Custom 3” stainless catback

Discussion in 'Generation 4 - Performance Upgrades' started by Zpak, Aug 3, 2020.

  1. Zpak

    Zpak Es Aich Oh!

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    Here it go’s.
    I don’t like the sound of any off the shelf catback, or a loud V6 in general for that matter. However, pushing for more power I know the skinny factory set up wasn’t doing me any favors. So, I set out to put together the most free flowing exhaust possible while trying my best to keep the volume down and tone deep and low.

    I’m far from an exhaust theory expert but have been researching this for a couple years. The general consensus among those who know far more than me is that in turbo applications the best exhaust post turbo is none. From there I knew 3” would be perfectly acceptable so I went for it.

    On to X pipes. I used the 3” MagnaFlow Tru-X crossover X pipe. I know there is much contention about their viability on an even firing V6, and even more so on a turbo where you lose the individual exhaust pulses. But, I believe there still may be some scavenging from side to side to take advantage of. Even if I’m wrong, I don’t see how it could hurt and if nothing else I’ll take the fact that they do help mellow the overall tone.

    Moving to resonators. Everything I’ve heard about their deletion is once gone, you get drone. I didn’t want either but needed something else there because for no other reason it would be way too loud with just the X and mufflers. So I took a page from my ‘60’s FE experience and put dual 4” body 22” long Thrush glasspacks on in place of a resonator.

    And finally, exiting through 3” MagnaFlow (cause deep and mellow) mufflers and factory style 4.25” tips.

    The set up. (Concise)
    2.5” PPE catted downpipes
    2.5 flange to 3” pipe
    3” MagnaFlow Tru-X
    Dual 3” Thrush glasspacks
    3” MagnaFlow mufflers

    Now for the result. For the sound I was hoping to achieve, couldn’t be happier. Honestly, not a ton louder than stock in decibels but far deeper and certainly more aggressive with a minimal amount of V6 rice. Performance, according to the butt dyno, most definitely noticeable. Feels strong. Where I failed... miserably, drone! About 1,600 rpm to around 2,100 it’s pretty bad. So, a Helmholtz resonator is most likely in my future. Overall I’m happy with the outcome and the sound is actually pretty decent... acceptable...for a V6. Far from obnoxious but still lets you know it’s ready for battle.

    Forgive the muck, it rained on the way home from picking it up.

    8877543D-615F-4457-8BE3-6BB6C228A722.jpeg
    02B5F22C-4797-4958-B3A1-FB8C1790DDAC.jpeg

    Video link with cold start and drive by’s.
     
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  2. SM105K

    SM105K Streetlight Grand Prix Champ/ IG @egocheckersho

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    I like it, it sounds better then 90% of the other cat backs for the SHO.
     
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  3. Zpak

    Zpak Es Aich Oh!

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    Thanks, if nothing else it should flow rather freely.
     
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  4. Lostdog45

    Lostdog45 New Member

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    Awesome, I like it.
     
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  5. skyshadow07

    skyshadow07 On a mission to get below 4000lbs

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    The tone pitch is a hair higher than I would like but I like how it dies out at higher rpm. My car has a damn trumpet sound at higher RPM.
     
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  6. GotGrip?

    GotGrip? Conversation Ruiner

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    Same here on the trumpet thing, getting that fixed on friday.
     
  7. Zpak

    Zpak Es Aich Oh!

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    Little update, after a couple hundred miles of getting everything nice and sooted up and a few heat cycles to settle everything in the drone as well as cabin volume has actually died down fairly substantially. Once you hit cruising altitude it’s actually quiet again. Strange, but I’ll take it for sure.

    Also, first trip to the track with the new setup gained me a PB of 12.11 at 114.9, almost 3 MPH faster trap. No other changes to the car with worse air and terrible 60’s.
     
    Last edited: Aug 12, 2020
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  8. SM105K

    SM105K Streetlight Grand Prix Champ/ IG @egocheckersho

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    What are your normal 60 foots and what where they on the 12.11 run? Damn pull the rear seats and you can touch an 11.
     
  9. Zpak

    Zpak Es Aich Oh!

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    Yeah the 12.11 was bitter sweet because with my 60’ from my last time it would have been an 11.98.
    12.11 with 1.88 60’. My best 60 last time was 1.75
    I’m painfully close to an 11 second pass.
     
  10. 802SHO

    802SHO FULL SEND

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    You’ll definitely snag an 11. It’s just one good launch away
     
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  11. skyshadow07

    skyshadow07 On a mission to get below 4000lbs

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    How you addressing it? I'm considering a Helmholtz resonator tube. That way I'm not impeding air flow at all and I'm affecting a specific hz range.
     
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  12. GotGrip?

    GotGrip? Conversation Ruiner

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    The exhaust shop I use knew exactly what it was before I even got the car there. The resonator apparently struggles to keep up with flow after downpipes so he is going to replace it with a magnaflow xpipe resonator. He said he sees this all the time on the SHOs and Stinger GTs, also mentioned that he often doesn't do much beyond what I was doing for exhaust work because they usually sound horrid. Debating on chopping the mufflers while its there and doing 3in straight pipe exits for weight reduction, but we will see what he says.
     
    Last edited: Aug 13, 2020
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  13. skyshadow07

    skyshadow07 On a mission to get below 4000lbs

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    @GotGrip? Are you keeping the duals or going single?
     
  14. SM105K

    SM105K Streetlight Grand Prix Champ/ IG @egocheckersho

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    He is going single....but keeping the duals....
     
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  15. GotGrip?

    GotGrip? Conversation Ruiner

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    Did you just ask me out?


    Probably going to stay duals, if I do get the whole exhaust done though, I'll probably do a Y pipe after the DPs to a single then Y it back out to duals at the end, should save a little weight and keep it stockish looking from the rear.
     
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