Catalytic Converter

A catalytic converter, or cat, is a component in the exhaust system that reduces harmful emissions. Inside is a honeycomb or mesh coated with precious metals such as platinum, palladium and rhodium. When the hot exhaust passes over it, carbon monoxide, unburnt hydrocarbons and nitrogen oxides are converted into carbon dioxide, water and nitrogen.

Modern road motorcycles need a cat to meet Euro 5 emission limits, and fuel injection with a lambda (oxygen) sensor keeps the mixture right so the cat works efficiently. It needs high temperature to operate, which is why it is often placed in the header pipes or under the engine.

Leaded fuel, oil burning and misfires can destroy a cat. Removing it may be illegal on public roads and can affect the inspection and your insurance, so check local rules before fitting an aftermarket system.