Why does the motorcycle exhaust pipe make abnormal noises after parking?
1 Answers
It is normal for the exhaust pipe to make a ticking sound after the engine is turned off. The exhaust pipe becomes very hot during engine operation and expands due to heat. When the engine is turned off, the temperature drops, causing the pipe to contract and produce such noises. If it is a new motorcycle with less carbon deposits inside the exhaust pipe, the sound may be clearer and more noticeable, which is a normal phenomenon. The three-way catalytic converter is the most important external purification device installed in the automobile exhaust system. It converts harmful gases such as CO, HC, and NOx emitted from vehicle exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions. When high-temperature exhaust gases pass through the purification device, the catalyst in the three-way catalytic converter enhances the activity of CO, HC, and NOx, promoting specific oxidation-reduction chemical reactions. CO is oxidized into colorless, non-toxic carbon dioxide gas at high temperatures; HC compounds are oxidized into water (H2O) and carbon dioxide; and NOx is reduced into nitrogen and oxygen. These three harmful gases are transformed into harmless gases, thereby purifying the vehicle exhaust. The exhaust pipe (three-way catalytic converter) mainly consists of an outer shell and internal components (carrier, inner pipe). Most outer shells and inner pipes are made of stainless steel; the carrier is made of metal ceramic or metal plates, forming a perforated honeycomb structure. The materials used for the outer shell, inner pipe, and carrier vary depending on their environment and purpose. Even for stainless steel materials, different grades are used: for example, the outer shell is mainly exposed to the external environment and is more prone to corrosion, requiring stainless steel with better anti-corrosion properties. In contrast, the inner pipe and carrier are enclosed by the outer shell, reducing the demand for anti-corrosion properties, so different grades of stainless steel are used.
