Secondary Catalytic Converter Removal HR12DDR

Howdy all,

Here in NZ we are lucky to have no emissions testing. While I was at the exhaust shop the other day the owner said I should consider removing the secondary cat to let the engine breath a little better. He would fit a small resonator in its place.

Has anyone done this on their car? Some people have told me I'll need to tune the ECU, others have said it'll be fine.


Hi there, I have removed my secondary catalytic converter on my HR12DE UK model, and I instantly noticed improved fuel economy of about 10%, and here in the UK we have an emissions test on our yearly MOT test, which it still passes easily, running at like 20% of the legal limits for emissions. No ECU modifications and I've been running it like that for the nearly 4 years I have owned the car, including upgrading to a stainless manifold-back exhaust approximately 2 years ago. Hope this helps
Hi, thank you. That helps a lot.
Did you notice any increase (detrimental) to noise volume or quality after removing the cat? Cheers
In the cabin, the noise didn't noticeably change with just the catalytic converter removal, it's now very loud as it has straight-through stainless system on!