3.0T Cat failure - Preventative Solution?

[g00se]

Hi All - I'm sure this has been done to death.. but having just gone MRC stage 2 I'm wondering how long the stock ceramic cats will last before the increased boost/heat will destroy them / possibly block them / cause potential engine damage.

Most seem to say either:-

1. Gut the stock cats (thus turning them into 'piggies', as the Americans call them), live with the CEL, and get to know your local MOT guy.

2. Gut the stock cats (thus turning them into 'piggies', as the Americans call them), and then weld some hi-flo cats in the downpipes.. either install O2 sensor spacers in the old location so you don't get a CEL, or extend the O2 sensors with extension cables to the new location by the new hi-flow cats.

3. Ditch the stock cats for catless "test pipes"... live with the CEL, wear ear plugs, and get to know your local MOT guy.

I'm sure there's a gazillion other variations of achieving what people are after.. but i want to retain as much of the stock system as poss, so ideally want: Test pipes (or piggies) & hi-flow/resonated downpipes, to mate to the std center resonator and back boxes. As far as i can see, the ONLY people who do this utopian solution off-the-shelf is JHM:

https://www.mlperformance.co.uk/pro...ith-integrated-baffle-system-inc-s4-a6-q5-sq5

To be clear, i want a worry free, performance enhancing, bolt-on solution.. with out shouty rasp and drone (i know - i don't want much right?!)

Anyone tried the above? I cant find anywhere, anyone who has tried this solution with a stock system.. only X pipes, or non-res aftermarket systems..

cheers,

goose

 

[Dippy]

Not really an answer to your question but I'm sticking with the OE cats. I do monitor cat temperatures on my FIS-Control MMI (note that they are all calculated - we don't have actual EGT sensors on our cars) and see that they peak with boost and thus I can see how my driving style affects them.

 

[Cjman17]

Mine is currently in the workshop awaiting a rebuild due to compression issues.

I've just dropped off a pair of redstar test pipes to fit while the engine is out. The rest of my exhaust is currently standard so I can let you know what it sounds like when it's all back together. I do have an x pipe but it's been sat in the shed for months, i'll see what it sounds like with the test pipes before I decide if I'm going to fit it or not.

 

[Cjman17]

 

[g00se]

Mine is currently in the workshop awaiting a rebuild due to compression issues.

I've just dropped off a pair of redstar test pipes to fit while the engine is out. The rest of my exhaust is currently standard so I can let you know what it sounds like when it's all back together. I do have an x pipe but it's been sat in the shed for months, i'll see what it sounds like with the test pipes before I decide if I'm going to fit it or not.

Sorry to hear about your compression issues :/

I'm super keen to hear what a stock exhaust with test pipes sounds like... try as i might i cant find anywhere on t'internet, and vids of what this sounds like.

Will you run it just like that (I've heard that heat wrapping them can help prevent rasp - but wrap in our weather long-term can also prematurely corrode the pipes), or will you add some sports cats further down the system ?

cheers
goose

 

[Cjman17]

Yeah I was too haha

I've been MRC tuned for a couple of thousand miles, was running 470bhp.

I'm not going to wrap them, it's always wet up north so thought it best not to, hopefully the fact that the rest of the system is still standard will limit the rasp/drone, not many people only fit test pipes so it'll be interesting to hear what it's like.

I'm doing it more for reliability than anything else, also bought a merc racing hx, didn't fancy getting the engine rebuild only for the cats to fall a few miles down the road.

I'm in the North East if you're anywhere near you can have a listen in person.

 

[ninjag]

Can you do option 3 and install the cats back on for the mot then remove again? Or too big a job?

 

[RyanJonS4]

may be worth getting back in touch with Chris, the exhaust work they do is pure welding porn!

 

[g00se]

may be worth getting back in touch with Chris, the exhaust work they do is pure welding porn!

Chris and the team really know their stuff... can i ask how much labour was involved in getting the old cats out, gutting them, and sports cat fab'd in the DPs?

Also, did they fit a spacer in the O2 sensor to stop any CEL lights coming on the dash?

And do you have any sound/vid clips pls??

Cheers
goose

 

[RyanJonS4]

Chris and the team really know their stuff... can i ask how much labour was involved in getting the old cats out, gutting them, and sports cat fab'd in the DPs?

Also, did they fit a spacer in the O2 sensor to stop any CEL lights coming on the dash?

And do you have any sound/vid clips pls??

Cheers
goose

Sorry mate, it’s not my car! I just remember seeing it on his instagram so found the link for you. I had my s4 fettled by him a few years back now when he first set up

 

[mercules]

I have been running gutted cats for 3yrs now due to one of them failing after going stage 2. It was not worth the money to replace them for a high chance of it happening again and there was not really any reliable products at the time. It cost between £6-700 for the labor to get this done I think it was around 8 hours in total. Would be interested if there's a reliable cat on the market for our cars now.

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[mercules]

It's loud for some but flyby just over 100db at approx 20m standing distance.



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[Cjman17]

I have been running gutted cats for 3yrs now due to one of them failing after going stage 2. It was not worth the money to replace them for a high chance of it happening again and there was not really any reliable products at the time. It cost between £6-700 for the labor to get this done I think it was around 8 hours in total. Would be interested if there's a reliable cat on the market for our cars now.

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Did you use O2 spacers or have the map altered to suit?

MRC mapped mine but now I'm taking the cats off I don't really want an 8hr round trip down to them just to get the map modified for the cat removal.

I've bought some O2 spacers but from what I've read it's hit and miss if they work or not!

 

[mercules]

Did you use O2 spacers or have the map altered to suit?

MRC mapped mine but now I'm taking the cats off I don't really want an 8hr round trip down to them just to get the map modified for the cat removal.

I've bought some O2 spacers but from what I've read it's hit and miss if they work or not!

I bought O2 spacers and took them to the garage but mechanic said unfortunately they were too long to fit in the space. There is mixed feedback on them in general not flagging a cel so I had to do the trip back to MRC to remove them from the map. I had to go anyway for a tweak as back pressure is reduced once the cats are gutted so you will be down on power slightly if mapped with the stock cats already. They can also add pops if you want and its only active on dynamic mode.

Are you in the North? I thought MRC had a "partner" garage a few years ago that uses their maps and pulleys. Might be closer to you.

I'm probably changing cars this year so will see what traction I get selling with no cats probably will be difficult. Will keep an eye out on some from a scap car. I think Audi wanted about £2k a pair.

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[Cjman17]

I bought O2 spacers and took them to the garage but mechanic said unfortunately they were too long to fit in the space. There is mixed feedback on them in general not flagging a cel so I had to do the trip back to MRC to remove them from the map. I had to go anyway for a tweak as back pressure is reduced once the cats are gutted so you will be down on power slightly if mapped with the stock cats already. They can also add pops if you want and its only active on dynamic mode.

Are you in the North? I thought MRC had a "partner" garage a few years ago that uses their maps and pulleys. Might be closer to you.

I'm probably changing cars this year so will see what traction I get selling with no cats probably will be difficult. Will keep an eye out on some from a scap car. I think Audi wanted about £2k a pair.

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Am I correct in thinking it won't cause any harm driving it with the CEL on? Planning a trip back to banbury might take a while, although I suppose I'm risking missing another fault that could crop up if the CEL is already on for the O2 sensors.

I've never understood the whole back pressure and loosing power thing, did MRC tell you that?

Yeah I'm up near Middlesbrough, I'll have to give them a ring tomorrow and ask!

I'm not going to worry about resale for a while, the amount the engine rebuild is going to cost me I'll be keeping the car for a good few years now

 

[mercules]

No it's all ok to drive with the cel. The cel is because the computer knows the cat efficiency is out on its defined range. It gets the results from the two O2 sensors which are positioned pre and post cat in stock setup.

It's said the incresed flow in the exhaust drops the boost they set on the map for the superchager and results in a small loss of HP and torque. From memory I think I was about 20 or 25hp out at the top end and mid and low was like 5hp difference will need to dig out the Dyno print. So not major but worth getting it done if you are there for the cel delete too.

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[Cjman17]

No it's all ok to drive with the cel. The cel is because the computer knows the cat efficiency is out on its defined range. It gets the results from the two O2 sensors which are positioned pre and post cat in stock setup.

It's said the incresed flow in the exhaust drops the boost they set on the map for the superchager and results in a small loss of HP and torque. From memory I think I was about 20 or 25hp out at the top end and mid and low was like 5hp difference will need to dig out the Dyno print. So not major but worth getting it done if you are there for the cel delete too.

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Yeah I just wasn't sure if the ecu would cut fueling or something, might just leave the spacers off and go for the tweaks, it was 470bhp when they did it, might get a few more hp now the cats are gone!

I've just had a look and they have a dealer in Leeds which is only an hour or so away from me, will have to give him a ring and see what he has to say.

 

[g00se]

Yeah I just wasn't sure if the ecu would cut fueling or something, might just leave the spacers off and go for the tweaks, it was 470bhp when they did it, might get a few more hp now the cats are gone!

I've just had a look and they have a dealer in Leeds which is only an hour or so away from me, will have to give him a ring and see what he has to say.

Talk to Chris at CM Tuning in Morley (as per the pic that RyanJonS4 posted above).. they are the northern MRC dealer that did my stage 2 package a few weeks ago. I too will be talking to them about gutting my stock cats, and welding in some hi-flo cats into my Scorpion resonated downpipes

goose

 

[audiwaterpump]

How much is a new Audi OEM Cat?

 

[mercules]

How much is a new Audi OEM Cat?

£1200 per side when I asked a couple years go.

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[g00se]

It's loud for some but flyby just over 100db at approx 20m standing distance.



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Hi Mercules - that sounds great.. so is that just gutted cats and stock exhaust, or do you an aftermarket system too?

Cheers,
goose

 

[mercules]

Hi Mercules - that sounds great.. so is that just gutted cats and stock exhaust, or do you an aftermarket system too?

Cheers,
goose

Hi mate,

It's milltek non res full cat back plus gutted stock cats.

Cheers

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[g00se]

Hi mate,

It's milltek non res full cat back plus gutted stock cats.

Cheers

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Yikes - I bet that's loud.. how's the drone and rasp?

For the life of me I cant find a vid anywhere online of a just a plain old bone stock exhaust system on a 3.0T with gutted cats only :/

Everyone seems to have either gutted cats and aftermarket, or test pipes / X pipe / res deletes / muffler deletes etc.

I think I'm just going to have to pull the trigger and pray the rasp isn't too bad

goose

 

[Cjman17]

Hang fire, I haven't forgot lol

Had a few hiccups with pistons and chains but I'm hoping to have it back on the road at some point next week!

 

[mercules]

Yikes - I bet that's loud.. how's the drone and rasp?

For the life of me I cant find a vid anywhere online of a just a plain old bone stock exhaust system on a 3.0T with gutted cats only :/

Everyone seems to have either gutted cats and aftermarket, or test pipes / X pipe / res deletes / muffler deletes etc.

I think I'm just going to have to pull the trigger and pray the rasp isn't too bad

goose

Yea it's all round loud for sure, all the neighbors definitely know the sound of my car just under normal driving in and out. It's a deep sound pretty close to v8 sound which milltek gives. The rasp is balanced but drone is noticeable at 60-70mph but that was there even before cats were gutted on this milltek exhaust. The cats gutted just enhanced everything louder.

I think gutted + stock exhaust with the additional resonators you should have a good balance. Stock exhaust really makes the car muted.

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[g00se]

Hang fire, I haven't forgot lol

Had a few hiccups with pistons and chains but I'm hoping to have it back on the road at some point next week!

Patiently hanging fire lol !!!!

Am itching to get this done.. as every time i drive the car hard i think a cat is going to sh1t itself and blow the engine

goose

 

[Cjman17]

Hahaha

Engine was fired up today, all seems to be good, my tech is using it to run around in, going to drop the oil on Saturday then give it a once over to make sure theres no leaks/loose bolts etc and I should be picking it up over the weekend.

Going to be a long 1000 miles running it in then another oil change before it gets some abuse

I'll get a video up ASAP

 

[Cjman17]

First impressions, don't do it

Not sure if it will quieten down a bit when it's had a chance to build up a layer of carbon/soot on the test pipes, but I'm not hopeful.

As it is, its very raspy, I'm going to have to get someone to do a driveby and see what its like from outside. Will get a video then.

I'm already thinking of bigger resonators in the downpipe maybe, but again not sure if that will help!

 

[PenttisHSR]

There's a ton of info about test pipes on the USA Forum, you could try wrapping them ?
I know you think the wrap would get wet. If the test pipes were stainless, then corrosion wouldn't be an issue?
Link here......... https://www.audizine.com/forum/showthread.php/865123-The-official-Catless-exhaust-thread

 

[g00se]

First impressions, don't do it

Not sure if it will quieten down a bit when it's had a chance to build up a layer of carbon/soot on the test pipes, but I'm not hopeful.

As it is, its very raspy, I'm going to have to get someone to do a driveby and see what its like from outside. Will get a video then.

I'm already thinking of bigger resonators in the downpipe maybe, but again not sure if that will help!

Oh jeez! Rasp is not cool, but i think with modding this particular Audi V6 its inevitable :/

It may not help you.. but I have heard that gutting the stock cats is a smidge less raspy than test pipes.

A vid will be helpful, as i really need to make a decision this week as to which way im going.

Cheers

goose

 

[Cjman17]

There's a ton of info about test pipes on the USA Forum, you could try wrapping them ?
I know you think the wrap would get wet. If the test pipes were stainless, then corrosion wouldn't be an issue?
Link here......... https://www.audizine.com/forum/showthread.php/865123-The-official-Catless-exhaust-thread

Yeah they're stainless, I'm not sure if wrapping them in situ will be possible, I'll have a look when it goes back in for an inspection once the engine is ran in.

Thanks for the link.

Oh jeez! Rasp is not cool, but i think with modding this particular Audi V6 its inevitable :/

It may not help you.. but I have heard that gutting the stock cats is a smidge less raspy than test pipes.

A vid will be helpful, as i really need to make a decision this week as to which way im going.

Cheers

goose

I'll get a video tomorrow night, although I'm currently under strict instructions not to go over 4k for the next 750 miles.

I think that the decats probably sound worse as they're stainless, I was talking to an engineer at work and he mentioned adding weights of some sort to the pipes could possibly alter the sound, might look into that!