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Straight pipes on 4.0

3K views 16 replies 12 participants last post by  Michaelgoesrawr 
#1 ·
I just put a straight pipe on my jeep and was wondering what the excessive gas smell could be when i pull it into my garage. What could be the cause???
It smell richer than when i had the aftermarket exhaust on it.

And is this a bad thing or a good thing?

btw it sounds awesome for a I-6
 
#2 ·
its sounds terrible i did it on mine and hated it. do you have a cat? if not thats the answer to your gas smell. also you just cut your gas mileage is half. your motor is dumping a lot more fyel with no back pressure. your plugs and ot sensor wont last long either
 
#4 ·
Put a muffler on that rig, it needs some back pressure to operate properly.
I know you want the whole world to hear you driving down the street but honestly you are not going to impress anyone with a rig that sounds like azz.

Dwayne
 
#5 ·
A muffler delete is a little different than a straight pipe or test pipe. With a test pipe, you delete the cat, which is bad. A muffler delete is fine and will not cause any mech. problems, but the noise would be too loud for me.

The smell could come from running a little richer because of less back pressure.
 
#10 ·
To much fuel. Very simple solution. If you want more noise and a little more power go with a high flow cat and a good muffler. Your neighbors and local cops will love you for it. A 4.0 is not a performance motor and doesnt sound good with "open headers" and or no muffler.
 
#13 ·
the CAT does provide some back pressure and muffling. Not sure how much on a Jeep, but on an 06 mustang GT I ran no mufflers for the whole 2 years, perfectly fine, sounds good, not obsurd. removing the cat or running a Hi-flow cat will make it stupidly obsurd and you should be shot.

When I switched my 2.5L to a new header, I had a 4" gap I needed branched between the downpipe and the cat -> muffler, sounded like a top fuel lawn mower.
 
#14 ·
the CAT does provide some back pressure and muffling. Not sure how much on a Jeep, but on an 06 mustang GT I ran no mufflers for the whole 2 years, perfectly fine, sounds good, not obsurd. removing the cat or running a Hi-flow cat will make it stupidly obsurd and you should be shot.

When I switched my 2.5L to a new header, I had a 4" gap I needed branched between the downpipe and the cat -> muffler, sounded like a top fuel lawn mower.
:laugh::laugh::laugh:
 
#16 ·
i straight piped my 87 cherokee but it was a pos and i used it for an ice fishing rig. i guess it didn't matter to me if it sounded like it looked and i would never do that to a daily driver. it definitly sounds terible but i won't stick money into this jeep it's been on it's last leg for years but won't die
 
#17 ·
The gas smell when you're pulling into the garage could be attributed to the vacuum that's created behind the Jeep when you're rolling. At speeds it's not bad because the exhaust has enough power to break the vacuum, so you don't smell it. But when you get off the gas, it kinda gets sucked into the cab. Happens to me but I never park inside anything so it's never that bad. This popped up in the "what did you do to your YJ" thread a few weeks ago I think.
 
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