Reduce Milltek exhaust rasp

[JRC1]

I have a full Milltek exhaust fitted (catless downpipes, non res centre section, valved backboxes).

The volume/loudness of the exhaust is great, and I'm happy with the decat too because it's the least restrictive and helps the car achieve its 450bhp (MRC Stage 2).

However, ultimately I'm not happy with the sound, it's too raspy. How can I eliminate the rasp whilst keeping the exhaust as least restrictive as possible?

Would a resonated centre section achieve this without impacting performance? Do I need an X pipe / H pipe (or does the Milltek already have one of these?) Has anyone ran a full Milltek decat with a resonated centre?

To summarise, I like it loud and don't want to lose volume - just want a deeper V8 soundtrack - I think the rasp can sound naff, especially on the overrun.

Cheers

[JamesBaby]

I'd like to know this too. I have the Pre cat delete Zinrams, with ECS H pipe, on OEM back boxes. I want more of the V8 purr.

I may try Modstock who modify rear back boxes to achieve the noise you want. Or new custom back boxes?

[JRC1]

I'd like to know this too. I have the Pre cat delete Zinrams, with ECS H pipe, on OEM back boxes. I want more of the V8 purr.

I may try Modstock who modify rear back boxes to achieve the noise you want. Or new custom back boxes?

I've looked into it a lot since posting this. Apparently resonators and X pipe are key.
The Milltek is a H pipe, and a H pipe provides more of a deep rumble, American V8. The H is also what causes the sort of fart/blow/rasp noise when you let off i.e. deaccelerate, which is what I dislike.
Apparently, the design of an X pipe, and the way the exhaust gasses flow because of this, eliminate it and help provide a European V8 scream. Adding a resonator is key too I think especially for the rasp element.

So I looked into whether anyone makes a resonated X pipe centre for the RS4 and the only company I could find was Supersprint. I have their exhaust on my other car and the quality is great but their customer service isn't, they can't provide me any sound clips or explain how their resonators work (it's a single chamber, rather than a resonator each side) so it would be a bit of a gamble to buy one. And they want close to £1k for it.

So I guess my options are:
a) risk buying the Supersprint resonated x-pipe
b) go to a custom exhaust Shop and ask them to make me a resonated x-pipe centre section to marry up to my Milltek
c) replace my Milltek (apart from the catless downpipes) with a full exhaust system that has resonated x-pipes in place already

[coffey555]

JHM do a full X-pipe res system and it sounds really lovely by all accounts. It is quite loud though, god knows why they also build a non-res version!
It also has the benefit of being a 2.75" system which is proven to give decent gains over the stock/Milktek exhaust.

https://www.mlperformance.co.uk/product ... ith-x-pipe

It's not a cheap option but it might work out cheaper than building a custom system and having to modify it a few times to get the sound right.

I currently have a full original system with the centre res delete (no x or h pipe, just straight tubes) and the sound is a very old school V8 with no rasp..... I am still running main and pre-cats though. After doing a bit of research, removing my pre-cats will add rasp and a bit of drone around 1800-2000rpm so I was going to sell the Zinram cats I have ready to go on.

But now I am thinking maybe I should give the Zinram cats a try with an original resonated centre section?

[JRC1]

JHM do a full X-pipe res system and it sounds really lovely by all accounts. It is quite loud though, god knows why they also build a non-res version!
It also has the benefit of being a 2.75" system which is proven to give decent gains over the stock/Milktek exhaust.

https://www.mlperformance.co.uk/product ... ith-x-pipe

It's not a cheap option but it might work out cheaper than building a custom system and having to modify it a few times to get the sound right.

I currently have a full original system with the centre res delete (no x or h pipe, just straight tubes) and the sound is a very old school V8 with no rasp..... I am still running main and pre-cats though. After doing a bit of research, removing my pre-cats will add rasp and a bit of drone around 1800-2000rpm so I was going to sell the Zinram cats I have ready to go on.

But now I am thinking maybe I should give the Zinram cats a try with an original resonated centre section?

The reason I don't have the cats is purely from a power perspective. They are known to be really restrictive on these and mine makes 450bhp with an MRC Stage 2 with the cats removed. It's like a totally different car compared to a standard one.

Previous owner fitted the Milltek non-res and it isn't something I would have done. Non-res combined with no cats just make it too raspy for me. Not even too loud, the noise level is fine, it's the rasp/fart noise off throttle that bothers me because it sounds crap. Have a listen here at 1:06 and you'll see what I mean (not my car but exact same setup) - https://www.youtube.com/watch?v=HW-kGZP8kZk

Also not overly impressed with the Milltek quality... meh it's ok but other exhaust systems I've seen are much better. I have Supersprint on my other car and the quality is far superior.

Thanks I did see the JHM exhaust on the link you posted but it says no longer available when changing the option to 'resonated'... The other one I've been seriously considering which is a similar price is the HMS exhaust. For me this sound is perfect and just what I'm looking for. This is a de-cat, resonated setup as well - https://www.youtube.com/watch?v=ACXrw_tHYrU & https://www.youtube.com/shorts/M4Id_ffqNTc

However, nothing is easy and I've been struggling to get hold of HMS. So I'm sort of not really making much progress at the moment. My options seem to be:

a) fit a supersprint resonated x-pipe to my current Milltek - ~£850 but not convinced diameter is the same as Milltek so will require some messing about to fit and also an unproven setup in terms of sound, it would be a gamble
b) fit a Milltek resonated centre section - ~£450. Might solve the rasp, but won't give me the high pitched/screaming V8 sound that I'm after as this is achieved via an x-pipe
c) get a custom setup made but as you say might mean modifying a few times to get right and the result is a half milltek half custom system ... meh
d) buy either a HMS or JHM setup if either are available, and sell on my (reasonably new) Milltek

Leaning towards D if I can source either of them, but that seems to be a problem!

You could try the Zinram sport cats but if you are keeping a resonated centre section and want more power then de-catting completely won't be overly noisy and will give you a great sound/power combo.

Sorry if a dumb question but what is the location of both the main and the pre cats? I assume the pre cats are part of the OE downpipes, and the main are part of the OE centre section, or is that incorrect? I have Milltek catless downpipes which I assumed replaced the pre-cats but I can't recall ever seeing main cats as part of the OE exhaust?

[coffey555]

Yeah, the 400 cell pre-cats are really restrictive. The main 200 cell cats are not too bad though so people just remove the restrictive pre-cats on the original cat pipes. But like you say, no cats will give the best flow....... assuming you have a friendly MOT tester near you

I have heard the same thing regarding Miltek quality and construction. Supersprint stuff is lovely, if I remember rightly they also do exhaust manifolds as well but these have been proven to be no better than the stock ones and you will never see them once fitted.

Shame the JHM system is no longer available or difficult to source but I have heard good things about the HMS one. Capristo is another option but personally I don't like the exhaust tips they come with as much as the big twin ovals.

I should probably try the ZInram cats first and see how they get on with my non-res and res centre sections seeing as that is what I have on hand.

First picture is the new Zinram 200e cell cat pipes, the pre-cats would normally sit to the right of the 45 degree bend, so downstream of the exhaust manifold flange connection.

The second is of the original cat pipe section on the car, both the 200 cell main cats and 400 cell pre-cats are located on the cat pipe sections.

[JRC1]

Yeah, the 400 cell pre-cats are really restrictive. The main 200 cell cats are not too bad though so people just remove the restrictive pre-cats on the original cat pipes. But like you say, no cats will give the best flow....... assuming you have a friendly MOT tester near you

I have heard the same thing regarding Miltek quality and construction. Supersprint stuff is lovely, if I remember rightly they also do exhaust manifolds as well but these have been proven to be no better than the stock ones and you will never see them once fitted.

Shame the JHM system is no longer available or difficult to source but I have heard good things about the HMS one. Capristo is another option but personally I don't like the exhaust tips they come with as much as the big twin ovals.

I should probably try the ZInram cats first and see how they get on with my non-res and res centre sections seeing as that is what I have on hand.

First picture is the new Zinram 200e cell cat pipes, the pre-cats would normally sit to the right of the 45 degree bend, so downstream of the exhaust manifold flange connection.

The second is of the original cat pipe section on the car, both the 200 cell main cats and 400 cell pre-cats are located on the cat pipe sections.

Ahh ok that makes sense, hence a single decat pipe in the same length/format as the Zinram one you posted a pic of gets rid of both the pre and main cats in one go.
I didn't realise that both the pre cats and main cats were so close to each other.

Yeah the Supersprint stuff is lovely but hugely expensive and not valved either from memory. Agreed I'm also not a big fan of the Capristo tips.

Report back with your findings of trying zinram sport cats vs res vs non res vs decat I'd be curious to know the sound differences. I'll also report back if I ever make a decision/manage to get hold of HMS!