EXHAUST

[RussellTW]

Hey guys, knew to this forum and was wondering if anyone could help by giving some advice. I have Milltek manifold upgrade along side my standard cat and have a piper back box with resonator deleted. . Way prefer the sound of the piper over the Milltek box. But want to buy a Milltek sports cat and have a non red link pipe however their pipe diameter is 69mm where as the piper box is connected to 55mm pipe. I want the sports cat so o can move onto more mods like cams and proper remap. Could I plug in Milltek sorts cat and link pipe then use a pipe converter sleeve to use piper box as it says it will be able to piece pipes together. I just want to know whether it’ll work or if it could lead to problems. I know nothing and have heard rumours of back pressure and stuff going wrong. Thanks in advance

[Gizza11]

With respect you can make most things fit with converter sleeves, but if this was me I would like to see the whole thing the same bore  from fount to back>For example on my focus St its 3" all the way through  downpipe to back box with a 200 cell sports cat. It could lead to problems in running if you do other mods  later but may be not. A miss match some ware  just may upset the max power you could achieve. Think of it this way some idiots just change the back box to a big bore they get lots off loud noise but the miss match actually reduces  any real power they already had just for that loud sound