Muffler talk

[Reecer]

This is a long story do I will compress it.
Rebuilt motor, MMX +30 NSR NTR cam. Hemifever tune. Mufflex 24”.
Caused severe resonance.
Little to no resonance before the new cam. It all started when I was testing the new tune, remote testing.
Put stock muffler on, still hurt my ears but they were and still are sensitive to whatever happened to them, so put the Diablo 87 tune back on it. Now the Diablo 87 tune with stock exhaust hurts my ears and makes them ring. ( been a year + )

Normal train of thought. Bigger muffler case is bettter. I recently grabbed a used 14” Total flow straight through oval for cheap and put it on. After two days is has to come out. Since it’s the low frequencies bugging me, I was hoping the 14” case would change the hz higher, but it went lower and wider.
I read that people have good luck with 6” round mufflers in regards to cabin noise.
Maybe round reflects sound waves in a smoother pattern than oval even though oval has more sound deadening material in it. ?
I have read pretty much everything including drone occurs when you have a muffler that has two exit points within the muffler?
Stainless can ring more than aluminized steel piping?
Have the dual exhaust tips further out from the bumper. ( I have a big horn edition 2011 )
I was going to try the Ultra flow 6” with a y after it, but since I live where I live the shop wanted 4-500 to put it in after I supplied the muffler and y pipe. lol

I have been thinking of the factory muffler with a j -pipe, and delete the factory resonators as they are probably not tuned right anymore, or add better ones.

Also still the Ultra flow 17223 6”, and if it’s too loud add a Vibrant resonator before muffler.

It would sure be nice to be able to use the Hemifever tune at some point again.

Things were so much easier with my 1969 F100, cammed 302, great sounding and never droned.

It sounds like the new cam shifted the exhaust frequency into a range that’s causing the drone more than the muffler itself. If it were my truck, I’d start with a J-pipe or tuned resonator before spending money on more mufflers. A 6” round muffler may help, but there’s no guarantee it’ll eliminate the issue. Hopefully you can get it dialed in and enjoy the Hemifever tune again.

 

[SD2020]

It sounds like the new cam shifted the exhaust frequency into a range that’s causing the drone more than the muffler itself. If it were my truck, I’d start with a J-pipe or tuned resonator before spending money on more mufflers. A 6” round muffler may help, but there’s no guarantee it’ll eliminate the issue. Hopefully you can get it dialed in and enjoy the Hemifever tune again.

I plan on getting a j pipe sooner than later, hopefully when things slow down for me a bit. I also thought about checking my cab vents to make sure they are in tact. On a facebook page, some folks had some that were falling apart, and that would let in some resonance I’m sure.

 

[04fxdwgi]

I plan on getting a j pipe sooner than later, hopefully when things slow down for me a bit. I also thought about checking my cab vents to make sure they are in tact. On a facebook page, some folks had some that were falling apart, and that would let in some resonance I’m sure.

Do a search and here for cab vent failures and the body count is very high, me included.

I was able to remove the rear seat (and did the fold down mod at same time) and install the new style vents from inside the cab, others have said they couldn't do it

 

[SD2020]

My vents were all just fine. Pushed on all of them and they snapped back. I was kinda hoping they were broke lol. I thought about the seat mod, but never did it…..yet. Honestly it’s probably a good idea for folks to pull those 18mm bolts out, clean them up and goop them up a bit as mine were a bit rusty/dirty. ( mostly the rear ones )