Vehicles with a catalytic converter in the exhaust system (Mazda Capella GC)

Hyundai vehicles are equipped with a catalytic converter as standard. If available, the use of unleaded gasoline is mandatory. Vehicles with a controlled catalytic converter must also be equipped with a variable mixture formation device.

A variable mixture control system is a fuel injection system in which the fuel/air ratio can be continuously varied depending on operating conditions and the oxygen content of the exhaust gases.

The mixture formation device receives control commands from the oxygen concentration sensor (lambda probe), which is installed in front of the catalytic converter or in the exhaust manifold and is blown by the exhaust gas flow. A lambda probe is an electrical sensor that detects the residual oxygen content in exhaust gases and generates a corresponding electrical signal. The signal magnitude allows us to draw a conclusion about the composition of the air-fuel mixture. In a split second, the lambda probe can send a corresponding signal to the electronic control unit, due to which the mixture composition can be constantly adjusted. On the one hand, this is necessary, since operating conditions are constantly changing (for example, full throttle, idle), on the other hand, because optimal afterburning occurs in the catalytic converter only if there is a sufficient amount of carbon particles in the exhaust gases (unburned gasoline).



Thus, in order for afterburning to occur at all in the catalytic converter at a temperature of 300–800°C, the exhaust gases must contain a greater amount of fuel than is required for complete combustion in the engine cylinders. Therefore, when operating a vehicle equipped with an engine with a catalytic converter, fuel consumption increases by approximately 5%. The catalytic converter is located in the engine compartment of the vehicle in place of the front muffler. The neutralizer consists of a ceramic honeycomb block coated with a noble metal catalyst – platinum or rhodium. An elastic, heat-resistant wire mesh is used to secure the impact-sensitive ceramic block.

The catalytic converter used is a so-called three-way catalytic converter. This means that it simultaneously oxidizes carbon monoxide (CO) and hydrocarbons (CH) and reduces the content of nitrogen oxides (NOx).

Operating Rules for Vehicles with a Catalytic Converter in the Exhaust System

To avoid damage to the oxygen concentration sensor (lambda probe) and catalytic converter, it is imperative to follow the following instructions.

Be sure to use unleaded petrol.

If leaded fuel was added by mistake, the exhaust manifold and catalytic converter must be replaced. Before installing new exhaust system components, the fuel tank should be completely filled with unleaded gasoline at least twice.

Starting a warm engine by pushing or towing is not permitted. An electric cable should be used to start the engine. Unburned fuel, when ignited, can cause the catalytic converter to overheat and subsequently fail.



Frequent cold starts following one another should be avoided. Otherwise, unburned fuel accumulates in the catalytic converter, which burns explosively when heated, damaging the converter.

If you have difficulty starting the engine, do not let the starter run for a long time, as fuel is injected during starting. The fault should be found and corrected, and then the engine should be started.

If there are interruptions in the operation of the ignition system, do not allow fuel injection when starting the engine until the cause of the malfunction has been determined.

Do not check for spark with the spark plug cap removed.

It is not possible to perform a balance test by disconnecting the high-voltage ignition wire of one of the cylinders. When disconnecting the high-voltage ignition wire of an individual cylinder, even with the help of a special tester, unburned fuel will enter the catalytic converter.

If the ignition system malfunctions, avoid running the engine at high crankshaft speed. Fix the problem as quickly as possible.

Do not park your vehicle on dry leaves or grass. The temperature of the exhaust system at the location where the catalytic converter is installed is very high, and heat is emitted even after the engine is turned off.

When adding engine oil, ensure that the maximum oil level on the dipstick is not exceeded. Otherwise, excess fluid may enter the catalytic converter and damage the coating or destroy it completely.

How to protect a neutralizer

Replacing a failed catalytic converter is expensive, so it's a good idea to know in advance what the situation is with catalytic converters on the auto parts market and what problems arise during their use.



Until recently, all we knew about a neutralizer was that it was a thing whose purpose was unclear, how it worked, and our gasoline "killed" it. Basically, it was nothing but trouble. Cut it out – no problem! But gradually, we began to get used to the fact that the catalytic converter isn't useless after all; at least, thoughts of "surgical intervention" in the exhaust system are occurring less and less frequently.

In the spring, when traffic police officers begin their "fight for clean air," we're faced with yet another problem: CO regulation. Owners of cars equipped with catalytic converters don't even think about it, and they pass CO checkpoints without a shudder or fear for their wallets. However, the same wallet can become significantly "thinner" for another reason. Fines for exceeding CO levels will seem like a pittance compared to the cost of purchasing and replacing a catalytic converter if it fails. That's why you need to know how to handle it, and to do this, you first need to understand how it is designed and how it works.

How does a neutralizer work?

When the fuel-air mixture burns, a number of products harmful to human health are formed: carbon monoxide (CO), various hydrocarbons (CH), nitrogen oxides (NO), etc. Although these substances make up only 1% of the total exhaust volume (the rest is nitrogen, carbon dioxide, and water vapor), they are very harmful and require neutralization. There are several ways to combat harmful exhaust emissions, such as leaning the mixture the engine runs on or exhaust gas recirculation, but none of them can compare in effectiveness to the result of 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 entirely covered with a thin layer of a special alloy – the catalyst itself, containing platinum, rhodium and palladium. It is these rare metals that are responsible for the wonderful properties of the neutralizer, 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 - into water and again into carbon dioxide, and nitrogen oxides - into water and nitrogen. All this is less harmful to the environment.

Catalytic converters are quite effective in reducing exhaust emissions, while having virtually no effect on fuel consumption or engine power. With a neutralizer, exhaust back pressure increases slightly, causing the engine to lose 2–3 hp, but this is practically the entire "price" for cleaning exhaust gases. However, installing a catalytic converter is not an ideal solution. Theoretically, it should last forever, since the above-mentioned metals serve only as a catalyst, which, as is known, is not consumed during a chemical reaction. In practice, the lifespan of a neutralizer has a limit...

Causes of neutralizer failure

Catalytic converter failure can occur for several reasons, although it is usually a gradual process that is impossible to detect without specialized equipment.



the "core" of most neutralizers is made of ceramic, a material known for its brittleness. A car can hit a pothole at speed, hit something, or even just scrape the catalytic converter housing against a rock, which can crack the catalytic converter. After this, it is only a matter of time before the "core" loses its working qualities.

New generation neutralizers containing a metal monolith are not so vulnerable in this regard. It is possible to break them, of course, but in any case it is not so easy.

Besides physical damage, another common cause of catalytic converter failure is fuel. It is extremely sensitive to fuel composition. If gasoline is leaded, the tetraethyl lead it contains is deposited on the active surface of the catalytic "brick" and quickly "contaminates" it, causing all reactions to cease. It seems like gas stations use different sized hose tips, paint their pumps different colors, and write about it everywhere, 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 to "kill" the neutralizer.

But it's not only leaded gasoline that is the enemy of the neutralizer. It can also be ruined by unleaded fuel if the engine management system is faulty, the fuel-air mixture does not burn completely, or the engine is heavily worn.

Triple catalytic converters (called "triple" because the catalyst is a combination of three metals) are only installed on vehicles whose engines are equipped with a closed-loop emission control system. An oxygen concentration sensor is installed in front of the neutralizer, which evaluates the composition of the exhaust gases and transmits this data to the central unit of the electronic engine control system. Depending on the oxygen content in the gases, the central unit regulates the composition of the combustible mixture and ignition so that their optimal values are maintained. This serves as the main protection for the neutralizer and ensures fuel economy and high engine efficiency. The neutralizer does not tolerate large deviations in one direction or another in the composition of the mixture. A poorly tuned engine with an increased content of hydrocarbons in the exhaust simply destroys the neutralizer. A mixture that's too lean can cause the catalytic converter to overheat, which will again cause physical damage to the unit. Thus, the catalytic converter's life depends on the proper functioning of the engine management system.



Much also depends on the serviceability of the oxygen sensor itself. With age, it becomes lazy or fails completely, which affects the composition of the working mixture and, accordingly, the serviceability of the neutralizer.

The exhaust from a heavily worn engine that burns oil can also damage the neutralizer. The latter, entering the neutralizer along with the exhaust, is "baked" onto the surface of the monolith, like varnish, and prevents the neutralizer from working.

There are other harmful factors. For example, spark plugs. Incorrect spark plugs will not burn completely, which can cause a destructive melting reaction in the converter.

Use caution when using gasoline or motor oil additives. Most drivers don't think about this, but additives can also have a harmful effect on the neutralizer. If a product doesn't say "catalytic converter compatible," it's best not to risk it.

Another dangerous situation is starting the engine by towing. In this case, pure gasoline may enter the neutralizer. This poisons the neutralizer and can also cause an immediate reaction and even an explosion.

Also, watch where you're driving and try not to get into deep puddles. The operating temperature of the neutralizer is approximately 900°C. Sudden exposure to water can be fatal.

In general, it has been noted that the service life of the neutralizer is also affected by operating conditions. The catalytic converters suffer more in cars operated in urban conditions, when the engine is frequently started and stopped. However, during long-term driving at high speed outside the city, the neutralizer also suffers, but from overheating.



Finally, you would be wise to inspect your exhaust system regularly. If the brackets are broken or the rubber mountings of the mufflers have fallen off, the exhaust pipe will vibrate, transmitting unnecessary loads to the neutralizer.

Based on website data Mazbook.ru