The pollutants in an exhaust are created under two different conditions. In either case, the pollutants that are produced are different. The first condition is when the amount of fuel is proportionally larger than the amount of air. The fuel mixture produced in this case is said to be rich mixture. This type of mixture produces hydrocarbon residues and carbon monoxide as pollutants. On the other hand, if the air is proportionally greater than the fuel, the mixture that is produced is called lean mixture. When this type of mixture is combusted, it produces nitrogen oxides as pollutants. To minimize these pollutants, anti-pollution devices, such as the catalytic converter, are installed as standard features of automobiles.
A catalytic converter does not actually participate in the elimination of pollutants. It merely facilitates the efficient combustion of fuel. Its operation is based on the principles of oxidation-reduction. It is attached to the down pipe of the exhaust system. It is basically a modified exhaust pipe. But it is easy to identify because of its bulky structure. Inside the catalytic converter is a ceramic honeycomb with thin layers of metal catalysts. The honeycomb is purposely designed to maximize the surface area. In this manner, the oxidation-reduction of the exhaust gases can be optimized.
Platinum, rhodium, and palladium are typically used as catalysts. Since these are rare and precious metals, it is not surprising why catalytic converters are expensive. Aside from these metals, cerium, iron, manganese and nickel are also used. Under oxidation reaction, the catalysts facilitate the reaction of oxygen molecules with the molecules of the incompletely burned hydrocarbon and carbon monoxide. On the other hand, a different set of catalysts facilitate the removal of oxygen molecules from the nitrogen oxides during reduction reaction. Through the oxidation-reduction reactions, the pollutants are removed and fuel efficiency is maintained.
The two types of brake systems are the brake drum system and the brake rotor system. Although the two are mechanically different, they have similar parts. For instance, both systems use brake pads. These components are basically the same in both systems. They have the same purpose and they operate in the same manner. The only big difference lies in the respective configurations. In a brake drum system, the brake pads are attached to the brake shoes. On the other hand, the brake pads in a brake rotor system are attached to the brake calipers. However, in both cases, the brake pads are pressed against a brake surface to stop the wheel rim from rotating.