Car catalyst is designed to neutralize harmful car exhausts and is part of exhaust system.
A catalyst is an element of an engine exhaust system designed to clean exhaust gases before they are released into the atmosphere. The need to develop this automobile motor assembly arose in 60s of the last century, when the world community was concerned about the state of ecology on our planet. At that time, the level of emissions from automobile exhaust pipes was not established at legislative level. The first standards for content of toxic products in car emissions were introduced in 1970s. Auto producers were required to equip cars with devices that reduce volume of carbon monoxide and products of combustion of hydrocarbons. Since 1975, catalyst has become an indispensable part of all cars coming off the assembly line.
Manufacturers install three types of catalysts on cars:
Ceramic item use a mechanical method of cleaning exhaust gases. It consist of ceramic plates coated with precious metals. Maximum resource of this type of work is 100 thousand kilometers. However, with poor fuel quality, its replacement is required after 70–80 thousand kilometers.
Metal catalyst has another construction. Its filling consists of metal honeycombs with increased elasticity. The design of such parts is reliable and more durable than ceramic catalysts.
Sports catalyst is considered to be the most reliable model. But at the same time it has a high cost. Made of metal it has greater bandwidth than the two previous options.
What does catalyst consist of and how it works?
Catalyst device has ceramic honeycombs in its basis. Structurally, catalytic converter is a ceramic substrate made in the form of honeycombs, inserted into a metal housing and protected by heat-insulating materials. Small cells of a catalyst have a special coating or working composition. The honeycomb composition is an alloy of platinum, rhodium and palladium, precious metals, the cost of which exceeds gold at least twice. The honeycomb structure of catalyst increases the contact area of toxic gases with neutralizing surface. Remains of harmful substances instantly burn out and do not enter in atmosphere.
The catalyst consists of the following parts:
Housing with inlet and outlet nozzles;
Ceramic block with porous structure;
Catalytic layer, spraying on cells of a ceramic block;
Sensor (lambda sensor) is a device that shows the pollution of gases after cleaning;
Metal casing performs the function of thermal insulation and protects housing from mechanical damage.
Catalyst circuit is installed after the exhaust pipe of an engine or in exhaust manifold. This arrangement is necessary for effective operation of a catalyst, since neutralization of toxic substances is possible only at high temperatures. The operation of a node is as follows:
Exhaust gases are sent through the inlet to the inside and enter ceramic block, filling the cells. Catalyst metals oxidize unburned hydrocarbons and carbon monoxide. Reducing metal, rhodium, neutralizes nitric oxide and turns it into a harmless substance. Pure gas is discharged into atmosphere through the outlet pipe.
It is important! The decisive role in the process of neutralizing toxic substances is played by the temperature. Conversion is possible at temperatures from 300 degrees, but basically the working temperature of a catalyst is in a range from 400 to 800 degrees.
At the time of engine warm-up, catalyst is inactive, and this is a significant drawback of models developed to date. Difficulty in organizing correct operation of the unit is danger of its overheating. If you place catalyst closer to an engine, service life will decrease dramatically due to systematic overheating. Most car manufacturers place the part in an area of a right front wheel, where it is possible to maintain the temperature at optimum level.
Catalyst is one of the parts that continues to raise interest of consumers even at the end of a service life. There are more and more announcements about the purchase of automotive catalysts by numerous businessmen. The reason for this is the content of precious metals. Quantity of precious metals depends on a model and mass of the catalyst. Average indicators are as follows:
Silver - from 5.5 to 15 g;
Palladium - from 0.05 to 4.95 g;
Platinum - from 0.1 to 1 g.
Extraction of precious metals from old catalyst is a technologically complicated and disadvantageous process at home. This can only be done in large volumes using special equipment and reagents. In order to decide if the catalytic converter has to be removed and changed, pay attention to causes and symptoms of its failure.
Catalyst is good for approximately 150 thousand kilometers. During operation time, the part gradually burns out, and the worse the fuel, the faster it happens. The fact is that artificial additives in bad gasoline contribute to increased heating of fuel, and catalyst cells melt and clog.
It is important! The failure is also facilitated by microdamage that occurs when driving on bumps, malfunctions of piston group and ignition. Accelerating the honeycomb contamination process is an aggressive riding style.
A malfunction of a catalyst is detected by lambda sensor, and the error “CHECK ENGINE” pops up on a dashboard. At low efficiency of the catalyst due to clogging on the panel, error “P0420” may be displayed.
In addition, symptoms of component failure are:
rattle and vibration under the bottom of a car. If a clang is heard during acceleration or relocation, it means that parts inside the catalyst body have crumbled.
decreased engine dynamics. The car slowly accelerates. As if it was being held in the back. This suggests that the cells are partially clogged.
temporary lack of traction at high speeds.
difficulties with starting the engine. With a complete breakdown of a catalyst, the car stalls immediately after starting.
gray shade of exhaust with a pungent, suffocating odor is a sign, which indicates a significant destruction or melting of honeycombs.
increased fuel consumption. This symptom is ambiguous and may indicate other problems. For example, gas mileage increases if fuel injectors are clogged.
All these signs indicate that the catalyst is still working, but cells are partially melted and their throughput is reduced. If you continue to operate the car in this situation, the engine may stop starting.
It is important! Ceramic particles of destroyed catalyst can get into cylinders, damage their walls and completely disable the engine.
How to check node status?
Each car owner can check the catalyst performance independently or by contacting a service center. There are 3 methods for verifying catalyst health:
Visual inspection of the housing. Deformation of housing always indicates a partial or complete malfunction of a catalyst. In this case, it must be removed. On some models, inspection without opening the case cannot be carried out.
Back pressure. The check can be carried out using a manometer and an adapter tube connected to it. The pressure gauge is put in place of lambda sensor and start the engine at 2.5-3 thousand turns for 15 seconds. On average, normal pressure values are 0.3 kg / cm2 and 0.35 kg / cm2 for modified engines. Indicators of 0.5 kg / cm2 and above indicate problems with the catalyst.
Diagnostics by a motor tester. This diagnostic option is possible with special equipment. The device is connected instead of spark plugs and takes data during engine start.
Car diagnostics. If you have special equipment, you can carry out diagnostics yourself.
Why should you remove a catalyst?
The ideal solution for a catalyst failure is to replace it with a new one. However, not everyone can afford the purchase of a new, original part, the cost of which is about 500 USD. An alternative version of Chinese production will cost 100 USD. But such expenses are unacceptable for some car owners, so they decide to remove the catalyst completely and weld an empty flame arrester.
It is important! Experts recommend changing the catalyst to the original only once, on new cars. Subsequent investment in an expensive original catalyst is impractical, because the motor works worse and cells become clogged twice as fast. Some universal models are several times cheaper than branded items and at the same time work with the same efficiency.