Cadillac STS-V custom exhaust project


I actually went with the Corsa axle-back on my STS-V.    The Install article is here, and the dyno article is here.


I have mentioned exhaust modifications for my 2008 Cadillac STS-V in earlier articles, but I think I am ready for this as my next modification.

The stock STS-V exhaust is a true dual 2.5″ exhaust.  It has a resonator (17) and the dual mufflers.

Now recall if you cut open the CTS-V muffler housing, they don’t look terrible for flow inside:

Inside the Cadillac CTS-V mufflers

although each 90 degree turn is a 50% loss of flow as I recall.  As we studied in a previous comparative article we think the STS-V flow is around 308 CFM.

Following along after Jaime I plan to replace the resonator with a Magnaflow True-X muffler, and the mufflers with high-flow Magnaflow performance mufflers.

I am working with True Street Motorsports in McKinney again, and here is our base plan:

1 Baseline dyno
2 Replace STS-V exhaust resonator, stock mufflers
Magnaflow part list:
(2) 14326 Magnaflow Polished Mufflers 2.5/2.5
(2) 35136 Magnaflow SS Tips or similar
(2) 13070 60* Mandrel Bent Pipes (stainless) or similar
(1) 14468 Magnaflow Tru-X Muffler (used instead of stock resonator)
3 ‘After’ Dyno
Magnaflow does make a cat-back system for the 320 hp Cadillac XLR, for which they got a 12 whp improvement.  If that improvement scales for the STS-V we would see 18 hp improvement from the planned changes.
The Magnaflow XLR system also appears to replace the resonator with an X pipe, the connecting piping, and the mufflers with performance models.   The XLR has some odd in and out of the front of the muffler flow pathing, but the principle is the same.  Likewise, the Borla system puts an X-pipe ahead of a resonator, then the dual mufflers.

Magnaflow says the Cadillac XLR 320 hp picks up 12 whp with Magnaflow catback

There are multiple variables to keep up with — my last mod was the intake, and it was 100F+ in the shop and much higher in my intercooler.  Now it is 40F in Texas, so I expect we will see a higher baseline now than the 375 whp we saw in August.  That’s part of why we dyno then mod then dyno.  Even with this approach we can’t control everything — the after dyno will be with the engine more heat-soaked than the before dyno — but you control what you can.


My goal for the STS-V is to hit 410 wheel HP, which with the automatic would make it a solid 500 crank HP Cadillac.

Other STS-V exhaust or muffler choices:

Borla made a custom cat-back system for the STS-V which is still available.  I love the Borla sound, but there have been some reports of drone with the system, and the need for some modified parts to be added.  Around $1500 + installation.
Corsa makes a axle-back (dual muffler) system for the STS, but not for the STS-V.  The STS version can be used with the STS-V, and that is what D3 does I believe.  Around $900 + installation.
Gibson also offers an axle-back (dual muffler) system.  It is available in stainless (preferred) or aluminized.  It looks like a nice set of mufflers, and has gotten good sound reviews.  Around $425 + installation.

Suggestions or Comments?  Please let me know what you think!


4 thoughts on “Cadillac STS-V custom exhaust project

  1. Pingback: Cadillac STS-V custom exhaust project | Cadillac Conversations » Magnaflow Exhausts - Everything About Magnaflow Exhausts

  2. I am new to Cadillac. I have lots of experience with Corvettes and drag race cars meaning drag strip only. I have NO experience with Cadillacs. This stated, I have plans.
    I am about to have my STS-V tuned and, if it is the same result as my C6 Vettes, the result will be dramatic. I also know that increasing breathing creates far more desirable results.
    I think I want to increase breathing for both performance and mileage but how does one do that and not have a Cadillac sound like a Corvette or Mustang? All of the systems I have experienced are on the loud side like my Vette with long tubes and a cat back.
    Is there a viable option that will increase exhaust flow and allow the car to still be relatively quiet?

  3. Great; please let us know what your tuning results are before/after etc.
    The noise question is giving me pause also; I went back to youtube to listen to 4.6L and 4.4L with magnaflow, and now I am leaning toward the albeit more expensive Corsa muffler solution. I think that would give more flow but keep closer to Cadillac sound levels. Let me know what you decide though!

  4. Pingback: Exhausting Cadillac STS-V options – Corsa | Cadillac Conversations

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