Interim exhaust catalyst pipe - a bypass for the CAT?

[Jeff210R]

Caterham supplied this from new on the car which I have recently purchased but seem unable to explain what it actually does!  Can anyone shed any light?

Jeff                                        

[Wrightpayne]

Basically an extra bit of exhaust piping which replaces the catalyst section straight after the MOT. Usually 4 into 1 style pipe.

[Wrightpayne]

Here are the two Sigma exhaust parts taken from the Caterham Parts website which show the principle....

[CtrMint]

https://www.caterham7diaries.com/post/caterham-7-420r-decat-install
 

just installed that myself.

[ScottR400D]

I fitted one a couple of years ago. No difference in performance as far as I can tell but presumably saves the cat. 

I just swap back and forth for the MOT, it's pretty straightforward though I’m not sure if it’s necessary!