Fig. 11.0. Suspension on five rubber supports of the exhaust system of the Fiesta car, consisting of two parts: 1 - oxygen concentration sensor, installed in the exhaust pipe; 2 – catalytic converter; 3 – flexible intermediate connector; 4 – central muffler; 5 – main muffler
The exhaust system ensures the removal of exhaust gases into the atmosphere, a decrease in the concentration of pollutants, a reduction in engine noise to the required level with minimal loss of engine power. In order for the exhaust system to perform its functions, it must be in good condition.
Initially, exhaust systems were designed only to reduce combustion noise in engine cylinders and to direct exhaust gases into the atmosphere. In the 1980s, the exhaust system changed dramatically: since then, catalytic converters remove up to 90% of the harmful substances in the exhaust gases. The Fiesta is equipped with a two-part exhaust system as standard. At the front of the car, it consists of a controlled three-way catalytic converter (diesel engine with oxidation catalytic converter) and a flexible intermediate connector. The exhaust gases then pass into the atmosphere through the central and main mufflers. Heat shields in the area of the catalytic converter and the muffler reduce the thermal impact on the underbody.
Service life of the exhaust system
When the fuel-air mixture burns, water is also formed, which promotes corrosion from the inside of the exhaust system. Exhaust system corrosion increases as the exhaust temperature decreases. If you use the car mainly in the city or for short distances, more condensate, soot and aggressive acids are deposited inside the exhaust pipes than when driving long distances with a fully warmed up exhaust system. However, as a rule, the components of the Fiesta exhaust system work normally for about 70,000 km of the car's mileage.
The least affected by negative influences is the front exhaust pipe with a catalytic converter and a flexible intermediate connector, through which exhaust gases exit, the temperature of which is 800–1000°C.
After the reaction in the catalytic converter, the exhaust gases gradually cool down and at the end of the exhaust pipe their temperature can drop to 200–350°C. This circumstance causes a large amount of moisture condensate to appear in the additional muffler, which mixes with the remains of combustion products and turns into aggressive acids, as a result of which the metal of the exhaust system rusts from the inside.
The front part of the exhaust system operates under extreme conditions during long-distance driving due to the temperature difference when water splashes constantly on the hot metal in rainy weather. Despite the flexible intermediate connector, thermal stress can cause the pipe to break or crack.
Regardless of the operating mode, water splashes and salt solutions promote corrosion on the outside of the exhaust system. Impacts from stones or solid road obstacles reduce the service life of the exhaust system, as does vibration due to damaged or missing exhaust system mounting parts. The harmful effects of temperature and vibration can cause the rubber suspension mounts to become brittle or break.