S4 B6 downpipe mod

[giohack]

My muffler shop has proposed me to remove the main cats (maintaining the oem precats). Is it a good idea?
I expect increases in throttle response and a better sound.

Gio

[xyber]

Remove the precats, not the main cats. The lambda bosses will need relocating aswell

do a search for 'piggy pipes'

[giohack]

I read about piggie pipes.. Is it better remove the precats instead of the main cats?
If I remove the main cats I don't need to relocate the lambda sensors.

[xyber]

If you have just precats it will fail emissions I would think.

[BlingBling]

As xyber stated remove the pre-cats leave the main ones in place. The pre-cats are too close the exhaust and restrictive

[xyber]

Milltek and the like position their cats in the precat position because the closer they are to the engine the smaller they can be, which saves manufacturing costs, but they have alot more surface area inside them to compensate the size reduction. That position isn't ideal though as placing the cats at the very far end of the downpipes would probably be better power wise from what I've read on ultra geeky exhaust design sites.

I've got full non-res milltek though and highly recommend them. Definatly more eager and alot more punch lower down

[giohack]

Thanks for your reply.