JimN

FWIW, had my local muffler shop install a hi-flow cat and Magnaflow muffler on my '99 XJ. All new tubing from the down pipe. Sounds and runs great, not too loud.

LiamLikeNeeson

Happened twice to me this past month. It slides back on to the pipe on the cat (with help from using a rubber mallet to bang it back on) but I can't tighten the bolts anymore. Oh and it's a cheap-o $15 muffler my dad installed pre-2000's and it's time for it to go. Need to replace exhaust pipe itself because it has a hole the size of 2 pennies next to each other near where it bends over the axle. Should I just go 2.5" for the pipe and new muffler? (As the whole system will eventually be 2.5") and what muffler should I get that is reliable and provides very good performance along with a subtle throaty tone without being too loud? (Shocker: 18 year old who doesn't want his ride to be loud). Or what mufflers should I stay away from?

Basslicks

I like 2.5". Seems to resonate better, IMO. Others may say otherwise, but mine is 2.5 from the downpipe all the way to the tail. I'm running a Thrush Turbo muffler (about $30 from Autozone or wherever) and it has a nice growl at idle and a nice tone on acceleration. With a carpeted Jeep you shouldn't really notice any drone either. Without carpet, just about anything except for OEM or Walker is going to be loud.

I've heard that the Thrush Welded sounds similar to a Flowmaster Super 40, but I can't verify that. I think that will be a little louder than what you're looking for though.

Thrush Turbo w/ 2.5" pipe and high-flow cat:


2.5" Straight pipe w/ cat:



2.5" Tailpipe w/ Magnaflow Cat, Flowmaster Super40 (Dukie964's jeep):

rconnorcook

Whats the best mild exhaust for a 4.0? everyone has told me flowmaster super 44, but i dont want anything too loud. I like the sound of the flowmaster 50

LiamLikeNeeson

Thanks Basslicks! I called the muffle shop and asked if they could do a 2.5 tailpipe and he said 2.25 was the max. And is the thrush muffler a straight through muffler (that you can see through) or has the foils inside of it (you can't see through it)? And does it sound more like a Cummins or kind of like a V8? (Just to get an idea of what it might sound like). I just want your opinion because it's sometimes hard to judge the sound from videos recorded with phones.

austinjoe13

Thrush Welded:


It is a chambered muffler like a Flowmaster. It has a V8ish sound I guess. It has a low pitch, drones a bit in town, but isn't bad at all on the highway.

Basslicks

It doesn't sound like either, to be honest. But it sounds better than any aftermarket exhaust on a V6 configuration. Ever hear an old Ford with the 300 online six and a lid exhaust? It kinda sounds like that. The straight pipe sounded like a Cummins. Flowmaster sounds like an 8 during certain rpms. But if v8 sound is what you're looking for, do an ls swap or by a grand Cherokee with a v8. The thrush turbo is a chambered and packed muffler. You can't see through it.

LiamLikeNeeson

Ok thanks. I might get a resonator tip if it drones too much. Or I can just suck it up lol

Ok thanks for clarifying that. I'll stick to driving my dads ZJ 5.2 liter V8.

Called the muffler shop guys to see how much I should expect for the tailpipe upgrade to 2.25" an they said $175-$180. Better than I expected.

SatiricalHen

if you want 2.5 go to another shop. 2.25 is factory size and you don't want to do exhaust multiple times if you don't have to... Just my opinion.

LiamLikeNeeson

I measured mine and it's 2" and its stock according to my dad who did any major fixes on it before I had it. And the estimate was just over the phone but I will be brining it in for an actual estimate and maybe the guy will then say 2.5 will fit.

austinjoe13

2.5" fit on my 89 and it fits fine in my 90. I will second that 2" is factory on the Renix models; both of mine had 2" pipe. Although, 2.5" livened them up a bit.

LiamLikeNeeson

I won't be doing a full 2.5" exhaust right away. Just the tailpipe and muffler for now. But what do you mean by more "livened up"?

EZEARL

This adapter would take you from 2" to 2.5":
https://www.summitracing.com/parts/wlk-41917/overview/

austinjoe13

Better throttle response, lower tone, and a little bit of power gain (just a tiny bit).

Otakuinajeep

It's a work of "basic" physics. a larger pipe the whole way through allows for the flow of exhaust gas to flow easier without causing backpressure on the engine. if the gas is hindered in some way of leaving the engine, it can put a bit of pressure back on the engine so the engine works a slight bit harder to push it out. That's why the, techically, best exhaust is a dump out as soon as possible (normally behind the front tires) because there are no limiters keeping the gas from getting out. A lot of horsepower in general is gained from improving the overall flow of the engine, something I'm learning as I work on my father's intake headers for his AMC 390 going into a 1969 SC/Rambler. The heads need to be ground down as the casting was very rough, leaving the intake and exhaust ports to have very rough walls that catch the air going in and out. Doing a good port 'n' polish gave the cast iron heads a considerable amount of HP boost. As I've gone through what I want to do for my stock+ exhaust setup, i've tried to learn what I can about the basic XJ setup. There's the exhaust header that flows all of the cylinders into one or two main pipes. if you've got the 48 states emissions setup, you'll have something called a "pre cat" that has two pipes finally leading into one, if it didn't come stock, you could get an exhaust head that ends in 1 instead of two and bypass extra piping. Exhaust heads get a lot of heat and the stock ones are known to sometimes crack, if you're getting a new exhaust head and have money to spare, you could get it "jet-hot-ed" which is a special coating process to keep it cooler and prolong the life of the part. the pre cat has plugs for O2 sensors that help the engine keep track of emissions output and will throw an error code if something is wrong with one of them. next is a line of pipe to the main catalytic converter, the little oval-ish box before the muffler. This is simply a box with a filtering brick to help catch more emissions fumes before they leave the exhaust. I'm in need of a new one of those as well and I hear the two choices are ceramic brick and metallic, I plan on going with metallic. The bricks over time grow brittle and can split and rattle in the compartment, I noticed mine doing this a while ago, it stopped which has me more worried than the rattle. Then of course we have the end of the exhaust that you are talking about, the muffler to the tail tip. Resonators and Mufflers do two different things, resonators don't do much to "muffle" the noise (hence the name of the next item on the list), instead they resonate a certain pitch, most of these are placed on tuners giving them a "fart can" sound. Mufflers can add a bit of tone as it does resonate through that length of piping, but it also helps to muffle the sound and make it a bit quieter than straight piping it from the main Cat. A lot of people here seem to prefer flowmaster or magnaflow, however I'm liking the tone of the dynomax superturbo. It isn't too loud and has a decent sound. When looking for cats and mufflers, you commonly have options as to how wide of pipes there are at entrance and exit, so if you want to bump up two 2.5 and you only want to swap out the cat and muffler, it'd be best to start at the end of your pre-cat and run 2.5 the whole way to the end. Best of luck! and sorry for the long ramble of information.. I tend to do that a lot