Is this a good idea???

Harley Kidd · 06-09-2022, 08:05 AM

I am planning on deleting the secondary cat and installing the Stainless Works Axle Back system. My question is the area on the stock pipes where GM crimped them down. I was thinking about taking those sections out and replacing with normal size pipe. Has anyone done this and is it a good idea? Lastly I have seen so many comments about going to the Roto Fab CAI. If you look on Summit there are a lot of different ones and part numbers. Which one is the right one? Not considering the Big Gulp as my car has less then 700 miles on it and I don't want to deal with losing my warranty at this time. Look for your advice.

joekd · 06-09-2022, 08:11 AM

The crimp pipes have been tested to show no resistance, you can remove them but really there is no reason to

As for the rotofab you have just a couple things to decide:
-Sound tube or no? I went without to eliminate all that ugly extra plumbing underhood
-Oil or dry filter? Not going to start a heated debate here but I decided the dry filter was best for my car

Harley Kidd · 06-09-2022, 08:49 AM

Many thanks for your advice. It is hard to understand how crimping the pipe does not effect exhaust gas exit or flow. As to sound tube my new car does not even have that tube. It has the small hole blocker on the firewall.

Vigilante375 · 06-09-2022, 09:16 AM

Quote:

Originally Posted by Harley Kidd

Many thanks for your advice. It is hard to understand how crimping the pipe does not effect exhaust gas exit or flow. As to sound tube my new car does not even have that tube. It has the small hole blocker on the firewall.

GM has been doing this for decades and it's shown to have no effect to the flow of exhaust.

So they seem to know what they are doing with this crimped exhaust if they are still using it.

LT4Greg · 06-09-2022, 09:39 AM

Get the regular RotoFab intake made for a ZL1. It’s an easy install and shouldn’t affect your warranty. You can always take it off and put the stock intake back on for warranty work. Most dealerships don’t mind a cold air intake as long as you don’t tune the car. You can cut out the crimped sections of pipe and have new pipe welded into the system but as was said it’s not really necessary or you can change to a new X-pipe to do away with that section since you are installing a axle back exhaust.

RobZL1 · 06-09-2022, 11:14 AM

I believe the crimped section was found to be good up to about 900 rwhp on a dynojet (CSP's test). I believe ARH has also done tests that show the stock axleback is good for a lot of HP. I think you have to look at the cross-sectional area of the crimps, plus realize that the exhaust gases are a lot cooler by the time they get back there, and don't need as much room.

Rwhp042 · 06-09-2022, 04:08 PM

Hooker makes a crimp delete kit. I used it on mine because I wanted to take the center center section of the exhaust off and do the secondary cat delete. Can’t say I noticed any power increase, but I like not having the secondary cats and the crimped section.

Harley Kidd · 06-09-2022, 06:54 PM

I too am getting to the point where I wanted to delete the secondary cats. But today while getting my car inspected I was told if I delete the secondary or the first for that matter no inspecting company can legally give my car a pass. I was told they look to see all equipment is still on the car including the cats when they look over the car. I know alot of members have deleted their cats so I am wondering how they can get away with that when it comes to having the car go through the annual state inspection. Maybe it is now the law in other states but I was told today it is the law in Texas. If anyone has some good information on this I would really like to hear it.

Gunkk · 06-09-2022, 09:15 PM

Quote:

Originally Posted by Harley Kidd

It is hard to understand how crimping the pipe does not effect exhaust gas exit or flow.

It doesn't. You'd be surprised how much you can bash the pipes before it matters. Engine masters did it. And it's been done here on the forum with crimp replacements using straight pipes. The verdict: no effect.

https://www.dailymotion.com/video/x3vupq0

RamAir02 · 06-09-2022, 11:02 PM

Quote:

Originally Posted by Gunkk

It doesn't. You'd be surprised how much you can bash the pipes before it matters. Engine masters did it. And it's been done here on the forum with crimp replacements using straight pipes. The verdict: no effect.

https://www.dailymotion.com/video/x3vupq0

Enjoyed watching that! Thanks for sharing.

KingLT1 · 06-10-2022, 08:00 AM

The way GM crimped the exhaust widened the pipe in that area so the flow is not effected much.

On a ZL1 there was about a 4-5 whp difference by removing the crimp section on a 800whp ZL1.

On a SS I believe the gains would be a little more substantial since it's slightly smaller diameter and has the AFM valves upstream of the crimp section on the A8/A10 cars. The AFM valve section is around 2.5".

Vigilante375 · 06-10-2022, 08:49 AM

If anyone wants to see why this crimped section works, just look up Continuity Equation or Bernoulli's Equation.

I know there is a scientific name for this and I know I've watched a video on it before. Just can't remember what it was exactly.

06-09-2022, 08:05 AM	#1
Harley Kidd Drives: Black 2022, ZL1, Hurst M6 NPP Join Date: Feb 2010 Location: Odessa, Texas Posts: 69	Is this a good idea??? I am planning on deleting the secondary cat and installing the Stainless Works Axle Back system. My question is the area on the stock pipes where GM crimped them down. I was thinking about taking those sections out and replacing with normal size pipe. Has anyone done this and is it a good idea? Lastly I have seen so many comments about going to the Roto Fab CAI. If you look on Summit there are a lot of different ones and part numbers. Which one is the right one? Not considering the Big Gulp as my car has less then 700 miles on it and I don't want to deal with losing my warranty at this time. Look for your advice.

06-09-2022, 08:11 AM	#2
joekd Drives: 2018 Camaro SS vert Join Date: Oct 2020 Location: CT Posts: 449	The crimp pipes have been tested to show no resistance, you can remove them but really there is no reason to As for the rotofab you have just a couple things to decide: -Sound tube or no? I went without to eliminate all that ugly extra plumbing underhood -Oil or dry filter? Not going to start a heated debate here but I decided the dry filter was best for my car __________________

06-09-2022, 08:49 AM	#3
Harley Kidd Drives: Black 2022, ZL1, Hurst M6 NPP Join Date: Feb 2010 Location: Odessa, Texas Posts: 69	Thanks JoeKD Many thanks for your advice. It is hard to understand how crimping the pipe does not effect exhaust gas exit or flow. As to sound tube my new car does not even have that tube. It has the small hole blocker on the firewall.

06-09-2022, 09:39 AM	#5
LT4Greg Drives: 2017 Camaro ZL1 Coupe Join Date: May 2016 Location: Georgia Posts: 5,811	Get the regular RotoFab intake made for a ZL1. It’s an easy install and shouldn’t affect your warranty. You can always take it off and put the stock intake back on for warranty work. Most dealerships don’t mind a cold air intake as long as you don’t tune the car. You can cut out the crimped sections of pipe and have new pipe welded into the system but as was said it’s not really necessary or you can change to a new X-pipe to do away with that section since you are installing a axle back exhaust. __________________ ZL1 Coupe, PDR, Exposed carbon fiber hood insert, My Link with Nav, M6 6 speed and Silver Ice Metallic. Mods done: ceramic window tint, GM Accessories Camaro floor mats and Roto-Fab CAI.

06-09-2022, 11:14 AM	#6
RobZL1 fo'shizZL1 Drives: 2017 ZL1 Join Date: Aug 2017 Location: ATL Posts: 1,281	I believe the crimped section was found to be good up to about 900 rwhp on a dynojet (CSP's test). I believe ARH has also done tests that show the stock axleback is good for a lot of HP. I think you have to look at the cross-sectional area of the crimps, plus realize that the exhaust gases are a lot cooler by the time they get back there, and don't need as much room. __________________ 2017 ZL1 M6 Black \| Maggie 2650 // 103TB // Big Gulp Past Rides- 2014 ZL1 M6 Red Hot \| Tons of mods 2004 CTS-V M6 Silver \| Many mods 1995 Corvette M6 Torch Red \| A few more mods 1992 Camaro M5 White \| A few mods

06-09-2022, 04:08 PM	#7
Rwhp042 Drives: 2021 ZL1 1LE A10 Join Date: Aug 2020 Location: Nebraska Posts: 21	Hooker makes a crimp delete kit. I used it on mine because I wanted to take the center center section of the exhaust off and do the secondary cat delete. Can’t say I noticed any power increase, but I like not having the secondary cats and the crimped section.

06-09-2022, 06:54 PM	#8
Harley Kidd Drives: Black 2022, ZL1, Hurst M6 NPP Join Date: Feb 2010 Location: Odessa, Texas Posts: 69	That last comment was interesting but is it Legal? I too am getting to the point where I wanted to delete the secondary cats. But today while getting my car inspected I was told if I delete the secondary or the first for that matter no inspecting company can legally give my car a pass. I was told they look to see all equipment is still on the car including the cats when they look over the car. I know alot of members have deleted their cats so I am wondering how they can get away with that when it comes to having the car go through the annual state inspection. Maybe it is now the law in other states but I was told today it is the law in Texas. If anyone has some good information on this I would really like to hear it.

06-10-2022, 08:00 AM	#11
KingLT1 Drives: 2016 1SS NFG A8 Join Date: Aug 2017 Location: 46804 Posts: 6,793	The way GM crimped the exhaust widened the pipe in that area so the flow is not effected much. On a ZL1 there was about a 4-5 whp difference by removing the crimp section on a 800whp ZL1. On a SS I believe the gains would be a little more substantial since it's slightly smaller diameter and has the AFM valves upstream of the crimp section on the A8/A10 cars. The AFM valve section is around 2.5". __________________ 2016 NFG 1SS A8 Options-2SS Leather/NPP Perf. mods-Whipple 2.9/Fuel System/Flex Fuel/103mm TB/Rotofab Big Gulp/Cat Deletes/Corsa NPP Per. times- 10.5 @ 137 w/ 1.8 60ft Full weight on 20's 1200DA

06-10-2022, 08:49 AM	#12
Vigilante375 Drives: 2018 Camaro ZL1 Join Date: Aug 2018 Location: Georgia Posts: 1,366	If anyone wants to see why this crimped section works, just look up Continuity Equation or Bernoulli's Equation. I know there is a scientific name for this and I know I've watched a video on it before. Just can't remember what it was exactly.

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