Aftermarket exhaust

[w8in4yurmom]

Can anyone suggest a decent system that sounds decent and has some mpg improvement?

 

[JeepinJarhead03]

nah sure can't sorry

 

[Minimike]

If it sounds good, you will most likely have your foot into it more often, which means less MPG. Cut off the stock muffler and install a flowmaster 40 for lots of low end noise, or a 50 for a nice balance between sound and your ears not being damaged after a long trip.

I have yet to install an exhaust or intake on a vehicle that helps raise MPG's simply because I like to hear it to much.

The Flowmaster 40
http://www.jegs.com/i/Flowmaster/389/952545/10002/-1?parentProductId=753276

The Flowmaster 50
http://www.jegs.com/i/Flowmaster/389/952545/10002/-1?parentProductId=753276

 

[JeepinJarhead03]

put whistle tips on it

 

[JeepinJarhead03]

cause...
they go Wooooo WOOOO

 

[speedracerbubba]

One time I installed ****** long tube super comps and dual 2.5" puppies and gained 3mpg city and lost 2mpg on the freeway in a ranchero with a mild 400M. Every other time exhaust had made no difference for me from an f150, srt4, gsxr600, or an svt ford focus.

 

[speedracerbubba]

cause...
they go Wooooo WOOOO

They are still doing some stupid stuff to their cars up in Oakland. Makes it entertaining to go, though.

 

[Okura_hubby]

First, nothing is going to gain back your investment in exhaust systems.

Several companies make Catback systems. The big two are Flowmaster and Magnaflow.

Flowmasters has a nice sound.. But they are made of aluminized steel (just like what is on your Liby from stock)

Magnaflow are totaly stainless (pipe and ****) so its a very long lasting setup. The sound is deaper than stock.

Magnaflow makes a catpipe and cat setup to replace that section so you could have total Stainless setup.

Im running JBA cermanic shorty headers for the Jeep Liby with the Magnaflow cat-back. Doesnt sound like one of those japanese street racer cars, doesnt sound stock.

Millage hard to say the gains just from this as I did other mods. I put on one of those K&N Cone filters to replace the airbox at the same time. I recently took that off and made a forced air induction. On a short 50 mlle trip I got 19.7, did some town driving which brought me back into 15ish then drove back home and topped out at 19.8. I am hoping with the long trip I have comingup I can get mid 20's

I found the number one thing you can do to improve gas economy on the Libby is how you drive it.. Smooth not agressive and temper yourself on take off's. Watch your RPM guage try to keep it below 2.

 

[J-Thompson]

I hope that your KJ is lifted and running larger than stock tires
other wise you may need a tune up or other mait.
My '03 BONE stock running gear
OME springs and 245/75 10ply MTR's and got the exact same
MPG ,if not better
As of now I get close to what you are getting out of my TJ

 

[Okura_hubby]

who you talking to J-Thompson.

Im getting above average than others here. And the two Liby owners I spoke to.. I just hit 30K on it, and I plan to put new plugs when I do the oil, and tran fluids in a week. Also going to change the rear gear lube.
With mods I gained about 2 MPG from what it was doing. And I noticed with the forced air induction that once you get on the highway MPG jumps very quick.

 

[hyde]

Flowmaster Super 50 here, 2 to 3 mpg on average, cost was $180 inc install.
3mpg =
1000 miles a month, at $4/gallon, instead of 13.5-14 it is 16.5. 2.5mpg
$296 down to $242.
It coasts much better too, I though the stock was too restrictive, but I have no clue, maybe my driving habits changed.
Savings of $50/month plus a nice sound.
Perfect situation to use Your mileage may vary statement...

 

[tjkj2002]

who you talking to J-Thompson.

Im getting above average than others here. And the two Liby owners I spoke to.. I just hit 30K on it, and I plan to put new plugs when I do the oil, and tran fluids in a week. Also going to change the rear gear lube.
With mods I gained about 2 MPG from what it was doing. And I noticed with the forced air induction that once you get on the highway MPG jumps very quick.

Before my SFA swap my Kj was 5500lbs,running 265/75R16's,4.10 gears,and could get just shy of 22mpg's at 78mph(would be 14mpg's at 65mph).If stock 20mpg's on the highway is not that great but it's a Jeep so who cares,not me.

Replacing a perfectly operating mufller on a KJ will not gain you any mpg's,now replacing a dented or otherwise plugged muffler will return you to stock mpg's.There is no way to gain mpg's in the muffler area on a KJ.

 

[tommudd]

Troy
Glad you posted that everytime I tell someone that mine gets better mileage at about 75 they say I'm nuts!
65 for mine is way too low in the RPM range and it lugs along
At 75 I can average 21-21.5 and I'd say mines close to what yours was ( before the SFA)
And yes the only thing you get from aftermarket is sound which makes you think you've got 150 more horsepower :Bye:

 

[ineedabouttreefiddy]

Ive heard that MBRP makes a nice exhaust from a few people and ive heard about 2 of them up at silver lake dunes. They sound good and have minimal drone. ive had good luck with flowmaster and magnaflow on my Ram and Mustang GT and there was a slight diference in gas milage going up (maybe 1-3) but like Minimike said youll have your foot in it more because it sounds nice. currently on my 02' limited i have the stock that i ripped the inside out of, sounds good and i get 24 highway

 

[Okura_hubby]

I got 21 once and I think the wind was pushing me.

Low RPM is good, means the engine is turning over less. More the engine turns over the more gas you consume. If your getting 22 at 77mph.. slow down to 65 I bet you would get 25 or better.

I am thinking I could get mid 20's if I had a long enough trip to benefit from cruising at 65mph. Just my trips are like an hour or so then a bunch of city stuff then more highway for an hour or so. I drove it once for 5 hours with just cone filter mod and hit 21 with it. I drove it once 1300 miles but had some exhause leaks due to poor installation and got 19.7 average. I put in the force air mod and have came close to that one short trips so I am guesing I will be mid 20's on this long trip. But I never gotten better than 21 ever (ever).. Maybe I should put new plugs in it.

 

[J-Thompson]

who you talking to J-Thompson.

Im getting above average than others here. And the two Liby owners I spoke to.. I just hit 30K on it, and I plan to put new plugs when I do the oil, and tran fluids in a week. Also going to change the rear gear lube.
With mods I gained about 2 MPG from what it was doing. And I noticed with the forced air induction that once you get on the highway MPG jumps very quick.

No your not
Not for a stock KJ
Like I said my '03 got 15 city and 20 highway
Running a lift and 245/75 10 ply MTR's
Before that we got 17/21
My TJ with lots of mods and heavier than stock parts
Gets 13 city and 17+ highway and it only has a 3 speed
auto tied to the fuel drinking 4.0
Proper tune up
Clean oil ,ful syn
Proper tire psi
And proper driving
Take 1 out and your mpg will tank

 

[Okura_hubby]

No your not
Not for a stock KJ
Like I said my '03 got 15 city and 20 highway
Running a lift and 245/75 10 ply MTR's
Before that we got 17/21
My TJ with lots of mods and heavier than stock parts
Gets 13 city and 17+ highway and it only has a 3 speed
auto tied to the fuel drinking 4.0
Proper tune up
Clean oil ,ful syn
Proper tire psi
And proper driving
Take 1 out and your mpg will tank

Other than new plugs (gapped right) what else do you call a tuneup?

 

[cplchris]

Other than new plugs (gapped right) what else do you call a tuneup?

plugs, wires, coils, oil change, air filter, clean iac valve, a good quality fuel system cleaner...not just plugs, oh and a fuel filter

 

[tjkj2002]

I got 21 once and I think the wind was pushing me.

Low RPM is good, means the engine is turning over less. More the engine turns over the more gas you consume. If your getting 22 at 77mph.. slow down to 65 I bet you would get 25 or better.

I am thinking I could get mid 20's if I had a long enough trip to benefit from cruising at 65mph. Just my trips are like an hour or so then a bunch of city stuff then more highway for an hour or so. I drove it once for 5 hours with just cone filter mod and hit 21 with it. I drove it once 1300 miles but had some exhause leaks due to poor installation and got 19.7 average. I put in the force air mod and have came close to that one short trips so I am guesing I will be mid 20's on this long trip. But I never gotten better than 21 ever (ever).. Maybe I should put new plugs in it.

Just by turning lower engine rpm's does not mean better mpg's,in most cases can actually make mpg's worse.Every engine has a peak torque(HP is fictional today) and for the 3.7 it's pretty high,like 4000rpm's or something,so the closer you run the engine rpm's to peak torque the better mpg's you will get.At least you need to stay in the "powerband" which is the rpm range that the engine makes at least 90% of it's peak torque,dropping out of that range and the engine bogs down returning worse mpg's.I have found that running the 3.7 at about 2800-2900rpm's will net the best mpg's which is in the powerband,drop below 2500rpm's and your bogging the engine.


Proper tune up for today's mordern multiport FI engines is the correct spark plugs that are gapped correctly,clean air filter,good working PCV valve,clean fuel filter,properly operating cooling system,no intake leaks,and the most neglected item is a clean intake track(IE fuel induction cleaning,not seafoaming) which will carbon up since all modern multiport FI engines are a "dry intake" system.

 

[tommudd]

I got 21 once and I think the wind was pushing me.

Low RPM is good, means the engine is turning over less. More the engine turns over the more gas you consume. If your getting 22 at 77mph.. slow down to 65 I bet you would get 25 or better.

Wrong at least on mine the motor is turning too low of RPMs its running out of its sweet spot, low RPMs does not always mean better mileage