Gutted Catalytic Converter VS Test Pipes?

[fowl]

As the title of my thread says Gutted Cats vs Test pipes. Here is a bit of back ground. I purchased the car in Sep 2020. It came with a bad PCV and water pump. Both were changed along with the thermostat by the Audi dealers. I have the JHM 207mm pulley, IE TCU and ECU tunes, Merc Racing HX and IE intake. Plugs are NGK BRKR9EIX gapped at .26.

Car ran great for a few months and then last week puff of white dust came through left tail pipe, change of exhaust note and loss of power. Chunks of Cat material started coming through the exhaust and right side cat seem to be going as well. I immediately knew what the issue was from reading threads here, but was concerned about loss of power. I suspect its down 30hp or more. Took it to mechanic and he said change both cats and confirmed that nothing is wrong with engine.

Now back to my thread title, I definitely do not want to put back the cats as I think they will fail again. So I am asking what's the pros and cons of Gutted Catalytic Converter vs Test Pipes and which one is preferable? Which one would you choose and why?. The answers would really help me to make up my mind. Oh, just a FYI, I have order the magnaflow 11385 as I was going to do the exhaust mod before the cats failed.

[RoofRails]

As the title of my thread says Gutted Cats vs Test pipes. Here is a bit of back ground. I purchased the car in Sep 2020. It came with a bad PCV and water pump. Both were changed along with the thermostat by the Audi dealers. I have the JHM 207mm pulley, IE TCU and ECU tunes, Merc Racing HX and IE intake. Plugs are NGK BRKR9EIX gapped at .26.

Car ran great for a few months and then last week puff of white dust came through left tail pipe, change of exhaust note and loss of power. Chunks of Cat material started coming through the exhaust and right side cat seem to be going as well. I immediately knew what the issue was from reading threads here, but was concerned about loss of power. I suspect its down 30hp or more. Took it to mechanic and he said change both cats and confirmed that nothing is wrong with engine.

Now back to my thread title, I definitely do not want to put back the cats as I think they will fail again. So I am asking what's the pros and cons of Gutted Catalytic Converter or Test Pipes and which one is preferable? Which one would you choose and why?. The answers would really help me to make up my mind. Oh, just a FYI, I have order the magnaflow 11385 as I was going to do the exhaust mod before the cats failed.

Most people will say that gutted cats sound better than test pipes. I think there is more then enough evidence of people's experiences to believe that is in fact the case. The gutted cats should have both the flanges welded to strengthen them and keep in mind that a gutted cat will be harder to re-install then a test pipe.

With Test pipes you can sell your cats or hang on to them for going back to stock. This isn't a option for you at this point. I have seen some people claim that a test pipe flows better then a gutted cat but I haven't seen any real evidence of that either way.



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[BrokeBichB8]

I am at a similar crossroads. The cost of test pipes are flippin expensive for being some pipe welded to a flange but, se la vie. If you can finagle the cats out without damage you get ~$300 back. Id say test pipes if you can afford the cost of buying, install, and getting exhaust to sound better. Gutted cats are cheap and risky but def more evidence of cleaning up the sound. With your mods, IMO, go test pipes.

[fowl]

Come on guys please help me out here, any further comments.

[RoofRails]

Come on guys please help me out here, any further comments.

This subject has been well discussed on this forum. I went through a ton of posts on here deciding what I would do when the time came and there was more then enough information to come to the conclusion that gutted cats sound better then test pipe. Because there isn't a Turbo wheel in our exhaust taking some of the bite out of the V6 exhaust note things can get ugly and loud in a hurry once the cats come out.

Because of the sound and smell I decided to order a set of RedStar HFC but if I were in your shoes having already blown one of my cats out, I would have went the gutted/reinforced cat route.

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[MSq5]

Come on guys please help me out here, any further comments.

Search is your friend. All of us have read the threads. You should, too. RoofRails summarized it well. If you want more details read and draw your own conclusion. There is no agreed-upon consensus on the total solution despite the issue being with us for years. There does seem to be agreement that gutted cats are less offensive than test pipes from a drone/rasp perspective, but are still unpleasant and loud.

FWIW: I'm stage 2 dual pulley and still on stock cats. I'm sure they will fail. When they do, I plan to remove, gut, reinforce and reinstall, maybe put in downstream high flow bottle cats for smell and maybe some drone/rasp mitigation. We have no emission testing here. I expect some unpleasant drone and rasp. I am still studying the best approach there.

Reasonable minds differ as we continue to explore various x-pipe, resonator and muffler combinations. Part of that problem is that ears being human and sounds being subjective, there will always be honest debate and disagreement on what "sounds good".

[JACKAL]

I agree with all the comments above. The sound is going to be somewhat subjective. I have test pipes and I've had quite a few different exhaust configurations since I bought the car. I like how my current setup sounds (see signature for the details) but it took awhile to get here:
https://www.youtube.com/watch?v=18d1...ature=youtu.be

The other variable you might or might not struggle with is your downstream O2 sensors. Do you plan to try spacers or will you be getting a specific tune?

[Morritse]

Most people will say that gutted cats sound better than test pipes. I think there is more then enough evidence of people's experiences to believe that is in fact the case. The gutted cats should have both the flanges welded to strengthen them and keep in mind that a gutted cat will be harder to re-install then a test pipe.

With Test pipes you can sell your cats or hang on to them for going back to stock. This isn't a option for you at this point. I have seen some people claim that a test pipe flows better then a gutted cat but I haven't seen any real evidence of that either way.



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This guy said everything that should be said ^

[fowl]

I was thinking of using spacers as I don’t think IE turns off the O2 sensors in their tunes.

[prabkaler]

I’d go with test pipes. Sound aside, getting the cats in and out is a huge pain in the a**. And not to mention test pipes are cheaper than how much you can sell your cats for. Bought my redstar test pipes for around 700 and sold my factory cats for 450 CAD a piece, and the passenger side was melting.


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[fowl]

Thanks to all for your comments.

[Hamsteak]

I know I'm a bit late to this thread but I got my Cats Gutted earlier this month with a healthy 1200$ expense, I wouldn't think the price would've been too much cheaper on the install if I had test pipes. But the cost overall would've put me at or almost at 2000$ total. Which, if you don't have that much to spend, simply gutting the cats would be the best alternative option IMO.

In terms of sounds the car is a decent bit louder and sounds good without being too obnoxious or raspy, just think about it like Stock Plus almost. However, while drone itself did not get louder, I do get a funky note coming from the cats on low-mid throttle at low-mid rpm. It's your preference whether you mind such a sound or not but that's all up to you. Personally I can live with it.

While the cats are a pain to get to, test pipes only really make the re-installation process easier. I haven't heard many people use this method but an easier way to get access to the cats ESPECIALLY the top bolts is to take off/un bolt the drive shaft and while you have to subframe loosened, use a ratchet strap to pull the transmission from one side to another to get some extra room.

IMPORTANT NOTE : Once the gutting was done I had no issues regarding the O2 sensors, I tuned to car with IE for Fuel-Cut launch prior to getting the work done.

[fowl]

I know I'm a bit late to this thread but I got my Cats Gutted earlier this month with a healthy 1200$ expense, I wouldn't think the price would've been too much cheaper on the install if I had test pipes. But the cost overall would've put me at or almost at 2000$ total. Which, if you don't have that much to spend, simply gutting the cats would be the best alternative option IMO.

In terms of sounds the car is a decent bit louder and sounds good without being too obnoxious or raspy, just think about it like Stock Plus almost. However, while drone itself did not get louder, I do get a funky note coming from the cats on low-mid throttle at low-mid rpm. It's your preference whether you mind such a sound or not but that's all up to you. Personally I can live with it.

While the cats are a pain to get to, test pipes only really make the re-installation process easier. I haven't heard many people use this method but an easier way to get access to the cats ESPECIALLY the top bolts is to take off/un bolt the drive shaft and while you have to subframe loosened, use a ratchet strap to pull the transmission from one side to another to get some extra room.

IMPORTANT NOTE : Once the gutting was done I had no issues regarding the O2 sensors, I tuned to car with IE for Fuel-Cut launch prior to getting the work done.

Thank you very much for this detailed explanation. It helped a lot.

[fowl]

What do you guys think about these? Let me know your thoughts.

https://www.ebay.com/itm/193933119655?ul_noapp=true

[prabkaler]

Never heard of them to be honest, but looks like they’re decent. Just make sure they’re 304L stainless steel and at least 2-2.5mm thick and you should be good!


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[MSq5]

What do you guys think about these? Let me know your thoughts.

https://www.ebay.com/itm/193933119655?ul_noapp=true

Never heard if them. I see Red Star Exhaust test pipes on the same eBay page for the same price. They are respected here.

[fowl]

Never heard if them. I see Red Star Exhaust test pipes on the same eBay page for the same price. They are respected here.

I saw the RSE ones as well but they will take 4-6 weeks to get to me and my car is down waiting on this test pipe. However these TP can get to me in 4-5 days. I found the Becker TP on eBay and its about $150 cheaper but there are several complaints about their quality on here so I am hesitant buy them.

[fowl]

[QUOTE=prabkaler;14479651]Never heard of them to be honest, but looks like they’re decent. Just make sure they’re 304L stainless steel and at least 2-2.5mm thick and you should be good!

The test pipes are Stainless steel 1.6mm thick mark 316, flanches out of 304 stainless steel.

[fowl]

Never heard of them to be honest, but looks like they’re decent. Just make sure they’re 304L stainless steel and at least 2-2.5mm thick and you should be good!


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May I ask why you said it should be 2-2.5mm thick when the Red Star is only 1.6mm?

this is a quote from their add on eBay. "Highest quality 1.6mm wall 304 stainless steel".

[ModItNow]

Fyi
https://www.audizine.com/forum/showthread.php?t=926300

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[mys4.org]

If you saw my thread at all I've recently went through all of this. My passenger side cat snapped at the flange connecting to the header. A friend wanted to weld it up, but all shops that I talked to said it was just going to break again. I finally went to a fabricator that offered really low price for custom made test pipes and catted down pipes installed for $1100. He explained to me as the pipe for the stock cats heat cycle the pipe absorb more carbon. which in turn make them brittle. He could weld them up but did not recommend so I went with him creating test pipes and catted down pipes. I know that cats are just going to be a problem with this platform, that said, now that they are in my down pipes I can easily replace them within a hour if they fail again. As for sound, yes they make your system loud and raspy (less raspy when the exhaust is warm). The sound evolved to be a little better over time but it still was too loud for my liking... I like sporty but not a "look at me" make babies cry volume.... so I installed Vibrant Ultra quiets where the stock mid muffler used to be just last week. Sound is much better, maybe a little too quiet, but zero drone on the highway and almost no rasp. I guess I'm getting old, but I'm happy and my car is really finally ready to go from single pulley to dual pulley later this summer.

https://www.audizine.com/forum/showt...ipe-Setup-B8-5