De-cat

An exhaust de-cat removes the primary or secondary cat from a vehicles exhaust system. Car enthusiasts opt to remove catalytic converters (cat) as they can restrictive to exhaust flow. In high performance applications exhaust back pressure is unwanted, removing the cat allows exhaust gasses to escape with less restriction.

WARNING Removing a Catalytic converter may not be legal in your country. Please ensure research this before installing a de-cat pipe.

Some cars such as the Audi RS6 V10 has four cats in total. A primary and secondary cat on each exhaust bank. The secondary cat reduces emmisions during a vehicles startup phase to give time for the primary cat to be brought up to temperature. This is because Catalytic converters are more efficient when they are hot

The downside to removing Catalytic converters is an increased amount of black smoke and poisonous gasses for the environment, this is typically why it is against the law to remove a Cat

In the UK, any vehicle made after K registration is legally required to have a Catalytic converter and without one will not pass an MOT Emmisions test