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TJ 4.0 cat / muffler delete

ChrisTothC T

Member
Joined
Aug 12, 2019
Messages
28
Location
Sterling, VA
Hey, so I have '99 TJ 4.0 and I'm considering doing a muffler or cat delete, not choosing a straight pipe since I had that on my 93 YJ 2.5 that and my neighbor complained about his windows shaking every time I started it up haha. Does anyone have any videos of their TJ 4.0 with a cat or muffler delete? Looking to get an idea of what it sounds like!

Thanks in advance!
 

Airjunky

TJ Enthusiast
Joined
Dec 13, 2018
Messages
320
Location
Liberty Lake WA
Here.....
 

Lou

TJ Enthusiast
Joined
Jun 16, 2016
Messages
181
Location
Long Beach
I have the stock mini cats, a maganaflow cat into a banks muffler dumping after the transfer case skid and I absolutely hate it. I would spend a fair bit of cash to get a tailpipe again.
 

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
40,688
Location
Salem, Oregon
Deleting the car will definitely give you a big increase in sound, I can tell you that as when I deleted mine it was a lot louder!

Deleting the muffler, now that's just stupid. You'll sound like a rice rocket basically.
 

GASnBRASS

TJ Enthusiast
Joined
Apr 6, 2017
Messages
263
Location
Minnesota
It's a straight six, which means the firing pulses will never sound like a V8. They might sound ok at idle but more 'ricer' at throttle. Only one inline 6 setup sounds 'throaty", the early ford mustangs with the 200ci six. Something about the firing order and using a shared 3/4 exhaust port so when it has a true dual exhaust each pipe actually receives four pulses.
 

GASnBRASS

TJ Enthusiast
Joined
Apr 6, 2017
Messages
263
Location
Minnesota
On second thought, the jeep 3/4 exhaust ports are next to each other. You could merge the ports together in the header and then into a dual pipe exhaust to duplicate the same effect, but you would still need dual upstream and downstream O2 sensors. I'm not sure if the PCM has the ability to accommodate that requirement. Sounds like an awful lot of work just to get a throaty exhaust.
 

rasband

J.ust E.xplore E.very P.lace
Supporting Member
Joined
Sep 11, 2018
Messages
1,290
Location
Highlands Ranch, CO
I really liked @jodomcfrodo 's sound, it was more subtle but enough to sound nice (and not annoy me being near him). Perhaps he can share a clip, I think it's a magnaflow muffler.
 

jodomcfrodo

TJ Addict
Supporting Member
Joined
Feb 24, 2016
Messages
1,689
Location
Evanston, IL, United States
I really liked @jodomcfrodo 's sound, it was more subtle but enough to sound nice (and not annoy me being near him). Perhaps he can share a clip, I think it's a magnaflow muffler.
That is surprising to me. My borla touring exhaust sounds very quiet to me, almost stock. My previous banks exhaust was much louder. I’ve considered switching back to the banks and deleting my cat as well.

But take this with a grain of salt. I’m an obnoxious 20 year old that likes irritating the general Chicago population with my hick-mobile.
 
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Reactions: rasband

Mumblewood

Member
Joined
Oct 9, 2019
Messages
82
Location
Renton Wa
I could never run no muffler in Washington state. The Forrest service will sometimes setup random checks out on trails to make sure your running a spark arresting muffler and if not, BAD News. Big tickets and or impounded rig. We hate Forrest fires.

I run a spin tech muffler that I had to shave and reweld just to fit with my 3 link bars. Would like to go with a different style(round) for a better fit, but I do like the sound of it. Not very much louder than stock , just enough so I can hear it while driving.
 

Nimbley

TJ Enthusiast
Joined
Jun 21, 2018
Messages
147
Location
Somewhere in the desert
I hollowed out the cat on my old xj due to the rattling driving me crazy. The catalyst had burnt out at about 200k miles and sounded like rocks rattling in a can. After that it definitely had a more throaty sound that I liked. To me all inline 6 engines sound like a tractor anyway. Without a muffler is terrible. I’ve found few aftermarket mufflers that’s make a 4.0 sound good. I’ll keep my big quiet muffler.

I’ve heard old Camaros and Mustangs that sounded ok with split headers and dual pipes through turbo mufflers. All inline 6 engines have the same firing order. 1-5-3-6-2-4. Even diesels.
 
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OP
C

ChrisTothC T

Member
Joined
Aug 12, 2019
Messages
28
Location
Sterling, VA
I could never run no muffler in Washington state. The Forrest service will sometimes setup random checks out on trails to make sure your running a spark arresting muffler and if not, BAD News. Big tickets and or impounded rig. We hate Forrest fires.

I run a spin tech muffler that I had to shave and reweld just to fit with my 3 link bars. Would like to go with a different style(round) for a better fit, but I do like the sound of it. Not very much louder than stock , just enough so I can hear it while driving.
I see, also what size tires are you running? They look massive
 
OP
C

ChrisTothC T

Member
Joined
Aug 12, 2019
Messages
28
Location
Sterling, VA
I hollowed out the cat on my old xj due to the rattling driving me crazy. The catalyst had burnt out at about 200k miles and sounded like rocks rattling in a can. After that it definitely had a more throaty sound that I liked. To me all inline 6 engines sound like a tractor anyway. Without a muffler is terrible. I’ve found few aftermarket mufflers that’s make a 4.0 sound good. I’ll keep my big quiet muffler.

I’ve heard old Camaros and Mustangs that sounded ok with split headers and dual pipes through turbo mufflers. All inline 6 engines have the same firing order. 1-5-3-6-2-4. Even diesels.
It's very true about the muffler delete/straight pipe. The reason I'd like to get a more deep and throaty sound is because a big jeep should have a sound to match it lol
 
OP
C

ChrisTothC T

Member
Joined
Aug 12, 2019
Messages
28
Location
Sterling, VA
That is surprising to me. My borla touring exhaust sounds very quiet to me, almost stock. My previous banks exhaust was much louder. I’ve considered switching back to the banks and deleting my cat as well.

But take this with a grain of salt. I’m an obnoxious 20 year old that likes irritating the general Chicago population with my hick-mobile.
I'm so into the Borla's because of their aggressive sound, but I know it'd bother the hell out of my neighbors lol