Will the noise increase if the car's three-way catalytic converter is removed?
2 Answers
Removing the car's three-way catalytic converter will increase the noise because it leaves a large exhaust space, allowing exhaust gases to rapidly discharge into the atmosphere, which naturally amplifies the engine noise. Below is relevant information about the car's three-way catalytic converter: Appearance: The three-way catalytic converter looks like a metal can, but inside it contains a 'substrate' for purifying exhaust gases. This honeycomb-shaped ceramic substrate is coated with a precious metal slurry, primarily composed of platinum, rhodium, and palladium. Function: The precious metals act as purifying agents, reducing HC and CO in the exhaust gases into water and CO2, while decomposing NOx into nitrogen and oxygen. This is the exhaust purification function of the three-way catalytic converter.
Removing the catalytic converter does make the car noticeably louder, and I've experienced this firsthand. I once drove an older car where the clogged converter was removed entirely, resulting in distinct popping sounds during acceleration and a roaring noise at higher RPMs, almost like the exhaust had a leak. The honeycomb ceramic structure inside the converter naturally muffles sound, so without it, the exhaust flow loses its buffer, making the noise much louder. Plus, emissions tests would definitely fail without it, making it non-compliant with environmental regulations. Looking back, it was pretty alarming—road noise on the highway was so bad I could barely hear the passenger. Eventually, I had to get an aftermarket converter installed at a repair shop, which brought the sound back to normal levels.