Pairing a cat-back to a downpipe

[Daks]

Presently I'm running a unitronic DP - there is a local selling a non resonated Milltek catback, which I am considering. The downpipe is 3" and came with a reducer for the stock catback. The Milltek unit is 3", and my assumption is that I will not need anything else outside of some sort of band to connect them both:

https://www.millteksport.com/non-resonated-cat-back-exhaust-system-ssxvw230mp.html

Is my assumption correct or will I need some sort of pipe section to fit them both together?

 

[oddspyke]

It's possible that you'll end up with a weird section between the DP and cat back where it necks down and multiple clamps. Some DP and exhausts include a second adapter for 3" straight through connections and you may want to look for one of those. Alternately, if you are having an exhaust shop install it, they can just cut some 3" pipe for you and put it in.

Also, I know you didn't ask, but a lot of users here have had bad experiences pairing unresonated systems with a DP. General feedback is that it can be too loud and drone heavy. Not saying don't do it, just be aware of what it will sound like and make sure that's what you want.

 

[GTI Jake]

Unitronic sells a 3” adapter to retain their V band connection, or like spyke said you can cut it off.

If you don’t want the volume & cabin drone to quadruple with the addition of the catback from where you’re at now a resonated Midpipe is definitely required.

If that’s the case, I know I guy who can take all the guess work out of that and make it happen

 

[El_bigote_AJ]

If it’s a good deal even when you consider you may need to get a resonator or resonated mid pipe made, go for it… there are plenty people who don’t mind the mayhem that comes with a DP and non resonated exhaust - you could be one of them but it’s better to at least keep in mind that you also
May not be one of them and need to
Spend the extra dough.

https://www.getunitronic.com/parts/exhausts/3in-vband-adapter

 

[Daks]

If it’s a good deal even when you consider you may need to get a resonator or resonated mid pipe made, go for it… there are plenty people who don’t mind the mayhem that comes with a DP and non resonated exhaust - you could be one of them but it’s better to at least keep in mind that you also
May not be one of them and need to
Spend the extra dough.

https://www.getunitronic.com/parts/exhausts/3in-vband-adapter

I had a Mk6R with a catted HPA downpipe and remus exhaust, I don't think it had a resonator, this was pretty much it and I loved the way that it sounded

 

[Daks]

The Milltek seems to have more sound deadening than the borla and AWE though...

 

[oddspyke]

The Milltek seems to have more sound deadening than the borla and AWE though...

View attachment 225545

That picture looks like it has a resonator, top right. I wonder if that's the wrong photo?

 

[Daks]

That picture looks like it has a resonator, top right. I wonder if that's the wrong photo?

No, thats their no res system. The resonated one is below

 

[El_bigote_AJ]

That picture looks like it has a resonator, top right. I wonder if that's the wrong photo?

I think it’s like Remus and being a euro company - many of them call mufflers resonators

https://www.millteksport.com/resonated-cat-back-exhaust-system-ssxvw227mp.html

 

[GTI Jake]

I’ve owned and modded Mk6 & Mk7, and they’re completely different when it comes to exhaust notes and requirements.

Perfect example, both of these cars have the same exhaust set up. Valved TBE with a 17950 & Borla XS Pro. The Mk7 is 30-40 dB louder across the board in both the valve closed and valve open positions.

If the Mk6 system didn’t have a resonator at all it would be roughly the same volume, but still less drone than the Mk7.

 

[Daks]

Is that all due to cost savings in the cabin?

 

[GTI Jake]

Is that all due to cost savings in the cabin?

No, they’re built the same in that sense.

The Gen3 TSI has a “Headifold”, aka the turbo bolts right to the block rather than having a manifold with exhaust runners like you’d conventionally have, which causes changes due to unequal lengths.

Then add in the variable exhaust cam timing and the fact that the Mk7 controls boost and drive pressure electronically via the DV & EWG and there’s a lot of differences making the Mk7 prone to undesirable exhaust notes.

While some people don’t mind a TBE without a resonator, the Honda/diesel Kubota sound is a basically undisputed side effect of that. Everyone has their own tolerance of course, and what size/how many mufflers are in use is also a big factor.

 

[Daks]

No, they’re built the same in that sense.

The Gen3 TSI has a “Headifold”, aka the turbo bolts right to the block rather than having a manifold with exhaust runners like you’d conventionally have, which causes changes due to unequal lengths.

Then add in the variable exhaust cam timing and the fact that the Mk7 controls boost and drive pressure electronically via the DV & EWG and there’s a lot of differences making the Mk7 prone to undesirable exhaust notes.

While some people don’t mind a TBE without a resonator, the Honda/diesel Kubota sound is a basically undisputed side effect of that. Everyone has their own tolerance of course, and what size/how many mufflers are in use is also a big factor.

Thanks for that explanation. But that Milltek, although "non-resonated" does seem to have some sort of resonator, no?

 

[GTI Jake]

Thanks for that explanation. But that Milltek, although "non-resonated" does seem to have some sort of resonator, no?

Idk what they call it, but I’ve personally added a resonator to one here in house & have a pending request for one to be built and shipped.