Name definition: what is EGR?
EGR is the abbreviation of Exhaust Gas Re-circulation in English, and the Chinese name is exhaust gas recirculation. The so-called EGR exhaust gas recirculation means that part of the exhaust gas discharged from the engine after combustion and work is re-entered into the intake manifold together with the fresh mixed gas and enters the cylinder for combustion again. Since a large amount of CO2 in the exhaust gas dilutes the oxygen concentration in the original mixture, the combustion speed slows down, and CO2 cannot be burned to absorb heat so that the maximum combustion temperature of the cylinder is reduced, reducing NOx emissions to reduce pollution and promote environmental protection.
The working state of EGR is different according to the type of fuel and the difference in power, but it is roughly divided into several states such as cold car state, low load and high load, and there are also differences in working conditions due to temperature differences. model to confirm.
The role and pros and cons of EGR
On the positive side, the role of EGR is firstly based on the purpose of environmental protection, because there is no EGR before the national one national two (or similar European standard, American standard), so its origin is for environmental protection. It is the first point; the second is that it can reduce the combustion temperature and suppress knocking, which is an auxiliary function, because there are many ways to achieve these two points, not only EGR can do it, we must be clear about this.
So to sum up, EGR is a power auxiliary equipment that is “forced” to develop and install for the purpose of environmental protection, and it is mandatory to install. Even if you have the ability to do it without it, it is not necessarily approved by the country, because These are laws and regulations; although laws and regulations are based on the basis and name of environmental protection, the process is also indispensable.
And environmental protection and power, economy, durability, and reliability have always been “opposed”; whether you agree or disagree, this is the fact that is naked in front of you. The relationship between environmental protection and the engine itself, to put it bluntly, is in a state of complete conflict. From the beginning of domestic implementation, from the beginning of the carburetor to EFI and EGR, various environmental protection measures have been adopted Got it in the car.
So after the advantages of EGR above, there must be disadvantages; from the time when there was no emission standard to buy a car and drive until now, the most obvious change is not the so-called three-way catalytic converter – because I drive more diesel engines For Isuzu, it almost includes many of its famous models, including 4JA1, 4JB1, 4JB1T, 4JK1, 4JJ1, RZ4E, 4KH1 has also been touched, and other Toyota, Nissan, Mitsubishi, Volkswagen and the like have also been driven Not a lot.
So for me, the most obvious thing is the DPF of China V Plus (Nation VI adds urea, of course, some models have already added urea); I have seen that it is not an accidental phenomenon that machines of various brands and displacements are blocked for no reason. I don’t know what kind of moths will appear in China VI, but the stricter the emissions, the more troubles the engine will cause and the higher the cost of use. There is no doubt about it.
Therefore, when there is a chance, it is still beneficial to buy a low-emission car; my mu-x is a China-4 model that I bought after China-5 was launched. Now it seems that it is really a happy thing to not have DPF.
Ok, let’s continue to talk about EGR;
EGR itself is a contradiction; it can reduce NOx emissions and lower combustion temperature (3.0L 4JJ1 has a lower compression ratio than 2.5L 4JK1, which is why it is easier to upgrade to China V); these are advantages, So what about the bad?
Let’s talk a little bit;
For the DPF that is necessary for the National V, EGR itself is a big trouble; because when EGR introduces the exhaust gas to reduce the oxygen content to achieve the purpose of cooling, it will also cause the degree of incomplete combustion of diesel fuel to increase; and there is a large amount of CO2 in the exhaust gas. After burning, it will cause a lot of particulate matter emissions; isn’t it a surprise! ? Because the purpose of adding DPF in China V is to reduce particulate matter emissions, and EGR is not helpful here, which makes the working condition of the buggy post-injection combustion treatment particulate filter system in China V even worse.
The result of EGR introducing exhaust gas combustion is to generate more (particulate matter) soot; part of the large amount of soot will be emitted to the DPF for treatment, which will reduce the life of the DPF and reduce the regeneration mileage. Part of it will adhere to the cylinder wall, rub against the piston, and eventually be cleaned by the oil. The last part will pass through the EGR system, from the EGR pipeline, cooler, valve, intake manifold, and valve to the cylinder, and then participate in combustion again, resulting in more soot, and the vicious circle repeats itself.
The soot composition is carbon black plus various salts, some of which are very hard, making these small particles equivalent to hard abrasives. Of course, good engine oil can quickly disperse the soot and dilute it into the engine oil, but the soot still passes through the clogging and wear of various systems before being dispersed and diluted by the engine oil. As the mileage increases, the engine oil will also be full of soot particles. These soot-containing engine oils are spread throughout the entire engine system, from the crankshaft, to the cylinder, including the valve stem, piston, and turbine. These abrasives move with the body driven by the piston. Constant wear and tear on all moving structural parts of the engine.
Therefore, if the production of soot can be suppressed to a certain extent, it will be beneficial to the entire engine, so I will not talk about how to suppress it first.
The word soot may be abstract, but you must have seen the blackness of diesel engine oil. Even if you wash it twice before changing the oil, after changing the oil again, you will run out of the 4S shop and take a look at the scale. You will find that it is black again… These “black machine oils” are mainly the reason for cleaning and dispersing soot. Soot can also cause partial blockage of the EGR system, valve failure, cooler efficiency reduction, severe wear of the valve, and smaller inner diameter of the intake manifold leading to power output failure and so on for many reasons.
The important reason for this problem is that the position of the EGR valve itself is behind the air regulating valve (it can be called a throttle valve, although it is not called so on a diesel engine); the air before entering the regulating valve is carefully filtered by the air filter , are all clean; while the exhaust gas from the EGR that directly enters the valve chamber is the exhaust gas from the engine, which is the thick gas rich in soot.
Smelling it is guaranteed to make you feel refreshed, and it can also treat SARS… .
Especially when the particulate matter emission of the diesel engine is compounded with the turbocharger for a long time, there will be some oil and gas combustion emissions. If the engine is not in good condition, such as a little bit of oil burning-because this is normal on a diesel engine, then In these cases, let everyone have the opportunity to ponder what the problems caused by letting the exhaust gas directly enter the valve chamber for a long time look like.
This is an exaggerated effect, but it can also be seen how serious it is.
If you want to say that EGR is not turned on all the time, but divided into various working conditions-yes, but everyone knows the truth of water dripping through stones, and you should also understand it by looking at your engine oil or looking at the world behind the EGR valve; your car It’s not that you can’t open it after three days and hang it on the wall as a background.
What to do?
EGR exists objectively, and its functions, pros and cons are clear; so you can figure out how to deal with it yourself; if you want the horse to run but also want the horse not to eat grass, there is no such thing as a good thing. Regarding the negative content of EGR, I don’t know why I can’t seem to find anything after searching the domestic webpage; if you want to know more, you can go to the external website. There are many things related to EGR. If you don’t speak English, you can Google it, but you don’t need to read it Text, look at the picture to know the general meaning.
Some of the pictures in the text are from the Internet, if there is anything wrong, please let me know and delete it, thank you.
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