGR and the main reason that uninformed guys with tools remove EGR systems.

Pcmenten 22:08, 29 December 2006 (UTC) Paul Menten

EGR can definitely hurt efficiency. I performed very careful measurements with a 1995 Toyota Corolla (1.8L non-Calif. model) on a weekly commute, mostly highway, air conditioner off. After EGR was disconnected, highway mileage went from 34-35 mpg to a consistent 38-40mpg. This makes sense, since EGR reduces combustion temperatures and thus Carnot efficiency. It is interesting to note that the 1.6L version of this car is not equipped with EGR, except in California. This leads me to think that its effect is largely detrimental, and it's there mainly as an emissions band-aid. This is a vacuum-modulated EGR valve with an ECU-controlled VSV acting as an on/off switch.

Also, the Heywood book is largely regarded as outmoded as far as its empirical data in it is concerned. The section on EGR seems to be based exclusively on simulations, which may not be terribly accurate. Unilaterally stating that EGR helps efficiency is obviously incorrect. 64.251.148.91 07:35, 31 July 2007 (UTC)
 * So, if EGR hurts fuel economy in order to reduce harmful emissions, how is that helpful? Surely you then have to buy fuel more frequently to offset the reduction in fuel economy, thus producing more emissions. Just curious, because I'm thinking of blocking the EGR valve off on my '91 Shogun[/Pajero/Montero]. ahpla 17:17, 13 September 2007 (UTC)

in a diesel engine using an egr system, is the aim to obtain an overall air / fuel ratio of 14.7:1 (the stochimetric ratio) by using the exhaust to subsitute the excess air? 84.66.42.255 22:48, 31 March 2007 (UTC)

in the 80's, it was smog reduction! So instead of running lean and efficient, they run EGR, run rich and burn up more fuel! Less nitrogen oxides tho, so less smog! 67.189.106.110 (talk) 06:02, 11 March 2012 (UTC)

Needs online References
at the time of this talk comment thier are no online references for this article, only 2 books. —Preceding Kateweb (talk • contribs) 02:09, 29 July 2010 (UTC) as an update I an waterppk are working to improve citations y adding ones that are accessible, if you find any resources that could apply and you don't know what part of the article to apply rhem to place them here and one of us will look at them. Kateweb (talk) 02:37, 29 July 2010 (UTC)


 * There needn't be any online refs. The criteria for refs are laid out in RS. Books are fine. —Scheinwerfermann T&middot;C 08:39, 5 February 2011 (UTC)

Diesel engine EGR
This section, even in its present bare-bones form, is idealogically lopsided. Dana60Cummins, it is very apparent from your contributions to this article, this talk page, and your own talk page that you don't like EGR on diesel engines. That in itself is a problem; theoretically it should not be possible to determine a good editor's personal preferences and opinions from the contributions s/he makes. At least you've supported your assertion with a couple of refs, which is good, but I'm afraid the notion just doesn't hold water that diesel EGR is a nefarious, thoughtless mistake forced on a sheeplike industry by ignorant morons at the EPA. In the very large and well-documented context of the overall vehicular-emissions cleanup effort over the last fifty years, that idea just isn't very sturdy. EGR gives benefits on diesel engines or it wouldn't be there. Whether those benefits are as large as stated and/or are equal to whatever drawbacks—those are debatable points, and as long as there's reliable support for assertions one way or the other, there's nothing wrong with including them in this article. But this "diesel EGR is bad" stuff just doesn't cut it on its own. —Scheinwerfermann T·C 02:52, 16 May 2011 (UTC)


 * The info I added, was word-for-word out of a text book. You just rewrote it to what it is now.  Others have added info against Diesel EGR in the past, but has got deleted and/or labeled vandalism.  My info just has a source which is rare.  So feel free to delete your own work and I'll just quit watching the page.  That is all.


 * NOx reduction is the only reason EGR exists on the diesel engine. It does drastically decrease fuel mileage.  But those that spend 60k on a pick up truck don't care much about fuel mileage as they do Horsepower. --Dana60Cummins (talk) 16:44, 16 May 2011 (UTC)


 * Taking text verbatim out of a book is not good practice on Wikipedia; we're not supposed to be cutting and pasting, we're supposed to be writing an encyclopædia. Moreover, I didn't dispute that the assertions present are supported by references. What I said is that we are presenting only one side of what is obviously a matter with at least two sides, and that's not OK. I don't have sources to sdd at the moment, but I and/or you and/or other editors eventually do need to add more sources representing more than just the one POV. —Scheinwerfermann T&middot;C 16:56, 16 May 2011 (UTC)


 * Verbatim isn't good. I know.  But when everything else gets deleted here.  Verbatim with a reference is a last resort.  As for a different POV I'm sure I and/or you and/or other editors could find something on a OEM website.--Dana60Cummins (talk) 17:38, 16 May 2011 (UTC)


 * ebay:Diesel EGR blocker (Signal,Code) Xb2u7Zjzc32 (talk) 10:48, 15 March 2015 (UTC)

″Exhaust gas—largely carbon dioxide and water vapor″  - well that might be true if the combustion was taking place in an oxygen enriched atmosphere. With combustion in air (or in air with recirculated exhaust gases) the exhaust gases will be predominantly nitrogen - I think between 73.8% and 79% depending on how much oxygen was consumed. — Preceding unsigned comment added by 2.125.187.47 (talk) 18:27, 27 September 2015 (UTC)


 * Another problem is that this section is 15 years (!) old now:
 * I'm not too familiar with diesel engines in trucks, but in passenger cars: The problem that EGR transports soot back into the engine and therefore reduces its normal lifetime is a problem of high pressure EGR only. In contrast, low pressure EGR takes exhaust after the DPF. Diesel engines have been using dual loop EGR for a couple of years now. These dual loop EGRs are composed of a high pressure EGR and a low pressure EGR. The low pressure EGR has a heat exchanger. The high pressure EGR may have a heat exchanges, but if it has, it also has a heat exchanger bypass. In such a dual loop set-up, high pressure EGR is mainly used to recircle hot air into the engine, so that it warms up more quickly. I don't think that one should refer to "modern diesel engines", and then not update it over time.

Alexander Noé (talk) 19:23, 17 October 2023 (UTC)

Exhaust pulse pressure charging
Although it wasn't designed as such, Exhaust pulse pressure charging is probably a form of Exhaust gas recirculation. Biscuittin (talk) 22:01, 27 April 2015 (UTC)
 * EGR doesn't just mean that exhaust gases are recirculated, it means that their recirculation leads to a drop in peak combustion temperature. Crossley's EPPR doesn't do that, in fact it would tend to the opposite. Andy Dingley (talk) 22:28, 27 April 2015 (UTC)

temperature
Does anyone know the peak temperature that is generated with, and without EGR? That is NOx generating temperture? There is discussion in RP-1 about NOx generation from rockets. Gah4 (talk) 18:02, 6 August 2020 (UTC)
 * From this EPA paper it seems to be 1300C is the magic temperature that you want to stay below. Gah4 (talk) 19:31, 6 August 2020 (UTC)