EGR valve: what is needed in the car and why is it jammed

The tightening of environmental standards has turned modern internal combustion engines into real chemical plants with a mass of devices for exhaust purification. One such system is the EGR. Why is it often turned off, and does it make sense

ЕГР клапан: для чего нужен в машине и зачем его глушат

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  • What is it
  • How it works
  • Where is
  • Cleaning
  • Faults
  • Why are they jamming

What is USR

EGR (from English Exhaust Gas Recirculation) — exhaust gas recirculation system used in gasoline and diesel engines. By directing part of them into the intake manifold, and then into the cylinders, a decrease in temperature in the combustion chamber is achieved, which makes it possible to limit the formation of «heat-loving» toxic nitrogen oxides NOx. Without the EGR, it is impossible to achieve compliance of the internal combustion engine with environmental standards from Euro-5 and higher.

The downside of using the USR is:

  • Increase in the content of soot in the exhaust, primarily in diesel engines due to the peculiarities of fuel combustion in them. This entails the need to install anti-particulate filters and, as a result, an increase in the cost of the car.
  • Increased wear of the cylinder-piston group, primarily due to the fact that soot in engines with USR is 50-60% harder than in internal combustion engines without this system.
  • Significant risk of formation of sulfuric and sulfurous acids inside diesel engines (with unpleasant consequences) when using fuel with a high sulfur content.
  • How the USR works

    The EGR effect is provided in two ways:

  • Selection and adjustment of gas distribution phases for internal combustion engines with phase shifters.
  • By means of a special valve/s in the bypass circuit/s connecting/their exhaust and intake systems. Further, we will talk about this particular version of the USR.
  • ЕГР клапан: для чего нужен в машине и зачем его глушат

    Photo: Schacal/drive2.ru

    Different types of valves can be used in EGR systems. The most advanced have an electric drive and «tied» to the electronic engine control unit. A healthy EGR valve is most often closed when the engine is running at full load, when all the power is required from it. However, some engines, such as Land Rover's Ingenium turbodiesels, have a second EGR circuit, which in this scenario allows recirculation of exhaust gases with reduced pressure without noticeable loss of ICE power.

    For turbodiesels, liquid heat exchangers are often built into the USR circuits for more precise control of the temperature of recirculated exhaust gases, as well as for accelerated heating of the internal combustion engine.

    In gasoline engines with the USR system, up to 20% (for direct injection more) of exhaust gases are recirculated, in diesel engines — up to 50%.

    Where is the EGR valve

    Being part of the «respiratory system» ICE, USR valves are located in the engine compartment between the intake and exhaust tracts. The specific installation location of the EGR unit depends on the engine model.

    Cleaning the EGR valve

    A properly working internal combustion engine has a minimum oil vapor content in the exhaust, therefore, when using high-quality fuel and engine oil, USR valves only need preventive cleaning at a mileage of about 50 000 km. The cost of this procedure is from 2500 rubles. Typically, the resource of the valve itself is 150 000 — 180 000 km.

    ЕГР клапан: для чего нужен в машине и зачем его глушат

    Photo: ridebuster.com

    Faulty EGR valve

    The EGR system fails mainly for two reasons:

  • Failure of the pneumatic or electric drive of the EGR valve.
  • Stucking of the EGR valve in the intermediate, fully open or closed position due to the accumulation of oil-like deposits that form from the mixture of exhaust and engine oil vapors.

    The latter appear as a result of wear of the cylinder-piston group and/or turbocharger seals, as well as the design features of the USR valve itself for some engines.

    Without eliminating the causes of these problems, cleaning or replacing the USR block will only give results for a short time, after which the exhaust gas recirculation valve will jam again. In this case, the motor will become unstable and lose power.

  • Why do they shut off the EGR valve

    Often, in the event of a failure of the USR system, they prefer not to repair it, but to turn it off in order to save money without regard to the environment. The valve block itself, depending on the manufacturer, can cost from several thousand to several tens of thousands of rubles, plus payment for work. A set & nbsp; of the same plugs that block the USR channels will cost several times cheaper. Quality plugs are made of stainless steel 2.5-3mm thick.

    However, in the case of modern DIC, such «surgical intervention» must be accompanied by a software shutdown of the USR and reloading of the control program. The best option is when there is software for the same engine, which comes from the factory for the markets of developing countries without an USR block. Otherwise, setting up a motor with a muffled USR system turns into a complex and expensive operation. If it fails, the Check engine alarm indicator will be constantly on on the dashboard, the emergency mode of forced engine power limitation may turn on, and fuel consumption will increase.

    ЕГР клапан: для чего нужен в машине и зачем его глушат

    Photo: Shutterstock

    Expert Comments

    Worth whether to jam the USR system? With this question, we turned to our expert, who, by virtue of his position in the official structures of a respected German brand, wished to remain incognito:

    «With a working engine, jamming the USR will save on preventive cleaning of the intake system, and reduce the amount of soot in the exhaust. However, on the other side of the scale  — environmental damage.

    By shutting off the EGR on a worn engine, you can achieve the elimination of black, soot smoke from the exhaust pipe. But this is purely an external effect. Without replacing, for example, injectors that pour fuel, there is a high risk of burnout of the pistons, since the temperature in the cylinders increased even more with the USR turned off.

    Jumping the USR is justified to some extent on a heavily worn diesel engine with insufficient compression, in which at the end of the compression stroke the temperature in the combustion chamber is too low for optimal ignition of the working mixture. By eliminating the USR, the temperature can be increased and thereby prolong the agony of such a motor».

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