i have a 4" mbrp catback that sounded great but not loud enough, so i removed the cat (for offroad use) and now i have a nasty sputtering from the tailpipe. it seems worse when the engine is cold or at least its more noticable. i can hear it in my house while the truck is idleing in the driveway. any ideas what could be causing it? i thought it may have something to do w/ the muffler or tip but it only does it w/ the cat off so im guessing the sound is coming from before the cat and was being muffled by the cat. it also does it w/ or w/o the tip installed. there are no leaks anywhere and the sound is definately coming straight out of the tailpipe/tip. could it be the turbo or anything else causing it??

 

Is it kinda more like a flutter.
Like turbo blade hitting the air and causing turbulence in the more free exhaust sytem.

I have heard some Fords with that VVT sounding kinda like that.

 

Youre not the only person to say that about the mbrp systems, and some have mentioned the same about the donaldson muffler. Must be the muffler design doing that.

 

Yeah nothing to worry about, mine does it a little when cold but goes away when warm, I think it sounds kind of good

 

it sounds exactly like an exhaust leak, only coming out the tailpipe. im going to remove the muffler and see if it changes. i dont think people w/ no muff/no cat have this sound so neither should i, we will see if its the muffler.

 

I'm pretty sure it is the muffler...

 

Mine has a similar sound. I had no cat (off road truck) and the MBRP straight thru muffler and it didnt make the noise until I took the muffler off. Mine still has the Resonator over the axle though (side bar: what is in a resonator anyway?)
When my engine is cold it sputters, almost like a miss and has a flutter to it if in the pedal hard too.

 

I get that too. Only when cold thought. (well I do have a leak to fix.) The welds must have been thin and with all that pressure I blue out some spots in the weld. Oops.

 

I believe what you're hearing is the 3rd injection event. The cat muffles or softens it but when you pull the cat it sounds like the cat box smells, crappy. Allot of folks describe it as a raspy sound.

 

would i hear 3rd injection event at idle? thats when its most noticable, i cant really tell if it sputters while driving because the deep exhaust tone is all i hear.

 

Do you mean a VGT(Variable Geometry Turbo)? The 6.0's run them and they have a real distinct sound to them at an idle, almost a whistle.

Can someone tell me what year the 3rd injection event was introduced, 04 & up?

 

My truck does the same thing when its cold...almost sputters at idle till it warms up...then its fine.

No worries...

 

I think so. The 3rd event is there to cause the cat to stay hot and keep the emissions in check.

 

Thats it, VGT
Thanks for the correction.

The ones I heard at light throttle is when it fluttered with a strai exhaust.

 

i notice it on my 12v after removing the cat and muff. It's exactly what you describe and the injector events. i think it sounds kinda cool, almost, gasser stright pipedish.