Flowmaster American Thunder for 2 door JK - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 9 Old 11-28-2016, 09:49 AM Thread Starter
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Flowmaster American Thunder for 2 door JK

I bought one, I don't suggest you do. Flowmaster claims its for two or four doors but its not that simple. We could not get it to fit (clearance issues) without cutting one of the hangers off. I liked the product since it tucks up high into the chassis but with these issues its not something that can be done in a driveway with a basic tool kit.

THIS is the one I'm talking about.

sorry if this isn't the right section to post this. wasn't too sure but I wanted it to be known.

This is my Signature

Last edited by mvjeeper; 11-28-2016 at 10:00 AM.
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post #2 of 9 Old 11-29-2016, 12:57 AM
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This kit comes with the full size Flowmaster HP-2 (18" length). I've got a 2 door auto 2012 JK and wanted a muffler that would fit between the Y pipe and stock resonator so I could delete the stock muffler but not lose the stock resonator. Basically add a muffler to where there was currently a straight pipe. The shorty version of this HP-2 (12") fit perfectly. While plenty of mufflers probably would have also fit this straight section, the HP-2 was the ONLY muffler/resonator in this size that wasn't a straight through design. I.e. you couldnt look right through it. I felt this would maximize the muffling effect. Now I've got a decent sound on start up but far from an obnoxious straight pipe exhaust thanks to the HP-2 and stock resonator combo. If this is what you're looking for save a heap of cash and just buy the HP-2 in your desired size (18" for 4 door and 12" for 2 door) and a couple exhaust pipe saddle clamps.

I'll add that one drawback to my method is the exhaust dumps out just behind the sway bar, where it connects to the OEM muffler. This could be a concern if travelling at slow enough speeds like rock crawling to accumulate exhaust gas under the chassis that will make its way into the cabin. But I guess you could just also keep the stock muffler too!

Last edited by Vintage; 11-29-2016 at 01:22 AM.
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post #3 of 9 Old 11-29-2016, 03:36 AM
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FWIW for the 4 door guys, this fits really damn well. If you have the stock rear plastic bumper though, it will melt it because of how high it locates the tip.


It sounded just OK on the 3.8, but on the 5.3 I really like it. Above about 4000 rpm though you quit hearing the burble of the exhaust (on my 5.3, with the 3.8 it just naturally sounded like the fucker was going to come apart any second anyhow) from in the cab when you are getting on it and I just hear the engine. No idea how it sounds from outside the Jeep though at the higher RPMs.

2007 JKU Sahara........................... 2015 JKU Sahara
5.3/6l80E......................................2.5" Rock Krawler Expedition Stage-1
Teraflex 44 front, Stock 44 rear........35's
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post #4 of 9 Old 11-29-2016, 04:15 PM
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Quote:
Originally Posted by Vintage View Post
While plenty of mufflers probably would have also fit this straight section, the HP-2 was the ONLY muffler/resonator in this size that wasn't a straight through design. I.e. you couldnt look right through it.
I gotta wonder if you actually looked through it. IMHO, it is a straight-through design.

What sets it apart from other straight through designs is its use of the laminar flow technobullpuckey. It is basically a mesh core but still straight through, albeit mildly impeded. I look at the HP2 as a spark arrestor.
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post #5 of 9 Old 12-01-2016, 11:07 PM
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Quote:
Originally Posted by D94R View Post
FWIW for the 4 door guys, this fits really damn well. If you have the stock rear plastic bumper though, it will melt it because of how high it locates the tip.


It sounded just OK on the 3.8, but on the 5.3 I really like it. Above about 4000 rpm though you quit hearing the burble of the exhaust (on my 5.3, with the 3.8 it just naturally sounded like the fucker was going to come apart any second anyhow) from in the cab when you are getting on it and I just hear the engine. No idea how it sounds from outside the Jeep though at the higher RPMs.
How's the sound compared to stock? Is there any drone?
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post #6 of 9 Old 12-01-2016, 11:58 PM
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Quote:
Originally Posted by White13JKUR View Post
I gotta wonder if you actually looked through it. IMHO, it is a straight-through design.
Let's say it's the only "linear" muffler that still has chambers, a feature of non-straight-through mufflers. If you compare it's cross section to all other linear mufflers in this size envelope, this is the only one you can't slide a 1.5" dowel straight through.
http://static.speedwaymotors.com/ima.../Hushpower.jpg

About the drone question. Sadly the one regrettable annoyance I have with the 12" version at least is it drones loudest between 2000-2500 rpm, exactly where my tachometer likes to sit. 3.6L auto.

Last edited by Vintage; 12-02-2016 at 12:01 AM.
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post #7 of 9 Old 12-02-2016, 03:26 AM
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Quote:
Originally Posted by karlduke View Post
How's the sound compared to stock? Is there any drone?
With both engines at cruise it is quieter than my tires. I can listen to the radio with out it being cranked.
When WOT it was an aggressive sound for the 3.8. Rumbly, but not ricer. With the 5.3 at WOT from a stand still it's "GET THE FUCK OUT OF MY WAY I'M GOING TO RUN YOU OVER" loud. It's a very nice sound still, and cold starts are pretty barky (in a good way).

This youtube video is a pretty good rep of how it sounds with my V8. Now, mines not a 502, and my idle is not as lumpy due to his cam, but the mid throttle acceleration is pretty close to the same sound. I should make a video some time.

2007 JKU Sahara........................... 2015 JKU Sahara
5.3/6l80E......................................2.5" Rock Krawler Expedition Stage-1
Teraflex 44 front, Stock 44 rear........35's
Bastard lift
Totaled; being rebuilt
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post #8 of 9 Old 12-05-2016, 02:12 PM Thread Starter
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The exhaust sounds pretty good at lower RPMS. I'd say after 4k it starts to just sound MEH.
on the 3.6

This is my Signature
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post #9 of 9 Old 02-06-2017, 02:54 PM
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Installed FM's Force 2 Catback with dual tips, easy install and looks good. There is slight drone but worth it.

Sent from my SM-G935T using Tapatalk
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