Cat problems

[Tj s4]

I have a 2013 Audi s4. Took it into the garage and they have said that the front pipe has broken and the cat has broke at the front. It’s 2500 to fit a Audi part and 1100 for a copy part they have found.
Does anyone have any other advice or options? Would decatting the front pipes be a good idea or does it cause problems? Really appreciate any help

 

[g00se]

One of the most common faults with these 3.0T supercharged engine is the location of the cats, right up by each bank of engine cylinders either side of the V (apparently done so to get these engines past emission regs).. the knock-on effect being that the cores of the cats breakdown over time due to the immense heat generated by these engines, and can get blocked and cause catastrophic engine damage (google it - there's been LOADS of cases!!).

The good news is, you have options:-

• Replace like for like in the stock location, and hope the above never happens
• Replace the old cats with hi-flo sports cats in the stock location... and hope the above never happens
• Remove the stock cats, gut them of material, and refit (this is the route i went - catless V6s become raspy)
• Remove the stock cats, and fit "test pipes" such as Red Star (again - raspy)
• Remove the stock cats, and fit "test pipes", and have cats welded into the system further downstream (many remove the downpipe resonators and put the cats in their location - this will get slightly louder as you've removed some silencers)

I'm sure there's a million other ways of doing the above (and manufacturers).. but these seem to be the most popular. Clearly decat options require some special attention come MOT time.

I did mine mostly for peace of mind... cat and crank pulley failure seem to be the 2 biggies. That said, if your cat broke at the front you may have some engine movement as the mounts can fail too.. so maybe worth checking those out too at the same time.

goose

 

[Tj s4]

One of the most common faults with these 3.0T supercharged engine is the location of the cats, right up by each bank of engine cylinders either side of the V (apparently done so to get these engines past emission regs).. the knock-on effect being that the cores of the cats breakdown over time due to the immense heat generated by these engines, and can get blocked and cause catastrophic engine damage (google it - there's been LOADS of cases!!).

The good news is, you have options:-

• Replace like for like in the stock location, and hope the above never happens
• Replace the old cats with hi-flo sports cats in the stock location... and hope the above never happens
• Remove the stock cats, gut them of material, and refit (this is the route i went - catless V6s become raspy)
• Remove the stock cats, and fit "test pipes" such as Red Star (again - raspy)
• Remove the stock cats, and fit "test pipes", and have cats welded into the system further downstream (many remove the downpipe resonators and put the cats in their location - this will get slightly louder as you've removed some silencers)

I'm sure there's a million other ways of doing the above (and manufacturers).. but these seem to be the most popular. Clearly decat options require some special attention come MOT time.

I did mine mostly for peace of mind... cat and crank pulley failure seem to be the 2 biggies. That said, if your cat broke at the front you may have some engine movement as the mounts can fail too.. so maybe worth checking those out too at the same time.

goose

Thanks for all this. The garage haven’t been the best communicating with me about it so I don’t know the exact part I need, they said it’s the part leading to the turbo and the car doesn’t have a turbo so I’ve took it out the garage. Are the cats located infront of this part?

 

[g00se]

The above are the Scorpion resonated downpipes.. i know as i have them and i recognize the part number I got these within 2 weeks of getting my car as the stock downpipes were rattling and the dealer i bought the car from paid for these as they were cheaper than OEM from Audi.

Here is the best pic i can find to explain our standard exhaust system:-

You can see here why some people gut/remove the cats, and weld sports cats in where the downpipe resonators are..

Hope this helps

goose

 

[g00se]

PS. Now is a good time to be buying exhausts as there are Black Friday deals on... prices will go up again in Dec

 

[ninjag]

One of the most common faults with these 3.0T supercharged engine is the location of the cats, right up by each bank of engine cylinders either side of the V (apparently done so to get these engines past emission regs).. the knock-on effect being that the cores of the cats breakdown over time due to the immense heat generated by these engines, and can get blocked and cause catastrophic engine damage (google it - there's been LOADS of cases!!).

The good news is, you have options:-

• Replace like for like in the stock location, and hope the above never happens
• Replace the old cats with hi-flo sports cats in the stock location... and hope the above never happens
• Remove the stock cats, gut them of material, and refit (this is the route i went - catless V6s become raspy)
• Remove the stock cats, and fit "test pipes" such as Red Star (again - raspy)
• Remove the stock cats, and fit "test pipes", and have cats welded into the system further downstream (many remove the downpipe resonators and put the cats in their location - this will get slightly louder as you've removed some silencers)

I'm sure there's a million other ways of doing the above (and manufacturers).. but these seem to be the most popular. Clearly decat options require some special attention come MOT time.

I did mine mostly for peace of mind... cat and crank pulley failure seem to be the 2 biggies. That said, if your cat broke at the front you may have some engine movement as the mounts can fail too.. so maybe worth checking those out too at the same time.

goose

Well this post has just terrified me.

 

[g00se]

Well this post has just terrified me.

hahahaha sorry chap.. but i speak the truth.

Coincidentally its also the reason i went stage 2, as MRC replace the two-piece crank pulley that fails with a single-piece billet pully So this and ditching the cats gives both great performance and piece of mind... at least that's what i told Mrs Goose lol!

goose

 

[Dippy]

Well this post has just terrified me.

It's easy to be terrified.
When I bought my 2001 S4 and then read about turbo failures I was terrified.
When I bought my 2015 S5 and then read about gearbox failures I was terrified.
Forum reports do not come with statistical failure rates. For every one failure we read about there are others that we don't, but likely many more which have not failed.
Often failure reports are missing valuable information. How has the car been driven? What is the maintenance record?
I'm not convince that our cats have a design fault, but certainly their location means that they are at risk of overheating, especially where the engine is tuned. That means that as drivers we can do something to mitigate the risk. In my case I have the EGT readings from the ECU (which are calculated I understand it) shown on my FIS-Control MMI. When I apply the boost I see those temps shoot up. But off boost they come back down fairly quickly. By keeping an eye on those temps I can adjust my driving to suit. If my cats do melt in the future it won't be because I abused them.

 

[ninjag]

The cat bit got my attention because I've noticed my fuel economy drop quite considerably over the last few months, even before getting cold. I've popped a bottle of snake oil in, usually I would get Archoil AR6400-P Max but it's pricey and I'm impatient to wait so I went with Wynn's Extreme Cleaner instead as at least it has PEA. Probably don't do anything.

Is the crank pulley an easy job?


Cheers

 

[Suths]

The cat bit got my attention because I've noticed my fuel economy drop quite considerably over the last few months, even before getting cold. I've popped a bottle of snake oil in, usually I would get Archoil AR6400-P Max but it's pricey and I'm impatient to wait so I went with Wynn's Extreme Cleaner instead as at least it has PEA. Probably don't do anything.

Is the crank pulley an easy job?


Cheers

Crank pulley is relatively easy. Biggest issue is getting access. Recommended method requires putting car into service position but some people have replaced it without doing this. There’s a thread on Audizine that addresses this method.

 

[ninjag]

Crank pulley is relatively easy. Biggest issue is getting access. Recommended method requires putting car into service position but some people have replaced it without doing this. There’s a thread on Audizine that addresses this method.

Thanks. I'm at 76k miles and my two main concerns are the CATs and the crank pulley, although there are nothing to indicate a problem and it's just the mileage.

 

[g00se]

Thanks. I'm at 76k miles and my two main concerns are the CATs and the crank pulley, although there are nothing to indicate a problem and it's just the mileage.

I too am at 76k miles Ninjag, but thankfully have addressed both cats and crank pulley... now I just lose sleep over gearbox woes and the dreaded timing chains

goose

 

[ninjag]

I too am at 76k miles Ninjag, but thankfully have addressed both cats and crank pulley... now I just lose sleep over gearbox woes and the dreaded timing chains

goose

My car is still stock so I'm hoping that will prolong the life of my CATs but the crank pulley is bugging me. I'll be doing my DSG fluid again soon so I might check it out then.

When getting my new tyres fitted last week the guy mentioned that some places can do the timing chain in situ. Is that really possible?

 

[Suths]

My car is still stock so I'm hoping that will prolong the life of my CATs but the crank pulley is bugging me. I'll be doing my DSG fluid again soon so I might check it out then.

When getting my new tyres fitted last week the guy mentioned that some places can do the timing chain in situ. Is that really possible?

Being stock certainly won't speed up cat problems. The oem cats are actually extremely high quality. the problem with them is the location and heat that they have to handle.

most catastrophic cat problems that I've seen have been accelerated by an underlying issue. leaking supercharger intercoolers is something that people rarely realise they have but the coolant getting into the exhaust gases can cause cat material degradation. It's important to stay on top of maintenance on these cars and understand where the potential pain points are. Keep an eye on coolant and oil levels. Neither are good for your cats.

As for timing chains, I believe the transmission and flywheel need to be removed. Most take the engine out to do it properly. No idea if it can be done in situ. Why do you think it needs to be replaced?

 

[Dippy]

Remember that for every report on a forum of a car having problems with a component there are hundreds or thousands of cars of a similar age and mileage which do not have that problem. Usage and maintenance are a big factor in reliability and so it would be wrong to assume that you'll eventually see the same failures that others have. The DSG is probably the biggest risk because we have genuine information about it: Audi did revise this gearbox in (AFAIK) 2011 and 2013. There are more reports of DSG failures in earlier versions and some proven fixes (e.g. specific known mechatronics repairs). With limited data it is possible to speculate that lack of DSG servicing can "promote" problems.

From my time spent on forums I'd say that timing chain problems tend to occur at higher mileage but do not require immediate attention. As @Suths noted it is usually an engine out job and this must surely be easier than trying to access in-situ from the transmission side, and with the cost of removing the transmission I wouldn't have thought it would be cheaper.

Crank pulley failure is definitely not common, but neither is it rare. Very few people change it as preventative maintenance - but there are a number of us who have taken the opportunity to replace it with an oversize pulley which avoids the failure mode. That mode is that the polymer (aka rubber) which holds the two parts together degrades. I believe (but do not know for sure) that this could be detected with periodic inspection. With good light and the right angle it is possible to see the pulley from above. If the polymer is starting to degrade enough to be a concern then a slight "wobble" should be visible. It might also be possible to do a limited visual inspection from below with a mirror tool and good light. The photo below is my OE pulley after it had been removed. The polymer is visible through the 5 ovals. At 8300 miles it is still smooth and crack-free. I have seen older pulleys where cracks are visible.

 

[ninjag]

Being stock certainly won't speed up cat problems. The oem cats are actually extremely high quality. the problem with them is the location and heat that they have to handle.

most catastrophic cat problems that I've seen have been accelerated by an underlying issue. leaking supercharger intercoolers is something that people rarely realise they have but the coolant getting into the exhaust gases can cause cat material degradation. It's important to stay on top of maintenance on these cars and understand where the potential pain points are. Keep an eye on coolant and oil levels. Neither are good for your cats.

As for timing chains, I believe the transmission and flywheel need to be removed. Most take the engine out to do it properly. No idea if it can be done in situ. Why do you think it needs to be replaced?

My chains are fine as far as I can tell, no new noises or anything, I'm just doing a little pre-emptive planning - or worrying!

Re. the CATs, my coolant seems to hold steady, but I do have to top my oil up once in a while. There's no consistency to it though, just out of the blue it will ask for a little oil so I keep a litre in the spare wheel well. I suppose a glass half full perspective could be that the engine is getting a little bit of new oil all the time!

 

[ninjag]

Remember that for every report on a forum of a car having problems with a component there are hundreds or thousands of cars of a similar age and mileage which do not have that problem. Usage and maintenance are a big factor in reliability and so it would be wrong to assume that you'll eventually see the same failures that others have. The DSG is probably the biggest risk because we have genuine information about it: Audi did revise this gearbox in (AFAIK) 2011 and 2013. There are more reports of DSG failures in earlier versions and some proven fixes (e.g. specific known mechatronics repairs). With limited data it is possible to speculate that lack of DSG servicing can "promote" problems.

From my time spent on forums I'd say that timing chain problems tend to occur at higher mileage but do not require immediate attention. As @Suths noted it is usually an engine out job and this must surely be easier than trying to access in-situ from the transmission side, and with the cost of removing the transmission I wouldn't have thought it would be cheaper.

Crank pulley failure is definitely not common, but neither is it rare. Very few people change it as preventative maintenance - but there are a number of us who have taken the opportunity to replace it with an oversize pulley which avoids the failure mode. That mode is that the polymer (aka rubber) which holds the two parts together degrades. I believe (but do not know for sure) that this could be detected with periodic inspection. With good light and the right angle it is possible to see the pulley from above. If the polymer is starting to degrade enough to be a concern then a slight "wobble" should be visible. It might also be possible to do a limited visual inspection from below with a mirror tool and good light. The photo below is my OE pulley after it had been removed. The polymer is visible through the 5 ovals. At 8300 miles it is still smooth and crack-free. I have seen older pulleys where cracks are visible.

View attachment 262982

Thanks for that, very helpful indeed. We've got a pretty decent camera snake at work and now that I know exactly what to look for hopefully the resolution will be good enough to see. If not then I'll see if my phone can squeeze in there. It's got a pretty decent macro mode so fingers crossed!

You mentioned that the replacement pulley is an oversized one. Does it have to be oversized and if so would I not need a remap to compliment this? Cheers.

 

[ninjag]

Came across this in the CREC engine study. Could the dual fuel injection system allow me to worry a little less about the CAT?...

Approaching full throttle, the multi-point injection component
is reduced resulting in more even basic homogenisation of the
air/fuel mixture and lower O2 emissions. Due to the lower O2
emissions in the exhaust gas there is less of an increase in the
catalytic converter temperature. This makes it possible to
reduce full throttle enrichment for the protection of the catalytic
converter and improve fuel economy still further.

 

[Dippy]

Maybe. Aside from other failure damaging the cats, the temperature is under driver control. The temperature is directly related to boost: In short bursts the temperature rises and falls. More constant use of boost keeps the temperature high.