Stock pipes / cat - why two collector pipes from the cat?

[AdamMathew]

I guess just a general question, does anybody know the reasoning behind two pipes one larger one smaller coming out of the cat linking to the end can?

I deleted the servo valve on my oem pipe but I’ve noticed there seems to be some sort of a block/plate on the smaller pipe too just wondering what it is basically 

[Antares]

Originally Posted by AdamMathew

I guess just a general question, does anybody know the reasoning behind two pipes one larger one smaller coming out of the cat linking to the end can?

I deleted the servo valve on my oem pipe but I’ve noticed there seems to be some sort of a block/plate on the smaller pipe too just wondering what it is basically 

Smaller is the bypass pipe when the exhaust valve is fully shut, exhaust gasses still need to get out of the exhaust and the smaller pipe leads into the outer chamber of the muffler, making sound quieter, as opposed to down the main straight of the muffler which is basically straight through.

[smithy]

This only applies to the Gen-1...Gen-2 has an internal by-pass and single exit pipe.

Smithy.