Secondary Cat Delete Via-Knock the Guts Out?

Gatorac · 09-19-2017, 02:28 PM

Looking under my new 1LE last weekend and thinking about adding a little more noise via a secondary cat delete. I hate the fact that there is no bolt in solution. It appears the cats are close enough to the inlets to be able to knock the guts out and actually leave the cans in place. I've done this on a couple of vehicles before. 1 wa a success, the other, not so much.

Looks to me like I can hang the exhaust down far enough to have everything fall out the front. I'll have the car up on a lift.

Anyone tried this on the Camaro? Any thoughts, ideas, opinions on the chance of success?

TJay74 · 09-19-2017, 05:42 PM

$150 to have a local muffler shop cut them out and weld in new pipes. That is what I did on my 1LE.

ULTRAZLS1 · 09-19-2017, 06:46 PM

you can get pretty decent money for the cats at a local junkyard. Typically 50-100 bucks each depending on prices at the time and type of cat

MAGAUSA · 09-19-2017, 07:42 PM

Theoretically, you could do this. Sounds like your desire to pass any sort of visual inspection rather than have them cut out. Personally I'd pay for the Borla mid pipe rather than hack up the underside, but sounds like you want it to look undisturbed. You can drop the exhaust except for the rear hangers and get a decent angle depending on how high you have the car up. I would be concerned about debris remaining, but could do it carefully and use a shop vac to clean up. Unfortunately, the stock exhaust is one big long honking piece of ugly metal.

SSTony · 09-19-2017, 08:15 PM

Secondary cats are not a requirement unless the state requires it. GM puts in on every car because it is easier.

keon718nyc · 09-19-2017, 09:08 PM

Quote:

Originally Posted by TJay74

$150 to have a local muffler shop cut them out and weld in new pipes. That is what I did on my 1LE.

+1, I paid about $140 to have my 2nd Cats deleted. Just make sure they weld completely around the area to be sealed to prevent any CEL's. Many have had this done before here in the forums and if you do a quick search you will find much more info on it like i did. Here is my before and after pics -

reeper · 09-20-2017, 09:12 AM

What is the diff in sound for secondary cat deletes?

KingLT1 · 09-20-2017, 09:20 AM

Quote:

Originally Posted by reeper

What is the diff in sound for secondary cat deletes?

louder at wot...not much difference at idle. The biggest difference in sound would be to delete the primary cats with bolt-in "test pipes" and leave the secondary. Would still pass "visual" inspection and look factory, but not a option in all states. Also you need to come up with a solution for keeping the CEL off by either tuning (which voids warranty) or "sims". Most just have the secondary cats deleted because it's easier and requires nothing else.

TJay74 · 09-20-2017, 03:34 PM

Actually closer to a 20% gain in sound volume at all levels, from start up, to idle to cruising to WOT. There is prob around a 5hp gain as well.

SK GT · 09-20-2017, 08:30 PM

Is there ANY drone from deleting the secondary cats? I have NPP

Is it still pretty tolerable volume wise in stealth and even sport/track mode?

Had some drone with an aftermarket exhaust on my s550 and do not want any this time around.

Thanks

TJay74 · 09-20-2017, 09:25 PM

I had the secondary cats off of my 2017 1LE with NPP from mile 500. No drone at all, just glorious sound coming from the rear of the car. Heck even with ARH catless full legnth headers I dont have any drone, just insanely loud when you got WOT.

Mercy to anyone if I got WOT while under a bridge, it is deafening...lol

MAGAUSA · 09-21-2017, 08:11 PM

Quote:

Originally Posted by SK GT

Is there ANY drone from deleting the secondary cats? I have NPP

Is it still pretty tolerable volume wise in stealth and even sport/track mode?

Had some drone with an aftermarket exhaust on my s550 and do not want any this time around.

Thanks

No.

Tcamaro · 09-22-2017, 07:29 AM

I hallowed out both primary and secondary cats after supercharger install and before tune. Sounds great for a stock npp! Do it

Gatorac · 10-02-2017, 06:20 AM

I'll give an update on the "knock the guts out" method. I wouldn't attempt this unless 1, you have a lift and 2, you have the time. It really is a pain in the ass. Best tool was a 3/8" paddle bit that was 12" long. Lots of drilling through the catalyst.

I am pleased with the final results.

09-19-2017, 02:28 PM	#1
Gatorac Chin Event Manager Drives: 2018 SS 1LE Join Date: Dec 2011 Location: Bradenton FL Posts: 50	Secondary Cat Delete Via-Knock the Guts Out? Looking under my new 1LE last weekend and thinking about adding a little more noise via a secondary cat delete. I hate the fact that there is no bolt in solution. It appears the cats are close enough to the inlets to be able to knock the guts out and actually leave the cans in place. I've done this on a couple of vehicles before. 1 wa a success, the other, not so much. Looks to me like I can hang the exhaust down far enough to have everything fall out the front. I'll have the car up on a lift. Anyone tried this on the Camaro? Any thoughts, ideas, opinions on the chance of success?

09-19-2017, 08:15 PM	#5
SSTony Drives: SS Camaro Join Date: Jul 2009 Location: Piscataway NJ Posts: 1,782 View My Garage	Secondary cats are not a requirement unless the state requires it. GM puts in on every car because it is easier. __________________

09-20-2017, 09:12 AM	#7
reeper Drives: 2010 HD D/A, 2015 Z06, 2016 2SS Join Date: Aug 2016 Location: Central WI Posts: 503	What is the diff in sound for secondary cat deletes? __________________ 2016 Hyper Blue A8 2SS GM Bodykit: Black MRR 017 wheels: Black OEM Blackout tail-lamps OEM SEMA Grille 35% window tint Black glow-tie BMR Suspension (Pretty much everything) ACS rear-deck spoiler Rotofab CAI Lolly-pop red rotors by Madison Powder Coating

10-02-2017, 06:20 AM	#14
Gatorac Chin Event Manager Drives: 2018 SS 1LE Join Date: Dec 2011 Location: Bradenton FL Posts: 50	I'll give an update on the "knock the guts out" method. I wouldn't attempt this unless 1, you have a lift and 2, you have the time. It really is a pain in the ass. Best tool was a 3/8" paddle bit that was 12" long. Lots of drilling through the catalyst. I am pleased with the final results. __________________ Jim Pomroy Chin Track Days Chief Instructor and Event Manager 2018 1LE 2015 Mustang GTPP 2011 Duramax Access to several Chin track cars...

09-19-2017, 05:42 PM	#2
TJay74 Drives: 17 Camaro SS 1LE & 16 Sierra AT CC Join Date: Nov 2016 Location: Norman, OK Posts: 2,424	$150 to have a local muffler shop cut them out and weld in new pipes. That is what I did on my 1LE.

09-19-2017, 06:46 PM	#3
ULTRAZLS1 Drives: 14 Silverado LTZ Z71, 16 Camaro SS Join Date: Nov 2009 Location: Jackson, Michigan Posts: 4,407	you can get pretty decent money for the cats at a local junkyard. Typically 50-100 bucks each depending on prices at the time and type of cat

09-19-2017, 07:42 PM	#4
MAGAUSA Drives: 2017 Hyper Blue 1LE Join Date: Dec 2016 Location: Tampa Posts: 579	Theoretically, you could do this. Sounds like your desire to pass any sort of visual inspection rather than have them cut out. Personally I'd pay for the Borla mid pipe rather than hack up the underside, but sounds like you want it to look undisturbed. You can drop the exhaust except for the rear hangers and get a decent angle depending on how high you have the car up. I would be concerned about debris remaining, but could do it carefully and use a shop vac to clean up. Unfortunately, the stock exhaust is one big long honking piece of ugly metal.

09-20-2017, 03:34 PM	#9
TJay74 Drives: 17 Camaro SS 1LE & 16 Sierra AT CC Join Date: Nov 2016 Location: Norman, OK Posts: 2,424	Actually closer to a 20% gain in sound volume at all levels, from start up, to idle to cruising to WOT. There is prob around a 5hp gain as well.

09-20-2017, 08:30 PM	#10
SK GT Drives: 18 Colorado ZR2, 17 1LE(sold) Join Date: Aug 2013 Location: Houston Posts: 169	Is there ANY drone from deleting the secondary cats? I have NPP Is it still pretty tolerable volume wise in stealth and even sport/track mode? Had some drone with an aftermarket exhaust on my s550 and do not want any this time around. Thanks

09-20-2017, 09:25 PM	#11
TJay74 Drives: 17 Camaro SS 1LE & 16 Sierra AT CC Join Date: Nov 2016 Location: Norman, OK Posts: 2,424	I had the secondary cats off of my 2017 1LE with NPP from mile 500. No drone at all, just glorious sound coming from the rear of the car. Heck even with ARH catless full legnth headers I dont have any drone, just insanely loud when you got WOT. Mercy to anyone if I got WOT while under a bridge, it is deafening...lol

09-22-2017, 07:29 AM	#13
Tcamaro Drives: 16' 2SS Join Date: Jul 2016 Location: Frankfort Posts: 80	I hallowed out both primary and secondary cats after supercharger install and before tune. Sounds great for a stock npp! Do it

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