I just installed a flow master super 44 but my question is, does it give me any HP or torque i do feel a diffrence when I take off or running my xj through the desert just curious what do you guys think? and other than that is sounds like a beast.

 

probably a small amount but I think your butt-dyno might be saying it gave you more than it actually did. Can't beat that flow master sound though.

 

Short answer: anything you "feel" is just your imagination. Placebo effect and confirmation bias.

 

With the stock 4.0, I doubt a muffler alone will do too much for you unless yours was dented flat. Upgrade the entire exhaust and intake and you will gain a little bit.

As far as the Super 44, I can't wait to get rid of mine lol. I put it on with my stroker/3" exhaust and my Jeep is way to loud now. Not sure what I am going to go with but it wont be another flow master. I have had a borla muffler, a dynomax muffler and a few others on previous XJs. This one is easily 3x as loud. Think I am going to go with an AFE muffler as I love their headers that I put on.

 

They don't call them "Flow Crappers" for nothing, all noise no go and on a 4.0 kind of a joke.

 

I'm running an mbrp cat back on my stock engine nice sound but I hangs down a bit more than stock unfortunately.

 

I really loved the stainless Magna Flo on my TJ but it was a cat back. All stainless, 2.5", Don't really know what options they offer. But the sound was just right!
JPLUG2007
98 Sport

 

Upgrading the muffler alone will not provide significant power gain. There are other factors that you need to consider.

 

Nothing like a good butt Dino for telling how much power is going to the wheels. I've been running a flowmaster 44 on my XJ for 8 years.

Seriously though I've grown out of my getting extra HP by bolting on stuff phase. Proper gearing is where that money should go.

On the plus side I love the way the 44 sounds and still think it's the most aggressive sounding muffler on a 4.0L.

 

A muffler alone will pretty much never give you a power gain, unless it was severely damaged or by far the most restrictive part of the stock system. Usually, the cat(s) are the most restrictive. For reference, I put a 44 on and ditched my cat since it has precats on the manifold and I can use that to pull the wool over the eyes of anyone inspecting it. It's certainly sounds much better, but I don't think I really gained much power. You have to remember that XJ's don't have much power to begin with, so something that may make a small difference on a V8, like a muffler and removing a cat, probably won't have a noticeable effect.

Just enjoy your XJ and keep pretending it's faster. That's what I do.

 

Usually not actually. I'm sure there can be exceptions to this, but I haven't encountered any, and the Jeep XJ/YJ/TJ/ZJ/WJ with a 4.0 is definitely not an exception. Even the stock cat will never be the bottleneck until you have, at least, a stroker with a nice intake, bored TB, and nice exhaust (by "nice" I'm talking about some serious stuff, not bang-for-buck bolt-ons). Commonly the stock cat's are as old as the XJ is in which case they are often reaching the end of their lifespan and are crumbling/clogging a bit, but that's not the fault of their design at all, and a fresh OEM cat will flow plenty.

Also, please don't violate federal law and dirty the air we all breathe by deleting your cat. They're not that expensive when bought from someone who isn't ripping you off (Performance-curve.com has great choices with great prices) especially when you subtract the scrap metal value of your old cat from the price of the new one. There is simply no excuse not to have a cat under your XJ.