The combustion of fuel in the powertrain of any vehicle requires an adequate supply of air. A mixture of 78 percent nitrogen and less than 22 percent oxygen enters the engine from the atmosphere. The chemical element nitrogen is slightly inert and can react with lithium.
Developers of power units try to make the efficiency of the motor as high as possible, for this purpose the temperature of the mixture and the pressure inside the system are raised. The hindering factor in the temperature increase is the thermal strength of the mixture, namely the nitrogen that is included in it. When the temperature of the inert gas rises to 2,000 degrees, it oxidizes. An increase in the percentage of oxygen leads to an increase in nitrogen oxides, the release of which into the atmosphere leads to environmental pollution. Installation of exhaust gas recirculation system or EGR allows to reduce the volume of nitrogen oxides in the exhaust of a diesel car.
The main purpose of a standard EGR module is to reduce nitrogen oxide emissions in the vehicle exhaust. To do this, a certain portion of the exhaust gases is redirected back into the intake manifold. This technology of operation provides a reduction of oxygen in the composition of the combustible mixture. As a result, the depleted composition emits less harmful substances. The main negative consequence of EGR operation is a decrease in the power of the power unit.
For most car service centers, as well as specialists in the field of ecology, disabling the exhaust gas recirculation system is acceptable. When EGR is operating, it does reduce the amount of nitrogen oxide emissions, but the amount of harmful exhaust components increases.
If the decision is made to disable EGR, the amount of soot, carbon dioxide and carbon monoxide emitted into the atmosphere is immediately reduced. The powertrain becomes more economical. Power and traction are increased. The engine runs smoothly for much longer, as no soot and tar from the exhaust gets into the cylinders. Accordingly, engine oil is no longer oxidized intensively and engine life is increased.
The exhaust gas recirculation system is installed on diesel power units only to reduce the amount of nitrogen oxide in the exhaust. EGR has no other practical value. There are several versions of the module, while the principle of operation of the equipment remains unchanged. The system takes a certain volume of exhaust gases and redirects them back into the combustion chamber. Recirculation provides a decrease in the combustion temperature of the fuel mixture and a reduction in the volume of nitrogen oxide. EGR installation is relevant not only for diesel engines, but also for gasoline engines.
The development and implementation of the recirculation system was carried out in accordance with the requirements of environmentalists. Earlier EGR was not installed on diesel and gasoline engines. The disadvantage of the system is its limited resource. After some time, the module stops working or functions with deviations. An alternative to repair is to disable EGR and operate the power unit without power reduction. In a serviceable state, the system initially does not work at high speeds, as well as when the motor goes into emergency mode. At the program level, the control module overrides the EGR operation.
Apart from the increase in the percentage of nitrogen oxide in the exhaust, there are no other negative consequences of disabling the gas recirculation system. At the same time, the engine runs reliably and smoothly. Environmental friendliness is an important component of modern cars, but the absence of costly repairs is a more important criterion.
Causes of breakdowns of the recirculation system
The EGR unit has been installed on cars for a long time. Specialized centers have long had a list of the main breakdowns of the recirculation system. The main faults are valve jamming, position sensor failure, actuator circuit breakage, exhaust leakage or suction. Each fault has several possible causes.
EGR failure due to valve jamming
The formation of large amounts of soot accompanies virtually any combustion process. For gasoline and diesel engines, pollutants settle in the valve. Accordingly, the mobility of the element is impaired. Over time, the valve jams, the system operation in normal mode becomes impossible.
Valve jamming is possible in the closed and open position. In the first case, soot does not enter the power unit. Accordingly, expensive internal combustion engine repair does not threaten the owner. Otherwise, the resource of the power unit is significantly reduced if the EGR is not blocked in time. In some cases, service centers programmatically close the valve of the recirculation system, although this method is not considered good.
In the permanently open position of the valve, residues from combustion processes directly enter the cylinders of the power unit. This position is the most dangerous for the engine. In the normal position at high speeds and at high load, the flap is also closed. At the same time, there are no negative changes in the operation of other systems when the EGR valve is disabled.
On power units of different makes and models, valve jamming is the most probable cause of EGR failure. The equipment ceases to function in the normal mode and negatively affects the operation of the motor. The main factors affecting the service life of the recirculation system are:
The use of low-quality oil and the same fuel, especially if the vehicle has a diesel power unit.
Lack of timely maintenance also affects the quality of the system. If a filter clogged with soot and tar is installed on the car, oil has not been changed for a long time, the system will quickly fail. If EGR has a quality, proven design and is timely serviced, it is enough for 150-180 thousand kilometers of mileage.
Another cause of EGR malfunction is a defect in the power unit. Any breakdown, which increases the amount of exhaust gases and their composition, inevitably affects the life of the recirculation system.
The cause of increased EGR wear is a dirty air filter, insufficient air supply to the combustion chamber, injector leaks or faulty piston rings. Some vehicle owners decide to fix EGR breakdowns while the defects on the powertrain remain. In such situations, the EGR system will soon begin to fail again.
Self-destruction of the valve is considered another EGR disease. Due to certain design features and specifics of work, the recirculation system can fail at the most unexpected moment. As the temperature in the combustion chamber rises, the volume of nitrogen oxides increases and the amount of solid soot particles decreases at the same time. When the exhaust gas is directed to recirculation, the amount of nitrogen oxide emissions decreases, but the amount of soot also increases. At some point, the soot clogs the filter element and causes the EGR to fail.
For designers, finding the optimal balance between the two components of exhaust gases is a perennial challenge. Engineers need to simultaneously meet the requirements of environmentalists and extend the life of the power unit. Very often, intensive operation of the recirculation system leads to equipment failure. Therefore, disconnecting the valve is one of the best options.
Other recirculation system defects include actuator circuit breaks and valve position sensor failure. The set and actual position of the working element do not match. Prior to repair, the system will need to be diagnosed with professional equipment. Another breakdown is considered to be the penetration of air inside. In such situations, the system is checked for tightness.
Methods of eliminating the defects mentioned above are very different. The nature of the repair depends on the type of breakdown, make and model of the power unit. To determine the cause of the error on the EGR, it is necessary to carry out diagnostics on a modern stand. The breakdown can be eliminated in several ways of varying degrees of effectiveness.
Exhaust gas recirculation system breakdowns
To eliminate breakdowns of the EGR system, several methods are used. Methods differ in the cost of work and spare parts, the main ones are considered:
- dismantling the failed valve and installing an original part in its place;
- analogous work using more affordable Chinese parts or parts from other manufacturers;
- removal of EGR from the car, program blocking of the function of exhaust gas recirculation;
- programmed closing of the system valve without dismantling the EGR unit.
The first option is the most expensive in terms of costs, but the desired effect is not always achieved. If the recirculation system has worked less than the prescribed period, it is first necessary to find and eliminate the failure of the power unit. Otherwise, repeated replacement of EGR may be required after several tens of thousands of kilometers of mileage. Accordingly, repair costs will increase significantly. The use of Chinese spare parts is the owner’s choice. In some cases there are really high quality parts, but most often in a short time the EGR repair procedure has to be repeated.
The technology of eliminating the defect by removing the block and blocking the function in a programmed way is the best way to work. Actions with mechanical units and program part require the involvement of qualified engineers, the use of modern equipment.
First of all, the movement of exhaust gases through the valve is blocked. To do this, a special plug is installed. It is quite difficult to do this, it requires experience and knowledge. It is not allowed to install plugs made of thin sheet steel or vaporite. Due to the high temperature of exhaust gases, the metal quickly burns through, in some cases degradation occurs during the first trip. The thickness of the plug should be at least 2.5-3 mm, stainless steel is used as a material.
In order to weld the valve and install the diffuser does not require special knowledge, the experience of a simple car mechanic is enough for this. Removal of the valve with a cooler requires more effort. For modifications of the valve with its own cooler, it is sufficient to install special plugs on the inlet and exhaust valves. BMW M-series powertrains are retrofitted in this manner. VW and BMW N-series vehicles are equipped with valves without a self-contained circuit. Therefore, cooling is looped in other ways.
The mechanical part of the engines of different makes and models is generally identical. Therefore, there are not many solutions with EGR disconnection, they are all similar. At the program level, different errors can occur. The issue with blocking the recirculation system is solved individually. There can be several options for disabling EGR.
At the program level, it is necessary to prohibit the opening of the EGR valve. Many specialists who have been working in this field for a long time, know the places of the firmware for editing on various makes and models of cars. In this case, the software begins to produce errors. Their exclusion is a more difficult task, but it is necessary to perform it.
The main difficulty of software customization is the potential risk of deleting unnecessary code fragments. If the engineer is not skilled enough, the control system settings can be reset, and diagnostics becomes complex and unpredictable. Fixing such problems requires significant time and financial investment.
When EGR breaks down, the recirculation system goes into emergency mode. At the program level, this function also needs to be disabled. Another software tuning task is to recalibrate the air maps. The flow distribution needs to be changed if EGR is disabled. If this issue is not worked through, the ECU functions with malfunctions. The system does not understand why there is a lot of oxygen in the incoming flow and no exhaust gases. Accordingly, the quality of the motor’s performance decreases.
Another way to disable EGR is to prohibit the opening of the valve at the program level. This method works, but it is not always recommended to use it. Most often this option is used if it is difficult or impossible to physically get to the EGR and block the valve without disassembling the engine. In situations where the valve is jammed, it will not be possible to block it by software. It is necessary to disassemble the unit and eliminate the breakage by mechanical means.
Software EGR shutdown does not always have the proper effect. The engineer cannot be 100 percent sure that the valve is closed. If even a small open channel remains, soot and other elements get into the cylinders. Also, unaccounted air enters the system. The optimal option for disabling the system is to perform operations at the program and mechanical level in a complex.
When it is necessary to disconnect EGR
For many owners of cars with an exhaust gas recirculation system, the question of disabling EGR arises unexpectedly. In this case, the timing of a visit to the car service is not always clear, because the car is functioning, although not properly.
If the car undergoes regular maintenance, the resource of the EGR valve is not less than 150 thousand kilometers of mileage. According to publicly available statistics, more owners of diesel vehicles go to service centers due to EGR failure. The ratio to gasoline engines is 80 to 20 percent. Diesel combustion produces much more soot, so the recirculation system is clogged faster.
Owners of any vehicles should monitor the condition of consumables, use quality filters, fuel and oils. In any case, the wear of the nodes and elements of the car is inevitable, so it is also necessary to carry out a comprehensive diagnosis of the engine. If problems are recorded in the work of EGR, it is necessary to check the condition of the motor in the first place. Replacement of a worn nozzle is a frequent solution to the problem with the operation of the recirculation system. If defects in the functioning of the cylinder-piston group are detected, it is not necessary to change the rings. It is easier and cheaper to plug the EGR.
Any, even minimal defect in the cylinder piston group leads to problems in EGR operation. It is expensive and unnecessary to repair the engine every time. In this case, the restoration of the recirculation system will give only a temporary effect. Therefore, disabling EGR in most cases is considered the best option.
The appearance of indication on the instrument panel in the form of the “Check engine” indicator, the transition of the system into emergency mode is not necessarily evidence of EGR breakdown. In such situations, it is necessary to carry out a comprehensive engine diagnostics, to determine the causes of reduced traction characteristics, loss of dynamics, increased smoke and fuel mixture consumption.