General exhaust question

[Classy Comanche]

So I plan to have my exhaust done relatively soon. Part of me wants to have a bit of fun and cut the existing exhaust off and temporarily straight pipe it then have exhaust put on. But I'm very hesitant because I've heard rumors that it messes with gas milage, throws back pressure off and could even backfire and mess the engine up. I guess what I'm asking is has anyone straight piped their Comanche/Cherokee? 

[gogmorgo]

I drove mine for a little bit with the exhaust dumping out the manifold. 200 miles to the city and back. Wasn’t too bad at idle but touch the throttle and you regretted it. Yeah, gas mileage tanks, because it stays in open loop without an O2 sensor plugged in. I put the down pipe and O2 back on when I got back, then drove 200 miles in the opposite direction. Still loud but not as bad, mpg came back up. I don’t remember whether there was much change in mpg or anything when I put the muffler back on. 
This was with a 4.0/aw4. I wouldn’t want to drive my 2.5 on the highway with no exhaust. 3k rpm is bad enough with a muffler. 

[Classy Comanche]

Ha, well that is certainly nice to know, yeah I'm not sure I want it that loud. I do prefer to hear my radio as well and not sound like a can of angry yellow jackets screaming down the road at 35. I'll stick to the ol' muffler with hole in it for now. I also prefer decent MPG and not "I can't pass a gas station without filling up". Already experienced that in my father's SRT8 SuperBee. Least it gets smiles per gallon

[jeff351]

Funny story, somewhat related.

Back in the 90s I was working on my 1970 Torino GT (351C, 4spd) and ordered set of headers. Naturally after taking the exhaust manifolds off and getting everything ready, the headers didn't fit. And I had to go to work in a few hours. 

I tell ya.... driving a V8 car with open exhaust straight out the heads is the definition of loud. Managed to do it for several days without the police taking notice. 

[Classy Comanche]

Ah man yeah that absolutely doesn't sound fun. Probably sounded amazing at a standstill. Yeah I know I've heard a downpipe on a 1971 Plymouth Cuda and I swear I thought my ears were bleeding it was so loud. So for now I'll shy away from the straight pipe idea. It's a fun thought to entertain for sure. Fun until you realize it's a vehicle you must drive on the road. And through town.....past a courthouse and police station. But cool story! That definitely gives me more to work with. Thank you!

[cruiser54]

Go have some fun and quit worrying. 

[pizzaman09]

Nothing wrong with running the exhaust with nothing after the O2 sensor.  Some vehicles sound amazing, others like trash with such a setup

[Classy Comanche]

Oh it's very tempting. The only thing that keeps me hesitant is that the troopers and city police are hot around this time of year. I even had a trooper riding my tailgate on my way to work because I was going 7 below the speed limit. I'm driving a brick on wheels lol, it ain't fast by no means. I'm just worried I'll get pulled for having no exhaust. I've never been pulled before so there's that. Troopers really like to ride behind me. Dunno if they are looking at my  truck or seeing if I do something dumb to give reason to ticket me. Who knows

[Big_Mark]

I was driving mine with what amounted to a straight pipe setup until a few months ago (2 years now?) the PO has cut off the cat back and replaced it with a straight pipe and a flowmaster muffler. Response was quick, no backfiring unsure of mileage as I wasn't keeping track.

After getting a new cat and pipe (I kept the muffler) i noticed a change in the response and powerband. Also under compression (letting off the gas to slow down to turn into my street) I heard a bunch of "POP POP POP" coming from under my feet (?)

I'm sure it's the cat in there that made the changes. Over time I've gotten used to the change, get great mileage and even the popping has reduced somewhat.

[Classy Comanche]

Heavily looking into it. Definitely getting some high dollar exhaust when the time comes. I should also mention. On YouTube if you look up "1988 Jeep Comanche straight piped" a video will pop up of a street Comanche. Only one I've ever seen. Has like side skirts/body kit? I could be wrong but that really made me full screen the video and go "wait wait wait...hang on" and look at it. I know that's up someone's alleyway. I know like 100 of them were built or something like that. Maybe he's in the group? Maybe he lives near one of you fellas. Don't mean to deviate....but it's sorta on topic?

[fiatslug87]

49 minutes ago, Classy Comanche said:

Troopers really like to ride behind me. Dunno if they are looking at my  truck or seeing if I do something dumb to give reason to ticket me. Who knows

They’re just admiring the Comanche.

[Classy Comanche]

I reckon that's correct. At one point and time I was riding around with my tags out 5 months. They had every right to stop me and ticket me. But they just rode my bumper or either got in the lane beside me and cruised a bit ahead, behind or right beside me. What's funny is when the new jeep gladiators come weaving in and out of traffic to catch up and try to figure out what in the world your driving. I do get thumbs up from a lot of fellow XJ Cherokee's  or a quick horn beep and lots of thumbs up from YJ owners. Anyways sorry for the off topic lol.

[Minuit]

I've driven my truck a grand total of about 5 miles with the exhaust dumping after the converter right under the cab and that was enough for me. I would class it as "hearing protection required" loud and I'm quite glad I just had to get to the parts store to get what I needed to hook my muffler up. We could go into the fluid dynamics of exhaust systems and I could tell you that you may or may not lose a handful of horsepower and you may or may not notice that, but by no means will it hurt anything. As long as your O2 sensor is hooked up, have at it. You'll probably hate it though. It's something every car guy should do for fun at least once.

[Classy Comanche]

Very true. Been listening to 4.0 straight pipe XJ and MJ's. They have a really mean tone to them. Sounds almost as good as a V8. Almost. If I do it I'll be excited to try a cold start in this 20°-35° weather. My neighbors for sure will hate me

[Pete M]

my neighbor straight piped his chevy truck.  I now hate him.  not sure what he needs to go get at 1am, but it wakes me up every single time.  even if he tries to idle out of the driveway, he can't get up that big hill at idle and the exhaust points right at my bedroom window.   

[Classy Comanche]

Yeah I got a straight piped civic that lives on my road. I think he works 3rd shift. Leaves about 12AM every night. I feel you there @Pete MI really do. So I think i may overall consider my neighbors and hearing safety since I'm "that guy that has cool truck down the road, ride by and you'll see it". Rather not be the "annoying guy with a cool truck and obnoxiously loud exhaust". It's so tempting as said. But I'll consider the neighborhood and my hearing protection. Already work in a loud facility, this wouldn't help matters lol. Nonetheless I love to hear feedback and your guy's experiences with the 2.5 and especially the 4.0 straight pipe or muffler delete. After all its a grocery getter. If I did a straight pipe it'd be like a bear with no teeth or claws. "Oh God you hear that! That sounds like a race car!" Then out turns a little faded red jeep truck. In terms we use modern-day "all bark no bite"