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Old 04-15-2013, 09:08 AM   #1
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Make your JK sound like a proper Jeep for $70 bucks

Coming from a VW background, I can understand exhaust systems and their benefits. Pairing a 3" downpipe to a full 3" catback does wonders for the car and it provides a great exhaust note that brings the V6 to life.

Doing the same for a Jeep... not so much. No offense to the guys with exhaust sytems here but a catback or an axle back exhaust system literally does nothing for your Jeep. It actually takes away a few HP and makes your rig sound like a Honda.

The issue is this, even though our exhaust systems are 2.5" at the rear, the headers are actually 2" and even go down to 1.75" at some of the bends on the drivers side header (yikes).

My solution was to get a motorized cutout as close to the stock headers as possible with plans to pair equal length and diameter headers in the future. This gives you the best of both worlds, especially in a town that isn't too friendly with modified cars. If you want loud and open, just flip a switch. Quiet, vice versa.

Now, with a cutout, it decreases backpressure on a NA car so you'll lose a bit of low-end torque but make up for it at WOT. Over the weekend, I found that I picked up about 2 extra MPG's. Not like I really care for an increase as 18 really isn't that much better than 16 haha At the end of the day, it makes the Jeep sound, well, like a Jeep. Angry, loud (but not annoying) and very comfortable at highway speeds and at idle.

This is everything you'll need to perform this task:
Time spent: 1 hour
Cost: $70 on the cheap, $200 on the fancy
Parts:
cutout: Magnaflow 10784 2.5" Inlet/Outlet Dual/Single Exhaust Cut-Out Pipe : Amazon.com : Automotive

make it motorized:
http://www.summitracing.com/parts/qtp-qtec25/overview/

exhaust hanger (not really needed):
Pypes Exhaust HVH13S 3" Diameter Stainless Steel Universal Exhaust Hanger : Amazon.com : Automotive

These are all the tools you'll need:


Pic of the before (yeah, it's dirty, sorry):


Underside pic of the cutable section:


Remove the 4 15m bolts to the diff plate:


Jack up the rig to get the sawzall under the jeep:


Remove the plate:


Measure twice, cut once:


After the carnage:




p.s. Don't forget to support the muffler or it will fall on your face. Ask me how I know.


The cutout fitted:




Dissasemble the universal hanger and trim off the end. Obviously, if you had access to a welder, this wouldn't be so ghetto rigged:




Add some bolts and washers, a lil bit of loctite and yer set. I chose not to use the hanger as after a solid shake test, the exhaust seemed to hang well adding no stress to the full exhaust without the hanger.

Now, with the diff plate back on, I found it created some tight quarters for the motorized unit so I'm planning on modifying it a tad to fit the unit next weekend. Right now, I'm running full open and at idle, it's bone silent. Weird for a V6 =\ But at full throttle, it sounds like a V8 from hell *score*

The cutout added no extra clearance issues as it doesn't drop below the diff plate. The images are a bit decieving.

And of course, video:
http://www.jkrew.com/jeep/exhaust/exhaust.mov

Cheers.

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Old 04-15-2013, 09:25 AM   #2
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Wow, beautiful work. I am definitely subscribing to this thread. Great ingenuity and execution. Could you tell a significant difference in performance?
Love that sound.

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Old 04-15-2013, 09:50 AM   #3
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Yeah, I'm gonna say maybe an extra 5-10HP after 3k. Throttle response is super quick after the initial climb to 3k. I'm going to cap the cutoff off and do a baseline dyno run this weekend just to get some real numbers. Stay tuned.
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Old 04-15-2013, 10:21 AM   #4
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People like you are dangerous. Making helpful, explanatory posts like this makes me think that I too could do stuff like this to my Jeep, then I end up surrounded by bits of car and trails of blood across my driveway, before in the end having to call my buddies who actually know what they're doing and buy them beer and put up with their mockery as they fix the shambolic mess I've made.

But thanks.
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Old 04-15-2013, 10:36 AM   #5
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hahahahaha Totally understand. Been there. Easiest way is to just jump in and learn. Start on a saturday when you have plenty of time to mess up, run to the emergency room etc etc. Nothing beats a project that you did yourself, even it if takes forever, it will be quicker with the next project

If you think this one's hard, wait till I swap in an Audi Q7 TDI engine in the bay in a few weeks haha

I'd rate this project as a fairly easy one. Once the exhaust portion is cutout, the rear pipe has a few inches of play front and back so it's easy to fit the cutout. Then it's just a matter of wrenching the exhaust clamps in place and making sure fitment is good.
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Old 04-15-2013, 11:02 AM   #6
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Old 04-15-2013, 11:08 AM   #7
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Thats a first, adding an electronic dumptube to a JK. Props for the work. The shorter dump will definitely give you a better throttle response and a few more ponies at the top end, so kudos, and the mod isn't a total waste. Nice writeup!
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Old 04-15-2013, 11:09 AM   #8
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So basically you have no muffler (if you flip the switch)? Doesn't seem street legal.
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Old 04-15-2013, 11:17 AM   #9
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So basically you have no muffler (if you flip the switch)? Doesn't seem street legal.
It is if only used offroad.
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Old 04-15-2013, 11:20 AM   #10
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Old 04-15-2013, 11:42 AM   #11
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No offense to the guys with exhaust sytems here but a catback or an axle back exhaust system literally does nothing for your Jeep. It actually takes away a few HP and makes your rig sound like a Honda.


Cheers.

I got a good laugh out of this. First of all lots of people redo the exhaust to get it away from the rear. Who wants that big oll ugly muffler hanging down and and allways geting smashed up on and draging on things?
.
Wouldnt this look great with a trash can sized muffler sitting back there all dinted up?

Very few people that mod a JEEP care about WOT. Most think it is stupid to give up a HUGE amount of low end to gain a little bit if WOT.

You say that any exhaust mods make a jeep sound like a Honda, and I say a dumped exhaust with no muffler sound like a POS to anyone but a teenage boy that is hard of hearing.

I am sure you love this mod and I have done it on a streat truck before, BUT it had headers wraped around a big block. And if you have never found a exhaust system that you liked that is understandable, but dont try to say that something
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literally does nothing for your Jeep.
if you dont like it.

Some might even say that installing a cutout literally does nothing for your Jeep. It actually takes away a few HP and makes your rig sound like a Honda.
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Old 04-15-2013, 11:54 AM   #12
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Ahhhh, I love the internet
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Old 04-15-2013, 12:04 PM   #13
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I applaud the effort, what I question is the dismissal of all the R & D aftermarket exhaust companies put into their products being written off as "useless".
Are there millions of dummies out there buying aftermaket CAI / Exhaust products ? JMO !
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Old 04-15-2013, 12:10 PM   #14
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Ahhhh, I love the internet
Me to. The fact that people thank that anything someone else does that they dont like or agree with is pointless, and there idea is the only good one is good for a laugh from time to time.

Don't get me wrong I didnt get butt hurt buy you post (as a mater of fact I thought it was cute) I was just simply pointing out that there is a point to doing exhaust mods.

It was a good wright up after the first 100 words or so at least.
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Old 04-15-2013, 12:40 PM   #15
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I'll give props to the OP for doing a good write up on his mod. Semi original on a JK and some folks will really dig it!

Not for me though, lol. I had exhaust dumps on my '68 Charger I used to bracket race.

I'm probably getting too old, but I like having lots of torque and a nice quiet exhaust when I'm finding my peace out on the trail.

Good job on the write up though, so enjoy!
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Old 04-15-2013, 12:41 PM   #16
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Yea, having a dumptube will gain you a few top end ponies, but will cost you a bunch of low end torque.....not something you can call "useful" on a Jeep. If you did this mod for power gains, you missed the mark. For sound, that's a different story.
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Old 04-15-2013, 12:47 PM   #17
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It is if only used offroad.
Hahaha wait are you saying it is street legal if used off road? lol

I agree, it is a great write up and a cheap mod for those that want that sound. Me personally, I like how the stock Jeep sounds. Maybe a little deeper but nothing I would spend money on to change.

With this mod, it sounds like a racing street truck. I do like the sound but not really on a Wrangler especially since they aren't meant to be WOT...unless you are stuck in mud and trying to signal for help
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Old 04-15-2013, 01:02 PM   #18
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Yea, having a dumptube will gain you a few top end ponies, but will cost you a bunch of low end torque.....not something you can call "useful" on a Jeep. If you did this mod for power gains, you missed the mark. For sound, that's a different story.
OP reckoned that it also produced an extra couple of MPG. For a Jeep that's primarily used on road, that's a good enough reason in and of itself.
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Old 04-15-2013, 01:08 PM   #19
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OP reckoned that it also produced an extra couple of MPG. For a Jeep that's primarily used on road, that's a good enough reason in and of itself.
But it isn't legal on road.
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Old 04-15-2013, 01:09 PM   #20
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But it isn't legal on road.
Nor is driving over the speed limit, or making a turn on red without coming to a complete stop, or answering your phone, or a whole bunch of other things that we all do.
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Old 04-15-2013, 01:21 PM   #21
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People tend to get touchy when their mods get bashed. Understandable. I wouldn't go this route but you did and you love it so that's what matters. And maybe other people will see this and love it too. That's what forums are for.
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Old 04-15-2013, 01:22 PM   #22
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... all I can say is, avoid mud and water
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Old 04-15-2013, 01:27 PM   #23
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Hahaha wait are you saying it is street legal if used off road? lol

I agree, it is a great write up and a cheap mod for those that want that sound. Me personally, I like how the stock Jeep sounds. Maybe a little deeper but nothing I would spend money on to change.

With this mod, it sounds like a racing street truck. I do like the sound but not really on a Wrangler especially since they aren't meant to be WOT...unless you are stuck in mud and trying to signal for help
I said legal only if used offroad. Never said anything about street legal.
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Old 04-15-2013, 01:27 PM   #24
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... all I can say is, avoid mud and water
Why? So long as the engine is running, you will have zero issues.
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Old 04-15-2013, 01:29 PM   #25
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Why? So long as the engine is running, you will have zero issues.
Correct. No different than a muffler being exposed.
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Old 04-15-2013, 01:47 PM   #26
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"back pressure" in any form is bad. the stock exhaust system is tuned for the most power/efficiency by maximizing exhaust scavenging. Scavenging helps to fill the combustion chamber. By altering the exhaust, you alter the effective scavenging, thus reducing engine efficiency....... and loosing HP.
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Old 04-15-2013, 02:17 PM   #27
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"back pressure" in any form is bad. the stock exhaust system is tuned for the most power/efficiency by maximizing exhaust scavenging. Scavenging helps to fill the combustion chamber. By altering the exhaust, you alter the effective scavenging, thus reducing engine efficiency....... and loosing HP.

Sorry chris but these statements are just not accurate.

Back pressure is not always bad and in many cases, some is desired in order to dictate low rpm power band.

The stock exhaust is tuned for noise level and emissions first. Power and efficiency are not highest on the list.

Stock exhausts do not maximize scavenging. Especially on the 4.0's and 3.8's. The 3.6's come much closer though. Seeing as they are part of the head now though, that leaves the aftermarket very little to work with in terms of new header design.

Scavenging helps empty the combustion chamber. It allows it to be refilled with a higher ratio of fresh air due to less already burned exhaust being "left over" from the previous combustion cycle. This is assuming the intake side is up to the task.

Altering exhaust doesn't necessarily mean you will lose hp. It really depends on many factors. The most common change when increasing the flow of exhaust is a higher peak hp number at a higher rpm than before. As for torque, that can go either way too. At the least, it will change the rpm at which peak torque is made, and usually it will be a higher rpm.
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Old 04-15-2013, 02:32 PM   #28
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Just to be clear, and I hope some dyno charts can show some positive numbers on both HP and torque, due to it being full open now with minimal restriction, there is a minor lag from pedal to initial "launch" in driving. That's pretty much the biggest drawback in this mod. Torque feels just the same as using the stock exhaust.

To be honest, I had a V6 turbo, 3" downpipe to a cutout and at idle, it sounded incredible. After this mod, I was expecting to hear something at idle yet the wierdest thing is, is that it's almost stone silent. It does go to show how and why Jeep designed this engine. As it's basically a tweaked minivan engine, it's built to be efficient as possible yet provide the torque when needed.

I realize this is an enthusiast website so a lot of you own Jeeps as weekend toys/serious crawlers. But a lot of us daily drive on 33's. I wanted something that would let me hear my engine a little more and give it a more aggressive tone. If I want peace and quiet, I drive as I normally do. If I want something louder and ballsy, I stand on the gas pedal. I think it's a nice combo of the two. Obviously in the video, I wanted to show the most dramatic result as possible so I revved it like a hoon.

I'm 36, my douchebag days are long over =)

No hate on anyone here, just trying to provide some different ways of enjoying our JKs *peace sign*
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Old 04-15-2013, 02:59 PM   #29
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Nor is driving over the speed limit, or making a turn on red without coming to a complete stop, or answering your phone, or a whole bunch of other things that we all do.
Not exactly sure what your point is by saying this. Are you saying because some people drive over the speed limit we can just start breaking other rules and laws?

Quote:
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I said legal only if used offroad. Never said anything about street legal.
Oh no I know. I was just being funny because it sounded weird. I said it didn't seem street legal and you said it is if used off-road. It is street legal off-road lol Just made me laugh.
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Old 04-15-2013, 03:09 PM   #30
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Not exactly sure what your point is by saying this. Are you saying because some people drive over the speed limit we can just start breaking other rules and laws?
No, I'm saying it seems a bit daft to object to someone making a modification that makes the vehicle capable of being operated illegally, when they come out of the factory already built with the capability to be operated illegally. How many other mods do people have that are technically illegal on road? I'd guess quite a few. I'm not sure why you're objecting to the legality of this one specifically.

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