Another Cat thread

[mercules]

Hi Gents,

I am stage 2 single pulley (Crank) about 470hp DSG 2013 87K miles milltek catback non res. One of my Cats looks like its gone, o2 sensor bank 1 voltage is as per the examples erratic exhaust slightly louder/rattle too. I had it on the dyno today and its dropped 50hp since first tuned.

I am worried to put in oem cats again so looking at catless option.

I was told that going catless for the sake of not having to pay the large labour cost again should the stock Cats fail again there would not be enough back pressure and i would still be around the 420hp mark and if i put in new oem cats i can get my gains back up to 470 is this true?

Im only going to be running pump fuel which is at best 99 ron.

Any advice would be greatly appreciated!

Thanks

[S4ork]

Hi Mercule,

My cat just went also and am planning to go catless so I am in the market for some good advice also. I am on a Dual Pulley EPL tune and power has dropped significantly with the super charger not spooling up. I have found chunks of honeycomb material in the mufflers which have been causing the rattle. I am still on stock exhaust so with this situation I will be upgrading this week.

[chilort]

Tag for replies. I still haven't made my mind up about what I'm going to do. Never thought about the cat material getting stuck in the muffler. That sucks.

[sonic32]

Hit up Evan @ Tampa Motorsports for catted/non catted test pipes, find him on the b8/8.5 Facebook group


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[AvusPdx]

on the same boat as well. Didn't know going catless will lose 50hp? I can understand losing some bottom end but should gain more top end with better flow?
I was told dealerships has a 80k warranty on cats? Then you can get a new cat, gut the old one etc.

[S4ork]

I have tried him twice last week after reading the threads and didn't get a response.

[mercules]

Hi Mercule,

My cat just went also and am planning to go catless so I am in the market for some good advice also. I am on a Dual Pulley EPL tune and power has dropped significantly with the super charger not spooling up. I have found chunks of honeycomb material in the mufflers which have been causing the rattle. I am still on stock exhaust so with this situation I will be upgrading this week.

Hi S4ork,

I would be so disappointed if I bought set of low mileage ones from Germany and they failed within a year or so. That is what is making me want to run catless but I don't want less power. Bad luck on finding chunks hopefully someone can clear this up.

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[mercules]

on the same boat as well. Didn't know going catless will lose 50hp? I can understand losing some bottom end but should gain more top end with better flow?
I was told dealerships has a 80k warranty on cats? Then you can get a new cat, gut the old one etc.

That's why I felt like I have to ask there's guys running catless and with cats on same power I just want to make sure they are not having to compensate by using meth. My existing blown one must be doing something to be dropping that type of power. I would prefer to run with cats for legal reasons but stock are the ones that hold up the best and they are still hit an miss on longevity. Then another part of me says put stock cats on cut my losses and sell the car get something that doesn't need this level of modding to get the power.

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[Bartlett]

Doesn't Evan make high flow cats?

[mercules]

Doesn't Evan make high flow cats?

Reliable high flow cats? That's the issue. Nobody wants to be doing it again. These cats get to crazy temps and I was told the stock Audi ones are made the best even if they still fail.

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[Bartlett]

Reliable high flow cats? That's the issue. Nobody wants to be doing it again. These cats get to crazy temps and I was told the stock Audi ones are made the best even if they still fail.

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I see. So it looks like test pipes are the best alternative?

[xpoweruk]

I see. So it looks like test pipes are the best alternative?

Why not just gut your cats if you are considering test pipes ?

[mercules]

Why not just gut your cats if you are considering test pipes ?

Yea that's probably the cheapest route but the main question I am trying to find out is if running test pipes or gutted cats was the back pressure will I or we loose power as I was told I would.

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[mercules]

I see. So it looks like test pipes are the best alternative?

I saw the V2 of the JHM racing pipes they said it's been tested for a year no issues. But if we are going to drop power what's the point might as well just gut the stock cats it's cheaper.

I'm sure someone will come along and clarify this for us.


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[Acejam]

Doesn't Evan make high flow cats?

Yes he does


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[AudBoost]

Doesn't Evan make high flow cats?

Yes he does.

Reliable high flow cats? That's the issue. Nobody wants to be doing it again. These cats get to crazy temps and I was told the stock Audi ones are made the best even if they still fail.

So far he has not had a failure come back yet. I take that back he had one set and it was an issue from the manufacturer. He posted pictures of a set after ~5000 miles of use and they looked brand new. He is only one that I am aware of that is using a metal substrate while others are using ceramic.

[mercules]

Yes he does.


So far he has not had a failure come back yet. I take that back he had one set and it was an issue from the manufacturer. He posted pictures of a set after ~5000 miles of use and they looked brand new. He is only one that I am aware of that is using a metal substrate while others are using ceramic.

I'll read up on them thanks it will provide some back pressure for sure. I'm hoping someone will come along and confirm that the exhaust system on this car doesn't loose power if cats are removed.

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[jimrobbington]

I don't know why people keep saying this. A boosted engine doesn't need back pressure. I find it hard to believe you will lose power from test pipes. You are reducing restriction.

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[mercules]

I don't know why people keep saying this. A boosted engine doesn't need back pressure. I find it hard to believe you will lose power from test pipes. You are reducing restriction.

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Tuner said it that's why i created this thread to confirm if this is the case.

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[jimrobbington]

Tuner said it that's why i created this thread to confirm if this is the case.

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Yeah, I can't confirm, but it sounds like nonsense, especially when every other boosted car if had they claim +15 to +25 hp from test pipes with tune

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[BigKeshy]

https://www.youtube.com/watch?v=jjPeP_Nn2B4&t=209s

This video is a fairly good overview of the differences between back-pressure (bad) vs. exhaust scavenging (good).

I'm not an exhaust expert, so please take this with a grain of salt: I think the reason for your power loss may be due to a hole in the honeycomb of your cat. If there is a hole, exhaust gases will take the path of least resistance through it. If that hole has a smaller diameter compared to the exhaust tubing in front, it'll create a reflected positive pressure wave (instead of the negative that you want). That would definitely interfere with the desired exhaust scavenging your exhaust was performing previous to cat failure and could be the explanation of your power loss.

If you hollow out your cats or replace them with test pipes, you will remove the sudden cross-sectional reduction which should return your exhaust scavenging effect back to around normal.

FWIW, I haven't heard/read about anyone losing power after converting to test-pipes. Usually it's anywhere from modest gains to no difference.

[MSq5]

on the same boat as well. Didn't know going catless will lose 50hp? I can understand losing some bottom end but should gain more top end with better flow?
I was told dealerships has a 80k warranty on cats? Then you can get a new cat, gut the old one etc.

Perhaps he meant that the blown cat was throwing the honeycomb guts downstream and clogging up a muffler, obstructing flow. Our engines do not need backpressure. A more open exhaust will not reduce power. It might sound terrible, though, without straight through tuning resonators.

[mercules]

Perhaps he meant that the blown cat was throwing the honeycomb guts downstream and clogging up a muffler, obstructing flow. Our engines do not need backpressure. A more open exhaust will not reduce power. It might sound terrible, though, without straight through tuning resonators.

I've not had a camera put up there yet but I've got all the symptoms. Thanks for clarifying that basically gives me the cheapest option of gutting the stock cats and removing the milltek non res downpipes and putting stock downpipes back on.


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[mercules]

https://www.youtube.com/watch?v=jjPeP_Nn2B4&t=209s

This video is a fairly good overview of the differences between back-pressure (bad) vs. exhaust scavenging (good).

I'm not an exhaust expert, so please take this with a grain of salt: I think the reason for your power loss may be due to a hole in the honeycomb of your cat. If there is a hole, exhaust gases will take the path of least resistance through it. If that hole has a smaller diameter compared to the exhaust tubing in front, it'll create a reflected positive pressure wave (instead of the negative that you want). That would definitely interfere with the desired exhaust scavenging your exhaust was performing previous to cat failure and could be the explanation of your power loss.

If you hollow out your cats or replace them with test pipes, you will remove the sudden cross-sectional reduction which should return your exhaust scavenging effect back to around normal.

FWIW, I haven't heard/read about anyone losing power after converting to test-pipes. Usually it's anywhere from modest gains to no difference.

Thanks for the explanation I think if the engine doesn't rely on much back pressure then test pies or gutting is the safest option but I'd have to pay to get cats and have installed if I ever wanted to sell the car.

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[mercules]

Yeah, I can't confirm, but it sounds like nonsense, especially when every other boosted car if had they claim +15 to +25 hp from test pipes with tune

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I'll contact them this week to get them to explain it a bit better and catless option.

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[ModItNow]

I noticed an increase in power in the mid-hi rpm range when I got test pipes put on. My cats never had a problem so in your case you'll notice a huge difference.

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[A.C.]

I noticed an increase in power in the mid-hi rpm range when I got test pipes put on. My cats never had a problem so in your case you'll notice a huge difference.

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Do you have a video with your test pipes? Curious on the sound. Thanks


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[ModItNow]

Do you have a video with your test pipes? Curious on the sound. Thanks


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I have a couple videos but the sound isn't very good. I have borla exhaust btw

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[A.C.]

I have a couple videos but the sound isn't very good. I have borla exhaust btw

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Ok thanks. I read your signature just to see how comparable it is from AWE track


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[ModItNow]

Ok thanks. I read your signature just to see how comparable it is from AWE track


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Here are a few short clips

https://youtu.be/beVpWE75R78

https://youtu.be/jogd6m7GpAw



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[cjw]

I'm hoping mine continue to hold up. I really don't want to go catless. Looks like the options are Crown Motorsports, JHM, or pay a bunch more for the newer JHM downpipe and cats that put them further downstream.

I really prefer to pay a lot just once if I have too.

[A.C.]

Here are a few short clips

https://youtu.be/beVpWE75R78

https://youtu.be/jogd6m7GpAw



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Damn that sounds mean!!


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[ModItNow]

Damn that sounds mean!!


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Yeah its pretty aggressive, I can rev at super cars and they hear me lol

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[waxxonMTL]

I'm hoping mine continue to hold up. I really don't want to go catless. Looks like the options are Crown Motorsports, JHM, or pay a bunch more for the newer JHM downpipe and cats that put them further downstream.

I really prefer to pay a lot just once if I have too.

Magnaflow does cat.

I don't like JHM because it does not work with the AWE ( or pretty much any aftermarket resonator).

So, anyone who has aftermarket downpipe, will be down to 3 options : Magnaflow, Tampasport, OEM. Personally, as of today, I would go OEM. Why ? no proven record of the 2 other options. I know others had less chances with OEM, but these cat can last 100-200k km before failing. So, i would assume, even at DP level power, it would still take 30-50k km before it get damaged again. People are quick to judge the oem, but I bet most have driven 50k kms or more with then before going DP/ultracharger and then failing.

If you do track, then I would say the excessive heat would just be too much for any options and would be better with a test pipe. But for daily-use, I think OEM can withstand a couple ten hundred KMs.

[cjw]

I'm running all stock, but I'd be curious as to the cost of each.

[Kiggy74]

My issues with the Evan/Tampa Autosports cat is that they are also wedged up in the same place where the stock cats are located. If they ever fail it will again be a very expensive repair.

At this point I'm most likely to retain/gut the stock cats and do the JHM catted X-pipes.

[luciddream71]

I’ve been tuned for 8,000 miles at this point (just hit 41k on my motor), most of which has been stage 2 and above. I don’t track, this is my daily, I drive aggressively sometimes. Cats holding up for now...


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[Nillamb]

No mention of emissions testing? Assuming your location is correct, no cats = MOT failure. You could try MRC in Banbury to see if they have any ideas?

[mercules]

No mention of emissions testing? Assuming your location is correct, no cats = MOT failure. You could try MRC in Banbury to see if they have any ideas?

Yea you are correct but I am able to get mot passed here though it's not legal.

MRC say stock cats.

I'm going to gut my stock cats and see if the tuner can do something with the cel. I'm not risking the new cats going again for all this hassle.

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[mercules]

Magnaflow does cat.

I don't like JHM because it does not work with the AWE ( or pretty much any aftermarket resonator).

So, anyone who has aftermarket downpipe, will be down to 3 options : Magnaflow, Tampasport, OEM. Personally, as of today, I would go OEM. Why ? no proven record of the 2 other options. I know others had less chances with OEM, but these cat can last 100-200k km before failing. So, i would assume, even at DP level power, it would still take 30-50k km before it get damaged again. People are quick to judge the oem, but I bet most have driven 50k kms or more with then before going DP/ultracharger and then failing.

If you do track, then I would say the excessive heat would just be too much for any options and would be better with a test pipe. But for daily-use, I think OEM can withstand a couple ten hundred KMs.

Regardless of people judging them they should not be failing. Imagine the amount that's also not on forums that the dealers an indys work with. It's poor design by Audi to have them be used at such high temps which is apparently higher than others an turbo cars. Obviously stage 2 will increase the failure as more power is more heat but it is a common failure on this platform from what has been logged so far. What they should of done on the facelift is moved them into a better location to be replaced easier.

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