Exhaust Fumes w/ Rear Window Removed - 1993 4.0 L6 - JeepForum.com
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Unread 03-19-2014, 06:44 PM   #1
Stingray427
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Exhaust Fumes w/ Rear Window Removed - 1993 4.0 L6

Quick question:

I have stock exhaust setup with a turn down tailpipe exiting at the right rear of the vehicle (turn down faces downward and is pointing straight out rearwards) and I get a lot of fumes in the cabin with the rear window removed, any suggestions?

Thanks!

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Unread 03-19-2014, 06:54 PM   #2
superj
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Run side pipes.

There is nothing you can do. The wind travels under the vehicle while driving and then comes up into the low pressure area created by the big square forcing itself through the air. You can try routing the exhaust differently or getting a bikini top so air is going around the sides and pushing the fumes away but until your aerodynamics change, that low pressure zone behind the jeep will stay there and all higher pressure air will continue to move into it while moving.
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Unread 03-19-2014, 06:54 PM   #3
XxoSPARKSoxX
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Fumes

My suggestion:

Put the window back in....

Problem solved..

All levity aside, it is very common.

Updraft from the large, flat back side of the vehicle pushes fumes right into the cabin.

Jeeps are certainly not famous for being very aerodynamic.

Unless you have the whole top off or have a bikini installed where a lot of fresh air can rush through and carry those fumes out, you are pretty well dealing with the same issue most of us jeepers (I think I can speak for many here) deal with regularly..

Good Luck!!


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Unread 03-19-2014, 07:59 PM   #4
bpounds
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Keeping the front windows open or removed should help to keep a front to rear draft going. As long as you are moving.
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Unread 03-19-2014, 08:15 PM   #5
Stingray427
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Thanks to all for the very detailed answers!

What about dumping the exhaust in front of the rear axle? I have heard of this but don't know if it would help.
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Unread 03-19-2014, 09:09 PM   #6
Longview
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Quote:
Originally Posted by Stingray427 View Post
Thanks to all for the very detailed answers!

What about dumping the exhaust in front of the rear axle? I have heard of this but don't know if it would help.
That is what i did, but i have not ran my jeep since i have done it, (Not street legal yet) But i have my drain plugs out and i feel like it will just drift into the cab that way.
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Unread 03-19-2014, 09:36 PM   #7
Stingray427
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Anyone else dropped the exhaust in front of the rear axle to help with fumes?
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Unread 03-19-2014, 09:56 PM   #8
Reno72
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Ya, not just a jeep issue. Any car with a rear window that can be opened will say do not run it that way. Heck we had an old Buick station wagon that had that warning. There is a low pressure zone behind any moving vehicle (that's how race cars get into another's drag ) so moving the tailpipe further forward won't stop fumes from coming in.
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Unread 03-19-2014, 10:54 PM   #9
Stingray427
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Thanks, has anyone else done this with their exhaust and did it help with the fumes?
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Unread 03-19-2014, 10:58 PM   #10
NonRubicon
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Watch the following video (skip to the 3:43 mark to get straight to the point):


The flat boxy rear end of the Jeep tends to cause turbulence which curls the airstream back into the cab. The only reasonable solution is to crack open the front windows or remove the side windows to allow some airflow to reduce the vortex effect.

Or you can go this route
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Unread 03-20-2014, 03:46 AM   #11
90DesertTanYJ
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Running the exhaust out the side will help. Maybe not solve but will help. Make sure the end of the pipe clears the body by a couple of inches as well.
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Unread 03-20-2014, 10:02 AM   #12
TheGanzman
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Quote:
Originally Posted by 90DesertTanYJ View Post
Running the exhaust out the side will help. Maybe not solve but will help. Make sure the end of the pipe clears the body by a couple of inches as well.
The trouble with THIS (ask any Midyear Corvette owner with side exhaust) is that "at idle" (like at stop lights), the exhaust wafts into your open side window(s). Prolly the only REAL "answer" is to upgrade to OBD2 and a late model engine with FULL emissions and catalytic convertor; I'm guessing that you don't wanna go to THAT level of expense JUST to run w/o a rear window...
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Unread 03-20-2014, 10:10 AM   #13
JohnnyZJ
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had this problem big time in the last YJ. when i finally took it in to teh shop i found out it had the CAT removed. hence it smelled so bad.

with the last TJ i had, (with a CAT) it wasn't as bad and the JK we had was a non issue.

the YJ i have now (CAT in place) is 100% better than the YJ without the CAT.

i tried everything. only thing that really worked (for me) was putting another CAT on it.

if you still have the CAT is it functioning? if it is, then gonna have to get used to teh smell lol
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Unread 03-20-2014, 11:25 AM   #14
Stingray427
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Quote:
Originally Posted by JohnnyZJ View Post
had this problem big time in the last YJ. when i finally took it in to teh shop i found out it had the CAT removed. hence it smelled so bad.

with the last TJ i had, (with a CAT) it wasn't as bad and the JK we had was a non issue.

the YJ i have now (CAT in place) is 100% better than the YJ without the CAT.

i tried everything. only thing that really worked (for me) was putting another CAT on it.

if you still have the CAT is it functioning? if it is, then gonna have to get used to teh smell lol
I just added a brand new cat to my exhaust a few months ago and your right the smell is less noticeable but still there.

Sounds like this is just one of those things about driving a Jeep that you learn to live with.
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Unread 03-20-2014, 02:42 PM   #15
fishadventure
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You learn to live with CO?! The exhaust smell is not the issue LOL

I remember when cats and no lead were new things- we all thought they stunk so bad! We were used to the non-catalyzed exhaust smell.
Now everybody is used to the catalyzed exhaust and they think non-emissions-equipped exhaust smells bad.

Either way carbon monoxide can kill you...OBD2, OBD1, or no cat whatsoever!

I still like to smell nitro racing fuel in an old muscle car
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