S4 exhaust cat removal

Stanningtonglen

Stanningtonglen

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When I got the car it can with a Milltek back section,still having Audi cats. I have been a 3 exhaust manufacturers and all have advised I leave the cats on. Saying that because its NA its not worth doing for the price it will cost. It will sound better thats all and will loose so much torque it will feel sluggish. If it was a turbo then yes there wouldn't be a problem and I agree as my last A4 had a stainless exhaust and cat removal and it made all the difference .
A Good map and decent fuel is whats recommend, I all ready had a stage 1 APR map done.
So what have you other S4 owners done ?
Thanks all.
 
A tad on the steep side but probably the most effective bolt on upgrade , i'd consider one if I had a 4.2 V8 ...:whistle2:

Upload 2019 10 21 20 22 21
 
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They said that as well Rob, stick a super charger on it and having seen some on YouTube it's not a bad idea, but as ya say its rather expensive
 
Or just drive it as it is, how it was meant to be driven.....enjoy the v8 experience, the sounds and sensations.:icon thumright::icon thumright::yahoo::yes:

I've got one in the garage that I don't use , flathead V8 0nly 90 hp but shed loads of torque and nostalgia by the bucket load.
 
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Not an S4 power house and most certainly lacking in high tech management systems...

V8yt
 
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Well have to meet up and go for a V8 run sometime :racer:
Love the sound of it, I think because I have done all my cars I'm wanting to do the same with this one. But even they never sounded quite the a V8
 
I've an 1996 XK8 soft top in the garage to, another V8 4.2 power house , well it's not though to be honest more of a laid back sort of cruiser .
4.2-litre V8 engine 300bhp with top speed of 155mph, not really that special but sounds great under load....feels like a slug compared to my A4 special edition though.
 
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Anyway, back on track,
there is a website that specialises in performance enhancements for the B7 S4 engine , covers a whole range of mods if you are looking to go that route chap.
 
I'll have a look back through my favourites list, not sure if I saved it though as it was a while back, if not I'll see if I can locate it for you.

yep , too many car really and way too many projects...:haha:
 
If you really want to do something with the cats, then I'd drill out the precats on the downpipes. They are an awful design, and can actually be responsible for leaking cam cover gaskets, as well as putting more strain on the internals and making the engine run hotter!

The precats are only a few inches from the exhaust headers, which causes all sorts of problems with airflow. Also, they are prone to blocking, which causes the increase in back pressure etc.

My S4 has milltek sports cats fitted by the previous owner. So I estimate only about 50k miles old tops, and they are blocked.

Its quite a common mod in USA to drill out the precats (leaving the main cats intact). Its easy to drill out the precat material, its just a pain removing and fitting the downpipes because you ideally need a lifter to get the ground clearance!

https://www.audizine.com/forum/showthread.php/250634-Dp-testing-and-results-THIS-IS-LONG-SUPER-LONG
 
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As for loosing torque when fully de cated, that doesnt seem to be the opinion of those in the states. They've had good gains with full de cats, however it is always about the whole system, rather than one mod. I agree however that its not really worth the money for bolt on decated downpipes.
 
Thanks fir the link, from what I see the way to go is pre -cat removal or as you say drill them out and keep the main cats. If ya full cat less the ya need either an H or X pipe to add some back pressure .
 
Stanningtonglen said:
Thanks fir the link, from what I see the way to go is pre -cat removal or as you say drill them out and keep the main cats. If ya full cat less the ya need either an H or X pipe to add some back pressure .
Click to expand...

Oh, sorry I should of mentioned about the x or h pipes. I read your bit about 3 exhaust manufacturers saying you'd loose torque etc, and just assumed they thought that no matter what you did, which doesnt seem to be the case.

And yeh, pre-cat does seem to be the way forward. As mine has milltek sports cats, sadly they are placed where the pre cats are, and they do away with the main cat. So although performance is increased slightly over stock, you end up with the same blocking and heat problems as you would normally. My big problem was what to do about my blocked cats. Mines a tiptronic, and you cannot buy a new set of Milltek downpipes for the Tip anymore (the manual ones are hard enough to come by) lol. Trying to get hold of stock downpipes second hand was a nightmare, and nearly ended up buying new from USA for £550. Finally found some B6 downpipes, drilled the pre cats out, and just waiting to fit them.

So if you want to mod them, then just drill the pre cats out, and have it remapped, thats the cheapest option, and still visibly stock as well.
 
Already done a stage one APR remap. Will have a chat with the guys that normally do my exhaust builds the last time I spoke to them was a couple of days after buying the car and about removing the main cats.
 
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Stanningtonglen said:
Already done a stage one APR remap. Will have a chat with the guys that normally do my exhaust builds the last time I spoke to them was a couple of days after buying the car and about removing the main cats.
Click to expand...

If you do anything with the downpipes, you would need it mapped again to code out the o2 sensor fault codes, which lights up the EML (unless of course the engine light doesnt bother you, in which case you wouldnt need it mapped again)
 
Did you go any further with this in the end? I've finally had my downpipes changed, and its transformed the car back again. The miltek high flow downpipes were completely broken inside, and reducing power a heck of a lot (pretty bad show form miltek, considering they'd be max 50k old)

Anyway, if you ever want to tinker, I've got a set of miltek tiptronic downpipes that just need a new cat, or drilling out, which will be going super cheap.
 
ramboDTM said:
Did you go any further with this in the end? I've finally had my downpipes changed, and its transformed the car back again. The miltek high flow downpipes were completely broken inside, and reducing power a heck of a lot (pretty bad show form miltek, considering they'd be max 50k old)

Anyway, if you ever want to tinker, I've got a set of miltek tiptronic downpipes that just need a new cat, or drilling out, which will be going super cheap.
Click to expand...

What downpipes have you put on ?
I went to a place in Doncaster a couple weeks ago and had a good chat with them,so next Friday I'm going back and were gonna try some various things out.
 
going in tomorrow to have my exhaust done, taking Milltek off so will be selling that. Drove it with no back section and not good .So we had a chat and going for one thats louder than the Milltek but not as loud as being without. Also with twin blue burnt ends.
 
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Well that's put a smile on my face, it looks and sounds so much better and they even flitted my new defuser .
Before with the Milltek as standard S4 defuser
20191206 124721

The new exhaust and defuser, I can't recommend these guys enough cracking job and build , listened to what I wanted and together came up with this, sounds and looks so goo/ATTACH]
20191206 154006
20191206 154013
 
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Glad it's all sorted chap, now it just needs a shampoo and set...:yes::thumbs up:
 
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Looks awesome now, proper tips, not those standard pea shooters....
 
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The diffuser makes the rear end look very business like, I like.
 
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Stanningtonglen said:
Rob, have ya ordered the carbon fiber one yet ?
Click to expand...

I have , it should have arrived on Monday but held up by shipping delay...wont be here for a few more weeks now so I don't expect it before xmas to be honest.
 
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Anychance of a short audio clip of it chap, must sound awesome now.
 
Did you do anything with the downpipes in the end? Love those tips!
 
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Never mind chap, best let you enjoy that glorious sound then..:icon thumright:
 
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