Why does the sound become louder after installing an aftermarket catalytic converter?

[MacLawson]

It may be due to a leak in the replaced catalytic converter, and it is recommended to replace it with a new one. The following details the differences between OEM and aftermarket catalytic converters: Suggestion: In fact, there is no problem with replacing it with a qualified aftermarket catalytic converter. However, the auto parts market is mixed with good and bad products. Without professional knowledge, it is best to choose to replace it with an OEM catalytic converter at a 4S shop. Difference: Generally speaking, OEM catalytic converters have better compatibility than aftermarket ones. Therefore, using an OEM catalytic converter can effectively catalyze harmful substances in the exhaust. If a low-quality catalytic converter is used, it will not only cause excessive emissions but also increase the exhaust pressure of the vehicle, which will have a negative impact on the engine's power output.

[DiPiper]

I've encountered many car owners reporting similar issues where the car becomes noticeably louder after installing an aftermarket catalytic converter. The core problem lies in the fact that aftermarket parts often cut corners to save costs, featuring thinner or less dense internal honeycomb structures that generate more noise when exhaust gases flow through. Improper installation is another common cause, such as misaligned or aged sealing gaskets leading to exhaust leaks and rumbling sounds. Additionally, aftermarket converters may not properly match the vehicle's original exhaust system, causing resonance noises that can be headache-inducing. To resolve this, first check for leaks at connections using soapy water, then re-tighten bolts and replace gaskets if necessary. If problems persist, switch to a certified brand converter - avoiding cheap options prevents future troubles and protects against long-term engine damage or increased fuel consumption. For best results, have the job done professionally next time to ensure correct installation.

[AllieAnn]

After installing an aftermarket catalytic converter on my car, the exhaust kept making a constant buzzing noise. Upon self-inspection, I found that the flexible pipe connection was loose. After reinforcing it, the noise reduced significantly. A friend who also used aftermarket parts complained about the same issue, mainly due to poor quality and thin materials, causing harsh noise from direct exhaust impact. If the installation is sloppy and the parts aren't compatible with the original vehicle, the situation worsens. Looking back, choosing aftermarket parts requires checking reputable brands—don’t just go for the cheapest option. Additionally, increased noise can distract drivers, posing safety risks. If the noise persists, it’s best to visit a repair shop rather than risk bigger problems. On a side note, regular maintenance of the exhaust system after replacement can help avoid further issues.

[VanHarley]

Aftermarket catalytic converters causing increased noise typically stem from two issues: improper installation leading to exhaust leaks, or poor-quality converters with insufficient sound dampening. First, manually check for noticeable gaps at exhaust pipe connections—if leaking, replace with new gaskets. Otherwise, the issue lies in the converter's inferior internal design causing airflow obstruction and amplified noise. Sometimes modifications trigger exhaust resonance, making it even louder. Quick fix: inspect and tighten all connection points. If unresolved, replace with OEM parts—don't cut corners to avoid bigger losses. Prevent subsequent risks like fuel consumption spikes.