Jump to content

Anyone with GM Performance Cat-Back Exhaust/Air Intake ?


Recommended Posts

5 hours ago, KARNUT said:


I’ve read on this site that the GM performance cat back had the flapper. I haven’t had performance exhaust at my bender in awhile, I suspect they will or have started addressing the cylinder deactivation changes in the muffler it self, with baffling and chambers. Seems logical. I’ll have to pay my exhaust bender a visit and find out. I’ve been thinking about putting exhaust on my V6-4cylinder vehicles only if their stock quiet at cruise.


Sent from my iPhone using Tapatalk

No flappers, no resonators on the GM performance. Good riddance as those flappers do nothing but squeak. There is no odd noises as it pertains to DFM. It seems to maintain a V8 “tone” regardless of mode. I believe the programming of the DFM and muffler design more or less eliminates the need for the adaptive valves.

  • Like 2
Link to comment
Share on other sites

Does anyone know exactly what "tuning" they do when you get these?  I was always told that the flappers were to kill the noise from the fuel management garbage.  If the flappers are not in the performance exhaust, then does that possibly mean they are tuning to turn the DFM off?!?!?!?  THAT is definitely worth $1,500 if so.  Trying real hard not to go on a DFM rant.

Link to comment
Share on other sites

On 3/15/2019 at 9:50 AM, Scooter Scott said:

I'm interested in your results on the 12909

So i just had the muffler installed yesterday $80 to cut off the two flappers and weld on the new adapters and muffler. I love the sound. On the freeway you don't hear much until you step on it. It's more noticeable at lower speeds around town. This particular shop does a lot of aftermarket exhaust installs and has done many GM trucks. He said the resonators are straight through and wouldn't make a difference on performance, but would change the sound a bit. He was happy to cut them off and weld in straight pipe for $100 both sides but said "don't waste your money". He also said in his opinion that a full cat back system wouldn't improve performance from the factory set up with the new Magnaflow muffler.GM is 3.5" mandrel bent stainless steel. When he cut the old one off it was HUGE and very heavy. The Magnaflow is a little shorter, lighter and straight through which is where you see the gain in HP. I highly recommend it. Note; I did keep the flappers just in case I wanted one or both reinstalled. I will post a pic so you can see how restrictive they are.

20190320_081503.jpg

Edited by BLACK AT4
Link to comment
Share on other sites

AT4 flapper valve in the fully open position. As you can see there is quite a restriction. Probably why the Cat back GM system doesn't use a flapper. Between removing 2 of these and installing a straight through muffler, that has to be 99% of the HP gain. Total cost including install was $198. BTW, that flapper valve fully open is a 1.25" restriction. 

20190321_144638.jpg

Edited by BLACK AT4
Link to comment
Share on other sites

1 hour ago, BLACK AT4 said:

AT4 flapper valve in the fully open position. As you can see there is quite a restriction. Probably why the Cat back GM system doesn't use a flapper. Between removing 2 of these and installing a straight through muffler, that has to be 99% of the HP gain. Total cost including install was $198. BTW, that flapper valve fully open is a 1.25" restriction. 

20190321_144638.jpg

You’re right, those flappers are unbelievably restrictive. I never would have guessed. That has to kill the bulk of the power right there. 

 

The stock 3.5” should be more than enough diameter, but the GM catback is supposed to be even larger. I haven’t measured it but it looks like a freaking sewer pipe down there. Nevertheless you got a nice deal there...most of the power gains at a fraction of the cost! :thumbs:

Link to comment
Share on other sites

1 hour ago, Scooter Scott said:

Thanks for sharing that! Any sound bites? I liked the 12909 on my 2018 6.2. Couldn’t beat it for the price.


Sent from my iPhone using Tapatalk

I'll see what i can do. The problem is, GM only lets you rev the motor to less than 3k in neutral.. what's up with that. The pedal feels like a sponge.... 

Link to comment
Share on other sites

  • 3 weeks later...
  • 4 months later...

I have a 2019 AT4 6.2L 10 speed with performance package, it's not worth the money. Traded a 2017 Silverado Double Cab LTZ , 6.2 L 8 speed with there Borla Exhaust but K & N Cold Air Induction,  it made 365 hp and  390 tq, the AT4 only made 346 hp and 370 tq, both dynode at the rear wheels, Lost 19 hp and 20 tq, with the 10 speed and there performance set up. On the 2017 Silverado I had it dynoed before I installed K & N Cold Air Induction then after it was installed, gain almost 13 hp after installation. So needless to say, I won't do that again, I'll go aftermarket. The performance package should have been closer to 25 to 30 hp and maybe 18 to 20 tq.

Edited by Dominick Galizia it
Link to comment
Share on other sites

  • 2 weeks later...
On 3/21/2019 at 4:39 PM, BLACK AT4 said:

So i just had the muffler installed yesterday $80 to cut off the two flappers and weld on the new adapters and muffler. I love the sound. On the freeway you don't hear much until you step on it. It's more noticeable at lower speeds around town. This particular shop does a lot of aftermarket exhaust installs and has done many GM trucks. He said the resonators are straight through and wouldn't make a difference on performance, but would change the sound a bit. He was happy to cut them off and weld in straight pipe for $100 both sides but said "don't waste your money". He also said in his opinion that a full cat back system wouldn't improve performance from the factory set up with the new Magnaflow muffler.GM is 3.5" mandrel bent stainless steel. When he cut the old one off it was HUGE and very heavy. The Magnaflow is a little shorter, lighter and straight through which is where you see the gain in HP. I highly recommend it. Note; I did keep the flappers just in case I wanted one or both reinstalled. I will post a pic so you can see how restrictive they are.

20190320_081503.jpg

This is great info. My local muffler shop recommended the Magnaflow and told me the drone sound wasn’t even noticeable. So, here is where I’m seeking your advice....I have a 2019 Silverado RST 5.3l and it has the single-side exit stock exhaust. I am debating whether I want to keep a single exit exhaust or go to dual rear split. If I go with the Magnaflow, what would you recommend? If I go with the single exit, then I can just leave the exit pipe and resonator and just add a tip. If I go with the dual split, he would probably put two new pipes and remove the resonator. Thoughts?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Forum Statistics

    245.8k
    Total Topics
    2.6m
    Total Posts
  • Member Statistics

    333,221
    Total Members
    8,960
    Most Online
    Mr Chips
    Newest Member
    Mr Chips
    Joined
  • Who's Online   2 Members, 0 Anonymous, 560 Guests (See full list)




×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.