Replacement catalytic converter for the S8
 

Hi folks

I'll pop this in as a place marker for this job, as it might prove useful in the future....

I've noticed a rattle from one of the cats since the summer - knowing that others have experienced the same with no major issues for literally years before the cat finally expired, I wasn't in any great rush to change it.

Fast forward a few months and after my round trip to Birmingham recently I noticed that the rattle was getting far worse, to the point it could be heard in the cabin with the windows shut when sat at idle!

I did some research at the time I first noticed this, and didn't find a reputable source (or even a disreputable one!) for a replacement unit. New OEM cats are still available exchange but you're looking at £950 each with a bit of discount, plus you need to pay a surcharge on returning the old one on top.

In the meantime I stumbled across a company in Germany that was linked from motor-talk.de forum that offers a refurbishment service:

http://www.uni-kat.de/

The replacements are proper 400 cell cats and involve opening the cans and replacing all the internals, before welding it all back up. Backed by a 2 year warranty.

I've dropped the car off with David http://www.dsautowerks.co.uk/ at lunchtime today and he'll hopefully drop the cats off with me tonight or tomorrow for packaging and shipping to Germany. The rest of the process is largely going to depend on how long it takes to get them to and from Germany.

When I've got the cats here I'll try and get some pics of the internals, if they're visible.

Be warned that the contact e-mail for Uni-kat works best if you Google translate a simple e-mail to them - I've been including the English too, in case it helps!

Cost to replace the internals will be €365 each, so even with 2 of them plus the associated costs of shipping and fitting, I'm expecting the total cost to work out under 1 new cat from Audi.

Adrian

OK, some pics of the removed cats attached - it's a weird setup as the right/offside cat goes right up to the manifold in one piece, whereas the left/nearside has an S bend section in between

Difficult to see from the images but the offside one internals have completely separated from the walls and the white powder inside the pipe is the substrate gradually smashing itself to pieces!

Unfortunately one of the 3 lambda probes didn't survive removal - am hoping the threads on the pipe will clean up OK, or it may need a new boss.

Need to figure out how to package them now!

Looks familiar I had the nearside one replaced a while back.
They couldn't get one of the lambdas out so that had to be replaced and, like your right one, the core had disintegrated - effectively none left inside so they sent an empty shell back (exchange)!

Definitely keep us updated. I'd be interested to see what the renewal involves.

Mine were rattling on my D2 when I got it. Didn't fancy spending a couple of thousand £ on new ones so I had the "sports cats" fitted, for about £150 if I remember correctly.

EML came on every now and again but was nothing that couldn't be cleared and there were no other problems as a result.

What's the mileage on yours Adrian? IIRC it fairly low so wondering why it has disintegrated.
Mine is 19 years old now, 142k miles, I have had it for last 8.5 years and as far as I know cats have never been replaced. Emissions have steadily improved over the years I have owned it. MOT test limits are 0.3% CO and 200ppm for fast idle and 0.5% CO for natural idle. It started with something like 0.01 % CO and about 30 ppm of HC, last 2 MOT's it was doing 0.00 CO in both fast idle and natural idle and HC was just 8ppm at fast idle.

Maybe PF cats were better made then cost saving cut in for PF so might be an idea to fit second hand PF cats if they fit physically, of course you would need to find a way to fit after cat lambdas as PF never had any.

It's noticeable how different the colour of the 2 cat substrates is - the nearside one is a nice dark grey colour, as you'd expect. The offside is a mixture of dark grey and an increasing amount of light grey as the substrate smashes itself to pieces and works its way out of the back!

Andrew - that's fortunate, as I think from reading the exchange bit of Etka it suggested there needed to be some content left to reclaim! Maybe the box alone is enough, as at least that can be cleaned up and effectively go through the same process mine are having done.

The company I'm using suggests it's essential to get both done as the replacement substrates will be suitable different to OEM that you might experience some running issues if one bank is different to the other. Not an issue if you go the OEM route as you can be confident the properties are the same.

The nearside lambda is the one that's refused to play ball on mine too - luckily the other one is further up, so doesn't need to be removed. Offside ones came out OK after heating. That's adding another £100+ to the bill. I need to mention it in the letter to the company to make sure they clean and check the threads. I'm assuming they would anyway, but knowing one is buggered I'll make sure by mentioning it.

Conquistador - I went through a similar thought process, but the only place local to me that would fit sports cats wasn't giving me confidence it'd be anything other than a bodge job using flexi pipes. I believe one option to prevent CEL coming on is to fit a spacer under the lambda probe so it sniffs a slightly less central bit of the gas flow, which is enough for it not to detect the occasional bit of over-fueling post cats.

Because of where I work and the legislation I'm responsible for managing I don't want to be doing anything that would be in any way illegal, irrespective of the likelihood of being caught out by it being virtually nil. The car passed its MOT with a knocking cat, but suspect it was working well enough at that point. When the new ones are on I'll ask the local MOT station if they'd mind running the gas analyser on the car to check the new ones are working as expected.

Hiya

Just passed 70k miles within the last couple of weeks, so yes very low for the age.

Cats failing is usually down to thermal shock or physical impacts, so either driving through flood water, or having a mechanic belt something too hard with a hammer could be enough to damage one. The nearside one is perfect still, but that's the one that failed on Andrew's....

The other possibility is engine related issues poisoning the cat. When the plugs were done very recently it turns out I'd been driving around for the last 5 years with 1 plug loose. That might've been enough to cause the cat to fail.

The problem for us is that the AVP and one other engine code fitted in the last 18 months of production are different to even earlier facelift cars. They are tucked in pretty tight, but without seeing ones for other engine codes from a facelift it's difficult to know if they could be made to fit.

Manufacturers have got wise to the problems caused by having cats under the car - they're now close-coupled to the manifolds because they avoid thermal shock up there, plus they light off more quickly too.

MOT testers aren't known for doing all they should with emissions testing - in theory with dual exhaust they should test both and take an average. I've never seen it done! My wife's car has 4 tailpipes (all connected to something, unlike Golf Rs!) and they definitely didn't on that!

Mine was rattling away when I bought the car at a lower mileage than that. But I factored it into the price and bought OEM - quite a bit later.
As for MOT's, it passed them all with flying colours, even with one cat doing nothing! :ROFL:

Mine passed in early September with flying colours, and given yours had gone for a long while after purchase without spectacularly failing I thought I'd be OK running it like that for years.

Given I believed I'd sold my car in theory, but will now need to start marketing in earnest now I haven't, I knew I couldn't leave it when it got a lot worse in a short period of time. I'm not the sort of bloke to sell a car with a known fault and it'd make it almost unsaleable without heavy discounting reflecting the OEM cost.

In the meantime, give it a blast with open pipes and make sure you record it and put it up on youtube :)

+++

Something like this:

https://www.youtube.com/watch?v=KkglRtuqDt8

They only need to test both sides if the sides are not connected with H pipe or X pipe. On A8 or S8 it is enough to test just one as they are connected with H-pipe. Also on true dual system where pipes are not connected I though if one side is over limit it is a fail, they do not take average, just the highest of 2 readings.

Well I managed to package both cats into a bicycle cardboard box and ship them via UPS and xxxxxxxxxx for just under £30 on Monday. They've been received today and I've paid the invoice via IBAN now I've had the total confirmed for refurbishing them both.

With exchange and processing fees from my bank the refurbishment and return shipping has come in just under £720

Not sure when they'll be shipped back to me - I suspect it will mostly depend on how long the payment takes to reach them, rather than the actual work!

ETA - have removed the reference to the company I used for shipping. They have 'hero' in their name but I cannot recommend their services, based on the speculative invoice for an extra £50 that they've sent me after the fact, claiming I misrepresented the dimensions of the box after an 'audit' by UPS of my parcel. Funnily enough UPS have confirmed they've done no such thing...

Well the cats arrived unannounced at David's workshop yesterday, all safe and sound :)

New internals visible through the ends:

http://forum.a8parts.co.uk/attachmen...1&d=1478004767

They've both been fitted, together with a new post cat lambda probe on the nearside.

I haven't picked the car up yet as David's going to road test and check over, but should have it back later today :)

Apols the photos are on the wonk!

Those cores look much better than the ceramic Audi stock ones. The new ones look like metal, spiral wrapped, hopefully should last much longer than the ceramic.

The S8 is now back home with me - a total of 8 working days turnaround from cats coming off to car being completed. They were shipped on a Monday, arrived Weds in Germany and as far I can tell were probably return shipped on Thursday, given that they turned up on the Monday morning in the UK!

As I mentioned before the cost of re-coring both cats, including return delivery was just under £720, plus £30 to get them to Germany, so call it £750 all in for the cats.

Removal and fitting, the cost of which you'd have whether fitting new or refurbished, came in at £270. Lambda probe was the only unexpected element at £110.

So all in I've spent £1,130 to have it back how it should be....

Sounds a lot, but if I'd gone the OEM route I would've spent £950 for one cat, plus probably £180 for fitting, just for the offside one so exactly the same spend!

I haven't driven it far yet, but the exhaust now sounds a lot sweeter - I suspect the failing cat was upsetting the exhaust balance. Not having a distinct rattle coming from under the car is also reminding me how smooth it used to sound!

It will be interesting to see if I can detect any difference in performance once I've had an opportunity to warm it through properly and exercise the engine a bit more :D

My cat had broken up so much, a large piece was at a 45 angle to the rear of the cat and partially blocking the exhaust. Its amazing how different the car feels now in 1st gear, I've got a bit of quattro-shunt, and now with the damaged cat gone its much less pronounced and smoother. Maybe a big part of the 'shunt' when going on and off throttle in 1st was due to the cat blocking the pipe.

Hi Adrian - I've got the same Cat problem - nasty rattle. Makes a nice noise when under full chat but I'm definately feeling a loss of performance since the Cat started rattling. Sounds nice but it seems to have lost its smooth pickup and shove above 3k revs.

Did you experience the same and was there a noticeable performance diff when you got your new cats on?

Mossy

Hiya

Mine developed a pretty mild rattle at idle - mainly when hot - and performance wasn't altered. I think usually that only happens if the cat breaks up and a piece gets stuck blocking the exhaust.

My car had a Milltek and I did notice it was a little more metallic sounding with the new metal cats (sounded better to me!) but I didn't do that many miles on them before I sold the car.

Hopefully the cats are working well - current owner may chip in :D

exhaust
 

Hi
talking exhaust can anyone tell me if the front box the one that bolts to the cats is this still available? also is this crossover box needed? any help would be great as my car is jacked up with no exhaust. cheers