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Egr Off, Good Thing Or Bad Thing?

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Hello, i've just read an article that makes me wonder about all the things i've ever read about EGR valve and its removing.

Here it is:


I just wana have your opinion about that?

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I'm not sure I'd agree with all the points made in that article. For a start when you are running with a closed throttle and generating that high vacuum you usually want the engine braking that it provides and the ECU will have completely cut off all the fuel. If the EGR effectively bypasses the throttle and reduces engine braking you'll be making more use of the brakes. Second, that argument can't apply to diesels because, as far as I know, most (but possibly not all) don't have a throttle butterfly - the engine is controlled entirely by the amount of fuel delivered. This means you don't get those pumping losses and little engine braking (that's why diesels need a separate vacuum pump for the brake servo) and there won't such a big difference between higher revs in a lower gear or lower revs in a high gear because the ECU delivers just enough fuel to balance the load. It may be true that the EGR reduces pumping losses when cruising at small throttle openings but that's about all I should say.

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This is just for diesel

EGR in spark-ignited enginesIn diesel enginesEdit

In modern diesel engines, the EGR gas is cooled with a heat exchanger to allow the introduction of a greater mass of recirculated gas. Unlike SI engines, diesels are not limited by the need for a contiguous flamefront; furthermore, since diesels always operate with excess air, they benefit from EGR rates as high as 50% (at idle, when there is otherwise a large excess of air) in controlling NOx emissions.[citation needed] Exhaust recirculated back into the cylinder can increase engine wear as carbon particulate wash past the rings and into the oil.[6]

Since diesel engines are unthrottled, EGR does not lower throttling losses in the way that it does for SI engines. Exhaust gaslargely carbon dioxide and water vaporhas a higher specific heat than air, so it still serves to lower peak combustion temperatures. However, adding EGR to a diesel reduces the specific heat ratio of the combustion gases in the power stroke. This reduces the amount of power that can be extracted by the piston. EGR also tends to reduce the amount of fuel burned in the power stroke. This is evident by the increase in particulate emissions that corresponds to an increase in EGR.[7]

[8] Particulate matter (mainly carbon) that is not burned in the power stroke is wasted energy. Stricter regulations on particulate matter(PM) call for further emission controls to be introduced to compensate for the PM emissions introduced by EGR. The most common is a diesel particulate filterin the exhaust system which cleans the exhaust but reduces fuel efficiency. Since EGR increases the amount of PM that must be dealt with and reduces the exhaust gas temperatures and available oxygen these filters need to function properly to burn off soot, automakers have inject fuel and air directly into the exhaust system to keep these filters from plugging up.

By feeding the lower oxygen exhaust gas into the intake, diesel EGR systems lower combustion temperature, reducing emissions of NOx. This makes combustion less efficient, compromising economy and power. The normally "dry" intake system of a diesel engine is now subject to fouling from soot, unburned fuel and oil in the EGR bleed, which has little effect on airflow, however, when combined with oil vapor from a PCV system, can cause buildup of sticky tar in the intake manifold and valves. It can also cause problems with components such as swirl flaps, where fitted. Diesel EGR also increases soot production, though this was masked in the US by the simultaneous introduction of diesel particulate filters.[9] EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine longevity.[10]

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Ive seen this before and the article is a load of garbage, refers to petrol-engined NA cars, not diesels/ turbos

Looking through the other articles there is other nonsense - for example claiming that twin 2-1/4" exhaust pipes will flow better than one singlle large diameter pipe - complete rubbish - a single large pipe flows more because it has a smaller surface area vs volume in a cross-section- it is also lighter - this shows the how ignorant the writer of these aticles actually is of these matters and is obviously just picking up bits of information here and there - - he claims to be an "arthor, entreprenur and automotive enthusiast" (writer is not even an engineer, mechanic or professional/ tuner)

Many members on the forum have blocked their EGR, with moticable improvements in turbo lag, better throttle response, performance and economy

As above, the EGR valve/ system deposits carbon all over the inside of the inlet manifold, etc choking the engine and reducing performance/ economy over time

Removing / blocking the EGR valve/ system (with a solid plate) also improves a cars' reliability

I did mine a long time ago - i have a clean manifold, dyno printowts etc as evedence- 160+ Hp from 113Hp stock - the EGR delete was a controbution to that

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The problem with all these emmision controls is that they are often working against each other, and require other systems to work harder to compensate. It creates a viscious circle that in the end leads to increased running costs, increased fuel use and increased CO2 emmisions. Also, with a potential reduction in life of modern vehicles, or their componants and consumables, this brings in a whole other environmental issue of disposal of waste and production of new material.

I can see from the other side, that exhaust emmisions are a bad thing. NOX causes smog which kills people. Particulates kill people. Something needs to be done about them. It's the disjoined approach that is the big problem. Let's bolt this bit on to deal with this emmision. That makes another emmision worse so lets bolt another bit on to deal with that.

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