Catalytic Converter - Negative Aspects

Negative Aspects

Some early converter designs greatly restricted the flow of exhaust, which negatively affected vehicle performance, driveability, and fuel economy. Because they were used with carburetors incapable of precise fuel-air mixture control, they could overheat and set fire to flammable materials under the car. Removing a modern catalytic converter in new condition will not increase vehicle performance without retuning, but their removal or "gutting" continues. In such cases, the converter may be replaced by a welded-in section of ordinary pipe or a flanged "test pipe" ostensibly meant to check if the converter is clogged by comparing how the engine runs with versus without the converter, which facilitates reinstallation of the converter in order to pass an emission test. In many jurisdictions, it is illegal to remove or disable a catalytic converter for any reason other than its direct and immediate replacement. In the United States, for example, it is a violation of Section 203(a)(3)(A) of the 1990 Clean Air Act for a vehicle repair shop to remove a converter from a vehicle, or cause a converter to be removed from a vehicle, except in order to replace it with another converter., and Section 203(a)(3)(B) makes it illegal for any person to sell or to install any part that would bypass, defeat, or render inoperative any emission control system, device, or design element. Vehicles without functioning catalytic converters generally fail emission inspections. The automotive aftermarket supplies high-flow converters for vehicles with upgraded engines, or whose owners prefer an exhaust system with larger-than-stock capacity.