How to knock out the catalyst? Why do you need a catalyst in the exhaust system of a car

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:41

Sooner or later, motorists are faced with a situation where the car, for unknown reasons, begins to lose power, and fuel consumption increases. The culprit could be a expired catalytic converter. How to return the car to working condition, is it possible to knock out the catalyst and how to do it painlessly, this article will tell.

A bit of history

Back in the 60s of the last century, the progressive minds of mankind began to sound the alarm associated with the deterioration of the ecology on the planet. Factories and factories were throwing harmful waste into the atmosphere without any restrictions, and the number of cars on the roads was steadily growing. Even then, megacities were covered in a blue haze of car exhaust.

In 1970, foreign manufacturers were required to equip cars with exhaust gas neutralizers. Carbon monoxide, a product of incomplete combustion of hydrocarbon fuel, was considered to be the main harmful emission. Since 1975 installation of catalytic converterswas a mandatory requirement for car manufacturers abroad.

Why do we need a catalyst and how does it work

As you know from chemistry lessons, a catalyst is a substance that stimulates a chemical reaction, while not participating in the creation of a new substance. Modern exhaust catalysts perform two functions:

• afterburning carbon monoxide (CO) until it turns into carbon dioxide (CO2);
• separation of nitric oxide into nitrogen and oxygen.

The fulfillment of these two functions has divided catalytic converters into two varieties: reducing and neutralizing catalysts. Often, two types of elements are installed in one housing to perform both functions.

In order for the reaction to proceed as efficiently as possible, the substance responsible for the reduction reactions is deposited on ceramic elements made in the form of honeycombs. Their hexagonal shape allows not only to create a large area of contact between the exhaust gases and the catalyst, but also gives high strength, which is important for brittle ceramics.

Varieties of Neutralizers

In addition to ceramic elements, there are metal ones. This variety is highly durable and has a small minus: in case of failure, it is impossible to knock out a metal catalyst like a ceramic one. You have to disassemble the case, the repair becomes more expensive.

Why knock out the catalyst? During operation, its flow area is constantly decreasing, and there comes a moment whenwhen normal engine operation becomes impossible. To restore the cross section of the exhaust system, ceramic elements are knocked out of the converter housing.

What is a lambda probe and its role in the exhaust system

Lambda probe or oxygen sensor is directly related to the catalyst. It measures the amount of oxygen in the exhaust gases. In accordance with the signal from the sensor, the car computer regulates the composition and amount of the fuel mixture.

Some car models have two oxygen sensors. One is installed before the catalyst, the second - after. This is done in order to improve the accuracy of the readings. However, this also creates problems in the case of tuning the exhaust system or when removing the car's catalyst. The sensor installed after the converter misleads the ECU, after which fuel consumption increases and engine power drops. Therefore, in the event of a repair, you need to know not only how to knock out the catalyst, but also what needs to be done after that in order to restore performance.

Catalyst location in the exhaust system

The catalytic converter is part of the vehicle's exhaust system. It is available both as a separate element and as an assembly with a silencer. The first option is much more convenient, since when replacing the catalyst, neither the replacement of the muffler nor the welding work on inserting a new part is required.

The catalyst is installed in two places depending on the car model. In the first case, in the engine compartment, immediately after graduationcollector. In the second version, also after the exhaust manifold, but under the bottom of the car.

The mounting holes for the oxygen sensors are welded into the exhaust pipe before and after the converter.

There are mufflers without a catalyst. There were no environmental safety requirements for cars of the Soviet era. Therefore, on the machines of that time, these elements of the exhaust system are not.

How to check if it works

The main symptom of a clogged catalytic converter may be loss of power. This is because the cross section becomes negligible and the exhaust gases cannot escape completely during the exhaust stroke of the engine. During the intake stroke, the exhaust gases mix with the fresh mixture, worsening combustion. The result is a drop in acceleration dynamics and an increase in fuel consumption. But how do you know for sure that the converter was the cause, and not something else?

There are three ways to do this:

1. Remove the catalyst and look at it through the light. This is the surest, but also the most time-consuming way. Requires demolition work. In addition, not every neutralizer can be tested in this way. Those that are welded into the exhaust system cannot be seen through the light.
2. Check with pressure. To do this, a pressure gauge is screwed into the second lambda probe, the engine starts. If at 2500 rpm the pressure is 0.3 kg/cm2 or less, replacement is not required.
3. Measuring pressure with a motor tester. To do this, in the candle holethe sensor is screwed in and the pressure in the exhaust system is measured. If it exceeds 200 kPa, then this indicates the need for replacement.

The last method is the most technologically advanced, it is performed only in specialized workshops, for example, muffler repair services in Moscow.

Replacing or deleting

When a car owner encounters this malfunction, the question arises before him: should the catalyst be knocked out or replaced with a new one. The answer lies on several levels. The first is the cost of a new part. The neutralizer is not cheap. It contains precious metals (platinum, gold, palladium), which determines the price. The cost can be so high that the owner definitely decides to knock out the catalyst.

How do drivers of another category view this problem? They believe that making changes to the design of the car does not lead to anything good. Therefore, they decide to install a new converter.

The third category of people also buys a new part. However, they are driven by a different motive. They are sincerely concerned about the ecology on the planet, they are not indifferent to what people who follow their car will breathe.

Can I clean the catalyst myself

The service life of the converter is 150 thousand kilometers. This is ideal: not a worn out engine, high-quality fuel. The usual option, when the catalyst begins to make itself felt, is a mileage of 70-80 thousand km. Is there any way to extend its lifespan? It turns out you can. For this ina list of scheduled maintenance work should include cleaning. It is done in several ways:

1. Addition of additives to the fuel tank, cleaning from carbon deposits. This method is good in that cleaning is performed without dismantling the part. The downside is that it is not known whether the goal has been achieved.
2. Blowing ceramic honeycombs with compressed air. This option allows you to visually determine the degree of contamination, as well as the final result.
3. Flushing honeycombs with aerosol compounds to clean carburetor jets.

The last two options involve dismantling the exhaust system. All these methods can increase the life of the catalyst, however, it must be understood that despite the good permeability of the exhaust gases, the catalyst elements have a certain life, after which they lose their effectiveness.

Tools needed for work

Before knocking out the catalyst, you need to determine what type of element is inside. If ceramic, then the scope of work includes dismantling, knocking out the element. If there is a metal element inside, then it will not work to knock it out. To remove it, you will have to cut the body of the converter, then weld it. Based on this, a different tool is needed. To carry out the work you will need:

1. A set of wrenches that includes both open-end wrenches and ratchet heads.
2. Spray penetrating lubricant like WD-40. From high temperatures, the bolts of the muffler connections turn very sour, it is almost impossible to unscrew them without lubrication.
3. Scrap orpry bar for knocking ceramics out of the body.
4. Grinding machine and welding machine in case of removal of the metal element from the catalyst. Also, these tools may be needed if the converter is welded to the exhaust pipe, as in the case of the Chevrolet Niva.
5. New gasket between catalytic converter and muffler. Usually, the elements of the exhaust system stick to each other, so they have to be separated from each other with a mount. At the same time, the gaskets between them suffer.

In addition to the above, you may need a lift, a viewing hole, depending on the model of the car. If the catalyst is installed in the engine compartment, then just a flat area is enough.

Dismantling instructions

It is easy to remove the internal elements of the catalyst yourself. The difficulty may lie only in unscrewing the stuck nuts. Therefore, it must be remembered that they should be unscrewed only after treatment with a penetrating lubricant. Also, they cannot be unscrewed in one pass. You need to do this “rolling”, turning away at a small angle, then returning back. If you try to unscrew it right away, you can break off the fastening studs, which will greatly complicate the repair.

In order to dismantle the catalyst, you need:

1. Put the car on a lift or on a viewing hole.
2. Disconnect the negative terminal from the battery.
3. Disconnect oxygen sensor wires from their connectors.
4. Unscrew the bolts connecting the main muffler and catalyst. If the catalyst is connected to the middle part of the exhaust system, then it will have to be completely dismantled.
5. Unhook the middle part of the muffler from the mounting rubber bands, remove the catalyst.

Knocking out the catalyst

After removing the converter, you need to carefully examine it and decide what to do next. If the case is heavily corroded, then it makes no sense to simply knock out the ceramic element. In this case, it is better to replace the part with a piece of pipe of a suitable section. Mounting flanges will need to be welded to this pipe. In other words, it is necessary to cut out a can of catalyst and weld a pipe of the same length instead. Then weld the nut into which the oxygen sensor will be screwed.

Car owners complain that after removing the catalyst, a ringing appeared in the muffler. This happens if you simply knock out the ceramic elements from the case. To prevent this from happening, you need to install a flame arrester, which will narrow the flow area and eliminate the resonating effect.

When dismantling, you also need to pay attention to the corrugation installed in front of the catalyst.

This part reduces vibration transmission from the muffler to the exhaust manifold, which is rigidly mounted on the engine. Usually, by 70 thousand kilometers, the corrugation rusts and exfoliates. Therefore, when working with a catalyst, it will not be superfluous to change this part.

The exhaust system is assembled in reverse order.

Firmware after removal

After removing the catalyst elements, the following happens. Vehicle power is increased, the engine runs smoother and fuel consumption is reduced. But this happens if one oxygen sensor is installed on the exhaust system. If there are two sensors, then in this case the on-board computer will not work correctly and the engine error message will be constantly lit on the instrument panel. What to do in this case?

There are two options. The first, less expensive, is the use of trickery. This is a device installed in place of the oxygen sensor, which gives the "correct" signal to the ECU. According to the principle of operation, snags are mechanical and electronic.

The second option is flashing the on-board computer. Usually the firmware version is changed to an earlier one, when the exhaust systems worked with only one oxygen sensor. For example, Euro-4 is changing to Euro-2. This method is more expensive, but at the same time more effective.

In addition, you can install firmware that changes the operation of the engine in the direction of increasing power or in the direction of efficiency. It is easier to find diagnosticians who change firmware in big cities. For example, Moscow muffler repair services will always tell you where to find such a specialist.