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problem with magnaflow muffler on 09 hemi

8K views 22 replies 16 participants last post by  theweavman 
#1 ·
I just had a magna flow muffler installed on my ram 09 hemi ,but I have a problem according to my evic system my fuel economy just went in the gutter,it is about 3 to 4 miles to the (bad) on highway and city driving .I talked to my dodge dealer and they seem to think that the MDS system does not like the change and it is staying in the 8 cylinder mode..?
 
#4 · (Edited)
Lots of guys have added the Mufflex Magnaflow kit in various sizes and none have had any MPG issues. The MDS still works too so the muffler itself should not be the source of the problem. When mine kicks in, the MPGs go up dramatically.

What exactly did they do? Did they weld on your truck? If so, where did they place the ground wire and was the battery left connected?
 
#6 · (Edited)
re: magnaflow problem

my truck does not have the indicator light for the mds sys. so I AM NOT SURE WHEN ITS IN 4 CYL MODE , there is a little 7 mile stretch of hwy that I take to and from work each day ,noting my evic mpg usually climb to about 19 or 20 mpg in that stretch , but now its no more than 15.1 , and less in the stop and go stuff.
also topgun ,I dont know where they grounded at when they welded on the magnaflow ,they did not un hook the battery...thanks for the help
 
#7 ·
I just installed an 18" magnaflow on my single piped 09. I took it out for a brief run on the highway and my MDS sounds like it is working. I can tell when it kicks in and out by watching the RPMs. They will jump ever so slightly when the MDS kicks in and drop a hair when all eight come to life. I can also tell by the sound, moreso now with the new exhaust.

I really like the Mufflex 18" kit. It took me about 45 min to install and is just the sound I was looking for. Any louder would be too much in cabin noise for my tastes.
 
#9 ·
I went back to the muffler place and had them remove the magnaflow and put my original muffler back on and now my evic mileage returned to normal, .go figure... (dual pipe exhaust )
So you are now back to a single exhaust and all is well?
Wow this is crazy but informative, I will stay away from exhaust mods of this type.
Glad you could get your sanity back but sorry it was at a cost to you.
 
#11 ·
That's really odd that you are having this issue. Guys have been adding the Mufflex kit to both the single and dual exhaust systems without any MPG problems. They have been using 14", 18" and 24" Magnaflow mufflers. Not sure how going to a muffler shop and having them splice one in would be any different. Makes no sence at all. :4-dontknow:
 
#13 ·
I finally installed my Mufflex kit and have no such issue. What size muffler were they installing?
 
#15 ·
#19 ·
could it be a problem with a heavy right foot wanting to hear the muffler. I just installed a CAI and I lost about 1.5 mpg, but I can promise you it is from the foot dilemma.
 
#20 ·
could it be a problem with a heavy right foot wanting to hear the muffler. I just installed a CAI and I lost about 1.5 mpg, but I can promise you it is from the foot dilemma.
lol I had the same problem when I did my CAI, cherry bomb extreme (dumped in front of the passenger tire) and DSP...I've settled down a little since then, but I still like to piss people off at WOT...she's loud lol
 
#22 ·
tell your dealer he's full of s mufler has nothing to do with it . quite a few of the mds 5.7s have this trouble , trouble is in the damn mdf sys . not working right . but you cant tell the damn dealer that they know everything . same thing happened when they came out with the 4 8 cad,s a few years back . mdf systems suck then and now .
 
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