I had an MBRP cat back SI/SO installed in my 2007 5.4 F-150 (supercab) last Friday at a local shop. There is a broad range of drone (1,400 rpm - 2,200 rpm) in the cab that is bad enough that I was going to take it out the day after I had it installed.

I thought I would first try adding a glasspack as a resonator in front of the muffler, as some have suggested on this site, in order to eliminate that drone.

Before adding the glasspack, I called MBRP this morning, to talk to them about it. They said to check the clamps for tightness and also to see if I could read the "MBRP" on the muffler from the passenger side. If it was readable from the drivers side, they said it was installed backwards and that could lead to louder exhaust tones. (BTW, I checked to make sure that the pipes were not touching the frame anywhere, and I did nothing to the intake during this install, which could have increased the drone).

Anyhow, it appears it is installed backwards. Has anyone else had this issue, and did flipping the muffler take care of the problem? Is there any drone in your trucks that have it installed correctly?

I'm wondering if I should install the glasspacks at the same time as the muffler flip... I definitely want to get rid of that drone!

BTW, MBRP told me they are now sending the F-150 (gas) setups with 3" pipes instead of the 3.5", as of Dec. 10th. Figures, I got the old setup..... I don't know if this was for more back pressure, less drone, better performance, or what.

Any insight would be appreciated.

 

now i wanna get a muffler installed backwards! Actually i have heard about diesels doing this with glasspacks to get that "straightpipe" sound and still get inspection stickers. What i would do is take your truck back the muffler shop and tell the guy to 'quickly' switch the muffler around, i hear that mbrp mufflers are one of the best sounding when installed correctly! good luck!

 

i would flip it around before putting the glasspack.

after you put the glasspack you may not like the sound, then your out more money

 

Sound clip?

 

I tried using my camera to make a sound clip this morning, but it doesn't have the audio quality needed to accurately hear the drone.

 

Take back to the shop, they are the retards that *******ed up...so it is on them. make them fix it and try and get some $$$ back too.

 

Everytime someone says "backpressure" it reminds me of farva in the movie super troopers when he said shennanigans. Lol

 

If some is talking about back pressure, maybe then need to see a chiropractor.

 

I took it back to the shop after talking to MBRP. The shop called me and said it could only be switched around if they cut the tailpipe off, as the tailpipe came from MBRP welded to the back of the muffler! I didn't even look at that when I
checked the direction of the muffler.

So, I called MBRP back to see if they had welded the muffler on wrong. Well...they changed their mind and said the gas mufflers work either way... Now I don't know what the true story is.

Long story short, I'm going to put a Thrush glasspack in front of the muffler on Tuesday to see what happens. I'll post the success, or lack of, in reducing the drone after Tuesday.

 

Or wait till someone here has an MBRP exhaust and see how theirs is installed!

 

How bad could the drone be, you still have the stock headers and cats? Just a replacement muffler really right? I know its a cat back with tail pipe, but I would guess the system is the same diameter and basic bends as the stock setup if its a SI/SO. Was the dampner removed when they took your old system off and put the new system on. Drone can come from other places than the muffler itself. Maybe get a pic of the setup? What size is the muffler

 

i have the SI/SO MBRP. from the passenger side you can read MBRP on the muffler

 

I have a siso MBRP. The sound is great from outside. The drone on the inside at around 1800 rpm almost makes my ears bleed. I had this set up for over a year now and just yesterday I questioned my sanity for not ripping it off earlier. I have also read about the muffler being backwards for some. I will look if I can read the MBRP from the passenger side. Our muffler can only be installed one way unless it was done backwards from factory. I was also thinking of a reasoner up front but never got around to it.

 

i want to say that the muffler wasnt welded to the tail pipe of mine. 99.9% sure

 

RiverRatF-150, so your muffler is installed the opposite direction of mine. Do you have the drone? If you do not have the drone, I will call MBRP again tomorrow morning and quiz them further to see if I should cut the muffler, flip it around and have it re-welded.

I just checked and the first tailipe section (about 18" with about a 30 degree bend) on mine was definitely welded at the factory.

To answer Toyz post, the only thing changed was the midpipe, muffler and tailpipe section. I did not do any other mods (i.e. CAI, etc.) and the exhaust is not touching the frame anywhere. However, the stock exhaust has a 2.5" O.D. pipe and this is a 3.5" I.D. pipe. I'm mainly concerned with others results with the same setup to see why some say they have no drone and I have a lot of drone.

Thanks to all for the help.