Delete secondary cats? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

flynhawaiianss · 08-11-2017, 01:58 AM

Ok, so I know I'm probably beating a dead horse on this issue with some parts and I have used the search function previously so please don't shoot me

I have been looking at doing exhaust here soon on my 2011 L99 and yes I know I should start from the front of the car and work my way back (LT headers are in the future plan) but in the meantime I have purchased a Stainless works muffler delete kit from a member here on the forum and the next purchase is an x-pipe from summit racing to remove the resonator. I was wanting to take it all in and have all the work done in one go. I was thinking about deleting the secondary cats as well. Yesterday, I talked to one of the mechanics my family and I have been using for years and we trust. I was getting an estimate for what I was wanting done and he said he wouldn't remove the secondary cats for reasons of being fined. On top of that, he said that there would be too much back pressure lost and tried to explain everything to me on how that works and cases of cars that have came back and needed work due to that happening. Now, I don't think he is just making this up but from my research (and I hate debating this topic) I didn't think there would be a loss of back pressure at all if the secondary cats were removed? Please correct me if I'm wrong but I thought the first set of cats did most of the work and removing the secondary cats would not throw a code unless the welds were shotty and there was a leak?

I'm just kind of up in arms if I should go to a different shop to see if I should have the secondary cats deleted or I should just not have it done. Anyone that knows or has had this done please feel free to chime in.

Ashen L99 · 08-11-2017, 05:29 AM

I've had it done and what I would tell him is that his statement of losing too much back pressure is a crock of shit, so is the getting fined part. Didn't engine masters on YouTube do a video about backpressure and they said that the engine actually made more hp with less? Correct me if I'm wrong but as long as the main ones stay, you'll be fine. There unmonitored so who cares if there there or not? You'll gain a little bit of noise but the hp gains would probably be negligible. Cut them off.

flynhawaiianss · 08-11-2017, 05:57 AM

I never saw that video but now that you mention it I will have to go look it up. From what I have read, people that have done it didn't notice any loss in back pressure and did seem to think they may have gained a few ponies. I will gladly take a few extra ponies if possible and a little added volume to the exhaust as well.

14Black1LESS · 08-11-2017, 06:43 AM

You don't lose back pressure by removing the cats. I don't have any cats on mine and Im not losing back pressure. As far as getting fined, that would probably be determined by where you live. We don't have emissions checks in Florida so I have nothing to worry about. If you do all of the exhaust work and put on LT headers then you need to get a tune also to get the full potential out of it. Even if you don't put the headers on yet but delete the cats you would still need a tune, otherwise you will get a CEL.

Ashen L99 · 08-11-2017, 06:55 AM

Quote:

Originally Posted by 14Black1LESS

You don't lose back pressure by removing the cats. I don't have any cats on mine and Im not losing back pressure. As far as getting fined, that would probably be determined by where you live. We don't have emissions checks in Florida so I have nothing to worry about. If you do all of the exhaust work and put on LT headers then you need to get a tune also to get the full potential out of it. Even if you don't put the headers on yet but delete the cats you would still need a tune, otherwise you will get a CEL.

Not for the secondaries

14Black1LESS · 08-11-2017, 07:06 AM

Quote:

Originally Posted by Ashen L99

Not for the secondaries

Correct but I'm talking about deleting both sets.

flynhawaiianss · 08-11-2017, 07:30 AM

Yeah I live in IL but not in Chicago and have never had to worry about getting my emissions checked. If that was the case my '96 Z28 would of neverrrrrr passed

So from the posts so far the consensus seems to be to remove the cats and there won't be a loss of back pressure. I have one other shop in mind and I haven't checked with them yet but I'm hoping if I stop by and talk to them they would do it.

InFiD3ViL · 08-11-2017, 08:56 AM

A lot of exhaust shops will not touch the cats due to the possible fines.

But I am sure you can find someone to do it if you can't do it yourself.

SSEssence · 08-11-2017, 11:24 AM

I have JBA high flow cats, tru x pipe and muffler delete and the car is perfect and just as mean and loud as I want it, that back pressure comment is crap.

onegoofydad · 08-11-2017, 02:51 PM

Here is my car . Stock l99 exhaust with LTH no cats.
https://youtu.be/AKpGDZsTvPo

These are speed engineering headers.

ChibiBlackSheep · 08-11-2017, 03:11 PM

From my understanding the shop can get fined for tinkering with your emissions, so a lot of them shy away from it.

Backpressure, not an issue.

Ideally you should just get the long-tubes with high-flows and call it a day. No need to get work done, only to redo that work with long-tubes.

kmarshall2121 · 08-11-2017, 03:12 PM

My muffler guy says back pressure is at the mufflers. I lost a bit by up-sizing my suitcases to Flowmasters from V8 they had, and I got a good deal on. lost some back pressure, but it sounds bitchin'!

Avenging Orange · 08-11-2017, 10:08 PM

You know......I was, once again, going to type a semi lengthy response as to why you should do things the way you admittedly know is the proper way. Then I thought.....why?

Gunmetal Speedster · 08-12-2017, 01:53 AM

Quote:

Originally Posted by Avenging Orange

You know......I was, once again, going to type a semi lengthy response as to why you should do things the way you admittedly know is the proper way. Then I thought.....why?

You should consider putting "For exhaust; start from the front and work your way back!" in your bio. It's your catch phrase

08-11-2017, 01:58 AM	#1
flynhawaiianss Drives: 2011 Chevy Camaro SS Join Date: Jun 2017 Location: IL, US Posts: 57	Delete secondary cats? Ok, so I know I'm probably beating a dead horse on this issue with some parts and I have used the search function previously so please don't shoot me I have been looking at doing exhaust here soon on my 2011 L99 and yes I know I should start from the front of the car and work my way back (LT headers are in the future plan) but in the meantime I have purchased a Stainless works muffler delete kit from a member here on the forum and the next purchase is an x-pipe from summit racing to remove the resonator. I was wanting to take it all in and have all the work done in one go. I was thinking about deleting the secondary cats as well. Yesterday, I talked to one of the mechanics my family and I have been using for years and we trust. I was getting an estimate for what I was wanting done and he said he wouldn't remove the secondary cats for reasons of being fined. On top of that, he said that there would be too much back pressure lost and tried to explain everything to me on how that works and cases of cars that have came back and needed work due to that happening. Now, I don't think he is just making this up but from my research (and I hate debating this topic) I didn't think there would be a loss of back pressure at all if the secondary cats were removed? Please correct me if I'm wrong but I thought the first set of cats did most of the work and removing the secondary cats would not throw a code unless the welds were shotty and there was a leak? I'm just kind of up in arms if I should go to a different shop to see if I should have the secondary cats deleted or I should just not have it done. Anyone that knows or has had this done please feel free to chime in. Last edited by flynhawaiianss; 08-11-2017 at 05:56 AM.

08-11-2017, 05:29 AM	#2
Ashen L99 Drives: Ashen grey, 1SS, L99 Join Date: Aug 2016 Location: Oklahoma Posts: 547	I've had it done and what I would tell him is that his statement of losing too much back pressure is a crock of shit, so is the getting fined part. Didn't engine masters on YouTube do a video about backpressure and they said that the engine actually made more hp with less? Correct me if I'm wrong but as long as the main ones stay, you'll be fine. There unmonitored so who cares if there there or not? You'll gain a little bit of noise but the hp gains would probably be negligible. Cut them off. __________________ Roto-fab big gulp, Nick Williams 102mm TB, Kong X-port LSA, Ported 821 heads, BTR stage 4 V2 pd cam, 416 CI bottom end, original block. TSP 2” long tubes, Corsa ZL-1 catback. Nitrous Outlet 102mm plate kit/100 shot JUST IN CASE. NGK BR7EF plugs with Taylor plug wires. DSX flex fuel kit, DSX aux pump, zl1 in tank. deatchwork 1000cc injectors. B&M deep trans pan, stock 6L90 converter, ZL1 diff 3.23 ratio. GM ground effects, T-Rex upper grill, Z/28 Spoiler, Forgestar F14s, 12” subwoofer, and custom paint matched interior.

08-11-2017, 06:43 AM	#4
14Black1LESS Drives: 2014 2SS/RS/1LE Join Date: Mar 2015 Location: Hurricane Alley Posts: 699	You don't lose back pressure by removing the cats. I don't have any cats on mine and Im not losing back pressure. As far as getting fined, that would probably be determined by where you live. We don't have emissions checks in Florida so I have nothing to worry about. If you do all of the exhaust work and put on LT headers then you need to get a tune also to get the full potential out of it. Even if you don't put the headers on yet but delete the cats you would still need a tune, otherwise you will get a CEL. __________________

08-11-2017, 08:56 AM	#8
InFiD3ViL Drives: 2010 CGM 2SS/RS LS3 Swapped A6 Join Date: Sep 2016 Location: Spring Hill, FL Posts: 4,734	A lot of exhaust shops will not touch the cats due to the possible fines. But I am sure you can find someone to do it if you can't do it yourself. __________________ 2010 CGM Camaro 2SS LS3 Swapped A6 - GPI LS3 SS1 .647/.638, (224/237, 112 +4, 7º overlap) on CamMotion 8620 core, BTR Platinum .660" Dual Spring kit w/titanium retainers, CHE bronze trunnion upgrade, stock heads milled @ .015, Melling HV 10296 oil pump, TSP 1-7/8" long tube headers (W/Catless Off-road Pipes), Corsa Xtreme 3" Catback, GPI Ported/Rod Mod Intake, Stage 2 Ported Throttle Body, Vararam OTR CAI, Mike Norris Gen 2 catch can + GM 1LE clean side separator, 160º thermostat - Megan Racing adjustable coilovers (lowered 1.75"), MRR M017 10/11" wheels-Tuned by Ryan @ GPI

08-11-2017, 02:51 PM	#10
onegoofydad Drives: 2014 Camaro 2SS Join Date: Nov 2016 Location: Georgia Posts: 141	Here is my car . Stock l99 exhaust with LTH no cats. https://youtu.be/AKpGDZsTvPo These are speed engineering headers. __________________ 2014 Black/Black Camaro 2SS RS L99, CAI Intake, Speed Engineering LTH. Jannetty Tuned.

08-11-2017, 05:57 AM	#3
flynhawaiianss Drives: 2011 Chevy Camaro SS Join Date: Jun 2017 Location: IL, US Posts: 57	I never saw that video but now that you mention it I will have to go look it up. From what I have read, people that have done it didn't notice any loss in back pressure and did seem to think they may have gained a few ponies. I will gladly take a few extra ponies if possible and a little added volume to the exhaust as well.

08-11-2017, 07:30 AM	#7
flynhawaiianss Drives: 2011 Chevy Camaro SS Join Date: Jun 2017 Location: IL, US Posts: 57	Yeah I live in IL but not in Chicago and have never had to worry about getting my emissions checked. If that was the case my '96 Z28 would of neverrrrrr passed So from the posts so far the consensus seems to be to remove the cats and there won't be a loss of back pressure. I have one other shop in mind and I haven't checked with them yet but I'm hoping if I stop by and talk to them they would do it.

08-11-2017, 11:24 AM	#9
SSEssence Instagram: Sangstah Drives: 2019 Camaro 1LE Join Date: Sep 2016 Location: Buena Park, CA. Posts: 2,836 View My Garage	I have JBA high flow cats, tru x pipe and muffler delete and the car is perfect and just as mean and loud as I want it, that back pressure comment is crap.

08-11-2017, 03:11 PM	#11
ChibiBlackSheep Drives: 2012 2SS/RS, 1968 SS Join Date: Feb 2012 Location: Southeast, PA Posts: 2,116	From my understanding the shop can get fined for tinkering with your emissions, so a lot of them shy away from it. Backpressure, not an issue. Ideally you should just get the long-tubes with high-flows and call it a day. No need to get work done, only to redo that work with long-tubes. __________________ LS3 Crate Engine Swap \| CSP Custom Cam 232/240 .615/.615 113 +3 \| Stainless Power LT Headers \| Z28 Intake \| Borla S-Type Exhaust \| FTI Triple-Disc Billet 3200 Stall 2012 Camaro 2SS/RS \| 1968 Camaro SS \| 2020 Cadillac CT5 Premium Luxury \| 2021 Spark LS

08-11-2017, 03:12 PM	#12
kmarshall2121 Drives: 2012 45th Anniversary Edition Join Date: Aug 2012 Location: San Diego, CA Posts: 1,618 View My Garage	My muffler guy says back pressure is at the mufflers. I lost a bit by up-sizing my suitcases to Flowmasters from V8 they had, and I got a good deal on. lost some back pressure, but it sounds bitchin'!

08-11-2017, 10:08 PM	#13
Avenging Orange Drives: 2010 Inferno Orange 2SS/RS Join Date: Apr 2010 Location: Clermont, IN Posts: 3,297	You know......I was, once again, going to type a semi lengthy response as to why you should do things the way you admittedly know is the proper way. Then I thought.....why? __________________ 2010 Inferno Orange 2SS/RS M6 Black Leather, Sun Roof, OBX Headers, Borla touring axle back, Cold Air Inductions CAI , non synthetic fluids, BMR total bushing upgrade/1" lowering springs, DSE 32mm rear sway bar. GM fe4 shocks/struts/LCA's, AAM 3.91 diff, Vertini RFS1.8 20x9 +30. Conti ExtremeContact Sport 275/35/20. sjm autoprod ABL dash kit. Mike Norris tuned 413/419. Avenging Orange: 43 years of not buying into the Hype........and damn proud of it!! https://youtu.be/9JD9it6SmB8 https://youtu.be/xmelTlEzI34 KICKING CANCERS ASS SINCE 2015!!