I have a friend (oh no, an 'I have a friend' thing) that has a cherry bomb on his xj. It sounds pretty good. He said he hasn't noticed any change in torque or hp. I want to say it's an 18". (?)

 

back pressure is only paert of the story.Base your decision on what else you have, some back pressure is is good a drag car has a blower and valves yhe size of a dinner plate, 2 ft ,4" pipes are right for it{also glassPak's are illegal for street use where I live.altho rarely enforced.}

 

I just ordered a flowmaster 10 series off ebay for $65 which was $30 cheaper than any store i went to, the local speed shop wanted $90 for it so i thought it was a pretty good deal. But the 10 series is the loudest muffler flowmaster makes, so if your looking for loud and good toned flowmaster 10 series would be a good choice. Heres a clip of it on a 4.0...

 

and no matter what the length of the glasspack a muffler will offer more back pressure cause a glass pack is a straight flow through design and the mufflers have chambers/baffles or whatever and i would def recomend getting a tail pipe having a turndown under the jeep you will get exhaust fumes inside the cab when idling at a stop or even when your crawlin down a trail

 

X2 i have a turndown now and hate it, everytime i let it sit idleing all you can smell is fume, im getting mine ran out the back ounce my muffler comes in.

 

i had a flow master exhaust with 3 inch pipe on it and it sounded like a pos rice burner so i had a stock muffler and stock size exhaust put back on it and it has more torque now but less hp on the bottom end. so the back pressure will effect it.

 

I've seen some XJs on youtube with glasspacks and in my opinion, they don't sound the greatest. The glasspacks give the exhaust a raspy tone which is what you don't want because it makes your XJ sound like a ricer. A glasspack is better suited on a vehicle with a V8 and maybe some 4 bangers but never on a 6 cylinder. You're better off taking the more expensive route and buying yourself a performance muffler. I'm running a Flowmaster 40 with a single inlet and dual outlet. It sounds great but it's a little on the loud side. Now about the outlets; if you're going to do some rock crawling, don't get dual outlets. They will just get smashed or hung up on rocks at some point unless your Jeep has tons of ground clearance. Your best bet is to do a single inlet/single outlet muffler and run your tailpipes out in front of your right rear wheel so it is never wedged between a rock and your rear bumper. I DD my XJ, take it muddin, hit the two tracks, go to the sand dunes, and do some other mild wheeling, but nothing close to rock crawling. I can run duals because I don't run as much of a risk as you do lol. Now with the outlets being larger or smaller, I wouldn't mess around with the sizes. Go with the same tail pipe size as the rest of your exhaust. There is really no reason to go larger or smaller. I'm pretty sure with the I6, you want some backpressure to keep your low end torque up. If you reduce it, you'll lose all the torque.

 

Sweet, that is a wealth of information. I'm definitely gonna reconsider keeping the tailpipe on now, and I'm leaning toward the muffler over the glasspack.

Does anyone know where I might be able to get a less restrictive downpipe than the stock "bent" one?

 

i never had issues wit my turndown pipe but then again i have NO rust on my xj at all so no hole in the floorboard for fumes to get into

 

my xj with a straight pipe then glasspack sounds nothin like a ricer,it pops wen i let off the gas and lopes wen the motor is at 210*(nothin like a ricer)

 

Then why even bother with an exhaust manifold?

 

its run hot and burn valve,drag racers use them for more power but they also rebuild there motors every run,but you do need some exhaust pipe but theres not a need for a exhaust that goes all the way back,mine runs better and better mpg with staright pipe and just a 27" glasspack,and dumps out b4 the rear axle,less pipe and less restriction is better but no pipe is real bad for the motor,its needs somethin to re-direct the heat away from the motor

 

yeah mines a california car so i have no rust either but all it takes is the windows down or a bad seal on the rear hatch and itll find its way in there the worst was when my exhaust manifold was cracked and i would turn the heater on now that was bad lol

im not sure what size tube xj's are stock but if you do go up maybe just go up a 1/4 to 1/2 "from the cat back and im pretty sure the only fix for the factory down pipe would be to have a muffler shop make you a new one without the dent in it

 

oh well never had issues wit mine yet,but im not that worried about it until that happens to me lol

 

I understand the less pipe(saves you some money), and not to be an *** just curious, does it really make that big of a difference in restriction going the few bends over the axles and out? i mean i understand that thinking on a drag car cuz they can use every single bit of power there is to get, but on a jeep? I have the turndown in front of the axle now and i just cant stand the fumes when i let it idle, especially with my kid on board. Not trying to start any arguements just my opinion.