What do you guys think? I've read that freeing up the exhaust would help get some better MPG, what do you guys think? I'm willing to go up to, headers to straight pipes, even out the sides if the pipes fit (can't be too ridiculously loud). Fuel cost/usage is killing me. Also currently running on LPG (Propane) with a mostly Lovato custom system, which I'm told kill the cats, and being in a country that apparently doesn't care about exhaust, I'm sure there aren't federal laws about removing them (they probably wouldn't care if fire came out the tailpipe). I know that this is a unique situation, but I was hoping that you guys could use your imaginations and give me a hand. I found a good muffler shop that could make headers and whatever else for me really reasonably, so let me know what you guys think.
BTW, I have a 2002 Sport 3.7L, in my normal "city" driving I'm getting around 13mpg in Gasoline and 10–11mpg with Propane. Also the propane system bypasses all the O2 sensors, but I do need it to run on Gasoline as a back-up.

Stop using propane and start using gas again,do a good tune-up and be happy.Straight piping will only reduce mpg's severly as the 3.7 likes some back pressure to make HP and torque.

Seriously?? Gasoline is more than US $4.30 a gallon here!! And LPG is half that, I'm sticking with it unless CNG gets around the island, subsidized to half the price of LPG, might have to switch.

Look, I love the comfort and capabilities but it's kind of ridiculous at 10 mpg.

So you're saying that if I nix the all the cats and install a glasspack I'll lose HP and Torque??

Foe the price your paying your getting about the best you will ever get with propane or CNG as both of those have alot less BTU then gas does and hence the low mpg's due to lower HP.The LPG conversion is your whole mpg issue.With proper driving and a good tune-up a 3.7 in a KJ can get over 16-18mpg's city and 22-23 highway on gas,and since LPG or CNG have 25%(or more) less BTU's then gas you will get 25%+ less mpg's so you are right where your best is anyways.

With the modern electronics in the KJ you are doing nothing but destroying the engine running LPG or CNG as it was not programmed for such or made to run such fuels.

WOW, are you referring to mpg for a 4x4, because the best I did before LPG was 17-18 hwy and averaged 12-13 just around.

But my "city" driving is 90% up and down dirt paths/roads (stuff that doesn't show up on google maps ) and 10% up and down the so called highway.

I understand that gasoline is better and I lose HP/mpg with propane but this is normal operating procedure down here. Heck my landlord has a $60k Lexus SUV with a $2k direct injection propane system and has no problems with it, not even one code/engine light.

I mostly use a light foot and rarely get it to 70 mph so I'm trying to consider all options to get the most out of my KJ.

I'm not sure what engine destruction you're referring to by running alternative fuel and I'm sure Lovato and Romano (2 big LPG system companies) would disagree with you. I'm told that there are even some benefits like that it burns cleaner and keeps the cylinder heads cleaner, also been told that I won't need to change the oil as frequently. But I'm not sure about this.

OK, first off, thank you for your help with my question. I'm new to Jeep forums and only have had my Liberty for about 8 months and still learning a lot about it.

Soooo, after talking to my mechanic stateside, I'm considering removing the cats and leaving the stock muffler. He thinks that with the exhaust manifold and muffler I'll have enough back pressure to run properly and that given my low mpg currently that one or more of my cats are crapped up anyway so might as well get rid of them.

But you guys are the experts on the KJ, so what do you think, would there be enough back pressure? Im talking about strictly of the exhaust set-up, not the O2 sensors and computer stuff.

If your cats are bad..... Get new or better ones.
I had the drivers side cat take a dump.... Literally all of the insides were gone.... Lost 5-7 mpg and lots of horse power....
Until i switched them out...

_________________
2000 Cherokee Trail Hawk
3.5" R.E Superflex Lift, R.E Quick Disconnects, R.E Rear Driveshaft, SYE, OME Steering Stabilizer, ARB Diff Covers, JW Speaker Black Heated Headlights, Mickey Thompson 16x8 wheels, 245/75r16 Toyo Open Country AT's, 15 lb Powertank

2003 KJ Sport (BLACK) 230,000+Miles (Decommissioned)

Is there a way to check the cats without removing them?

BTW, I'm at 184,600 miles!!

Its a jeep. If you want MPGs get a diesel jeep or a honda.

_________________
Fran:2002 Jeep Grand Cherokee Limited 4.7 quadra drive. 31in General Grabber AT2, OME HD, bilstein, IRO sway links, addco rear sway. Kolak 3in cat back flowmaster SUV 50, magnaflow 3in cat, airaid JR kit, ram air, P.I.E. aux adapter, surco 45x50, husky liners.http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=6&t=65276&p=719908#p719908