Exhaust Options

[RS6Rottweiler]

I am considering getting a 3" exhaust built for the RS6 C5 from the Turbo's back, full system but with 100 cell Cats. However, the guy who is going to do the work is asking whether I want cross over pipes fitted but I do not think the RS6 has this as its an 'H' configuration but is it best to stick with this or go for the cross over system?

I'm also looking at putting valves in so that I can either go down the American route where they fit a 'Y' piece in after the Cats and bypass the rear mufflers through a switch inside the car. Or, as this guy prefers the European route where there is straight pipes from the turbo's through to the rear outlets with the mufflers fitted between the pipes and valves to divert it through the mufflers for quiet option or by-pass the mufflers for noisy option via switch inside the car. What's your thoughts and is there sufficient space under the RS6 to fit the pipes centrally inside the two main pipes. I have never seen under the car to check this myself so would appreciate you guys opinions.

Looking forward to your thoughts, Cheers

[Shoppinit]

You wouldn’t look forward to *my* thoughts.

[V!per]

X pipe defo won't work with RS6. It's best on non turbo cars

[Mɐʇʇ]

Yes. It won’t mess anything up, but won’t add anything that way it does on an NA car.

And diverters, valves etc? Defo not, IMVHO.
I used to run a straight through exhaust on the Ultima with its turbo motor. It sounded naff at idle and was just ridiculously loud when giving it some beans. In the end, I put muffler back
In.

[IchBautAuto]

My early Miltek is not joined anywhere. Turbo back, 100 cel cats and miltek rear mufflers only. Plenty loud under full throttle but no drone at cruise. It's a design that works. At least if you copy that you won't be shortchanged.

[Gregstv]

I changed the rear mufflers to 6inch diameter instead of the 8inch std. Secondary cats removed and it sounds great. I do plan on getting rid of the pre CATs and putting the secondary ones back on. It will be interesting to see the difference in sound.

[IchBautAuto]

To add to my last, there is a bit of science and testing involved in getting a system working across the whole RPM range and staying legal in a road car. That said, if you copy a good system design that has proven itself, there will be no difference between the brand name and a good exhaust Shop made (or even DIY if your welding is up to it) product.

These are my RS4 manifolds so you can make a system from pre formed bends and do away with the expensive pipe benders, if you can weld, that is.

[Human Joist]

Non res miltek. Fit it and enjoy ..... simples !!

[Mɐʇʇ]

This is my choice. Non-resonating is just right, IMVHO.

Non res miltek. Fit it and enjoy ..... simples !!

[RS6Rottweiler]

I'm definitely not going down the Miltek route, read a lot of bad press on Miltek products these days, poor welding, corrosion, Cats failing etc so it would appear they are not as good build quality as they used to be. I believe they were taken over but not sure so Miltek is out for me it will be a custom system but which way I am not sure hence why I'm asking here for your thoughts.

Likewise; Miltek Res or Non-Res system, Non-Res very boomy inside the cabin and I certainly don't want that as I do regular long journeys. I'm looking for an option that will give me good sound (turn Heads) under normal driving conditions without the boom but should I want noise then flick a switch and its there, Miltek its either there or its not.

The reason I'm considering 3" pipes is due to a guy who was on this forum from South Africa, they don't have emission laws over there so he had 3" pipes straight through from Turbos, no Cats or mufflers and he said it sounded awesome, can't vouch for that as he didn't send audio clip but photos looked great, two massive 3" pipes running straight through under the car, will look for the post. Miltek is 2.75" so 3" only marginally bigger but could still stick with 2.75" if that's the way to go, standard is 2.5" I believe?

The other benefit of custom build is it has lifetime guarantee with exception of Cats but I'm not going to fit cheap Cats, anyone got recommendations for good quality Cats. The company I'm using (Pipe Dynamic's in Leven) come highly recommended so it comes down to what's the best way to go, food for thought but it will be a custom build?

[sb79]

non res millteks all day I've had a couple of these now and all have millteks my plus have them now with black tip awesome sound

[Human Joist]

I have never seen a post on this site with anything negative to say about miltek on these cars

[IchBautAuto]

You've decided not to buy a miltek product and that's fine, your choice. My comments were about the design and specifications. You'll need one of those to even get started. Pretty sure my early miltek is 3 inch (the non CAT non res "race" system) and most of my driving is long distance so I can say the combo I have works, but it brings some minor ECU map issues as the rear lambdas aren't used. It did come with the car so no choice by me, I would have gone with the resonated system but couldn't be bothered fitting a set now. It's quiet at idle but LOUD at full throttle and high revs.

Boom isn't just resonators, pipe wall thickness, pipe hangers and pipe diameter are all in play. That's where a custom made is a take your chances option as the development and testing isn't there.

For anywhere near normal driving a dual 3 inch system is overkill. Some of the yank V8's and buzz box 4's need that sort of advertising to make them sound like serious players, the RS6 doesn't need that at all. It's all about walk softly and carry a big stick.

[Ben_r1]

Think it’s the other way round with Millteks, they used to have some quality control issues with the welds going back 10 years or so now but have upped their game since and appear to be well regarded for quality these days.

[RS6Rottweiler]

Okay, seems there are lots of different opinions on exhaust for the C5 RS6 so what do you guys think is the best way to go, Milltek options, they do not provide the pipes down from the turbos with the Cats so what have you guys done that have fitted Millteks.

What grade of Cats did you use as I was thing 100 Cell but is this good to get through emission tests, plus did you fit all 4 Cats or just the 2.

What mufflers did you fit, size etc, Resonated or Non-resonated option?

I want a good noise during regular driving including around town but I don't want any drone as I do regular long journeys but I'm looking for an awesome sound when giving it some Yee Haa, hope to get some good ides from you guys with the experience.