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Drone Fixed! V6 Convertible w/ aftermarket mufflers

davekro

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As many of you know, my journey to quell the drone after adding Magnaflow 11365 Mufflers (4x8" oval x 11" L straight thru) has been a long one. After having gone back to stock since last summer, I decided to try making branch resonators and giving them a try. I only wanted a moderately louder exhaust note, but stock was just too quiet. Up front, I want to thank Zackmd1 for his ideas and guidance last summer. Also big thanks to UglyJohn for not only sharing his learning down this road, but for most generously sharing the Excel spread sheets he had created showing the lengths required for differing rpm range drones.

So much information and I know I'll forget to mention a lot, but I'll post lots of pictures as well as sound videos (stock as well as MF 11365's w/ & w/o the new resonators) just so you can hear back to back. My muffler/ sound level preference is not 'Attack' or muffler delete loud, but more subtle. I am very happy with my exhaust sound, but I know it would be too tame for many. Viva la difference! ;)

I can share more detail later if desired (God knows I went into the minutia), just ask if you have any questions.


Before: (w/ Magnaflow 11365's)
11365%20orig.%20install.-900.jpg




Rear view: two 45" long 2.25" branch resonators w/ mandrel bend 180º's (4" CL radius) and very nice Borla double wall tips to finish.
Rear%20on%20jacks-622.jpg




Stealth look from the back. resonators not visible. :)
Rear%20level-622.jpg




A view from passenger side showing resonator curving up behind the rear valance. I used three band clamps per side because the resonators were designed to be adjustable from ≈ 40" to 50" and to be removable from the stub I had welded into the main exh. pipe. Turns out my 45" 'flow length' worked out better than I could have hoped for, so I did no adjusting! :D
Psgr%20side-622.jpg




A view of the branch resonator tube w/o the muffler. The top of the resonator has about 3/8" to 1/2" clearance between the cross member, the frame rail and the spare tire sump, so I partially wraapped w/ 3/8" thick black pipe insulation to insure it would not come in contact with any of those surfaces. I wanted to keep the mufflers removable, so the saddle clamp is tack welded to the main tail pipe. the hanger bracket seen above mounts with a 1 1/4" band clamp at the back of the muffler because it is off center and wants to rotate w/o it.
Dr.%20Sd%20wo%20Muf-640.jpg


***The secret to making this adjustable was finding tubing that had and i.d. that snugly slipped over 2 1/4" (o.d.) exhaust pipe. Turns out that galvanized fence post from Home Depot was a sung fit, but with sanding the interior seam a bit, it slipped right on (w/ help of WD-40 too).


A close up of the rear end of the resonator. It is secured with a heavy duty rubber hanger strap that the 3/8" muffler hanger prong goes thru (into the oem isolator above valance) while it's other end is bolted to an 'L' bracket secured to the trunk sump. A saddle claamp aattaches the resonator to the rubber strap.
Res%20Mtg-640.jpg



A look at how the resonator fits above xmember and between frame and spare tire sump. At the left you can just see the end of the other end of the rubber strap that the muffler prong goes thru (then into the oem isolator).
Res%20fit%20front-640.jpg



A view from in front of the muffler looking back. The yellow stuff in the frame rail and xmember is that expanding household foam I had used last summer to try to deaden the resonance/drone from the mufflers transferring to the body (made ZERO difference :headbonk:). And the cardboard you may notice above the xmember (above photo) was to confine the foam to the xmember.
Res%20fit%20rear-640.jpg



Another angle of the whole assembly.




Thanks to UglyJohn for these charts that give the needed resonator lengths given where your drone range is centered and it's associated frequency (Hz) at various average temperatures inside your res. tube.
The average exterior temp of my res tube on a 72º day was ≈ 100ºf.
[note: The formula used for these charts are based on 6 cylinders! At any given RPM range/ freq., the length needed for a V8 would be much shorter] My drone range was lower in the rpm range than most others, meaning my res. tube needed to be longer than most, hence the 45" for my situation.

Here is the chart for a V6 in the 1000 - 1700 rpm centered range.
UJ%20Chart-1700-.jpg

Here is the chart for a V6 with drone centered at 1800 - 2500 rpms:
UJ%20Chart-1800.jpg



And for the final touch, the sound videos, I'll put them in post #2

:cheers:

Thanks,
Dave
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davekro

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Sound clip w/ and w/o ressonator (& interior :eek:)

Here is the new No Drone with new 45" resonators:
(I aplologize that I must have inadvertently set the camera for macro, because it is very blurry. But the sound is what we are here for.)

The rest of exhaust is stock (w/ suitcase resonator in place and factory exh. manifolds)

[ame]


Here is the video from the inside of the car with the top up to confirm there is no drone! :cheers:

[ame]


And for a frame of reference, here are the stock mufflers that I had been running again since last summer.

[ame]

I am blown away at how much more I now enjoy driving the Mustang with it's new sound I L O V E it! !
 
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zackmd1

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Excellent work! Glad you finally got it acceptable to you!
 
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davekro

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My MMD Foose SPoiler arrives next Tuesday!

I'm all set for a while for mods after I get the new Foose spoiler can't wait to see how it looks with my CDC lightbar. Like Tina Fey says on the American Express commercials...
It's All Happening! LOL
(OK, you can see how the new exhaust sound has me all giddy.) :lol:
 
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davekro

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Excellent work! Glad you finally got it acceptable to you!
Now I wish I had not been so stubborn and tried your idea LAST SUMMER. ;) Thanks again for your wealth of info and blazing the exhausting trail that you have! :lol:
 
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Bay1Stang

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Happy for you. Seems like you've been struggling with this since forever.
 

six_shooter

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Great work, very detailed. I'm sure there are others out there that will benefit from this!
 

Blaster

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Truly amazing Dave. :cheers:

One can only imagine what a guy like you could accomplish if you were the type of person that stuck with problems till resolved completely. ;)

If it's not too much trouble could you please fix Ford's INSANE double honk when walking away from the vehicle with FOB while car is running. :crazy:
 
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davekro

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Truly amazing Dave. :cheers:

One can only imagine what a guy like you could accomplish if you were the type of person that stuck with problems till resolved completely. ;)

If it's not too much trouble could you please fix Ford's INSANE double honk when walking away from the vehicle with FOB while car is running. :crazy:
All I gotta say is that I'm glad to no longer be seriously unsatisfied with my exhaust. :D

 

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davekro

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few more bits of info...

I used Dorman 2 1/4" freeze plugs to cap the ends of my resonator tubes (pressed in + J-B weld).

Making the holes in the oem pipe was easier than expected. A fresh/new
2 1/4" hole saw worked well.



A shot at the muffler shop showing the welded stub, next the 2 1/4" i.d. 16 ga galvanized fence post tubing. slipping over the mandrel bent 2 1/4" o.d. pipe. There was no room for error on the exact orientation of the stub, so the resonator had to be mounted in place solidly, then sliding the 'slider' w/ stub on it up to the oem pipe to be welded. The welder did not listen and welded part of the passenger side slider to stub AND slider to mandrel bent 180º pipe. :frusty: :frusty: Thank God he stopped after the galvanized pipe (which he was told NOT to weld) flamed up his MIG welding tip. I am thankful that my initial calculation of 45" worked out great, otherwise, I'd have to grind off a bunch of his mistaken welds. On the other side)



Now cutting the stubs to fit the cutout hole was a lot more work. roughed out with a cutting wheel, then cleaned up with a bench grinder and wire wheel.
 

Terminator2

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Convertibles definitely suffer from more drone than coupes. My 99 GT vert had dynomax ultra flow SS mufflers on it which are the second quietest dynomax makes and it had a ton of drone. My 16 GT coupe has dynomax bullets which are the loudest dynomax makes and the suitcase resonator replaced with and X pipe and In my opinion no drone at all compared to my old vert.
 

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Thanks for the chart, it's super helpful! I've been looking for a solution to the drone on my exhaust setup as well (Flowmaster Outlaws with H-Pipe) and haven't had much luck. Where did you get the resonance pipes from?
 
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davekro

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Thanks for the chart, it's super helpful! I've been looking for a solution to the drone on my exhaust setup as well (Flowmaster Outlaws with H-Pipe) and haven't had much luck. Where did you get the resonance pipes from?
I started with (2) 2 1/4" [4" CL radius] mandrel bent 180º 'U' pipes. Even though to do it again I would not bothered to make it 'as' adjustable. At least the top leg needs to be a slip fit 'IF' your drone range requires a 45" long tube as mine did. The tight space of needing to get that ≈ 20" long upper leg up in above the frame's cross brace, means it has to be shorter then 'slid' out to make it longer once in place.

If you find a muffler shop willing to try/do all this for you and try to make it work, you could just buy the mandrel bent pieces and let them try to create it. Not sure if they could though. Read my first post about the 2 3/8" i.d. Home Depot fence post (red text) I used that very tightly slides 'over' 2 1/4" exhaust pipe. I decide to build my own and fit it in so I could be sure it was centered in the tight upper space. If aligned right, you get ≈ 3/8" clearance on the upper leg. I wrapped the upper leg in 3/8" thick water pipe insulation to act as spacers (and anti vibration, should the tube try to wander closer to the frame rail ;o).

Note the muffler shop will not like to work with the galvanized H Depot pipe as it catches fire when MIG welded and my guy had to keep cleaning sludge out out his MIG tip. But my guy was told NOT to weld that part (for my adjustability)... But... "Oh, I thought you wanted it all welded."
I'm glad I was right there when it started flaming up and he complained...
:frusty:

PS. I need to do a better drive away/ drive by sound video than the one posted.
 

Dangerboy

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Hi Dave,
I realize this is an old post, but would you happen to still have the exhaust pics? I love what you did there, but the pics in the post have the Photo Bucket logo over them so it's hard to see details & share with my muffler guy. Any way you could email them to me? If so, awesome! and I'll share my email.

Thanks for all your research!

Dan
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