What one is the main cat?

[dmur197]

Hi
I bought a clio 197 last week and it has a milltek decat, it is under the car (not under the manifold) I read on a forum that there is a main cat and secondary cat, is the one closest to the engine the main cat? if so, will I pass an MOT with the secondary cat decat. the exhaust is standard apart from this. will this exaggerate the "flat spot"? also, how would this compare sound wise to the standard exhaust with the cat.

Thanks.

 

[Chris]

The main cat is the one most commonly decatted, as the secondary cat is part of the manifold. The one closest to the engine is the secondary cat. It should still pass an emissions test with a secondary cat in place and the main cat gone but, not in all cases.

Usually it will exaggerate a flat spot but not in all cases.