I'm trying to figure out the best size and setup of a new Magnaflow muffler?

I'm going for a better sound, but an MPG increase would be a nice bonus

So basically I need to know what type/size/shape would work the best and which in/out configuration would be easiest to work with.

 

I'd like to know too. I guess I'll end up just crawling under mine with a tape measure. I know I need a 2.5" center inlet and 2.5" outlet. I have narrowed my choices down to a flowmaster or a magnaflow muffler. I am leaning towards the smaller magnaflow at this time. I'll post what I end up doing.

 

This is the one I'm looking at:

http://store.summitracing.com/partdetail.asp?autofilter=1&part=MPE%2D10416&N=700 +4294922710+4294891681+4294791974+4294791975+42949 06131+4294906132+4294906122+4294906130+115&autovie w=sku"]http://store.summitracing.com/partdetail.asp?autofilter=1&part=MPE%2D10416&N=700 +4294922710+4294891681+4294791974+4294791975+42949 06131+4294906132+4294906122+4294906130+115&autovie w=sku

Case Length (in): 14.000 in.
Case Outside Diameter (in): 4.000 in.
Overall Length (in): 20.000 in.

$58.95 + shipping

 

check out MBRP, they already have it figured out for relocations

 

I used a 6" universal round Magnaflow that is 18" long. It's the second from the bottom on this list
http://w ww.a-1performance.com/magnaflow/mufflers/mfm_6round_al.cfmI moved the muffler up under the drivers seat by cutting out a section of pipe that was the length of the muffler, then putting the muffler on, clamping it, then putting the back end of the pipe on the muffler with the bend over the axle. All you have to do when you move the muffler under the seat is buy the muffler and 2 clamps. I also added the borla 2.5" venturi to get some back pressure back and I'm seeing at best, 21mpg on the highway with a 4 door auto 3:73's. I like to think that's pretty good. The best thing I've seen is the throttle response.
Good luck to you guys, it sounds pretty good when your done.

 

Here are some pics of mine. Might I suggest getting some BBQ black paint and painting it all while you have it cut up, I wish I'd done mine so it wasn't so rusty. Also, I'm going to redo the venturi, It's welded on the end to see what kind of results I'd get and I'm pretty happy with it. I just want to clean it all up because it looks like a rusty mess.

Don't forget that mufflers have a breaking period where they are quieter and don't have their full performance.

 

I used the 4" round X 18" long Magnaflow on mine. I went 4" because it's right next to the evap canister and I wanted plenty of room for air flow. Driven it about 2500 miles now with no problems. I think the 6" there would pretty tight. The evap canister is only plastic you know? Also another point to remember is a round muffler's noise cancellation comes much more from a muffler's length than it's diameter. I think the 14" length will be too loud. You should look at the 18" and there's actually room for one longer than that. The 18 sound fine for me.

 

I used the Hushpower and moved it in front of axle and really like the sound.


Chris

 

I've had my 6" round on for 20,000 miles now with no problem. I've got the 18" long one and it's been a great muffler. You can hear it inside the jeep under acceleration, but when you cruise it's pretty quiet. If the radio is on at all you can't hear it. I'd be interested in checking out the 4" muffler. These 3.8's don't like free flow exhaust like I had hoped. Keep in mind that the 3.8 was built wanting a lot of back pressure. Before I installed the venturi the best mpg I ever got was 19.

 

Then somethin's wrong with yours. Adding that Magnaflow to mine made a very noticable "seat of the pants" feel. Much less downshifting going up hills. Definately an increase in power, no doubt about it. In fact, I think you're the only person I've seen so far whose done this that has not gotten a slight increase in power.