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post #1 of 25 Old 01-25-2012, 10:25 PM Thread Starter
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straight pipes

i live in fl. we have no smog or emissions test. whats stopping me from running straight pipes?
i define straight pipe as header and pipe no cats.
or cutting the cats and putting the muffler right behind it.
or put a muffler directly behind the cats.

ive heard jeeps that have the aftermarket mufflers and exhaust. its still very quiet. i think it loses a lot of the pressure by the time it gets to the muffler to actually have a good sound. so cut out all the extra stuff where the pressure is higher?
cause i know i step on it and i hear the exhaust under the passenger floorboard.not in the back. at all.

im taking my muffler off next week to see how it sounds without it.


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post #2 of 25 Old 01-25-2012, 11:02 PM
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It's going to sound like an effed-up minivan.

2-door, locked, 5.13's, 37's.
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post #3 of 25 Old 01-25-2012, 11:23 PM
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Straight pipes will more than likely sound like ass with the 3.8 dude.

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post #4 of 25 Old 01-25-2012, 11:32 PM
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Not to mention you'll likely LOSE power.

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post #5 of 25 Old 01-25-2012, 11:35 PM
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As I mentioned elsewhere. You'll lose power. It will sound like ass.

This is a bad idea.


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post #6 of 25 Old 01-26-2012, 01:36 AM
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If this question is related to your JK, don't do it. The shit is so computer controled with sensors everywhere its just not gonna run right imo.

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post #7 of 25 Old 01-26-2012, 02:08 AM
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The JK's need the back-pressure in the exhaust system so as mentioned if you do this you will lose power. This is unfortunately true for a lot of the modern engines. They're all designed to be 'emissions friendly' which means they're designed to perform with the cats and mufflers in place, without them many will see a loss in power. Not positive but you might even have trouble keeping the engine running right without cats and 02 sensors as the ECM uses the readings to determine if the motor is running rich/lean and thus adjusts the fuel-air mixture accordingly. On another note, I've heard even going to a true dual exhaust on the JKs results in a loss in power because of the loss of back pressure.

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post #8 of 25 Old 01-26-2012, 06:05 AM
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You only have hamsters under that hood to begin with. And the muffler is the only thing that stops them from escaping. You'll loose one without that it!

There's a guy in town that took his muffler off. It sounds like shit!
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post #9 of 25 Old 01-26-2012, 06:24 AM
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I don't care for the sound of open exhaust and have heard it on a JK. It's a low displacement, low overlap little minivan motor..The 3.8L will also benefit from the backpressure.

I've gotten some comments on my knock-off flowmaster. Sounds alright.

When I was 18, I ran around with my 'Cuda dumped at the headers in Vegas. Sounded awesome, but it's annoying as hell. You don't want a daily driver that is annoyingly loud everywhere you go. It gets old on long highway trips..

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post #10 of 25 Old 01-26-2012, 08:08 AM
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We dont have emissions either and I thought that since the stock 08 has 4 cats, might as well get rid of them and make some more power so I bought the Borla long tube headers - essentially exactly what you are asking for.

First off, I lost 10 HP as measured on the dyno right off the bat. I tried emailing Borla about this several times but no ever responded.

Second, good luck trying to dial in the sound. I matched it with a flow master 44 and at idle and lower PRM, it sounded great. Get into the higher rpm band, and you have a screaming prepubescent boy. I added an additional magnaflow reasonator and it got much better but still not perfect.

As for the electronics, you can turn all of that stuff off with a Diablo.

Based on my experiences, I would not spend the money on an exhaust side modification to this 3.8.
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post #11 of 25 Old 01-26-2012, 08:10 AM
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Quote:
Originally Posted by RiverCityOffroad View Post
As I mentioned elsewhere. You'll lose power. It will sound like ass.

This is a bad idea.
So naturally he's gonna do it

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post #12 of 25 Old 01-26-2012, 08:37 AM
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Read some of Offroadpr's early posts. He cut out the cats and faked it with extended bungs for the o2 sensors. Might be a fluke but the engine blew up in short order.

Like everybody else said, modern vehicles need all that stuff in place to run properly. You don't gain anything by removing it.

If you gotta do something just stick a flowmaster in line, get rid of the trash can muffler and call it a day.

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So naturally he's gonna do it
Hahaha

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post #13 of 25 Old 01-26-2012, 08:45 AM
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Did anyone order rice?



Trying to explain back pressure, valve overlap, and scavenging to people who don't really understand the mechanics of engines can be pretty difficult.

Corey, don't, that is all.

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Last edited by JKCTAZ; 01-26-2012 at 09:04 AM. Reason: Lap, overlap, I knew what I meant damnit!
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post #14 of 25 Old 01-26-2012, 10:11 AM Thread Starter
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Lol I'm not gonna do it. Might cut it after the cats. Put a muffler there. If I don't like the tone ill put on in the back lol. It might get the deeper tone at high rpms. Most are looking for. I'm trying to get it to be louder lol


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post #15 of 25 Old 01-26-2012, 10:50 AM
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I went from a flowmaster to no muffler, I still have the cats, but I notice no power loss, actually the opposite. The back pressure the motor needs is provided by the 4 cats. I got a noticeable increase in power with muffler removed. It's a little louder than the flowmaster but not much, at our last jk run to the highlakes nobody even knew I had no muffler


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post #16 of 25 Old 01-26-2012, 06:23 PM
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Quote:
Originally Posted by THECHAD View Post
I went from a flowmaster to no muffler, I still have the cats, but I notice no power loss, actually the opposite. The back pressure the motor needs is provided by the 4 cats. I got a noticeable increase in power with muffler removed. It's a little louder than the flowmaster but not much, at our last jk run to the highlakes nobody even knew I had no muffler


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same here. except i just went to no muffler from stock. eventually i may put a FM in or something, but it sounds good to me and a few people have complimented on it too. i didnt notice a power loss or gain removing the muffler, but all my cats are still there.

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post #17 of 25 Old 01-26-2012, 06:37 PM
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Originally Posted by leman View Post
same here. except i just went to no muffler from stock. eventually i may put a FM in or something, but it sounds good to me and a few people have complimented on it too. i didnt notice a power loss or gain removing the muffler, but all my cats are still there.
X2 me and leman have been running this way for a coons age.. I think it sounds alright I took mine off bc I kept hitting it on stuff
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post #18 of 25 Old 01-26-2012, 06:45 PM
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Originally Posted by RiverCityOffroad View Post
As I mentioned elsewhere. You'll lose power. It will sound like ass.

This is a bad idea.
where is stigo with some sweet audio clips!?
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post #19 of 25 Old 01-26-2012, 06:57 PM
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where is stigo with some sweet audio clips!?
Lmao!! I didn't want to throw him under the bus. I meant to ask him if he was going to correct that before KOH.


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post #20 of 25 Old 01-26-2012, 11:09 PM Thread Starter
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lol i asked stigo for a video. maybe hell post it here too lol


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post #21 of 25 Old 01-27-2012, 03:31 PM
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Mine was straight piped (after the CATS) for a couple of days after I did my long arm conversion, and it sounded like a lawn tractor gone horribly wrong!
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post #22 of 25 Old 01-28-2012, 12:43 PM
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Here's a video of my 2012 with the muffler removed.

Jeep JKU Pentastar Muffler Removed Startup - YouTube
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post #23 of 25 Old 01-28-2012, 01:15 PM
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Did you reinstall it? Kinda sounds like an outboard out of water

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post #24 of 25 Old 01-28-2012, 01:25 PM
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i chopped my exhaust right past the cats and threw in a FM 44 which is basically under the driver seat and then ran a new pipe out to the back. my buttdyno says theres a little more power, the tone isnt too bad either. sounds a lot deeper than in ranjrs video and isnt too annoying on the highway.

the "brain" of the JK wasnt too happy with the new muffler at first, ran a little rough for the first few minutes but has been fine since


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post #25 of 25 Old 01-28-2012, 01:28 PM
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Quote:
Originally Posted by Goodysgotacuda View Post
Did you reinstall it? Kinda sounds like an outboard out of water
I installed the new Dynomax dual tip kit.

Jeep JKU Rubicon Pentastar with Dynomax Muffler Kit 39510 F - YouTube
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