New lift and muffler, bad MPG

spymoto · **Posted:** Sun Oct 24, 2010 11:10 pm

Hey everyone!

I'm excited that I got my lift in this weekend, a Franky Premium 2 with Al's 4.5 UCA and 2 extra spacers in the rear, but it seems like the front is still higher. Next is wheels and tires :wink:

I was wondering if this sounds weird or not... I put my lift in and installed a Super 44 Flowmaster muffler. I always ran about 19 MPG on the highway. I drove it to my parents to do the install about 150 miles away and was getting 19MPG on the upper center read out. After the install, I drove it back home after the alignment and now only getting 15/16 MPG. I realize lifting it may decrease MPH, but thought the new muffler would help it and it would equal it out.

Is this normal?

Thanks!

tjkj2002 · **Posted:** Sun Oct 24, 2010 11:28 pm

Very normal,I suppose you disconnected the battery which will also wipeout your PCM memory(RAM) which will also result in bad mpg's till the PCM and TCM "relearns" your driving which can take 7-14 days.

Sitting higher equals more wind you have to travel through which = poor mpg's.

Not enough back pressure(muffler and such) can also result in poor mpg's as you loose low end torque on the 3.7.

Wait till you get the bigger tires and you'll be happy with 15mpg's.

spymoto · **Posted:** Sun Oct 24, 2010 11:54 pm

Thanks for the info! I think the Super 44 is a bit loud for my on-road taste since it's my DD. I think I should have gone with the "50". Anyone wana buy an exhaust??? haha

liquidxit2 · **Posted:** Mon Oct 25, 2010 1:04 am

I loved my super 44 but I can say Im happy with my dynomax ultra flow. Performance seems a bit stronger and its MUCH quieter. as for fuel mileage performance upgrades dont yield too much on these vehicles (power and efficiency) as vehicles made past 2000 seem to be setup pretty well from the factory. The only difference I noticed was a slight increase in butt dyno power (mostly throttle response) but zero MPG gains.

spymoto · **Posted:** Mon Oct 25, 2010 6:15 am

How is the sound with your Dynomax? Does it still have a good rumble? What about interior sound? Right now I think it sounds like a tractor when I have the windows up because it just echoes when driving around town. It's not too bad at highway speed. I'm hoping to get something that sounds more like a good sounding V8 thats not drounding the interior of the liberty.

LibertyCRD · **Posted:** Mon Oct 25, 2010 7:52 am

spymoto wrote:

Flowmaster muffler.

Thanks!

There is your problem. There is already a thread recently where we discuss this.

riptricket · **Posted:** Mon Oct 25, 2010 2:03 pm

I love my super 44!
I have just installed my franky and have my stock sized tires on and I still get what I got with just the muffler... 19.
now when I install my 245/75's it will go down, but my brother has a truck that gets 12(stock) and my mom's lexus lx470 gets about 9, so I ain't too worried!

liquidxit2 · **Posted:** Tue Oct 26, 2010 1:35 am

spymoto wrote:

How is the sound with your Dynomax? Does it still have a good rumble? What about interior sound? Right now I think it sounds like a tractor when I have the windows up because it just echoes when driving around town. It's not too bad at highway speed. I'm hoping to get something that sounds more like a good sounding V8 thats not drounding the interior of the liberty.

MUCH MUCH quieter then the super 44. Here is a clip of my Jeep, unfortunately my cameras sound recording kinda sucks.

http://www.youtube.com/watch?v=0IcuD-XWpTM

spymoto · **Posted:** Sat Nov 06, 2010 1:00 am

tjkj2002 wrote:

Very normal,I suppose you disconnected the battery which will also wipeout your PCM memory(RAM) which will also result in bad mpg's till the PCM and TCM "relearns" your driving which can take 7-14 days.

Sitting higher equals more wind you have to travel through which = poor mpg's.

Not enough back pressure(muffler and such) can also result in poor mpg's as you loose low end torque on the 3.7.

Wait till you get the bigger tires and you'll be happy with 15mpg's.

You were right, It went back up to about 17.5 mpg, but now that I have the new wheels on its back down to 15 mpg :dizzy:

New lift and muffler, bad MPG

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