Sooner or later, car enthusiasts are faced with a situation where the car for some reason begins to lose power, and fuel consumption increases. The culprit may be a spent 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 environmental degradation on the planet. Factories and plants, without any restrictions, emitted hazardous waste into the atmosphere, and the number of cars on the roads grew steadily. Even then, megalopolises were inhaled by the blue fog of car exhaust.
In 1970, a requirement was made to foreign manufacturers - to equip the machines with an exhaust gas neutralizer. Carbon monoxide, a product of incomplete combustion of hydrocarbon fuel, was considered the main harmful emission. Since 1975, the installation of catalysts has been a mandatory requirement for car manufacturers abroad.
Why is a catalyst needed and how does it work
As is known from chemistry lessons, a catalyst is a substance that stimulates a chemical reaction, while not participating in the creation of a new substance. Modern catalysts for exhaust systems perform two functions:
- afterburning of carbon monoxide (CO) before its transition to the state of carbon dioxide (CO2);
- separation of nitric oxide into nitrogen and oxygen.
The performance of these two functions divided the catalytic converters into two varieties: reducing and neutralizing catalysts. Often, two types of elements are installed in one housing in order to perform both functions.
In order for the reaction to proceed as efficiently as possible, the substance responsible for the reduction reactions is applied to ceramic elements made in the form of honeycombs. Their hexagonal shape allows you to create not only a large area of contact of the exhaust gases with 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 characterized by high strength and has a small minus: in case of failure, it is impossible to knock out a metal catalyst like a ceramic one. We have to disassemble the case, repairs become more expensive.
Why knock out the catalyst? During operation, its flow area is constantly reduced, and there comes a time when normal operation of the engine 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
A lambda probe or oxygen sensor is directly related to the catalyst. It measures the amount of oxygen in the exhaust. In accordance with the signal from the sensor, the car computer controls the composition and quantity 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 increase the accuracy of the readings. However, this also creates problems in the case of tuning the exhaust system or when removing the auto catalyst. The sensor installed after the converter misleads the computer, after which the fuel consumption increases and the engine power drops. Therefore, in the case of repair, you need to know, not only how to knock out the catalyst, but also what needs to be done after this in order to restore operability.
The place of the catalyst in the exhaust system
The catalytic converter is part of the vehicle’s exhaust system. It happens both in the form of a separate element, and assembled with a silencer. The first option is much more convenient, since when replacing the catalyst, neither replacement of the muffler nor welding work on inserting a new part is required.
The catalyst is installed in two places, depending on the model of car. In the first case, in the engine compartment, immediately after the exhaust manifold. In the second version, also after the exhaust manifold, but under the bottom of the car.
Landing holes for oxygen sensors are welded into the exhaust pipe before and after the converter.
There are silencers without catalyst. The cars of the Soviet era did not have environmental safety requirements. Therefore, on the machines of that time, these elements of the exhaust system are not.
How to check performance
The main symptom of a clogged catalyst may be loss of power. This is because the flow cross section becomes negligible and the exhaust fumes cannot exit to the end during the exhaust cycle of the engine. During the intake stroke, the exhaust gases are mixed with the fresh mixture, impairing combustion. As a result, there is a drop in acceleration dynamics and an increase in fuel consumption. But how to understand for sure that it was the neutralizer that caused the cause, and not anything else?
There are three ways to do this:
- Remove the catalyst and look at its clearance. This is the surest, but also time-consuming method. Requires dismantling work. In addition, not every neutralizer can be checked in this way. Those that are welded into the exhaust system cannot see through the lumen.
- Check with pressure. To do this, a manometer is screwed into the second lambda probe, the engine starts. If at a crankshaft speed of 2500 rpm the pressure is 0.3 kg / cm 2 or less, then replacement is not required.
- Measurement of pressure by a motor tester. To do this, a sensor is screwed into the spark plug hole and the pressure in the exhaust system is measured. If it exceeds 200 kPa, then this indicates the need for replacement.
The latter method is the most technologically advanced, it is performed only in specialized workshops, for example, auto repair services for muffler repair in Moscow.
Replacement or removal
When the car owner encounters this malfunction, the question arises before him: is it necessary to knock out the catalyst or replace it with a new one. The answer lies in several planes. The first is the cost of the new part. A neutralizer is not an expensive thing. It contains precious metals (platinum, gold, palladium), which determines the price. The cost can be so high that the owner will definitely decide to knock out the catalyst.
How do drivers of a different category look at 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.
A third category of people also buys a new part. However, they are driven by a different motive. They sincerely worry about the ecology on the planet, they are not indifferent to the way people who follow their car will breathe.
Is it possible to clean the catalyst myself
The service life of the converter is 150 thousand kilometers. This is ideal: not worn out engine, high-quality fuel. The usual option, when the catalyst begins to make itself felt, is the mileage of 70-80 thousand km. Is there any way to extend its life? It turns out you can. For this, cleaning should be included in the list of scheduled maintenance work. It is done in several ways:
- Adding additives to the fuel tank that cleanse carbon deposits. This method is good in that it is cleaned without dismantling the part. The downside is that it is not known whether the goal is achieved.
- Blowing out ceramic honeycombs with compressed air. This option allows you to visually determine the degree of contamination, as well as the final result.
- Washing cells with aerosol formulations to clean carburetor jets.
The last two options involve disassembling the exhaust system. All these methods can increase the life of the catalyst, however, it must be understood that despite the good passability of exhaust gases, the elements of the catalyst have a certain service life, after which they lose their effectiveness.
Tools required for work
Before knocking out the catalyst, you need to determine what type of element is inside. If ceramic, then the amount of work includes dismantling, knocking out an element. If there is a metal element inside, then it will not work out. To remove it, you will have to cut the converter body, then brew it. Based on this, a different tool is needed. To carry out the work you will need:
- A set of keys, which includes both open-end wrenches and ratchets with heads.
- Spray lubricant like WD-40. From high temperatures, the bolts of the silencer connections become very acidic; it is almost impossible to turn them off without lubrication.
- Scrap or mount for knocking out ceramics from the body.
- Grinder and welding machine in case of removal of a 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.
- New gasket between catalyst and silencer. Usually the elements of the exhaust system stick to each other, so they have to be separated from each other with the help of a mount. At the same time, the gaskets located between them suffer.
In addition to the above, you may need a lift, a viewing hole, depending on the model of car. If the catalyst is installed in the engine compartment, then just a flat area.
Disassembly instructions
It is not difficult to independently remove the internal elements of the catalyst. The difficulty can only be in loosening the attached nuts. Therefore, it must be remembered that they should only be turned off after treatment with penetrating lubricant. Also, they can not be unscrewed in one pass. This must be done by a “little doctor”, turning away at a small angle, then returning back. If you try to unscrew immediately, then you can break off the mounting studs, which will greatly complicate the repair.
In order to dismantle the catalyst, you need to:
- Place the machine on a lift or on a viewing hole.
- Disconnect the negative terminal from the battery.
- Disconnect the oxygen sensor wires from their connectors.
- Remove the bolts connecting the main muffler and catalyst. If the catalyst is connected together with the middle part of the exhaust system, you will have to completely dismantle it.
- Having unhooked the middle part of the muffler from the fastening rubber, remove the catalyst.
Knocking out the catalyst
After removing the converter, you need to carefully inspect 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 instead weld a pipe of the same length. Then weld a nut into which the oxygen sensor will be screwed.
Car owners complain that after removing the catalyst in the muffler there was a ringing. This happens if you simply knock out ceramic elements from the body. To avoid this, you need to install a flame arrester, which will narrow the flow area and eliminate the resonant effect.
When dismantling, you also need to pay attention to the corrugation installed in front of the catalyst.
This part reduces the transmission of vibration from the muffler to the exhaust manifold, rigidly mounted on the engine. Typically, up to 70 thousand km of run, the corrugation rusts and delaminates. Therefore, making work with the catalyst, it will not be superfluous to change this part.
The exhaust system is going in reverse order.
Firmware after removal
After removal of the catalyst elements, the following occurs. Car power increases, the engine runs more smoothly, 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 constantly light up on the instrument panel. What to do in this case?
There are two options. The first, less expensive is the use of snag. This device is installed instead of an oxygen sensor, which gives the “correct” ECU signal. According to the principle of action, there are mechanical and electronic frauds.
The second option is flashing the on-board computer. Usually, the firmware version changes 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. Diagnostics that change firmware are easier to find in big cities. For example, in Moscow muffler repair services they will always tell you where to find such a specialist.