Exhaust and cats - two options, which is better?

[Sql_RS4]

My car is in the shop now as I still did not figure out the cause of the noise that is coming from the engine. First I changed all the bearings on the belts etc, then both tensioners, chains etc. Nothing changed. It still ticks/rattles.

While it is there I was thinking about gutting the precats but the guy from the shop told me they were pretty successful leaving precats intact but getting rid of main cats and middle silencer in B5 RS4s they worked on earlier.

Do you think it is a good option? As I understand it can still be not that good with precats there that stop better airflow to this exhaust anyway...

What do you think? Thanks in advance!

[RS4_fin]

Ok, just some comments. Haven't actually seen any real proven data as to where is the most restricting part (cats/silencers/diameter of pipes etc) or what is 2nd, and so forth....
But as easily seen from the forum, most people seem to go for getting work done on the pre-cats while not having main cats removed completely. I reckon there would also be a fail in emissions check (MOT/similar) without main cats. Though I guess there are ways around this too.

To get some good power out, all of exhaust (incl. cats) need to be touched, among other things. Depends what you want.

To your question, which is better - myself would do the more common(?) way of poking with pre-cats....

Oh, and that ticking noise - have you checked the cams?

[eep]

I'm no expert but i believe the precats are 400 cell and the main cats 200 cell. The main advantage of dropping the precats is they are the most restrictive bit of the exhaust system.

[Sql_RS4]

Thanks for opinions guys.

Today it turned out one of my exhaust manifolds is cracked so engine is out on monday - that way I will get easy access to precats so I guess they will be gutted. I am not sure if I should get rid of both main cats and middle silencer as well as I would not like it to be to loud and I am not sure if it would really add a lot when it comes to output.

And as we speak exhaust manifolds - what would you recommend? OEM? Autospeed? Custom made? Any experiences?

Thanks a lot!

[rhunter203]

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