EGR in a diesel engine: what is this EGR system

The recirculation system in the engine serves to redirect the unburned fuel mixture from the exhaust tract to the intake tract, where the gases can be recycled, resulting in better combustion.

With an exhaust gas recirculation system (EGR), exhaust toxicity is reduced and fuel is consumed more economically. But the elements and channels of the system become clogged over time, and it is not always possible to clean them. It is for this reason that car owners are often interested in how to turn off the EGR valve on a diesel engine - it is on diesel power units that the EGR valve causes the most trouble.

If the USR valve fails, it is not always possible to restore its functionality, and not everyone can buy a new mechanism - the device for many cars is very expensive. In this article we will look at how to correctly eliminate the recirculation system without loss of engine power.

How to plug the EGR valve

When the EGR channels on an engine become clogged and the recirculation valve (EGR) stops working, soot flies into the intake tract and the gases are not cleaned. Instead of an environmentally friendly exhaust, the output turns out to be soot, and the internal combustion engine not only smokes, but also loses dynamics and operates with failures.

The design of exhaust gas recirculation may vary depending on the car model, but the principle of the EGR design is the same on all cars. How to turn off the EGR valve? Basically it is jammed very simply:

the device is completely removed from the engine;
a plug made of heat-resistant material is installed in its place.

But not on all car models you can simply install a plug - the electronics detect a violation of the mixture proportions, and in this case the Check Engine lamp lights up on the instrument panel. There is a way to programmatically disable the USR by flashing the control unit.

Let's look at an example of how you can eliminate the recirculation system on a gasoline internal combustion engine of a Chevrolet Lacetti. We proceed as follows:

First of all, we find the EGR valve itself; on a 16-valve engine it is located behind the valve cover, next to the ignition coils;
bending the plastic latch, disconnect the wires from the valve, unscrew the two bolts, remove the mechanism;
We remove the old gasket with two holes for the channels, but using its template, another one with one hole should be made;
a new gasket can be made of brass, it looks something like the picture below;
We install the manufactured gasket and mount the EGR valve in place.

Now exhaust gases will not enter the intake manifold, and soot will stop clogging the intake tract.

Check engine light on dashboard

The fact is that the car is equipped with sensors that can determine the content of harmful substances in the exhaust gases. If the content is high, this indicates the ineffectiveness of the exhaust gas recirculation system. At the same time, the Check engine light comes on. To be sure of this, you need to read the error code. This can be done either using a special scanner or using the car’s on-board computer (the error is read differently on different cars). For example, if the EGR valve in an Opel Astra is faulty, error code P0400 will be displayed. This error can be reset by disconnecting the battery terminals for 5 minutes, however, over time, the sensor will again detect an increased level of nitrogen oxide in the exhaust gases, and the “Check Engine” light will come on again.

What happens if you turn off the EGR valve on a diesel engine?

There is information on the Internet that if you turn off the EGR valve on a diesel engine, the engine will not only emit more harmful exhaust into the atmosphere, but will also overheat. One can argue about the theory for a long time, but practice shows that car owners do not experience any special problems with the engine after turning off the USR valve; on the contrary, diesel engines work even better:

dips disappear when you press the gas pedal;
vehicle dynamics are improved;
the smoke that is present when the recirculation system is clogged disappears.

Of course, the toxicity of exhaust gases with recirculation turned off will be slightly higher than with a working EGR valve. But if there are soot deposits in the SRVG (and if the quality of diesel fuel is poor, they accumulate quickly), then with recirculation turned on, there are even more harmful impurities in the exhaust. SRVG can work normally on cars that are operated in Europe with good diesel fuel. In Russia, the EGR valve does more harm to the engine than good, and it doesn’t matter what kind of car it is - Toyota Corona or Volkswagen Passat, it makes no difference.

Problems with the EGR valve

Ford Transit, Opel Astra, Chevrolet Lacetti and other cars that operate an exhaust gas recirculation system may experience some problems with its operation. This is a rather problematic system, and its weak point is the valve position sensor. If it does not work properly or does not work at all, then the ECU cannot accurately regulate the flow of exhaust gases to the intake. Starting with cars equipped with EURO-4 engines, a malfunction of the USR system requires immediate repair, since the engine power is severely limited.

Typically, if the USR system malfunctions, the following problems are possible:

The valve is fully functional, but the valve position sensor is not. In this case, the system does not understand whether the valve is in the correct position. If this happens on EURO-3 engines, then there is no loss in power, but on EURO-4 engines there are losses.
The second common problem is the EGR valve jamming in the closed position. In this case, on a EURO-3 engine there are no problems with engine operation. On EURO 4, the engine power limitation mode will be automatically activated.
The EGR valve is stuck in the open position - exhaust gases will constantly flow into the combustion chambers. In this case, there will be a noticeable loss of power on EURO-3 and EURO-4 engines. The latter will also work with restrictions due to the activation of the corresponding mode. A characteristic sign of a stuck valve will be a large amount of smoke from the exhaust pipe.
Coolant leak. There is usually no sign of a leak other than a drop in the coolant level in the coolant container.

Checking the EGR valve Opel Astra G

If the fuel consumption of an Opel Astra has increased, the car has become “dull” and smokes, you should first carry out diagnostics. If error P1405 is detected, it is necessary to inspect the USR valve, since the error indicates that the malfunction is associated with this device.

To find out what condition the valve is in, it needs to be removed; we carry out the removal work in the following order:

dismantle the upper decorative engine cover;
we find the valve, it is located behind the valve cover, next to the crankcase ventilation pipe;
pull off the plug with wires from the valve, unscrew the two bolts that secure this device;
Having removed the mechanism, we inspect its channels. If the EGR valve is not too dirty, we clean it. To clean the channels, it is best to use a carburetor cleaner; this product removes soot from the surface of the parts well. If desired, you can also plug the recirculation system by installing a solid gasket under the valve, without a hole for the channel.

How does the USR work on a turbodiesel?

The main function of the EGR system is the partial return of exhaust gas to the intake manifold for the purpose of afterburning. On a diesel engine, this solution allows for softer and smoother operation of the engine, which improves its performance and reduces fuel consumption, and the exhaust reduces its toxicity. The appearance of exhaust gases in the intake does not change the ratio of the main components of the combustible mixture, power is not lost in different operating modes, and fuel is saved.

The principle of operation of the USR valve on diesel engines is the connection of part of the exhaust gases with air entering through the intake manifold. Engine exhaust contains nitrogen oxides due to increased heating of gases in the combustion chamber. When the EGR system is activated, combustion occurs at a lower temperature, and the level of harmful substances in the exhaust becomes lower. On diesel engines, the valve opens automatically at idle, and closes under load and maximum power.

Harm and benefits of the EGR valve

The EGR system is primarily designed to purify exhaust gases and reduce their toxicity. Recirculation is most often found on diesel internal combustion engines, since the issue of reducing the level of CO in the exhaust tract is most relevant for diesel engines. But if you read reviews from Russian car owners on forums, it becomes clear that there is practically no benefit from SRVG. Among the disadvantages of the system (when channels become coked), car owners note:

premature wear of piston group parts due to a clogged USR system;
failures with a sharp increase in speed, decrease in power;
increased fuel consumption.

The fact that more fuel is consumed with a faulty SRVG is logical - the engine runs on soot and soot, so the air-fuel mixture burns worse. The USR system works well on new engines, but as the internal combustion engine parts wear out, it only causes harm.

Purpose

The USR system allows you to reduce the level of emissions of harmful substances onto the street. Its work is based on replacing part of the oxygen with an oxygen-free mixture (exhaust gases). Due to this, the likelihood of nitrogen oxidation in the combustion chambers of the engine will be reduced. Most drivers believe that through the USR system, exhaust gases are fed back into the engine for afterburning, which is incorrect. There is no afterburning, just the volume of oxygen in the combustion chambers is reduced, and nothing more.

It is worth noting that the USR valve is just one of the elements of the entire system, and it is the main one. Like any other valves, it passes through itself a certain amount of exhaust gases, which subsequently enter the combustion chambers. It is controlled by the vehicle's electronic system and opens/closes strictly according to ECU commands.

How to turn off the egr valve on a diesel engine: video

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Why is the USR system needed?

The appearance of the USR (Exhaust Gas Recirculation system) in a car engine is not so much connected with the fight for environmental friendliness, but was the result of the struggle to increase its engine life. The method of returning part of the exhaust gases to the combustion chamber was patented and applied by German designers back in the 30s of the last century. At that time, few people thought about reducing the toxicity of car exhaust. The main task of “diluting” the working mixture with exhaust gases was to reduce the maximum temperature of its combustion to prevent detonation, which destroys the parts of the CPG.

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Symptoms of a problem

Valve failure can lead to adverse consequences, so drivers should promptly determine if this part is faulty. Here are a few signs that will help you:

unstable engine operation at idle speed;
regular engine stops and detonation;
jerky movement and noticeable misfires;
The check light on the dashboard comes on.

Valve failure can be identified using the electronic control unit. The system will generate errors during diagnostics. If their code corresponds to P04XX (instead of XX, a number from 00 to 04), then the problem lies in the EGR valve. In the technical manual of the ECU you can see the decoding for each of these errors. If the above-described signs are detected, we recommend conducting computer diagnostics (either on your own or in a specialized technical center).

How does the air recirculation (EGR) system work?

The operating principle of EGR is the same on all engine models. During maximum load at medium speeds, a strictly defined amount of exhaust gases from the exhaust manifold is supplied to the intake manifold. The volume of supplied exhaust gases (5 - 12% of the total volume of air in the mixture) increases simultaneously with an increase in the ignition timing and falls when it decreases.

The supply is controlled by a valve that opens when a certain number of engine speeds is reached (usually from 1500 rpm). It closes after reaching maximum speed or dropping to “idle”.

The valve drive can be vacuum or electronic. Depends on the year of manufacture, type and design of the engine.

Diesel fuel and USR

Cars running on diesel fuel are a separate issue and it’s worth weighing everything before turning off the EGR valve on a diesel engine. Car owners often complain about a decrease in power and engine smoke. The myth that turning off the USR valve on a diesel engine increases engine power is refuted by scientific tests. Power is increased due to the absence of carbon deposits on the walls of the intake manifold, channels and the valve itself. When answering the question of how to properly shut off the USR valve on a diesel engine, you should pay attention to two mandatory steps: