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[Whitee]

Has anyone done a full header back exhaust? if so info would be great., pics too if you have em.

 

[tommudd]

Not much you can do or vary from the stock exhaust since you have to have the cats/ etc in there. Stock cats flow as good or better than aftermarket so not going much there. So you are left to whats behind ( from muffler on back )

 

[renegade 04]

Why even mess around with exhaust, I think the stock exhaust sounds great. Also need to be cautious because you do not want to lose back pressure when you change mufflers and you will lose power if you lose back pressure on the 3.7.

 

[CactusJacked]

Can't tell you how many times I've seen the "less back pressure causes power loss" myth get thrown around on different forums. The simple truth is, too much back pressure is a bad thing. One part that can have a big effect on an exhaust (and engine's) performance is the pipe diameter. Going too big can negatively effect "scavenging"; how well and how fast the exhaust gases flow. This write up gives a good explanation on exhaust: exhaustbackpressure
Now, if you feel that more back pressure is a good thing to have (it isn't), then by all means, install one of these to the tailpipe. : O Pipe (Single Exhaust) - $125.00 : KaleCoAuto.com, Your home for the rare, unusual, and hard to find auto parts.
With that said, don't expect great power gains in your Jeep from a "performance exhaust". Replacing the system for that sole purpose wouldn't be the best investment. However if your system is all rusted out and in need of a replacement, then you can go for an aftermarket cat back system.

 

[Whitee]

Thanks for the input, Im not expecting much of or any power gain, just had rattling from the cat (I hope) and prolly need to change it out, its old and rusty

 

[CzarKJ]

Thanks for the input, Im not expecting much of or any power gain, just had rattling from the cat (I hope) and prolly need to change it out, its old and rusty

Check the heat shields on the front cats. They get loose. Might not be inside the cat if you are lucky

 

[dude1116]

Check the heat shields on the front cats. They get loose. Might not be inside the cat if you are lucky

You have a picture of that? I never noticed a heat shield there before.

Thank you!!!

 

[Renedave]

Can't tell you how many times I've seen the "less back pressure causes power loss" myth get thrown around on different forums. The simple truth is, too much back pressure is a bad thing.

And so is too little, which is the point made above and is definitively not a myth unless you have some evidence that the Liberty exhaust is too restrictive. Plus, "bad thing" is an oversimplification - the exhaust is tuned to match the valve timing and optimized for a particular RPM. Pull the exhaust of and you can sure make a heck of a lot more HP out of an engine... with the proper retuning. Likewise, a more or less restrictive exhaust can change how the engine produces torque and HP at different RPMs to meet a particular driver's needs, but the range is limited by the rest of the engine's tune, and I'd want to see testing data and the trade offs before making a change.

Regardless, I've done a full exhaust replacement on the Liberty. Not by choice, a rock found its way between the skids and made a mess of one of the cats and the muffler. The back half is a piece of cake, two nuts at the flange in front of the muffler and a couple of hangers and it'll come out. I may have had to raise the Jeep to twist the exhaust around the axle, but not by too much. The section from the downpipe to the muffler flange required lifting the Jeep and removing the crossmember, which means you'll also need to support the transmission. It's not too difficult, I was able to do it in my driveway, but you may want help if you haven't done something like that before, and you want to make sure you get the torque right on the crossmember when it's reinstalled.

FWIW, it's readily apparent when one of the downpipe flanges is loose, which has happened a couple times since I replaced the cats. I usually average in the mid-17 MPG range, and it'll drop down to 15. Of course, with a smashed cat and muffler I was getting a whopping 13MPG!