Muffler vs Full Exhaust?

desertkj · **Joined:** Mon Jan 30, 2006 8:24 pm **Posts:** 677

Ok, in order to help a little with gas mileage, I have heard quite a few people recommend upgrading the exhuast. My question is: if I just replace the muffler will I get the gas mileage as well as the sound, or do I need to get a full exhuast like a Magnaflow to get the improvement? Also, what muffler works well on the Liberty? I prefer a deeper rumble over a whiny Honda sound.

uvalax236 · **Posted:** Wed Aug 02, 2006 2:00 am

Flowmaster Mufflers are awsome! They are a skidplate in themselves as well. Great rumble with the 40 series. I would reccomend doing a Flowmaster Muffler and Magnaflow cat for the best milage increase as well as sound.

desertkj · **Joined:** Mon Jan 30, 2006 8:24 pm **Posts:** 677

Can you recommend a good cat from Magnaflow? Another question I have is: My jeep is just about to turn 5 (wow) and its gonna need to go through emissions here in Arizona. Will that setup be an issue for that or no? I just want to make sure before I go putting it on.

JJsTJ · **Posted:** Wed Aug 02, 2006 10:59 am

I agree on the Flowmaster muffler for sound quality and ruggedness. In your post in the for sale section I thought you were looking into a full exhaust? The factory exhaust tubing is perfect for just a muffler upgrade. I don't know about the cats, but I doubt a smog checker will notice an aftermarket cat. I question how much of a real difference it will make though. Soon I will be looking into aftermarket cats for my KJ for it's SFA change as the exhaust will need to be rerouted a little and cats moved so let us know what you find out and what you use.

desertkj · **Joined:** Mon Jan 30, 2006 8:24 pm **Posts:** 677

I would like a full exhaust. I was just trying to see cost vs benefits. Plus, I've never done a custom exhaust before so Im learning. Anyway, wouldnt the cat and the muffler pretty much be a new full exhuast anyway and would need new pipes all the way back?

* Edit: Sorry, I just saw the comment about factory pipes. But couldnt I have a shop do custom piping?

uvalax236 · **Posted:** Wed Aug 02, 2006 12:37 pm

desertkj wrote:

But couldnt I have a shop do custom piping?

I was running my KJ with no muffler for a little while. I had the piping from the Cat to the tailpipe ripped off the KJ so I had to get new pipes. I did learn that yes the KJ has 2.5" pipes, but that is Outside Diameter (OD). I told my shop to replace my pipes with 2.5" Inside Diameter piping. This helped to give a little deeper growl with the muffler.

As far as the full exhaust, I can only tell you that you can opt for the full catback kits and spend tons of cash on it, or you can do a custom kit and save tons of cash. A higher flowing cat will give you quite a good increase in milage. Pair it with a "Street Intake" and you will be seeing great numbers.

*When I say street intake, I mean some form of a Cold Air Intake system for the street, and the stock airbox for wheeling.*

VTNomad · **Posted:** Wed Aug 02, 2006 12:40 pm

Be sure to take it to your emissions test hot. Drive it for at least 20 minutes before going in. Catalytic converters do their best work at higher temperatures.

raceinfan · **Posted:** Wed Aug 02, 2006 1:20 pm

from what I've read around here all you have to do is replace the muffler all the stock piping is 2.5 already,when I get around to it I'll just be doing my muffler

kj@best · **Posted:** Wed Aug 02, 2006 1:32 pm

I would say all you have to purchase is the muffler, because the tubing that goes over the axel is already mandrel bent, unless you want a fake dual exhaust which is dumb anyway

JFortier777 · **Posted:** Wed Aug 02, 2006 3:22 pm

I have the Magnaflow muffler and new pipe back.

The only thing that inspired me to get the full thing was the fact that I'm leasing.

If I had only bought the muffler I would have had to cut the stock pipe since it is welded to the stock muffler.

MolodoGuy (Phil) has the same muffler and just the factory pipe.

Our exhausts sound identical even at high rpm. I dont think the magnaflow pipe is necessary at all unless you dont feel like chopping the stock pipe off.

I really like the look of the new stainless tip though.
Gives it a nice *It-kind-of-looks-like-it-might-go-fast-even-though-it-wont* look.

desertkj · **Joined:** Mon Jan 30, 2006 8:24 pm **Posts:** 677

SO buying a full kit is kinda a waste, if Im understanding this correctly. Do I just need the muffler or would a new cat be beneficial too? No matter what, it sounds like Im just modifying the existing system and not ordering an entirely new one.

raceinfan · **Posted:** Wed Aug 02, 2006 7:42 pm

I would just do the muffler but that's me

MoladoGuy · **Posted:** Thu Aug 03, 2006 6:53 am

JFortier777 wrote:

MolodoGuy (Phil) has the same muffler and just the factory pipe.

Our exhausts sound identical even at high rpm. I dont think the magnaflow pipe is necessary at all unless you dont feel like chopping the stock pipe off.

The sounds are identical, but I do wish that mine had the sweet exhaust tip. Fabrication time!!

You can get away with just the muffler at this time. You will not see a major gas mileage increase though. I did a month survey recently and found that I am achieving about .35+ better gas mileage than stock. The reason, more flow with the muffler. However you will not see some significant savings happening and with that increase it would take years to pay back the $100+ cost/installation.

I plan to get a new Cat due to the research of it actually increasing gas mileage when running with the magnaflow/flowmaster mufflers.

JJsTJ · **Posted:** Thu Aug 03, 2006 7:39 am

If you are looking for a mileage increase over stock that will equate to a Real savings in fuel costs then don't bother at all. If you are looking for a better sounding exhaust or beefier muffler you can drag on the rocks then go w/ Just a Flowmaster muffler. I really don't think You will be able to gain enough of a mileage improvement to offset the costs involved in changing the exhaust. I have a Flowmaster muffler on my KJ and my wifes has a full Borla exhaust and Neither of them gets any better than stock MPG at Best and then only on hwy. trips. Around town mileage is sad. BTW, the Borla isn't up to the task of wheeling either as the tip got pushed up into the bumper and muffler crushed in Moab.

FWIW, My flowmaster installed on the existing pipe was free as I only traded my stock system for it and the Borla on my wifes was already there when we bought her KJ. I would have only gone w/ another Flowmaster for her KJ and then only for the sound and beefier muffler for wheeling.

MoladoGuy · **Posted:** Thu Aug 03, 2006 8:30 am

JJsKJ wrote:

If you are looking for a mileage increase over stock that will equate to a Real savings in fuel costs then don't bother at all.

I agree with this statement. As I mentioned in my above post there is not justification thinking you will save more on gas by paying for an upgrade. However, the slight increase will occur and you will not notice it.

Get the muffler and do it for the beefier sound!! It really does sound cool driving under a bridge and flooring it....

quivvy · **Posted:** Fri Aug 04, 2006 12:19 am

MoladoGuy wrote:

Get the muffler and do it for the beefier sound!! It really does sound cool driving under a bridge and flooring it....

hellz yeah. i've got a flowmaster 40 series. got it on ebay for $55 shipped new. if you or your buddies can weld installation is free. otherwise it will cost around $30 depending on where or who you go to.

after hearing about this cat talk i may look into a new cat if it will actually help mileage.

Muffler vs Full Exhaust?

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