RS4 Cats on K04 S4

**Audi_S4** · 04-05-2008 12:08 PM

since i live in belgium and we have to go to a car inspection facility every damn year where the car is being tested for springs, shocks, steering,brakes ,emission and so on...

i was wonderin since i wanted to go stage 3 but i want to pass the test, meaning i need Cats, they have to have original audi emblems,diameter and the CO can not be more then listed. or else i have to change them every year

a B5 RS4 got bigger cats and diamter downpipes then a B5 and makes 380 bhp so for a stage 3 like i want it, let's say 380-400hp it would be grate my guess???

but is it and will it just fit and let enough flow on the stage 3?

i'm just not in it for working on the car for hours or days every year to pass the test, we can't do bigger brakes,or lower the car without special fitting papers and special papers from the distributor so i have to do everything a little less then you guys , if they pic me off the streat and take me to a inspection immediatly (wich happens sometimes if you get busted streetracing or whatsoever) i want to be legal, cat-back is not so bad, bigger turbos and IC's and remap they won't see so i can do stage 3 but with things the eye does not see immediatly when lookin under the car and opening the hood...

**AudiA4_20T** · 04-05-2008 12:18 PM

I'm sure they will work but the price will probably be killer

**Audi_S4** · 04-05-2008 12:41 PM

Originally Posted by AudiA4_20T

I'm sure they will work but the price will probably be killer

here in europe you can find them regularly on ebay for nice prices

**Audi_S4** · 04-08-2008 11:33 AM

is it bad to run k04's with stock cats for the life of the turbo?

i know it will flow less but is the difference extreme?

it's because i'm in the same shit here in belgium, every year the inspection where youre car is being checked completely for exhaust, brakes,emission test and so on...

we can have mods like turbos,ic's and stuff , they won't see that and it doesn't matter if the car makes 400bhp as long as the CO output is ok!

**Audi_S4** · 04-08-2008 02:24 PM

no one?

**Das General** · 04-08-2008 02:36 PM

why dont you just buy a hi flow aftermarket cat?

it will allow you to pass emissions and still have some fair gains in performance.

**S4Per** · 04-08-2008 03:15 PM

Originally Posted by deb38

why dont you just buy a hi flow aftermarket cat?

it will allow you to pass emissions and still have some fair gains in performance.

because:

...they have to have original audi emblems,diameter and the CO can not be more then listed...

**Audi_S4** · 04-08-2008 04:24 PM

it has to look like an original audi part

but if it has NO emblems on it and it's not 3inch piping it would work maybe...

wich brand sells unmarked 2.5 inch dp's and cat?

and aftermarket cat's that flow enough will still pass emission tests?

**joules** · 04-08-2008 09:28 PM

Your stock cats will flow plenty good for what you want. The stock Audi cat is of high quality, and an aftermarket may or may not be such good quality, and even though it claims "high flow", it may not be. Until you are looking for the last 5 horsepower from your setup, don't worry about different cats...

The single most important thing, and most worth spending $ on, AFTER going Stage 3, would be your fueling and tuning. Your gains there can far exceed the difference between RS4, S4 and aftermarket cats.