Until recently, we knew only the following about the catalytic converter: it is a thing that is not clear why it is needed, it is not clear how it works, that our gasoline "kills" it, in general - only troubles. Cut it out - and no problems! But gradually we began to get used to the fact that the catalytic converter is not a useless thing, at least thoughts about "surgical intervention" in the exhaust system visit fewer and fewer people.
In the spring, when the traffic police begin their "fight for clean air", another problem falls on us - we need to regulate CO. Owners of cars equipped with catalytic converters do not even think about it, and they pass CO checkpoints without trembling in their knees and fear for their wallet. However, the same wallet can "lose weight" for another reason. Fines for exceeding the CO level will seem like a pittance compared to the costs of buying and replacing a catalytic converter if it fails. Therefore, it is not at all harmful to know how to use it, and for this you first need to understand how it is designed and how it works.
How do they work?
When the working mixture burns, a number of combustion products are formed that are harmful to human health, in particular, carbon monoxide (CO), various hydrocarbons (CH) and nitrogen oxides (NO). Although these substances make up only 1% of the total exhaust (the rest is nitrogen, carbon dioxide and water vapor), they are very harmful and require neutralization. There are several ways to combat harmful exhausts - for example, leaning the mixture on which the engine runs or exhaust recirculation - but none of them can compare in efficiency with a catalytic converter.
As experts say, a catalytic converter is a simple device in which a complex chemical process takes place. "Inside the stainless steel housing is a ceramic or metal "brick" with a honeycomb structure. This monolith has a huge surface area, and it is all covered with a thin layer of a special alloy - the catalyst itself, containing platinum, rhodium and palladium. These precious metals are responsible for the wonderful properties of the catalyst, and they also determine its high cost."
Exhaust gases "wash" the surface of the monolith, and when the temperature reaches the "critical" value of 270°C, a catalytic reaction begins. Carbon monoxide is converted into dioxide (carbon dioxide), hydrocarbons turn into water and again carbon dioxide, and nitrogen oxides turn into water and nitrogen. All this is less harmful to the environment.
Catalytic converters are quite effective in reducing exhaust toxicity, while they do not affect fuel consumption or engine power. With a catalytic converter, exhaust back pressure increases slightly, causing the engine to lose 2-3 hp, but this is practically the entire "price" for cleaning the exhaust. However, installing a catalytic converter is not an ideal solution. Theoretically, it should last forever, since the above-mentioned precious metals serve only as a catalyst, which, as is known, is not consumed during a chemical reaction. In practice, the life of a catalyst has its limit...
What is killing them?
Catalytic converter failure can occur for several reasons, although it is usually a gradual process that is impossible to detect without special equipment.
The "core" of most catalytic converters is made of ceramics, a material known for its fragility. A car can hit a pothole at speed, hit something, or even just "scratch" the catalytic converter body on a rock, and this can cause the catalytic "brick" to crack. After that, it's only a matter of time before the "core" loses its working qualities.
New generation converters containing a metal monolith are not so vulnerable in this regard. Of course, it is possible to break them, but in any case, it is not so easy.
Enemies of the Catalyst
In addition to physical destruction, there is another common reason for the failure of the catalytic converter. Fuel. It is extremely sensitive to the composition of the fuel. If the gasoline is leaded, then the tetraethyl lead contained in it is deposited on the active surface of the catalytic "brick" and quickly "greases" it, which stops all reactions. It seems that at gas stations, hose tips have begun to be of different sizes, and dispensing columns are painted in different colors, and they write about this on every corner, but still, consumers sometimes get confused and fill up with the wrong gasoline. But it is enough to "burn" half a tank of such gasoline, and the catalyst will perish irrevocably.
But it is not only leaded gasoline that is the enemy of the catalytic converter. The catalytic converter can be destroyed by unleaded gasoline if the engine management system is faulty, the mixture does not burn completely, or the engine is heavily worn out.
Triple catalytic converters ("triple" because the catalyst is a combination of three precious metals) are installed only on those cars whose engines are equipped with a closed exhaust control system. An oxygen sensor is installed in front of the catalyst, which monitors the composition of the exhaust and transmits this data to the central processor. Depending on the oxygen content in the exhaust, the ECU regulates the composition of the combustible mixture and ignition so that their optimal values are maintained. This serves as the main protection for the catalyst, and also ensures fuel economy and engine efficiency. The catalyst does not tolerate large deviations in the composition of the working mixture. A poorly adjusted engine with an increased content of hydrocarbons in the exhaust simply ruins the catalyst. If the mixture is too lean, this can cause a sharp overheating of the catalyst, which will again damage the monolith, only this time "physically". Thus, the "life" of the catalyst depends on the serviceability of the engine management system.
Much also depends on the serviceability of the oxygen sensor itself. With "age" it becomes "lazy" or completely fails, which affects the composition of the mixture and, accordingly, the serviceability of the catalyst.
The exhaust of a heavily worn engine burning oil can also damage the catalytic converter. Oil, getting into the catalytic converter along with the exhaust, "bakes" on the surface of the monolith, like varnish, and prevents the catalytic converter from working.
There are other harmful factors. For example, spark plugs. Unsuitable spark plugs will not provide complete combustion, which can cause a destructive melting reaction in the catalyst.
Be very careful when using additives to gasoline or oil. Most people don't think about it, but additives can also have a harmful effect on the catalyst. If the product doesn't say "compatible with the catalyst", it's better not to risk it.
Another dangerous case is starting the engine by towing. In this case, pure gasoline can get into the catalytic converter. Firstly, this poisons the catalytic converter, but it can also cause an immediate reaction and even an explosion. Also, watch where you are driving – try not to get into deep puddles. The operating temperature of the catalytic converter is about 900°C. Its sudden entry into water can be fatal.
In general, it has been noted that the service life of the catalyst is affected by operating conditions. Catalysts on cars operated in urban conditions, when the engine is started frequently, suffer more. On the other hand, during long-term high-speed driving on highways, the catalyst also deteriorates due to overheating.
Finally, you would be wise to regularly inspect the entire exhaust system. If the brackets are broken or the rubber hangers have fallen off, the exhaust pipe will vibrate, transferring unnecessary stress to the catalytic converter.