Which part is primarily responsible for controlling emissions in an engine?

The catalytic converter is primarily responsible for controlling emissions in an engine. This component is designed to facilitate chemical reactions that convert harmful pollutants in the exhaust gases into less harmful substances before they are released into the atmosphere.

When exhaust gases flow through the catalytic converter, they pass over a catalyst, usually made of precious metals like platinum, palladium, and rhodium. These metals promote reactions that convert carbon monoxide (a harmful gas), hydrocarbons (unburned fuel), and nitrogen oxides (which can contribute to smog) into carbon dioxide, nitrogen, and water vapor—substances that are far less harmful.

In contrast, while the air filter, crankshaft, and fuel injector play crucial roles in the overall performance and efficiency of the engine, they do not directly address emission control. The air filter is responsible for filtering out contaminants from the air entering the engine, the crankshaft converts linear motion from the pistons into rotational motion to power the vehicle, and the fuel injector precisely delivers the fuel-air mixture to the combustion chamber. None of these components have the direct function of reducing or managing emissions after combustion.