Can I take the cat off my car (de-cat) to improve performance?

Removing the cat (Catalytic converter) from any exhaust system will often improve a cars performance due to the increase in exhaust gas flow it allows. You should however consider it seriously before going down this route. There are a few myths that surround the legality of cat removal in Europe and a few things worth noting if you do remove it.

Myths:

a) Removing the cat is illegal.

This is simply not true, you are perfectly entitled to remove the CAT from your car and fit a de-cat (straight through) pipe as long it will still pass the relevant emissions test (dependent on which country you live in).

b) If you remove the cat it WILL fail the emissions tests.

Again this may not be the case. The Japanese car industry had far stricter emissions requirements than Europe and cat’s were fitted to home market Japanese cars for a long time prior to them becoming a requirement in Europe. In most cases you can quite easily remove the cat from any Japanese grey import car that was first registered on, or before, 31st July 1995 (M-reg or earlier) and still pass the less stringent emissions test. Removing a cat from a more modern car will almost definitely mean failure of the later more stringent emissions limits. It is worth noting that some tuned Evo’s with an aftermarket ECU can pass the later emissions test even with the cat removed.