Secondary cat delete pros and cons

[DreamTime]

Hello everyone,

Disclaimer - this is a long “question”. Please don’t judge, but also answer wholeheartedly. Thank you.

I just recently picked up a Borla ATAK that I got for a hell of deal - $750 and the thing looked barely used. So, I feel like I can justify some extra funds going to the exhaust portion of my winter project list, and I want to get the opinions of others who know more than I do. Plus, my local opinions have been divided, so I thought I would ask on the forum.

First off - I know Borla is not everyone’s favorite on here, but I love the sound of this exhaust so I was pretty damn stoked to find what I wanted for such a good price. Really my only issue is with the tips, which I am changing out soon anyways. My local exhaust guy said he has a whole catalog of custom tips I can choose from, so that should be fun. But, I am now wondering if there is anything else I should have done while the car is at the exhaust shop.

I only wonder because one of my buddies who was at the shop while we installed the ATAK suggested I remove the secondary cats (while keeping the resonators I assume?). His line of reasoning was that they were not really necessary and that the overall sound would be just a little bit louder if I removed them. I also had a couple other friends suggest removing the secondary cats with this exhaust as well. So, now I have some questions. Below is what I need help with, thank you in advance for any insight. I’m sorry if some of these questions are stupid. I am learning about all of this as I go and I am having a hard time finding solid advice/info online for my specific questions and situation, so I was hoping someone with some direct knowledge might chime it.

Just for the record, I would be happy if it was just a tad louder… which is why I am considering this.

1. Will removing the secondary cats change the tone of the exhaust sound that is produced by my ATAK? Or, will it simply just be louder? Or, is there even any way to tell without just doing it? I am really happy with the tone right now, so I am nervous to start messing around with the remaining stock parts of my exhaust without having a good idea of what I am getting myself into.

2. Will my engine performance be affected at all by removing the secondary cats? If so, how? Air/fuel mixture? Would it cause a CEL? I don’t want to do anything that upsets the balance of my engine simply for more noise, even though I like (relatively) loud.

3. The state of SC does not require emissions testing so I am not worried about whether or not I would be able to pass emissions tests… now. But, who knows what the future holds with these types of things. If I remove the secondary cats, would there be issues with passing emissions tests? (I am pretty sure the answer to this is yes)

Thank you for any and all opinions/advice

[redline9001]

Have you removed the primary cats? If not that’s the ones I would remove first...

Cat removal will change the tone, volume and smell.

If you going to go catless just buy an aftermarket x pipe.

[EJT86]

I think you might want to consider test pipes which will turn your setup into a high flow cat setup. You’ll gain the volume you want and still leave the resonators in place

Hi btw lol

[StripclubDJ]

I've always had test pipes , stock xpipe, Megan rear

Once I removed the secondary cats... I can't even drive with my windows down, or if I i back into the garage and get out my cloths smell so bad when I go in the house lol


So just take the smell into account , cuz it's pretty dang bad lol

[DreamTime]

Originally Posted by redline9001

Have you removed the primary cats? If not that’s the ones I would remove first...

Cat removal will change the tone, volume and smell.

If you going to go catless just buy an aftermarket x pipe.

I have not removed the primary cats, everything is stock upwards of my ATAK axle back. I guess you're right, instead of cutting apart the remaining stock section of my exhaust I should just go with an aftermarket piece if I want to go catless.

Originally Posted by EJT86

I think you might want to consider test pipes which will turn your setup into a high flow cat setup. You’ll gain the volume you want and still leave the resonators in place

Hi btw lol

Hey How are you? Missed you at the tail. I will start perusing test pipe options in my spare time. Thanks!

Originally Posted by StripclubDJ

I've always had test pipes , stock xpipe, Megan rear

Once I removed the secondary cats... I can't even drive with my windows down, or if I i back into the garage and get out my cloths smell so bad when I go in the house lol


So just take the smell into account , cuz it's pretty dang bad lol

Lol, that whole long ass post I made and I didn't even consider this smell that you guys are talking about. Sounds awful. Is that specific to secondary cat removal? I am glad I got more info before making my decision.


Thanks guys, it looks like the short answer is - don't remove secondary cats. I'm just going to switch out my tips for now and focus on the rest of my huge winter project list. I am happy with the sound of my exhaust right now, so later on I will check out some other fun options.

[BPMSport]

Removing the secondary cats will not provide much of a performance difference, but will significantly increase the raspyness from our experience.

[redline9001]

Originally Posted by DreamTime

I have not removed the primary cats, everything is stock upwards of my ATAK axle back. I guess you're right, instead of cutting apart the remaining stock section of my exhaust I should just go with an aftermarket piece if I want to go catless.

Lol, that whole long ass post I made and I didn't even consider this smell that you guys are talking about. Sounds awful. Is that specific to secondary cat removal? I am glad I got more info before making my decision.

Thanks guys, it looks like the short answer is - don't remove secondary cats. I'm just going to switch out my tips for now and focus on the rest of my huge winter project list. I am happy with the sound of my exhaust right now, so later on I will check out some other fun options.

With my akra x-pipe, no primary cats and hi flow secondary cats I get a little smell on cold start and one they are warmed up no smell. If you live in place with emissions testing go with aftermarket xpipe cause them you can swap the stock one back in for testing.

The power comes from removal of the primary cats and not the seconardary ones which is the big reason why people remove the cats in the first place. If you are not on a quest for more power then your fine with the stock xpipe

[eatsleepboost]

1) As bpmsport said above.
2)No cel. Your car has no way to know if the secondary cats are there. The car only monitors the primary cats.
3) No issue passing emmissions due to secondary cat removal as stated above. No cel.

My personal experience with borla atak is that I loved the sound with stock xpipe. Once I went to an aftermarket xpipe that even is quad resonated the borla atak became too loud. I suspect simply removing secondary OR primary cats only will be a perfect setup for that rear section. I wanted to keep the catless xpipe since I am SC'D so I changed rear section.

[Powashiftin]

Just got a full aftermarket x pipe. They can be had well under $1000. Test pipes plus install will run you half that.

I went fully catless with the BW x pipe with dual resonators and absolutely love it. (Corsa mufflers).

[Adrian g.]

Originally Posted by BPMSport

Removing the secondary cats will not provide much of a performance difference, but will significantly increase the raspyness from our experience.

Which x-pipe configuration will result in less rasp?

1) HFC in the secondary position and dual resonated like Evolve or
2) Quad resonated and fully catless like Dinan or Borla

[brodiem]

I have the ATAK on my car, and initially it was just the rear section. Like you, I hoped it would have had a bit more volume. I’m also not a fan of the tips, though seeing how they’re angled it doesn’t look all that trivial to replace them, but maybe it isn’t a big deal for an exhaust shop.

I later added AA test pipes and kept the stock X, and I was pretty shocked at how much the sound changed. Volume increase was substantial enough that I had to get back under the car to see if I had messed up something like leaking exhaust before the mufflers. The tone itself I would say became more raw sounding rather than the hint of exotic refined sound prior, but I don’t think I could go back, it just sounds so mean now. The volume is perfect now as a non-DD, and it’s true that the test pipes reduce drone.

[DreamTime]

Thanks everyone, there is some good stuff in here.

Originally Posted by BPMSport

Removing the secondary cats will not provide much of a performance difference, but will significantly increase the raspyness from our experience.

This helps my decision a lot. As I mentioned, I don't want to alter the sound my exhaust currently makes. I certainly don't want it to be more raspy, not that there is anything wrong with that.

Originally Posted by redline9001

With my akra x-pipe, no primary cats and hi flow secondary cats I get a little smell on cold start and one they are warmed up no smell. If you live in place with emissions testing go with aftermarket xpipe cause them you can swap the stock one back in for testing.

The power comes from removal of the primary cats and not the seconardary ones which is the big reason why people remove the cats in the first place. If you are not on a quest for more power then your fine with the stock xpipe

This is great. I am not on a quest for more power, this car will actually be mostly retired from the track by the end of next year. I just want it to sound good I think sticking with my current setup will suffice for now.

Originally Posted by eatsleepboost

1) As bpmsport said above.
2)No cel. Your car has no way to know if the secondary cats are there. The car only monitors the primary cats.
3) No issue passing emmissions due to secondary cat removal as stated above. No cel.

My personal experience with borla atak is that I loved the sound with stock xpipe. Once I went to an aftermarket xpipe that even is quad resonated the borla atak became too loud. I suspect simply removing secondary OR primary cats only will be a perfect setup for that rear section. I wanted to keep the catless xpipe since I am SC'D so I changed rear section.

I appreciate you answering my numbered questions! I had found conflicting info about secondary cats, sensors, and air/fuel mixtures so that was something I wanted to get a definite answer about.

Also, thanks for the feedback on personal experience with the ATAK and different x pipe configurations. Your comment on removing one of the sets of cats is interesting to me. Do you feel that is true because the sound level would be about right if only primary or secondary cats were removed? I am hesitant to remove my primary cats because (although I do modify the car a good bit) I truthfully want to keep the engine performance output at stock levels for longevity's sake. Not sure if this is warranted, but it makes me feel better. Car now has 120k miles on it, will be retired from the track soon, and starting next winter I will start replacing all engine, transmission/clutch, and suspension wear items that have not already been replaced. I want to keep the car running and happy for many many miles

Originally Posted by M3Post

Remove the primary cats for increased power.

Use high flow secondaries <=200 cells per square inch.

If you keep secondaries then the smell isn't that bad.

Volume of exhaust sound will increase when primaries removed.

No cell tripped if keep primary and secondary O2 sensors.

Use a resonated X pipe to minimize any drone.

Thanks! This seems like a very complete list of a good option. I'm not looking to increase power, but I do enjoy learning about what all possible options are.

Originally Posted by Powashiftin

Just got a full aftermarket x pipe. They can be had well under $1000. Test pipes plus install will run you half that.

I went fully catless with the BW x pipe with dual resonators and absolutely love it. (Corsa mufflers).

I had a feeling something like this might be a valid solution from the get go lol. I feel like if I would choose to remove cats, that I should just go with something aftermarket instead of cutting apart my stock exhaust.

[EJT86]

Originally Posted by DreamTime

Hello everyone,

Disclaimer - this is a long “question”. Please don’t judge, but also answer wholeheartedly. Thank you.

I just recently picked up a Borla ATAK that I got for a hell of deal - $750 and the thing looked barely used. So, I feel like I can justify some extra funds going to the exhaust portion of my winter project list, and I want to get the opinions of others who know more than I do. Plus, my local opinions have been divided, so I thought I would ask on the forum.

First off - I know Borla is not everyone’s favorite on here, but I love the sound of this exhaust so I was pretty damn stoked to find what I wanted for such a good price. Really my only issue is with the tips, which I am changing out soon anyways. My local exhaust guy said he has a whole catalog of custom tips I can choose from, so that should be fun. But, I am now wondering if there is anything else I should have done while the car is at the exhaust shop.

I only wonder because one of my buddies who was at the shop while we installed the ATAK suggested I remove the secondary cats (while keeping the resonators I assume?). His line of reasoning was that they were not really necessary and that the overall sound would be just a little bit louder if I removed them. I also had a couple other friends suggest removing the secondary cats with this exhaust as well. So, now I have some questions. Below is what I need help with, thank you in advance for any insight. I’m sorry if some of these questions are stupid. I am learning about all of this as I go and I am having a hard time finding solid advice/info online for my specific questions and situation, so I was hoping someone with some direct knowledge might chime it.

Just for the record, I would be happy if it was just a tad louder… which is why I am considering this.

1. Will removing the secondary cats change the tone of the exhaust sound that is produced by my ATAK? Or, will it simply just be louder? Or, is there even any way to tell without just doing it? I am really happy with the tone right now, so I am nervous to start messing around with the remaining stock parts of my exhaust without having a good idea of what I am getting myself into.

2. Will my engine performance be affected at all by removing the secondary cats? If so, how? Air/fuel mixture? Would it cause a CEL? I don’t want to do anything that upsets the balance of my engine simply for more noise, even though I like (relatively) loud.

3. The state of SC does not require emissions testing so I am not worried about whether or not I would be able to pass emissions tests… now. But, who knows what the future holds with these types of things. If I remove the secondary cats, would there be issues with passing emissions tests? (I am pretty sure the answer to this is yes)

Thank you for any and all opinions/advice

Hey, a friend of mine is selling turner test pipes welded to a stock X pipe. He wants closer to full catless volume. Feel free to text me if your interested

[DreamTime]

Originally Posted by brodiem

I have the ATAK on my car, and initially it was just the rear section. Like you, I hoped it would have had a bit more volume. I’m also not a fan of the tips, though seeing how they’re angled it doesn’t look all that trivial to replace them, but maybe it isn’t a big deal for an exhaust shop.

I later added AA test pipes and kept the stock X, and I was pretty shocked at how much the sound changed. Volume increase was substantial enough that I had to get back under the car to see if I had messed up something like leaking exhaust before the mufflers. The tone itself I would say became more raw sounding rather than the hint of exotic refined sound prior, but I don’t think I could go back, it just sounds so mean now. The volume is perfect now as a non-DD, and it’s true that the test pipes reduce drone.

When we were installing the exhaust I did look at how the tips were attached which is why I decided to just go get something custom done. Again, I justified that extra little cost by finding a good deal on the ATAK

Oh.. this is very interesting feedback about your current setup though. It sounds exactly like the sound I want produced, although it's hard to tell without hearing it. I have an exhaust newbie question - please don't judge lol... which part of the exhaust is removed/replaced by the test pipes? Are either of the cats removed?

[DreamTime]

Originally Posted by EJT86

Hey, a friend of mine is selling turner test pipes welded to a stock X pipe. He wants closer to full catless volume. Feel free to text me if your interested

I'm gonna text you tomorrow... I do have questions. But, I must pull myself out of car mod land for now and go finish my Christmas shopping before it gets any later lmao

[EJT86]

Originally Posted by DreamTime

I'm gonna text you tomorrow... I do have questions. But, I must pull myself out of car mod land for now and go finish my Christmas shopping before it gets any later lmao

[brodiem]

Originally Posted by DreamTime

When we were installing the exhaust I did look at how the tips were attached which is why I decided to just go get something custom done. Again, I justified that extra little cost by finding a good deal on the ATAK

Oh.. this is very interesting feedback about your current setup though. It sounds exactly like the sound I want produced, although it's hard to tell without hearing it. I have an exhaust newbie question - please don't judge lol... which part of the exhaust is removed/replaced by the test pipes? Are either of the cats removed?

No worries, the test pipes replace (delete) the primary cats, so assuming the stock X pipe is used, you’re left with a pair of secondary cats and resonators before reaching the atak rear section. Take a look at the AA installation instructions to get a better visual of what this looks like, and this applies to all test pipes, not just AA

http://images.activeautowerke.com/Installation%20PDF's/AA%20E9x%20M3%20%20TSP%20-%20Test%20Pipe%20Exhaust%20instructions.pdf

[BRNDNSLVRA]

I have a OEM 4 pipe mod and removed my secondaries two days ago. Here's a clip.

No smell and theres minimal rasp due to the muffler mod. Also no light. That only happens when you remove primaries.

[DreamTime]

Originally Posted by brodiem

No worries, the test pipes replace (delete) the primary cats, so assuming the stock X pipe is used, you’re left with a pair of secondary cats and resonators before reaching the atak rear section. Take a look at the AA installation instructions to get a better visual of what this looks like, and this applies to all test pipes, not just AA

http://images.activeautowerke.com/In...structions.pdf

Omg. Thank you, seriously. That link was perfect, now I know

I have recently become very interested in my exhaust system as a whole and all of the options that are out there to modify it. It is so interesting to me. It is such a basic part of the car, but there are a lot of mod options that I know little to nothing about, and I have limited spare time right now for hours of researching. Your answer is very much appreciated!! If only I could double appreciate a post lol

[DreamTime]

Originally Posted by 954MM

I have a OEM 4 pipe mod and removed my secondaries two days ago. Here's a clip.

No smell and theres minimal rasp due to the muffler mod. Also no light. That only happens when you remove primaries.

That sounds nice man. Thanks for the video! I could listen to exhaust clips all night, although sleep is good too

One of the first things I did to my car when I got it was the OEM exhaust mod, but I have been longing for something louder... hence the atak. I hadn't considered secondary cat delete with my OEM exhaust mod. Your combo is a winner, sounds amazing!

[bigjae1976]

This is a good video. The first half is an modified OEM exhaust and a straight thru X-pipe. Its really loud just in the video. Not even mentioning when they put the straight pipes in place of the modded OEM exhaust.

I'd delete the primary cats and modify the OEM rear exhaust to get more exhaust noise. Especially if you have a DCT because its hard to hear the motor going over 100mph with the windows down and helmet on.


The S65 induction noise sounds too good to drown it out with exhaust noise. Unlike the S54 which sounds like garbage. So I just go for lots of hot, loud garbage so you can't even tell it sounds bad.

[DreamTime]

Originally Posted by bigjae1976

This is a good video. The first half is an modified OEM exhaust and a straight thru X-pipe. Its really loud just in the video. Not even mentioning when they put the straight pipes in place of the modded OEM exhaust.

I'd delete the primary cats and modify the OEM rear exhaust to get more exhaust noise. Especially if you have a DCT because its hard to hear the motor going over 100mph with the windows down and helmet on.


The S65 induction noise sounds too good to drown it out with exhaust noise. Unlike the S54 which sounds like garbage. So I just go for lots of hot, loud garbage so you can't even tell it sounds bad.

Omg, I did not see a notification for this post! Sorry man!

I have a friend who had a straight piped E92 M3 and it was ridiculously loud. Definitely more than what I am looking for right now lol. To be completely honest, I am really happy with the current setup. I think you are absolutely right - the beautiful music of the S65 is too perfect to drown out simply with loud ass exhaust noise. I had the OEM exhaust mod and it was not quite loud enough, but the ATAK muffler gives me the best of both worlds. I have my lovely exhaust note but I can still hear the sound of my engine while driving. I guess my main question was whether or not it was wise to delete secondary cats for a slightly louder exhaust with the ATAK. Based off of the answers I have determined removing the secondary cats is not something I am going to do.

Great advice in here though, I appreciate the feedback!

Hope you had a great Christmas!! I can already hardly wait for next track season