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  #1  
Old 10-18-2016, 11:09 AM
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Stock Exhaust Design

Newby here so I apologize if this has been answered before.
For the newer Hemi 5.7 can anyone tell me what the suitcase resonator and the rear mufflers look like inside? If you have your original system off why not cut one open and take a picture for us. Is there an internal crossover within the suitcase? My bet there is as this softens the tone a lot. Is the exhaust path in the mufflers just a curve path straight through or chambered? If the stock exhaust is efficient then what HP and TQ gains will one get with an axle back like Gibson or the Cat Backs like Borla and Corsa? Has anybody dynoed before and after being sure to disconnect the battery for awhile and then driving so the system learns / compensates for the changes? I want to be able to hear the engine as this is part of the driving experience and a form of feedback but for a nice vehicle I don't want loud or drone. My guess is lower restriction air intake and axle back together would add a little area under the curve everywhere - but not much as they system is pretty good already.

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Old 10-18-2016, 12:57 PM
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Re: Stock Exhaust Design

Don't expect any gains. Sound only mod for sure.
I am pretty sure the middle suitcase is straight through but has a ton of baffling to reduce sound.
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Old 10-19-2016, 08:15 PM
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Re: Stock Exhaust Design

Thanks for the feedback.
Has anyone actually cut the top off a suitcase resonator and rear muffler to look like inside? If so, were there baffles and chambers or sound deadening material around a vented portion of exhaust pipe? Does the suitcase internally cross connect the left and right sides?
Has anybody dynoed before and then a few hundred miles after cold air inlet and exhaust modes ? If so, what was the result?
I have done mods on several cars and dynoed before and after but not on a motor that already makes good power (360 HP for 345 CI). The Grand Cherokee is quiet enough that I suspect these mods will result in some power gain. I have my guess but I will save that as I would rather have some real data points.
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Old 10-20-2016, 12:49 PM
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Re: Stock Exhaust Design

Where are ya, I see stock exhausts on Clist all the time, one listed at $100..be a pioneer. Sacrificing one might not be worth it to someone else.
I see what you're getting at but I stopped trying to build a better mousetrap. If you're after sound commensurate with the forward motion, the mechanics of the OE muffler may not play as big as role as sound clips, the internal designs of non OE mufflers, and other peoples first hand experience, like what your asking for but more accurately related to the end effect. Also all of this is on here already and very searchable. Minus your internal view, but even some dyno numbers.

Im sure someone has one sitting somewhere, but I think it might be tough also because the OE 5.7 exhaust has value as an upgrade to people with the 3.6. The OE exhaust is a very good design and I think even without replacing the suitcase it will outflow anything short of a blown motor, sound is a very different thing.. The gains may be negligible OE against even the best non OE stuff but the hemi responds better than most to well placed mods, on the charger and other forums there's a wealth of dyno numbers for different packages..
Good luck
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Old 10-20-2016, 01:13 PM
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Re: Stock Exhaust Design

The stock suitcase on my old srt crossed like a x pipe. The rest of the muffler looked like honeycomb. I would imagine the jeep's is the same.
Rears should be hollow.
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Old 10-20-2016, 01:17 PM
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Re: Stock Exhaust Design

Thanks. That makes sense. I will check the other forums and look for dyno gains on similar Hemi 5.7 applications. If I replace my mufflers I will cut the right side muffler open and have a look. That way maybe someone could use the left side on a single system. All I would want would be the shipping costs.
My best guess is a slightly less restrictive cold air intake and less restrictive mufflers would gain around 7-9 HP as the stock system seems to be well designed for flow and power - just a tad too quiet - for some of us.
On my 1996 SS Imapla a K&N air intake and Corsa cat back added a true 15 rear wheel HP (based on dyno test) but that was on a car where the stock items were probably more restrictive than on the Jeep Grand Cherokee.
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Old 10-20-2016, 01:20 PM
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Re: Stock Exhaust Design

Lx forums is a great forum and you should be able to find what you are looking for👍👍
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Old 10-20-2016, 06:37 PM
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Re: Stock Exhaust Design

I did a dyno test with the stk. OEM exhaust vs. the Corsa cat-back (14991) and I saw basically no gain to the tires. We made a total of 5 passes with the new exhaust system and saw the following. One run it gained 1-awhp, on the next one it lost 2-awhp, let it cool down and the next pass saw a gain of almost 2-awhp, next pass no gain, next pass a gain of almost 1-awhp. My Jeep 5.7L is basically stk (K&N CAI and Diablosport tune).

After all that, I called Corsa while still at the dyno and was told they thought it should of made more power to all the wheels. They said if I modified the vehicle some more I'll see more gains from the exhaust cat-back system. After a two days of driving with the Corsa cat-back, I decided to take it off and sell it. This is my opinion on the Corsa cat-back exhaust system.
* Sounds nice at start-up
* Sounds nice at idle
* Sounds nice at WOT
* Hated the fart can sound between shifts at WOT
* Hated the drone/moaning it made at low speeds with the MDS on.

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Old 10-20-2016, 10:35 PM
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Re: Stock Exhaust Design

Oddly that Impala sits right under the 917/30 on my top 100 list. Awesome car but now I'd swap the LT1 for an LS9. The Hemi can make some great sounds and I'd bet you can end up +5-10whp with nothing intrusive. If you go with a tuner you'll see signicant improvements.
You'll definitely get an awesome sounding Jeep getting it right takes exactly what your already doing. I've read about many configurations and they've all had their attributes. I've heard mflow and a corsa on the wktoo, I like maganflow stuff but would be curious what a fmaster 50 would do. I've heard dozens of systems on Rams and 300's

Awesome info coming in! Wardo called it, the LX forums are insane, from mild builds to 9 second cars.
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Old 10-21-2016, 12:56 PM
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Re: Stock Exhaust Design

Suitcase muffler exposed

Just a minute of search here. More time spared for typing the post


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Old 10-21-2016, 03:55 PM
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Re: Stock Exhaust Design

Quote:
Originally Posted by TomS View Post
Thanks for the feedback.
Has anyone actually cut the top off a suitcase resonator and rear muffler to look like inside? If so, were there baffles and chambers or sound deadening material around a vented portion of exhaust pipe? Does the suitcase internally cross connect the left and right sides?
Has anybody dynoed before and then a few hundred miles after cold air inlet and exhaust modes ? If so, what was the result?
I have done mods on several cars and dynoed before and after but not on a motor that already makes good power (360 HP for 345 CI). The Grand Cherokee is quiet enough that I suspect these mods will result in some power gain. I have my guess but I will save that as I would rather have some real data points.
I took off my mufflers and put straight pipe there, the sound is much better, I get a little drone sometimes but nothing bad, on the freeway (in normal speeds) is pretty quite but when I push it sounds great, it's perfect for me!

I "felt" a performance increase and better throttle response but I haven't done any Dyno so I don't know how much.

The driving experience is much better!
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