If the EGR (EGR) valve stops working properly, then certain symptoms may appear in your car that clearly indicate a malfunction in the exhaust gas recirculation system. Fortunately, most often this does not mean that it is time to change the valve. In many cases, you can easily fix everything yourself.
Exhaust gas recirculation in diesel and gasoline engines
It may seem a little odd that engine exhaust gases do not always exit all the way through the exhaust pipe right away. In fact, the exhaust gases are returned to. This technical trick lowers the combustion temperature of diesel fuel, which subsequently reduces the formation of harmful nitrogen oxide (NOx). The recirculated exhaust gases displace the fresh air in the intake duct, namely the low oxygen level in the exhaust gases, and then absorb some of the heat of combustion in the combustion chamber, resulting in a significant decrease in combustion temperature. As a result, the formation of harmful nitric oxide drops sharply.
This EGR valve is vacuum operated. When the valve (inside) opens, it makes a path for the exhaust gases to enter the intake port.
Gasoline engines also use an exhaust gas recirculation system. Here, the return of exhaust gases to the engine serves to reduce fuel consumption, since the throttle valve can be additionally opened due to the pressure of the returned exhaust gases. This reduces the so-called energy loss when opening the throttle, which helps to reduce fuel consumption and, accordingly, leads to a decrease in the level of harmful substances in the exhaust system.
Internal and external exhaust gas recirculation
In internal combustion engines (ICEs), there are, as a rule, two exhaust gas recirculation systems - internal and external. The internal exhaust gas recirculation of the engine does not require additional components, as it is implemented by the design of the power unit. So, during the design of engines, engineers adjust the valve timing so that they remain open at the beginning of the intake stroke for a while. As a result, part of the previously released exhaust gases is again sucked back into the combustion chamber.
With external recirculation, exhaust gases are sent to the intake duct through the external pipeline of the exhaust gas system (EGR-EGR system). Many diesel and some gasoline engines use an aftercooler for the EGR. This cooler cools the exhaust gases with antifreeze (coolant), which significantly lowers the temperature of the exhaust gases, leading not only to a reduction in fuel consumption, but also to a significant reduction in the level of harmful substances in the vehicle's exhaust system (combustion temperature decreases).
EGR valve function
When and how much to send exhaust gases to an external gas recirculation system is controlled through the exhaust gas recirculation valve - often called the exhaust gas recirculation (exhaust gas) valve - or EGR / USR.
The EGR valve usually consists of a poppet valve or a special gate valve. This valve releases or prevents the movement of exhaust gases to the engine intake tract.
Using sensors such as a mass air flow sensor and an oxygen sensor (lambda probe), the engine control unit calculates the ideal amount of exhaust gas recirculation and controls the exhaust gas recirculation valve (EGR valve) accordingly.
The mechanical movement of the EGR valve device is usually performed electro-pneumatically or electrically using a servomotor.
In some vehicles, the EGR valve is also equipped with a position sensor that controls the correct opening and closing of the damper or pushrod. By the way, exhaust gas recirculation occurs only in the region of partial engine load.
EGR valve: defects and symptoms
Often the exhaust gas valve (EGR) is covered with a mixture of soot and oil. In the photo you can see what the EGR valve looks like after thousands of kilometers of vehicle operation.
An EGR valve malfunction can manifest itself in different ways. Here are signs that may indicate a malfunctioning exhaust gas recirculation valve:
- When accelerating, the car picks up speed jerkily
- Vibrations at idle
- Loss of engine power
- The appearance on the dashboard of the icon " " (Check engine - emergency engine operation program)
- The level of nitric oxide in the exhaust gases increases
- Black smoke from the exhaust pipe
- Increased fuel consumption
Since the EGR valve with its adjustment mechanism is located in the exhaust stream, it is the most sensitive component of the EGR system. Due to the soot contained in the exhaust gases, the EGR valve adjustment mechanism may malfunction over time - the valve may no longer open or close normally.
Also, the valve can become dirty due to oil vapor from the oil separator, which, in combination with soot, do their evil work over time.
As a result of incorrect operation of the exhaust gas valve, the level of harmful substances in the exhaust system can increase significantly. You may also experience delayed vehicle response when you press the gas pedal (throttle response). Including the most common symptom of an exhaust gas valve malfunction is a severe loss of engine power. This usually happens if the valve fails to close properly. Along with the loss of power in this case, black smoke may appear in the exhaust pipe, which is formed due to the lack of the necessary portion of fresh air, at full load.
If the EGR valve (EGR) is stuck in the closed position, then you may not notice any signs of malfunction while driving the car. But if, with this type of malfunction, you measure the level of nitric oxide, then you will find it is significantly higher than normal.
Including a dirty exhaust valve (which also inevitably means contamination in the engine intake system) can lead to an increase in fuel consumption. By the way, sometimes all these signs can appear periodically (not constantly), since the USR valve can restore its function on its own. However, even temporary symptoms should not be ignored, as this clearly indicates its malfunction. And this means that in the near future problems with the exhaust gas valve will become more frequent and sooner or later this will lead to valve failure.
The check engine light is on due to the exhaust valve.
Another sign of a malfunctioning EGR valve (EGR) is the appearance of an engine error (Check Engine) on the instrument cluster. True, the appearance of an engine error is not necessarily associated with an EGR valve position sensor, which usually detects an incorrect valve position in some cars.
A faulty EGR valve can also be detected by other vehicle sensors, such as pressure or temperature sensors, which can send inconsistent values to the engine control unit due to the lack of exhaust gases in the EGR system. As a result, if the sensors detect a malfunction in the operation of the engine, the Check Engine warning lamp (Check engine) lights up on the car's instrument cluster.
Also, an error code is recorded in the memory of the engine control unit, which led to the appearance of the "Check Engine" icon.
So, in the computer's memory, when the "Check engine" icon appears due to improper operation of the exhaust gas valve, an error code may appear, which means, for example, "Exhaust gas recirculation is too low."
Including an error may appear, meaning "Leak in the intake system." This error can occur when the valve is stuck in the open position. However, please note that sometimes exhaust gas error codes can mean other engine malfunctions that are not related to defects in the EGR valve.
Can I drive a car with a bad EGR valve?
Short-term signs of a malfunctioning EGR valve are generally not to be feared. But if, due to the operation of the exhaust gas valve, the “Check Engine” icon appears on the instrument panel and the engine goes into emergency operation, then you need to contact the technical center for computer diagnostics as soon as possible, and also get advice from a car mechanic.
If during the diagnostic process it turns out that the EGR valve is stuck in the open position (usually recognized by a loss of power at full engine load), then this leads to a constant supply of exhaust gases to the intake system. As a result, exhaust gas recirculation increases beyond partial engine load, resulting in incorrect fuel injection. Thus, at full engine load, incomplete combustion of the fuel occurs. This in turn leads to excessive soot formation, which, for example, in a diesel engine can clog the particulate filter. In the worst case, a malfunctioning EGR valve that is stuck open can result in turbocharger (turbine) failure.
Causes of a faulty EGR valve
If the EGR valve (EGR) is dirty, the most common malfunction is the valve mechanism stuck in the open or closed position. And this is a completely natural process. After all, the exhaust gas valve mechanism is located in the unfiltered exhaust gas stream. This will inevitably lead to its failure sooner or later. Typically, the exhaust gas valve has a fairly long resource. This is especially true for older cars. But in more modern cars, the EGR valve fails much faster. For example, in the past, on cars, the exhaust gas valve could work for decades and quietly last at least 200,000 kilometers. But modern cars have received new software that is tuned to lower levels of harmful substances in the exhaust system (due to new tougher environmental regulations recently adopted by the EU).
As a result, the software in new vehicles contributes to the acceleration of exhaust gas recirculation. This is done to reduce nitrogen oxide emissions. So in modern cars, the life of the exhaust gas valve has become significantly less than in older cars.
In addition, faulty contacts on the electrical line plug can lead to a malfunction in the EGR valve. Also, sometimes the cause of the incorrect operation of the exhaust gas valve can be damage to the external exhaust gas recirculation line. Thus, the exhaust gas recirculation pipe may be damaged. For example, cracks may appear in it. Including rubber seals can be damaged, which will lead to leakage of exhaust gases. As a result, the exhaust gas recirculation system will not work properly.
Another common exhaust valve malfunction is associated with oil loss in the area of \u200b\u200bthe engine block head. In this case, oil fumes resulting from combustion can lead to contamination of the EGR valve.
In this case, cleaning the old dirty exhaust gas valve or replacing it with a new one is advisable only if the cause of the oil vapors has been eliminated. Do not forget about the vacuum hoses, which, if damaged, can lead to improper operation of the exhaust gas valve. The fact is that due to damage to the hoses, a vacuum leak will occur, which will interfere with the opening of the EGR valve.
Finally, a malfunctioning exhaust valve may be caused by a broken mass air flow sensor.
Cleaning the EGR valve
If a faulty EGR valve is suspected, it should be checked first for possible contamination. If heavy soot deposits are found inside the valve, this clearly indicates a possible cause of the EGR valve (EGR) malfunctioning. Luckily, in most cases you can clean the valve and get it working again.
Here is the EGR valve on the Lexus IS 220d. To get to the exhaust valve for cleaning, just remove the decorative cover on top of the engine
Caring for the environment is everyone's business, and especially car manufacturers. As you know, in the process of burning fuel, a lot of harmful substances are released that pollute the surrounding air. Various systems are installed on cars to reduce the harmfulness of emissions to the environment, and automakers are always looking for new solutions.
ValveEGR (EGR) is one of the modern ways to combat environmental pollution. It is installed in almost every modern car, and many drivers may not even know about its existence, while it brings significant benefits. However, there are situations when the EGR valve needs to be turned off, for example, if it breaks down. Let's consider this system in more detail within the framework of the article.
Table of contents:What is an EGR valve
As noted above, the EGR valve is one of the systems that serves to reduce the harmfulness of exhaust. Specifically, its task is to reduce the amount of nitrogen oxides in the exhaust of a car.
The EGR valve works very simply. Most often, it is installed perpendicular to the direction of exhaust gas outlet. As they follow the exhaust, some of them enter the valve and are sent back to the internal combustion engine to be re-introduced into the exhaust. This recirculation of exhaust gases through the car engine is necessary to reduce the combustion temperature, which has a positive effect on the quality of the exhaust, reducing the amount of harmful nitrogen oxides in it that occur at high temperatures.
It is worth noting the important fact that the EGR system only works in a "calm" driving mode. That is, at higher speeds, it turns off.
Like any mechanism, the EGR valve can fail, and then it may be necessary to turn it off. Consider the main causes of the failure of this mechanism.
Causes of valve failure USR
The EGR valve can fail for many reasons, the main of which we will consider below, dwelling on each of them in detail.
Valve mechanism jamming
Perhaps the most common EGR malfunction occurs due to jamming of the valve mechanism. As can be understood from his work, he can jam in a closed or open state, depending on which the corresponding problems will result.
If the EGR valve remains open when stuck, this will cause all the exhaust gases and their accompanying combustion products to end up in the cylinder over time. This is due to the fact that the valve will be open even at high speeds, while during standard operation it should be closed in this mode.
Please note: SystemEGR can be “tied up” with other systems, as a result of which its jamming in one position or another can affect their work.
If the USR valve is closed as a result of jamming, we can assume that the driver is lucky, in fact, the only harm from this will be the environment.
Jamming of the valve mechanism most often occurs due to the deposition of soot on it, which is inherently present among the products of fuel combustion.
To avoid jamming the USR valve, it is important to monitor which is used in the car, as well as. Refuel your car only at large gas stations from trusted fuel suppliers, avoiding unfamiliar gas stations.
Important: Depending on the quality of the system EGR, its service life can vary from 150 to 200 thousand kilometers. Of course, such a range of mileage should be considered only when it comes to the operation of the system with proper care of the engine with high-quality fuel.
Engine problems
Also cause valve malfunctionEGR can and the engine itself, being a catalyst for its failure. The list of engine problems that can cause the EGR system to fail is extensive. It includes both banal reasons, such as untimely, and more serious problems, for example,.
Accordingly, if the EGR fails due to a faulty engine, the first step is to diagnose the internal combustion engine, detect and fix the malfunction, and only then proceed to restore the EGR valve itself. If you perform these steps in reverse order, it is unlikely that the valve will work for a long time after repair.
EGR valve aging
Over time, the valve itself fails, and this happens the faster, the more soot particles settle on it. By itself, the process of soot particles settling can be considered normal, since they are formed during the combustion of the mixture. But here it is worth noting one important nuance. The level of nitric oxide that the valve is supposed to protect the environment from increases with increasing temperature. In this case, the number of solid soot particles, on the contrary, increases with decreasing temperature.
From this we can conclude that environmentalists want to reduce the emission of nitrogen oxides into the environment, for which it is necessary to lower the temperature, but this leads to the formation of soot particles that destroy the engine. Engine designers have to find a compromise between two extremes, but it is impossible to completely avoid the aging process of the EGR valve due to the deposition of soot particles on it. It can be considered that in this way the system “gets old”, actually destroying itself, since its task is to reduce the temperature.
System leakage
The most obvious problem of all. If the system is not airtight, air from the outside will appear in it. Since this air is not taken into account in the program of the control unit, it can adversely affect the operation of the system.
Electronic problems
It should be noted that electronic malfunctions that can lead to failure of the EGR system. Among them, problems such as an open circuit or valve position sensor most often occur. If such a malfunction occurs, there will be a discrepancy between the calculated software and physical position of the valve.
What to do if the EGR fails
If the EGR valve is broken and not doing its job, there are several ways to solve this problem.
Valve replacement
The first thing that comes to mind when any part of the car fails, especially the non-repairable one, is its replacement. EGR valve if desired, it can be replaced at specialized service centers, but such a service will cost a lot of money. The cost of the mechanism itself is very high, both in the original version and in the “Chinese version”.
The benefits of installing a new EGR valve are obvious - the car will continue to release less nitrogen oxide into the environment than if this system was not working.
Please note: If the valveThe EGR failed much earlier than 100-200 thousand kilometers, which most likely indicates that there are problems in the engine. Accordingly, when installing a new valve, it is necessary to carry out a complete diagnosis of the motor in order to determine the cause that prompted the valve to fail.
Mechanical and software shutdown of the USR valve
The most common and cheapest method used when exiting a systemEGR failure is its complete shutdown.
The first step of such work involves the mechanical closing of the valve. For this, special plugs made of high-quality steel are used. The thickness of such a plug is about 3 mm.
Important: You need to pay attention to the selection of material for the manufacture of the plug. If you put a low quality part, it will “burn out” pretty quickly.
The second step is the software elimination of errors that may be associated with the EGR system. For an electronic control unit of a car, the absence of an EGR system is a stressful situation. The task of the programmer is to find all references to EGR in the car's firmware and remove them.
Important: Work on the software removal of the system EGR from a car must be performed in high-quality service centers where professionals work. The danger of turning to amateurs is that they can remove all programs in the firmware that contain the designation EGR, and often these are diagnostic programs that will not work correctly afterwards.
It is worth noting that on some cars it is also required in the firmware to calibrate the map over the air.
Silencing the EGR valve programmatically
This method should be used in a situation where it is extremely difficult to close the valve mechanically. It consists in the fact that a command is given programmatically to close the valve, and this action is stored in the firmware.
The disadvantages of this method are obvious. If the valve is stuck, the given command will not work. In addition, since there is no way to physically see the valve closing process, it cannot be said with full certainty that it is completely closed and soot particles, as well as other harmful elements, will not enter the cylinders.
Many motorists believe that the USR valve must be turned off. But others are sure that you should not do this. Let's take a look at what this system is.
The recirculation system (EGR) often fails and causes instability in the engine at idle. In some cases, due to such a malfunction, the car may simply "get up" at the traffic light. Naturally, such problems do not deliver any joy. And not all masters can cope with this disaster. Many are accustomed to "treating" standard malfunctions when it twitches or does not start. EGR failure is a very difficult problem to solve, which can be disguised as a misfire or "pretend" to suck in abnormal air. The engine may start and run normally at first, but will soon give out strange interruptions. Therefore, diagnosing a system breakdown is not easy. And not every workshop has equipment for checking the USR.
What is the EGR for?
Her primary mission is to protect the environment. Part of the exhaust gases is directed to the cylinders through the system nozzles, thereby reducing the combustion temperature and, accordingly, the amount of CO2. But not everything is so perfect, this magnificent system is the EGR valve. Many people think that this part is not needed at all, but it is constantly interrogated by the “brains” of the car and affects the injection system. Therefore, if you simply disconnect the terminal from this part, the onboard computer will torment you with complaints about an engine control error. In addition, the operation of the motor will be adjusted taking into account the "malfunction", which will lead to an increase in diesel fuel consumption, loss of power and other "charms". But there are options here. In some cars, control occurs through the EGR solenoid valve and vacuum from, and in others - based on data and other sensors.
Valve failure symptoms
This is usually expressed in the form of jerks when driving at low speeds. You may lose power and increase consumption. But the most reliable indicator is the corresponding error.
How and why can I turn off the EGR valve?
First, about the goal. Shut off the valve so that soot does not flow back into the manifold. As a result, more pure oxygen enters the cylinders, and the fuel burns better. Many come to the decision that it is worth turning off the USR valve after several cleanings. Usually, environmentalists only need to look at the not-too-pleasant substance adhering to the valve a couple of times to understand that they do not want it to fly back into the intake manifold.
To close the EGR valve, the photo of which is no longer pleasing to the eye, you need to unscrew the bolts and remove the gasket. Next, cut a new blank gasket from the steel sheet according to its shape, in which there should be only 2 holes for the bolts. Now put both gaskets in place. You can also disconnect the vacuum hose.
Many car owners note that after such actions, the turbo lag disappears, smoke disappears during sharp acceleration, climbing uphill and at high speeds, dynamics and the number of positive emotions improve.
In most cases, turning off the EGR (exhaust gas recirculation) is necessary, because the intake manifold becomes dirty during the operation of the car. Various impurities form a resin that settles on the engine and system valves.
It leads to:
- a decrease in the overall efficiency of the power unit, there is a significant loss of power;
- increase in soot emissions, the exhaust system is quickly contaminated.
Removing the USR and its software shutdown solves the above problems.
What is the device of the EGR system?
As you know, the mixture burned in the cylinders consists of:
- air (21% oxygen and 78% nitrogen);
- diesel fuel, gas or petrol.
During combustion, nitrogen oxides, which are harmful to the environment, are formed. The USR system is designed to reduce the emission of these environmentally harmful substances into the atmosphere.
Principle of operation
The EGR system consists of:
- pipes attached to the exhaust and intake manifolds;
- drive;
- valve.
The last detail is the most important element in the EGR. Its operation is controlled by the ECU. The firmware of the electronic module contains the parameters of the air-fuel mixture for the operation of the vehicle in various modes.
If the engine develops power close to maximum, clean air is supplied to the cylinders. During normal driving, which does not require high loads, the system strictly controls the ratio of the mixture supplied to the cylinders and exhaust gases with the help of a valve to reduce the amount of harmful emissions.
When and why is it necessary to disable the EGR?
The operation of the EGR valve negatively affects engine performance. When the system is contaminated, its effectiveness is completely lost. As a result, even more harmful substances are released into the atmosphere. Now even environmentalists doubt the need to install exhaust gas recirculation systems on modern cars.
Besides:
- engine power is reduced;
- fuel consumption increases;
- there is a loss of momentum.
That is why it is important to make a shutdown in a timely manner. Experts recommend that you perform the USR removal procedure without fail if the car's mileage has exceeded 100,000 km.
Many vehicle owners try to do everything themselves, but this does not always lead to positive results. Failures often occur in electronic systems.
To avoid the adverse consequences of an unprofessional shutdown of the USR, you should use the services of specialized service centers. Experienced craftsmen will shut off the valve mechanically and flash the ECU to eliminate errors and failures.
Ways to disable the USR
To remove the EGR, more than just a valve plug is needed. You will also need to flash the ECU and install new software.
Let's consider these stages of car service in more detail.
Mechanical shutdown of the USR valve
The physical removal of the USR is divided into several stages.
- Air ducts are thoroughly cleaned.
- The valve is removed. It is located between the second and third nozzles. The device is very difficult to access. You will need a special key.
If the old seal is burned out, a new one is made. It is cut from asbestos sheet.
- A stub is being produced.
To close the exhaust gas channel, a special metal gasket is used with holes made only for mounting.
Software shutdown of the EGR system valve
At the stage of software shutdown of the USR, the ECU is flashed. This task is performed differently depending on the brand of car and the presence or absence of protection against reprogramming. If there is a special connector in the car interior, then the installation of new software will be very fast.
Before performing a software removal of the USR, specialists will make a thorough diagnosis of the engine and related systems. This will reveal the degree of contamination of the power unit and malfunctions.
Having received all the necessary data, the masters will reconfigure the electronic control unit. The optimal settings will be set. After a software shutdown, the on-board computer will forever “forget” about the existence of EGR.
Removing the particulate filter
In many cases, along with disabling the USR, the removal of the particulate filter is carried out. This is due to the fact that after the valve is plugged, the content of harmful impurities in the exhaust gas stream increases. The exhaust system element quickly clogs and fails.
A dirty particulate filter leads to:
- reduction in engine power;
- excessive increase in oil level;
- increase in fuel consumption.
Frequent active regeneration adversely affects the life of the power unit. There may even be a breakdown that requires urgent repair.
Oil entering the intercooler and cylinders is highly likely to cause an uncontrolled burning process. This will cause critical damage to the motor.
Removing the particulate filter helps to avoid the above problems and the cost of servicing and replacing this element of the exhaust system.
This stage of vehicle performance optimization includes:
- particulate filter compartment;
- sawing a special hole;
- matrix extraction;
- welding of the structure and its installation in the right place.
Pros and cons of shutdown
Disabling the USR and the subsequent removal of the particulate filter lead to a number of positive results.
- Firstly, the physical removal of devices and flashing the ECU will exclude the start of an emergency operation of the engine. Motor power will not be limited. In turbocharged powertrains, the main elements will not turn off.
- Secondly, the absence of a particulate filter will lead to getting rid of the active regeneration procedure, which is accompanied by a significant increase in fuel consumption. The efficiency of the engine will increase by reducing the resistance in the exhaust system. The increase in power can reach 25%.
This will extend the service life and reduce the likelihood of failure of the power unit. Avoid engine oil leaks. Its level will not exceed the maximum value.
Do not forget that recirculation also increases the rate of engine wear and adversely affects the quality of the lubricant. That is why the USR is turned off and the particulate filter is removed in most cases at the same time. This allows you to forget about the problems associated with these devices once and for all.
- Thirdly, after plugging the valve, the engine will become much cleaner. Its dynamic characteristics will improve. The efficiency of the power unit will further increase due to the absence of carbon deposits on the walls of the channels, the valve itself and the intake manifold.
- Fourthly, disabling the USR and optimizing the operation of the exhaust system will allow car owners to avoid the serious costs associated with the replacement and maintenance of expensive equipment.
For example, the cost of installing a new particulate filter can reach 150,000 rubles. In our conditions, the devices fail much earlier than the service life declared by the manufacturers.
Since there is no practical need for the USR system and the particulate filter within Russia, these costs are considered simply unjustified.
The negative consequences include only the deterioration of the environmental performance of the car and the inability to travel to the EU.
The cost of disabling and removing the USR
The total cost depends on:
- car brands;
- type of electronic control unit;
- difficulty in gaining access to the board.
At PowerChip, the service for removing the USR using the software method costs consumers 5–9 thousand rubles.
The EGR (Exhaust Gas Recirculation) system is a solution that reduces the level of nitrogen oxides in the exhaust gases of a gasoline or diesel engine. This system in relation to modern internal combustion engines is absent only on gasoline ones.
The main task of the EGR system is to effectively reduce the level of nitrogen oxides in the exhaust. The formation of nitrogen oxides during engine operation is caused by high temperatures. The increase in temperature in the combustion chamber leads to an active increase in the content of nitrogen oxides in the fuel-air mixture. The high temperature in the combustion chamber of the internal combustion engine leads to the fact that oxygen and nitrogen, which are contained in the supplied air, begin to interact with each other.
Air enters the heated combustion chamber of the engine, where nitrogen oxides are further actively formed. This means that oxygen, which is necessary for the full combustion of gasoline in units of this type, begins to be replaced by the indicated nitrogen oxides. The working mixture, under the condition of a lack of oxygen, does not burn out completely, as a result of which engine power is lost, fuel consumption increases markedly, and the toxicity of ICE exhaust gases also increases.
By returning part of the exhaust gases to the intake manifold, this slightly lowers the combustion temperature of the air-fuel mixture. Lowering the temperature automatically reduces the rate of formation of nitrogen oxides.
The ingress of part of the exhaust gases back into the intake practically does not change the required ratio of basic components to obtain a high-quality fuel-air mixture, the engine itself does not lose power in various modes, and fuel economy is also observed.
Disabling the EGR valve
In Europe and other developed countries, environmental issues are approached quite strictly. There are many disputes on the territory of the CIS on the issue of the USR. The topics of discussion among motorists are topics regarding how to “mute” the EGR of a diesel or gasoline engine, neutralize the exhaust gas recirculation system, turn off the EGR valve of a diesel engine, etc.
Many are sure that the recirculation system “strangles” the engine and the USR takes power, preventing the engine cylinders from being filled with clean air to the fullest. These include amateurs. An equally common reason for refusal to recirculate is the severe contamination of the intake manifold and the rapid failure of the system sensors, as well as the EGR valve.
All elements of the recirculation system suffer from carbon deposits when the engine is operated on low-quality fuel. Repair of the system requires certain financial costs. For this reason, some drivers immediately turn off the exhaust gas recirculation and do not care about the advisability of such a solution.
Exhaust gas recirculation: EGR valve
The main element of the exhaust gas recirculation system is the EGR valve. The entire system is based on this valve. It is the USR valve that is the solution that allows a certain part of the exhaust gases to enter the intake manifold, where they are then mixed again with the next portion of the air entering the intake.
The more oxygen is in the combustion chamber, the higher the combustion temperature of the fuel-air mixture. Adding part of the exhaust gases to the mixture means a forced reduction in the amount of oxygen. Thus, a decrease in the combustion temperature of the working mixture in the chamber is achieved. Less oxygen means less interaction with nitrogen, which ultimately reduces the amount of nitrogen oxides in the exhaust.
The EGR valve of a diesel or gasoline engine does not work the same, which depends on the characteristics of a particular type of internal combustion engine. The diesel engine has an EGR valve that opens at idle, halving the intake of fresh air. As the load on the engine increases, the EGR passes less exhaust gases into the intake, and at times of peak loads, the valve is completely closed. This valve also closes when the diesel engine is warming up. As for gasoline ICEs, the EGR valve is closed at idle, as well as during the engine reaching maximum torque. If the load on the motor is low or medium, then the valve provides only up to 10% of the air intake.
Recirculation systems operate on the principle of a closed circuit, and the EGR valve itself can be controlled:
- electrical controller;
- electropneumatically;
For the first solution, the system relies on data that comes from the position sensor to the internal combustion engine controller. It is the controller that sends the control signal to the valve. In the second case, the EGR valve is adjusted based on the readings from the intake manifold pressure sensor, the mass air flow sensor and the intake air temperature sensor.
There are engine designs that imply improved exhaust gas cooling during the operation of the recirculation system. The EGR valve in such designs is integrated into the engine cooling system. The system becomes more complex, but nitrogen oxide levels are reduced even more effectively.
According to manufacturers, the exhaust gas recirculation system has a certain number of advantages during the operation of internal combustion engines. For gasoline engines, the advantage of the USR is a lower pressure drop in the throttle area. The lower combustion temperature reduces knocking, allowing for earlier ignition for better engine torque. A diesel engine with an EGR runs softer and quieter at idle, as a lower oxygen content leads to a decrease in pressure at the time of combustion of the fuel-air mixture.
Types of diesel exhaust gas recirculation systems
High pressure EGR is installed on diesel engines that meet the requirements of Euro 4. The permissible content of nitrogen oxide in the exhaust gases according to these requirements should not exceed 0.25 g / km. The high pressure recirculation system partially removes exhaust gases from the exhaust manifold of the turbodiesel, taking them before the turbine. Next, the system redirects these gases to the channel, from where they enter the intake manifold.
The system has the following elements in its device:
- recirculation valve with electric or pneumatic actuator;
- branch pipes for removal of the fulfilled gases;
The recirculation valve (EGR valve) bypasses exhaust gases from the exhaust system to the intake. The pneumatic valve works due to the vacuum that is created in the intake manifold of gasoline ICEs. In diesel units, this vacuum is created by a vacuum pump. The vacuum that acts on the recirculation valve is in turn controlled by a control solenoid valve.
The exhaust gas recirculation process becomes more or less intense depending on the different operating modes of the power unit. The degree of intensity directly depends on the difference in pressure at the inlet and outlet. The pressure in the intake system is controlled by a throttle valve. A closed throttle means the intake pressure drops. At this point, exhaust gas recirculation proceeds more intensively. Large recirculation leads to a decrease in the flow of exhaust gases, which is directed to the turbocharger. It turns out that at the time of active exhaust gas recirculation, the turbocharging pressure of a diesel engine, which is equipped with a similar type of USR, drops slightly.
The USR system is not active in idle mode, at the moment of full throttle opening, as well as during engine warm-up and until the engine reaches operating temperature. Control over the operation of the recirculation system is carried out. The recirculation valve comes into operation at the signal of the internal combustion engine electronic control unit, which controls the position of the throttle valve using a potentiometric sensor.
Diesel internal combustion engines that comply with the Euro 5 standard imply a level of nitrogen oxide in the exhaust gases that should not exceed 0.18 g / km. These engines have a low pressure EGR system. A feature of this system is that the exhaust gases are removed behind the diesel particulate filter. Further, the gases enter the radiator of the recirculation system for additional cooling. The next step is the passage of gases through the recirculation valve and penetration into the intake in front of the turbine.
The low pressure EGR system provides the following benefits:
- reducing the amount of soot particles;
- exhaust gas temperature is effectively lowered;
- a significant reduction in the level of nitrogen oxides in exhaust gases;
An additional plus is that the exhaust gases pass through the turbocharger. This allows this recirculation system to work efficiently without reducing the boost pressure. It turns out that the engine runs without loss of power.
The recirculation rate is implemented by the engine ECU. Control is carried out using the following elements:
- throttle valve;
- recirculation damper;
- exhaust flap;
All dampers function due to the presence of an electric drive. The opening of the dampers by one or another value is measured by potentiometric sensors. The degree of damper opening level is based on a special program. This digital circuit is hardwired into the ECU, takes into account the filling of the engine cylinders, the turbocharging pressure indicator and the degree of intensity of the USR system in relation to various operating modes of the internal combustion engine.
Euro 6 diesel engines, according to which the nitrogen oxide content in the exhaust should not exceed 0.08 g / km, receive a combined recirculation system. A feature of such a system is two separate lines through which exhaust gases are recirculated. One of the lines of the combined EGR system is a high pressure line, and the other is a low pressure line.
The combined system works similarly to the recirculation system on Euro 5 engines. Additionally, exhaust gases can be supplied from the high pressure line, which is activated in certain operating modes of the power unit. The main task is to reduce the level of nitrogen oxides in the exhaust as much as possible. It should be noted that the exhaust gas cooling radiator in the combined system is absent in relation to the high pressure line.
The main causes of EGR malfunctions
The most common cause of EGR system malfunctions is carbon deposits. Intensive carbon deposits are affecting the EGR valve seat or plate. Carbon deposits are formed as a result of the operation of internal combustion engines on low-quality fuel. The recirculation system also fails due to malfunctions and malfunctions in the diesel engine power system, incomplete combustion of the fuel-air mixture, deviations in the functioning of the crankcase ventilation system, etc. The EGR system suffers from carbon deposits as a result of mechanical wear of the turbocharger, pistons and cylinders, coking of injector nozzles, as well as various malfunctions in the sensors that transmit signals to the ECU to control the EGR valve.
If the EGR valve is clogged, then it may not work correctly or jam. In the first case, untimely valve operation is noted, which is noticeable in idle mode and does not have obvious symptoms and consequences for the internal combustion engine. In the second case, the EGR valve may stick at the moment of opening or closing. Gasoline units with a stuck valve in the recirculation system are extremely unstable at idle, fuel consumption increases. Diesel engines with an inoperative EGR valve lose power, run rougher and noisier.
To identify faults in the exhaust gas recirculation system, it is necessary to conduct a visual inspection of the condition of pipelines, electrical connectors of sensors and other systems. Advanced diagnostics involves electronic scanning and a series of procedures to check the functionality of the actuators and the EGR valve itself.
It is necessary to check the resistance, as well as the presence of control signals. For this, an oscilloscope and a multimeter are used. If the scan showed that the intake pressure is different from the norm, and there is also an increased air flow, then the valve may be stuck. Replacing the EGR valve in parallel requires a thorough cleaning of the associated lines and connectors, since carbon deposits in the system can lead to the recurrence of faults in the exhaust gas recirculation system after a short period of time.
