Thanks for the input.

I have a 04.5 5.9 that I had to replace the exhaust. I went with a cat back 4" system. Before purchasing, I listened to a buddy's 07.5 6.7 that had a dpf delete and cat delete (4'" straight to (same mfg) muffler and stock tailpipe). It was really mellow and not that much louder than stock WITHOUT a cat.

I ordered and installed mine and it was noticably louder both in cab and out. I figured it "might" be due to resonation within my cat and then promptly purchased a downpipe and cat delete.

that didnt help.

At idle, mine is 4db louder and under load even moreso. According to the mfg., there was a slight internal design change of some sort between the two mufflers, but they think the decrease in note might be due to the new turbo design and different motor.

Any thoughts? They really do sound different..and whereas I cant specify an exact percentage..it is enough for me to figure out where I am at. (wife hates it..lol)

So my question is: (for those that have owned/know both motors)...

"Do you think that the "base exhaust note" coming out of these two motors should be notably different with both being "straight piped" ?

I guess another way of putting it is:

"if a 5.9 and 6.7 were sitting side by side and both were turbo back 4" straight piped and NO muffler/no cat and no dpf..would the 6.7 bigger motor indeed be more quiet? (i.e at idle and under load?)

thanks, bc3

I am leaving out the name of the mfg intentionally, but can tell you it is not MBRP

 

It's a combination of turbocharger, camshaft, fuel timing and egr that makes for a different sound.

 

I believe that there is additional injection events, also. May have something to do with the larger displacement, too.

 

Actually I have heard that pulling the VGT will make the 6.7 sound just like a late 5.9.

There is a 4th event, but the Smarty/H&S disables that.

I think the sound difference is mostly all in the turbo.

Of course logic does tell me the larger displacement has something to do with it also.

 

Blake - larger displacement is quieter? Also (to the others) even at idle..the turbo is cutting back the exhaust note? Do you think that swapping out the muffler with the newer/changed version might help? as far as sound..different is ok, but 30% (guestimate) LOUDER is the issue I have. My 5.9 is louder, deeper and raspier.

 

I never heard one with the turbo swapped out yet but i bet it sounds like a Kenworth going down the road

 

No not really quieter, but been told deeper.

Your best bet would be a quality muffler like the Aero series.

 

Add a 2nd 24/30 inch straight thru muffler and you will be amazed how it quiets down.i TRIED A flow master,magnaflow,51 inch nelson,flo pro.I now combined the magnaflow up front,flo pro back,really nice,took the sharpness out and a lot of the diesel rattle.