[Redlinez]

IF only my exhaust shop would remove my new car's 2nd cat.....best $50 mod I ever did.

[versionx]

Can you pass inspection if you delete the 2nd cats?

[Idyll]

Originally Posted by versionx

Can you pass inspection if you delete the 2nd cats?

Speaking for TX, yes. The secondary cats are mainly a CA thing to help burn off emissions before the primary cats are heated up. Since they're behind the last O2 sensor, they are not read by the computer. The key is to make sure there's no leaks in the weld or under decel cold air can be sucked in and trip the nearby O2 sensor.

Thanks for the replies guys, sounds like a no-brainer.

[ctrlz]

Originally Posted by versionx

Can you pass inspection if you delete the 2nd cats?

Depends on the inspector.
technically, under the Clean Air Act, it is against federal law to delete any emissions equipment.

[Boost Creep]

Are the secondary cats ceramic or metallic?


In case mine get clogged and I have clean them out, the ceramic would be easier to knock the stuffing out.

[Idyll]

Originally Posted by Boost Creep

Are the secondary cats ceramic or metallic?


In case mine get clogged and I have clean them out, the ceramic would be easier to knock the stuffing out.

No idea? But I should know in a couple hours!

[Boost Creep]

Originally Posted by Idyll

No idea? But I should know in a couple hours!

Thanks.

[Idyll]

Originally Posted by Boost Creep

Thanks.

They're metallic. Just posted lots of pics in separate thread.

[Boost Creep]

Originally Posted by Idyll

They're metallic. Just posted lots of pics in separate thread.

Thanks.
I was hoping I could gut them rather than cut them out. Don't know how well gutting metallic cats would go.

[Techn9cian805]

I recently installed the MRT 3" piping that comes with a direct bolt on secondary cat deleting pipe, which made a small difference, definly not something you'll regret doing as the difference isnt that drastic.

I also have CA Performance test pipes that once in a while i'll bolt on and off, those DEFINITELY make a big difference, and i could see you regretting cutting these off... unless you can find some bolt on test pipes for cheap, that way you can just jack your car up whenever you wanna change it up from loud to obnoxious and back with no regrets or permanent cuts.

[s346k]

i'm not sure if it's impressive, or just sad, that there is so much discussion over a "mod" that does nothing for performance and increases the exhaust noise by 2.5 db.

buford t justice does not approve.

[Idyll]

Originally Posted by s346k

i'm not sure if it's impressive, or just sad, that there is so much discussion over a "mod" that does nothing for performance and increases the exhaust noise by 2.5 db.

buford t justice does not approve.

2.5 db is the difference between a lawn mower at 3' and a power saw at 3'. It's noticeable, but not drastic, which is exactly what I was going for.

[cmitchell17]

Originally Posted by Idyll

I get what you're saying, but I've spent too much time and money in the past experimenting with various mufflers, headers, high flow cats, etc. I plan to either leave this stock, or delete the secondary cats. Just curious if anyone wasn't happy with the change (other than those that had weld leaks).

Since you said that, I would advise you to leave it. I "gutted" my primary cats, because I dropped a socket into the header when putting on my cam and heads. It eventually ended up cracking the drivers side primary. I removed the socket and put it back together and then took it off a few months later and was surprised the whole inside of the cat was gone, so it had blown out the tailpipe and I guess didn't clog anything up.

Anyway, I ended up ordering primary cat delete pipes. The sound with the delete pipes was extremely obnoxious, and unrefined. It sounded like a kids truck who just straight piped it. I figured if I put the stock pipes back on but "gutted" them it would be better since I didn't notice any difference when it blew out the drivers side cat with the stock pipe. So that's what I did, it is certainly a lot better with the stock gutted pipes back on (maybe because of the thicker material or double wall I'm not sure?).

But by gutting the primary cats it has made the bad, unrefined sounds of the NPP come out. It did make it louder, to where no when you go WOT it wakes everyone within a 5 mile radius up. It is also very raspy and really sounds like crap honestly. I had a lot of disappointments with the sound of the NPP stock but generally it was pretty good. At part throttle the sound of the NPP is very very good, but too me it is too loud at WOT and there is too much rasp. Removing the cats will make all these bad noises worse, I would not do it if I had the chance to go back. I will not say it increases airflow until I can get my own flow bench and flow it myself.

That being said it wouldnt' be too hard to hook pressure gauges up to the exhaust and see if it did anything but too much money for that.

[Idyll]

Originally Posted by cmitchell17

Since you said that, I would advise you to leave it. I "gutted" my primary cats, because I dropped a socket into the header when putting on my cam and heads. It eventually ended up cracking the drivers side primary. I removed the socket and put it back together and then took it off a few months later and was surprised the whole inside of the cat was gone, so it had blown out the tailpipe and I guess didn't clog anything up.

Anyway, I ended up ordering primary cat delete pipes. The sound with the delete pipes was extremely obnoxious, and unrefined. It sounded like a kids truck who just straight piped it. I figured if I put the stock pipes back on but "gutted" them it would be better since I didn't notice any difference when it blew out the drivers side cat with the stock pipe. So that's what I did, it is certainly a lot better with the stock gutted pipes back on (maybe because of the thicker material or double wall I'm not sure?).

But by gutting the primary cats it has made the bad, unrefined sounds of the NPP come out. It did make it louder, to where no when you go WOT it wakes everyone within a 5 mile radius up. It is also very raspy and really sounds like crap honestly. I had a lot of disappointments with the sound of the NPP stock but generally it was pretty good. At part throttle the sound of the NPP is very very good, but too me it is too loud at WOT and there is too much rasp. Removing the cats will make all these bad noises worse, I would not do it if I had the chance to go back. I will not say it increases airflow until I can get my own flow bench and flow it myself.

That being said it wouldnt' be too hard to hook pressure gauges up to the exhaust and see if it did anything but too much money for that.

Removing primary cats was never a consideration - been there done that...more than once. You're right, it makes it obnoxious and raspy; the GT500 was embarrassing to drive until I got it all worked out.

I had the secondary cats removed this morning and so far so good; pics posted in separate thread.