A catalytic converter (popularly just a catalyst) is an element of the car exhaust system designed to reduce the toxicity of the combustion products of the air-fuel mixture. Partially muffles the sound of the exhaust due to the selection of heat. It is controlled by one or two oxygen sensors (lambda probes), based on the signals from which the ECU (electronic control unit) adjusts the proportions of the air-fuel mixture. In general, it does not affect anything, except for an attempt to preserve the ecology on planet Earth.

Catalyst removal is an illegal intervention in the design of the exhaust system of a car, which consists in cutting out the element completely, or in knocking out its filling. This is done for several reasons, but the result is always the same - the car emits exhaust gases into the atmosphere without any reduction in toxicity. It is also believed that the removal of the catalyst can reduce fuel and engine oil consumption, as well as increase engine power.

The article turned out in such a way that the author, on many points, almost in plain text discourages removing the catalyst without installing a new one. In fact, the purpose of the material is not to convince anyone of something. The purpose of the article is to collect in one place as much unbiased and understandable information as possible, on the basis of which the reader could draw the most objective conclusions and broaden his horizons.

Why remove the catalytic converter

Very rarely, when removing the catalyst, the goal is to increase engine power or reduce fuel consumption. In general, no one remembers this element of the car's exhaust system as long as it works properly. However, like any other part of the car, the catalytic converter is far from eternal.

The main reason for the removal of the catalyst is its high cost
The main reason for the removal of the catalyst is its high cost

He works under extremely harsh conditions. Literally at the forefront. Takes on the exhaust gases directly from the exhaust manifold. And here they are hot, dense and moving fast. Accordingly, over time, the catalyst fails - it clogs, melts, or even crumbles. As a result, the throughput of the exhaust system decreases and the engine, as they say, chokes itself.

This is the most common reason for catalytic converter removal. Approximately 25% of domestic motorists buy and install a new one. The rest are cut out worn out, and various folk methods are trying to get around with new problems that have arisen. But we'll talk about them later.

Why can't you just take it and replace the failed catalyst? Everything is simple. This item is not cheap. If you buy a new neutralizer in the original design, then even for the simplest car it can cost 10-30 thousand rubles. In this case, it is not advisable to resort to searching for a used catalyst. As well as buying a cheap fake for the original.

It is clear that such expenses for many motorists are considerable, if not unaffordable at all. Especially when you consider that replacing a clogged catalyst personally will not bring any tangible benefits to the car owner. As they say, this detail does not affect the speed. Only for the environment.

To be fair, this is not the only purpose of catalyst removal. There are cases when masters from service stations insist on this (of course, not from dealerships), promising a significant increase in power, throttle response and, of course, a reduction in fuel consumption by almost one and a half to two times. There are those who, after reading a couple of articles on the Internet, came to the hasty conclusion that removing the catalyst is an excellent and cheap form of tuning.

Be that as it may, most often the catalyst is removed without replacement for the same reason - the old one clogged (crumbled, melted), and the new original one costs at least two or three full tanks of gasoline. So, it turns out that 75% of cars with a mileage of more than a hundred thousand kilometers drive on domestic roads without catalysts.

Catalyst life

Broken catalyst
Broken catalyst

The service life of the catalyst varies from a couple of hundred to 150 thousand kilometers. This mileage depends on many factors:

  • original spare part or fake;
  • fuel quality;
  • gasoline octane number;
  • timely replacement of the air filter;
  • driving style;
  • technical condition of the engine;
  • dustiness of the environment;
  • average temperature in the region;
  • condition of roads (deep pits, sprinkling with reagents, etc.).

Under ideal conditions, the catalytic converter is fully capable of working out 100 - 150 thousand kilometers. After that the problems will start. In particular, the power and throttle response of the engine will decrease, fuel consumption will gradually increase, idle speed may fluctuate, and so on. When a full fox comes to the catalyst, the car will be difficult to start, it may stall on the go, or its operation will become completely impossible.

By the way, although few people are interested in this, the decrease in exhaust toxicity also worsens over time. The active surface of the catalyst filling decreases, and more and more harmful compounds “leak” into the atmosphere. A completely clogged catalyst does not help in the fight for the notorious ecology in any way.

Signs of a dead catalyst

A working catalyst must be fully translucent
A working catalyst must be fully translucent

There are several indirect signs indicating partial or complete wear of the catalytic converter:

  • the level of carbon monoxide in the exhaust gases has increased (but this must be measured);
  • the engine power has decreased (you can’t really determine it by eye either);
  • increased fuel consumption;
  • idle speed began to “float”;
  • exhaust gases have a sharper and more noticeable smell;
  • the noise level of the exhaust system has increased;
  • visible smoke began to appear;
  • Check light on dashboard engine;
  • the catalyst "departed" for more than 100 thousand kilometers.

It is worth noting that almost none of these signs separately allows you to accurately establish the fact of serious wear of the catalyst. The most obvious and guaranteed way to verify this is barbaric disassembly with a grinder. Also, in some advanced cases, wear can be seen if you simply remove the catalyst. It either does not shine through (it clogged tightly or melted), or its filling spills out (shedding).

Removing the catalyst and saving on buying a new one

The catalyst is in this location
The catalyst is in this location

If we are honest about the pros and cons of removing the catalyst, then this item is the only adequate advantage (and at the same time an excuse). As mentioned above, the part in the original version costs relatively a lot of money. And taking into account the uselessness of the catalyst in terms of the dynamic characteristics of the car, its replacement naturally raises doubts among many.

Of course, just taking it and removing the catalyst without other actions (and expenses) will not work. You will have to at least insert a flame arrester in its place. And it will also be necessary to somehow “deceive” the ECU so that it “does not notice” the loss. And the procedure itself, if you do not dare to do it yourself, costs money. In general, expenses cannot be avoided. Although it is possible to reduce them, of course.

Catalyst removal and fuel consumption

On this point, who says what. Some argue that the consumption after removing the catalyst does not change. Others note with sadness that the car began to take even more fuel than before. Naturally, there are those who talk about reducing consumption, naming different indicators. For some, this is 3%, and for those who are more interested in convincing you to remove the catalyst, they promise up to 30% fuel savings.

After removing the catalyst, the flow rate may decrease, increase, and stay the same
After removing the catalyst, the flow rate may decrease, increase, and stay the same

In fact, the situation with fuel consumption after the removal of the catalytic converter is far from always unambiguous. If we reduce all similar factors, then we can leave only three possible outcomes:

  1. Fuel consumption will increase. This happens when the catalyst is removed without any manipulation of the oxygen sensors or the ECU firmware. The latter "detects" the loss, and begins to rigorously adjust the composition of the air-fuel mixture. As a result, the car stops driving normally, and consumption rises.
  2. Fuel consumption will not change. Such a “success” awaits those who, after removing the catalyst, installed a new spare part, or successfully “deceived” the ECU by slipping it an adapted firmware or dummy oxygen sensors (the so-called snags).
  3. Fuel consumption will decrease. For this to happen, many conditions are needed. First, the removed catalyst must be killed tightly. Secondly, the cutting was done correctly, taking into account the "needs" of the computer. Thirdly, if the consumption decreases, then not much.

In any case, the flow rate after the removal of the catalyst will not decrease in any way more than to the nominal value. And even then, hardly. As practice shows, if in reality it turns out to achieve some kind of reduction in consumption, then perhaps by a miserable couple of percent. You can save much more if you read how to shift gears on a mechanic, or to drive an automatic.

Well, in conclusion, on fuel consumption after removing the catalyst, I would like to say a few words about the opinion of a colleague. Yes, if you remove a clogged catalyst from the path of the exhaust gases, the resistance will theoretically decrease. So, fuel consumption is simply bound to be reduced. But. Almost no one leaves the place of the remote catalyst empty. At a minimum, a flame arrester is installed in this part of the exhaust system, which, again, creates resistance to the exhaust gases. Why it is installed - it is said below.

Catalyst removal and engine power

The increase in power after the removal of the catalyst is not a fact, but it is possible (by 5 percent, no more)
The increase in power after the removal of the catalyst is not a fact, but it is possible (by 5 percent, no more)

Here everything is the same as with fuel consumption. It is impossible to say with absolute certainty that after the procedure in question, the engine power will certainly increase. Therefore, it is also impossible to rank this item among the advantages of removing the catalyst. To really increase the power, you need to try harder. If, however, it is not possible to fully “deceive” the ECU, there is nothing to dream of any increase in horses. Everything will be rather the opposite.

Catalyst removal and engine oil consumption

In some interested sources, the advantages of removing the catalytic converter without replacing it with a new one attributed to reducing engine oil burn. Don't be naive Internet users. If the engine of your car eats oil in buckets, then removing the catalyst will not help you at all. Yes, the throughput of the exhaust system indirectly affects the consumption of engine oil. But it is so negligible that it is foolish to hope for noticeable improvements only after cutting out the converter.

Catalyst removal and exhaust system noise

We smoothly move on to 100 percent minuses of removing the catalytic converter. The first thing to consider here, perhaps, is to consider an increase in the noise of the exhaust system. The worst outcome in this regard is obtained when the “bank” of the catalyst is cut with a grinder, the contents are removed, after which the outer shell is simply welded.

If the catalytic converter is simply removed, the exhaust noise will be louder
If the catalytic converter is simply removed, the exhaust noise will be louder

Let's say that a welder from God was engaged in repairs, and it turned out even hermetically. However, after such a “tuning”, the exhaust system will significantly increase the noise. Moreover, a loud and clearly audible ringing sound will appear. It is the hot and fast-moving exhaust gases that resonate in the empty "bank" of the catalyst. If the car with poor sound insulation, then this ringing will pester you in the cabin while driving.

The result will be slightly better if, instead of the barbarously withdrawn catalyst filling, a so-called flame arrester is inserted into the empty “jar”. A similar "success" can be achieved if the part is completely cut off through the pipes, and a full-fledged flame arrester is welded in its place. This solution helps due to the fact that the exhaust gases here are partially cooled, slowed down and dissipated. The bonus is a slight increase in the resource of the resonator, in particular, and the entire exhaust system, in general.

To achieve the same volume and tone of the exhaust system, as expected, is possible only by installing a new catalyst. No flame arresters or any other collective farm will help here. Moreover, it is possible to repair before the fact that the machine will noticeably lose power and throttle response, as well as increase fuel consumption. That's it. Sometimes it happens.

Catalyst removal and bad smell

After removing the catalytic converter, the exhaust gases leave the exhaust system "as is". First, the high concentration of carbon monoxide. Secondly, a higher temperature than expected. Thirdly, other smelly impurities that burn out and decompose in the working catalyst. We will not touch the quality of our domestic fuel yet.

Due to its properties, the catalyst filling neutralizes the pungent exhaust odor
Due to its properties, the catalyst filling neutralizes the pungent exhaust odor

Based on the combination of all these factors, such a sharp and unpleasant smell begins to come from the exhaust pipe that many people note this minus on the forums as the most important. For some, the stench penetrates into the cabin, and not only during the engine warm-up, but also when driving. There is no way to get rid of this pungent odor. Nothing can beat him either. By the way, you won’t envy those who drive behind you in a dense stream and with the stove turned on.

Catalyst removal and ecology

Not everyone is interested in ecology, but the catalyst was invented precisely to preserve it
Not everyone is interested in ecology, but the catalyst was invented precisely to preserve it

The biggest disadvantage of removing the catalyst in fact is a multiple increase in exhaust toxicity. This means air pollution and environmental degradation. Of course, for many, this disadvantage is not significant. Yes, what is there. Most don't care at all. Especially against the backdrop of high prices for new catalysts. The loss of several thousand money is in every way more noticeable and real than the deterioration of the environment, which everyone talks about, but few people see.

It is also worth adding here the opinion that a small car without a catalyst, in general, does not affect the environment so much. Especially often this meager harm is compared with sky-smoking factories, jet planes, multi-ton ships, and so on. Like, what is my runabout compared to all this? This position seems to be correct. But it only seems.

Catalyst Removal and Law

No mandatory technical inspection - no problem
No mandatory technical inspection - no problem

It is prohibited by law to modify the factory design of a vehicle's exhaust system. Both article and punishment are provided. But at the time of writing this material, all this works extremely inefficiently. No one controls the presence and performance of catalysts on the roads. Inspection in many countries is not mandatory. Accordingly, most do not even know that such a law exists at all. In the western part of Europe, for example, this issue is taken more seriously. For toxic exhaust, they are punished with an amount that significantly exceeds the cost of a new original catalyst.

Pros and Cons of Catalyst Removal - Summary Table

In order to collect all the pros and cons of removing the catalyst as clearly as possible, there is no better way than a table. Here she is.


What does catalytic converter removal do?

Catalyst removal - is it necessary

Cost savings - a new original spare part is relatively expensive, but does not bring obvious benefits to the car owner.

A direct violation of the current legislation, although at the moment it is almost not controlled in any serious way.

Fuel consumption - under certain conditions, it can decrease by a couple of ridiculous percentages, but nonetheless.

Causing harm to the environment, which, given the current number of cars driving without catalysts, does not look so harmless.

Engine power - there is a possibility that it will increase, as well as throttle response, but again, far from a fact.

Increased exhaust system noise, ringing resonating sounds.

Engine oil consumption is very remotely connected with the catalyst, and you should not count on any noticeable result after its removal.

A pungent, sharp and unpleasant smell from the exhaust pipe that enters the cabin, and not only to you.

As a result - one confident plus, and the rest are doubtful.

The check is on after removing the catalyst, which, in general, is easily eliminated.

After cutting out the catalyst filling, the exhaust system needs to be finalized in order to “deceive” the ECU.

In case of unsuccessful removal, in addition to all of the above:

1.       Fuel consumption rises.

2.       Acceptance deteriorates.

3.       The power is decreasing.

4.       The resonator is damaged.



It is also worth noting that snags, which are designed to replace a full-fledged catalyst, clog rather quickly, fail, and often require replacement. With flashing the ECU, too, everything is not as simple as they say in the advertisements. In general, it turns out only one plus, and as a gift, as they say, a wagon and a small cart of minuses.

This is what a typical car catalytic converter looks like
This is what a typical car catalytic converter looks like

It is clear that the removal of the catalyst for most domestic motorists is a forced procedure. Still, the standard of living in the country, salaries and prices for spare parts are, to put it mildly, not balanced. So, it turns out that for the sake of one plus you have to put up with a dozen minuses. Moreover, this applies not only to the removal of the catalyst.

VIDEO: test with catalyst and no catalyst