Jeep Garage  - Jeep Forum

Jeep Garage - Jeep Forum (
-   Engine Performance/Intake/Exhaust (
-   -   Magnaflow 12589 (

BlueDevil23 01-04-2013 03:22 PM

Magnaflow 12589
Hey everyone, I can't seem to find a whole lot of detail about this muffler, except that it seems to be one that is often recommended. I have a '05 5.7L. I'm looking to basically just swap this muffler with the stock one. I ordered the Magnaflow 12589 because of other user's recommendations here and other forums. Does anyone have any experience with this muffler, or more particularly a 3" inlet/outlet. I've visited two muffler shops now: one told me that the stock pipe was 2.25" and he wasn't sure a 3" tail pipe would fit out the back(I suggested that I might as well go 3" all the way out if it wasn't a lot of money) and the second shop told me it was a waste of money to try and swap this muffler for the stock one, and that the largest tailpipe that would fit would be 2.5" -- this shop also said the stock pipe is also 2.25". Although neither shop took the time to actually look under the vehicle. From what I've been reading, the stock pipe is supposedly a weird size, metric, and closer to 2.75". I'm so confused now. My questions are... Are these shops right? Do I need to look for a better shop? Anyone that installed the Magnaflow 12589, how did you do it? Will a 3" tailpipe not fit?(I thought their was cat back system that ran 3" all the way through).

Thanks for any and all help!

jeepgcoman 01-04-2013 03:57 PM

Re: Magnaflow 12589
I may be able to help you a little. First, there are many configurations that are in use, and everyone has their own opinions and preferences. Be aware that, while helping somewhat, a complete 3 in. system is not the "cure all" for the 5.7 exhaust system. The biggest restrictions are the crappy cast iron log exhaust manifolds with tiny 1 7/8 in. outlets. Some "fix" options there are Hemi LX manifolds with 2 5/8 in. collectors, WK SRT-8 exhaust manifolds (requires some modding), 6.1 long tube headers or, like I did, custom headers. Also, if you plan to keep the stock tubing (less than 3 in.) it makes no sense to stick a 3 in. in/out muffleer on it. If at some point you intend to go complete 3 in. system, then by all means do it. It can easily be done by any muffler shop that's worth its salt.

In addition to the custom tubular headers, with 3 in. collectors, I have the Magnaflow 14589 (3 in. in/out) on mine. I believe it is a little longer than the one you're talking about. To get it so it doesn't drone when in MDS mode, I also have a 3 in. by 12 in. glasspack in front of the Magnaflow and an Xlerator AP XS1229 (3 in. in/out) in the stock resonator position. This seems to work the best for me, and more importantly, it passes the wife test with flying colors, there is no drone, and almost no note change in and out of MDS.

Hope this helps you a little.

BlueDevil23 01-04-2013 04:35 PM

Re: Magnaflow 12589
Thanks for the help! I'm aware that a 3" in/out muffler along with a 3" tailpipe is not a whole lot of help for the Hemi. I'll be the first to admit, I'm almost clueless when it comes to exhaust systems. I' basically bought this muffler from suggestions floating around this forum and others. It seems to be fairly popular. The only reason I suggested the 3" tailpipe is for simplicity, and to know I've got 3" pipe from the muffler out...because I can't seem to figure out the quirky size of the stock pipe. I'm still not clear if 3" in piping will fit for the tailpipe. And my next question would be....should I send back this muffler and find one that is more easily swappable with the stock pipe?(What size in/out would that be?)

Gojeep 01-05-2013 04:32 AM

Re: Magnaflow 12589
The 3" one is a good choice as the next size down is 2.5" and smaller than the stock 2.75". No point causing a restriction even if you don't get the full benefit of the 3" replacement.

jeepgcoman 01-05-2013 10:53 AM

Re: Magnaflow 12589
Maybe do a little research to see what the differences between them are? Also, your personal preferences are the most important factor. If indeed yours is a little shorter, you'll probably be a little louder. If you plan to keep the stock resonator, you'll probably be alright. If you remove it, for sure you'll get the "MDS drone". Any muffler shop should be able to adapt the larger muffler without any big fanfare. I also agree with Gojeep, either leave the stock size tubing or go to 3 in. Do not go smaller, although the smaller may help the low end slightly, it'll make your top end worse than it already is. It took me 3 tries to get my system the way it is now. First, the 3 in. system with the Magnaflow and two glasspacks, then the custom headers, and finally removing the rear glasspack and installing the Xlerator AP unit.

BlueDevil23 01-06-2013 08:22 PM

Re: Magnaflow 12589
Thanks for the helps guys. What I take away from this is...and what really threw me off in the first place -- both muffler shops were completely clueless of my stock pipe size. It's also pretty clear that a 3" tailpipe WILL fit. For now, I think I'm just going to have them adapt the inlet side and put a new 3" tailpipe out the back. I'm undecided about leaving the resonator on or not, I am somewhat worried about the "MDS Drone"...but I feel leaving it on is defeating the purpose of the muffler swap. I guess I'll just have to experiment and see regarding that issue. Thanks again!

jeepgcoman 01-07-2013 02:16 PM

Re: Magnaflow 12589
There should be no problem with putting 3 in. tubing from the muffler aft, and yes, it won't give you the full benefit, but it's a start. My guy custom made the entire 3 in. system, from the headers to the tailpipe. And, it did take some experimenting. My guy was clueless about the MDS but, after I explained the system to him he said that running a 2.85 liter 4 cylinder engine with a 3 in. exhaust is going to sound terrible. Hence the experimenting. He originally started with the Magnaflow and a 3 in. X 12 in. glasspack in the resonator position. Then he added another glasspack in front of the Magnaflow, and left the one in the resonator position. It was "OK" for a while, but after the glasspacks got "burned in" it started getting louder, and droning was noticeable. Finally he ended up putting the Xlerator muffler (not a resonator) in place of the rear glasspack, and now it is perfect IMO. Since exhaust sound is almost totally user preference (and maybe the wife too), everyone's idea of a good sound is different. I think the way you're planning to go (with the experimenting) is good. I've done that with almost everything I've modded on my WK. This way I know for myself exactly what works and what doesn't....for my purposes.

BlueDevil23 01-08-2013 12:05 AM

Re: Magnaflow 12589
Do you have any videos of your exhaust?

06HemiLtd 01-08-2013 03:36 PM

Re: Magnaflow 12589
I had the magnaflow 12589 muffler on my 06 Hemi for a few months. My exhaust shop did not have any troubles at all installing it. At idle and at cruise, it was not much louder than stock. At WOT, it was noticeable. I didn't have any drone but I have MDS disabled with a Predator tuner. The one thing I really disliked was that my "off the line" torque seemed to really decrease after the install. That's actually why i bought the Predator but it didn't seem to increase the torque at all. I had the original muffler reinstalled and it made a huge difference. any good shop can easily install it an a 3" tailpipe.

jeepgcoman 01-08-2013 08:55 PM

Re: Magnaflow 12589
2 Attachment(s)
Here's the threads on the headers:

Here's a pix of the front glasspack and Magnaflow, and one of the glasspack in the resonator position. I don't have one of the Xlerator AP muffler that ultimately replaced the rear glasspack, but it had to be turned on its side and tucked up a little so it would fit.

All times are GMT -5. The time now is 09:42 PM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 2012 - JeepGarage.Org
The Jeep Grand Cherokee Owners Community