Exhaust break-in

OVERKILL

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I'm going to preface this with the fact that this is only OEM exhaust system I have experienced this with. Many aftermarket mufflers (like Magnaflow) have a break-in period during which they get louder. My Charger had "Active Exhaust", which meant that it had flaps in the exhaust that opened, changing the tone, when you "got on it" or put it in Sport mode. The Jeep does not have this. I'm coming up on 40,000Km on the Jeep now and the exhaust is most definitely significantly throatier than in the past. It has a more noticeable bark and just in general, is louder than it has been. I mentioned it to my buddy that owns the dealership and he's observed the same thing with his TrackHawk shrug I'm wondering if this is a GC or a GC SRT thing? Anybody with a 5.7 notice this happening? It doesn't bother me, as I have had some pretty loud cars, but I could see somebody coming from a Benz or Bimmer (my M5 was deathly quiet) perhaps finding it a bit obnoxious perhaps.
 
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My father has a 2013 GC Trailhawk with the 5.7L. It is at 140k miles now, and while not obnoxious the exhaust definitely has a bit more of a growl now compared to when it was bought new with 5 miles on it. I assume it has to do with sound deadening material in the mufflers breaking in/wearing out.
 

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Originally Posted by jeepman3071
My father has a 2013 GC Trailhawk with the 5.7L. It is at 140k miles now, and while not obnoxious the exhaust definitely has a bit more of a growl now compared to when it was bought new with 5 miles on it. I assume it has to do with sound deadening material in the mufflers breaking in/wearing out.
OK, thanks for confirming. Yeah, that's kinda what I figured was going on, though it appears to happen reasonably rapidly on the SRT's shrug I assume it'll hit a point and then stop.
 

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Originally Posted by Quattro Pete
Originally Posted by OVERKILL
finding it a bit obnoxious perhaps.
A bit obnoxious was one of the reasons I bought my SRT. smile
grin
 

JHZR2

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Needs some relative basis here... Have I ever experienced exhaust systems getting louder without change to them? No. But I'd suspect this could also be gradual such that it wouldn't be readily noticed. I can't imagine a vehicle even like your Jeep having such a loud exhaust that it would be obnoxious. If there are active controlled parts in there, I can see how they would have the potential to get fouled, gunked, etc., and maybe be slower to actuate or revert.
 

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Originally Posted by JHZR2
Needs some relative basis here... Have I ever experienced exhaust systems getting louder without change to them? No. But I'd suspect this could also be gradual such that it wouldn't be readily noticed. I can't imagine a vehicle even like your Jeep having such a loud exhaust that it would be obnoxious. If there are active controlled parts in there, I can see how they would have the potential to get fouled, gunked, etc., and maybe be slower to actuate or revert.
The TrackHawk is surprisingly loud. As I noted in the OP, while the Charger had active exhaust, there's nothing like that on the Jeep. It's jut a pretty short large diameter exhaust system with dual exits. The Jeep is not a long vehicle, so the plumbing is significantly shorter than on the Charger. I wouldn't say it's like a Mustang with no cats and Flowmaster 40's on it loud, LOL! Nowhere near that level of crazy. It's just significantly louder than what you'd expect from stock exhaust. And it has gotten noticeably louder in the time I've owned it. It has a wonderful engine note, so I'm not complaining, it sounds bloody amazing. I'm just questioning what appears to be a break-in of sorts happening shrug
 

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Originally Posted by AZjeff
Wonder what's inside the mufflers? If all metal baffles hard to imagine changing volume, if some sort of batting then yes. Intentional perhaps?
Just found a thread where a guy hacked apart the stock mufflers. Yep, they are straight-through perforated pipe surrounded by batting: [Linked Image] Apparently the big "H-pipe" style main muffler is the exact same with the exception that it has a big chamber in the centre where both dump before going into the perforated sections surrounded by batting. So, given the batting, it now makes sense why they would get louder.
 
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Can't say for sure about the oem system, as I had bought my Durango used. But my Gibson axle back definitely broke in. For the 5.7 guys, removing the rear resonators will give you a decent amount of good sounding noise while not being obnoxious, but WILL DRONE while in MDS. No drone while operating as a proper v8 though, at least to my ears. The SRT sounds so good though slobber
 
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I actually work for a company that builds exhaust systems. That material you see above is a fiberglass type material that does break down over time. This is actually a resonator not a muffler. The resonators are designed to take the high pitch out of the exhaust note and the tune code is a much deeper sound that most people prefer. Most mufflers do not contain that material.
 
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I remember having Yoshimura exhaust on my last bike. That internal fiberglass was only good for about 5K miles, and then it would get louder, so it had to be re-packed.
 

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Originally Posted by spk2000
I actually work for a company that builds exhaust systems. That material you see above is a fiberglass type material that does break down over time. This is actually a resonator not a muffler. The resonators are designed to take the high pitch out of the exhaust note and the tune code is a much deeper sound that most people prefer. Most mufflers do not contain that material.
Yes, technically the rear two are resonators. Apparently, the muffler (which is a large single unit that sort of looks like a ProChamber inside) is setup in the same manner according to the guy cutting them open:
Originally Posted by Vettepro
The big muffler in the middle is different. The front section is completely open with no packing. The exhaust dumps into a big chamber and exits via 2 holes that lead into the rear section. The rear section is just like the rear mufflers. Straight pipes that are perforated and have a bunch of fiberglass packing around them.
From this thread: https://www.cherokeesrt8.com/forums...338-interesting-exhaust-experiments.html Thoughts?
 

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Originally Posted by Astro14
So...more "break down" than "break in"?
Yes, which is quite common with glasspack mufflers as noted by spk2000 and as I noted in the OP with aftermarket mufflers as well. Curious OEM choice though, don't you think? I mean, based on the design of this setup, I expect it flows phenomenally well, but it looks like it is guaranteed to get louder when it gets some miles on it.
 
Referring back to the 2nd post in this thread... wink
Originally Posted by Quattro Pete
Originally Posted by OVERKILL
finding it a bit obnoxious perhaps.
A bit obnoxious was one of the reasons I bought my SRT. smile
Hope as the batting wears out you don't get an annoying drone as the engineered sound modifier changes.
 
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I remember my old cammed LS6 Cadillac CTS-V had headers, cat delete and stock mufflers. It had plenty of miles on it already but after I did a long road trip (5000 miles) the exhaust was noticably louder. The insulation burns up over time. I think cruising 85-95 mph for hours straight in summer heat smoked the insulation in mine.
 
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