No exhaust threads any more.

06 T-RED S/C GT · Dec 14, 2020

Enfield said:
Just got my '07, and it has serious drone problems, first at 12-1500 rpm and again just past 2000. Above 2800 the sound sweetens, but it's garbage down low. JLT3 up front.
Original owner installed BBK LT's - 1 5/8" to 2 1/2", followed by BBK catless x-pipe and Flowmaster Am Thunder - all 2 1/2". Somewhere along the way a PO added M-80's before the axle - no doubt to try to deal with the drone. They didn't work, and with 1" lowering springs they occasionally bottom on hard bumps at higher speeds.
This car is a cruiser, with no plan for track use, so I'm OK with running a lot quieter so long as the tune doesn't get messed up. It appears to be a Bama 93 that came with an old Diablo. Not crazy about the tune, but it gives good economy at cruising speeds. As an old hot rodder buddy put it, a lot of these canned tunes seem to feature hair-trigger throttle response off idle to make you think your car is a fire-breathing dragon.
At some point I'll want to add some grunt to the mid-range, but for now the priority is getting rid of the drone. It seems there are two choices for doing this: replace the Flowmaster AT's with stock-like mufflers, or add a Helmholtz setup. So far, this site's Search function hasn't returned any first-person accounts of a successful Helmholtz installation, but I'm willing to spend a little MIG wire on 2" and 4" pipes to fabricate a system.
The math is pretty simple, so long as you know the offending frequency - which by all accounts is around 80 Hz in the 12-1500 range. If anyone has a more specific number please let me know; I was using a freebie sound spectrum phone app that jumped back and forth between 60 and 120 as I droned along. A Youtube Helmholtz site featured a little chart that suggested a V8's problem frequency is right around 80 at the lower rpm range, so that looks like a good bet to plug into the equation.
The value I'm less sure about is the temperature of the exhaust gases within that 12-1500 range. I have no idea how to measure that within the area of the resonators - short of installing a set of old snowmobile EGT gauges that I used for tuning a road race car. After the 4.6 is warmed up, idling exhaust at the tailpipe is 175 degrees F, but I'm thinking that the critical vibration is coming from up around the M80's. I'm guessing it's 300 degrees F at 1350 rpm there, and have included the recognized speed of sound for 300 in my equation. If I install the EGT's, it will be through holes that can then be enlarged to weld in the J-pipes.
So, with 300 degrees and 80 Hz, the Helmholtz equation indicates that a 10.5" J of 2" pipe into a 4" can that's 8" long will effectively cancel the drone.
All suggestions, comments, criticism and so on are welcomed - including advice on moving this request to a different forum. Sure, you guys have beat the exhaust question to death for years, and every car is a little different with its tune and what-not, but S197forum does not seem to have much practical advice ion Helmholtz that I could find. Plenty of good ideas about exhaust and noise, though.
Enfield - 2007 GT convertible 4.6 5-spd with JLT3, BBK LT and catless X, M80's, and Flowmaster American Thunder axlebacks. Also lowered, and with 3.73's.

Even with the stock exhaust in place, Flowmasters have a horrible drone to them, to begin with aka Dronemasters lol. Once you modify from the stock exhaust by eliminating the OEM cats and especially going to LT headers, the frequencies that produce interior resonance drone are amplified twice as much. With the stock exhaust in place, there are 5 aftermarket axle back exhaust mufflers that are designed to either reduce or eliminate interior resonance drone altogether. Corsa performance exhaust, followed by Ford Racing M-5230-S aka GT500KR axle backs, MBRP, Roush extreme cat-back exhaust and Borla touring axle backs which are also an excellent choice for off/road, LT header applications for keeping resonance drone to a minimum. All are straight thru design, rather than chambered as the Flowmaster/Dronemasters are lol. Other than for the Borla touring axle backs, I can't really say for certain how effective the other exhaust systems mentioned would work out on off/road, LT headers applications, but have read on this site along with other Mustang forums that the Borla touring axle back mufflers do in fact work very well, so you may want to consider trying out the Borla Touring mufflers for your particular application. As for Helmholtz/J-pipe applications? there are 2 manufacturers I'm familiar with. Synapse engineering, no drone resonators http://synapseengineering.com/synapseusa/products/nodrone.html and Solo performance exhaust. Just keep in mind that Solo performance only offers J-pipe/resonator exhaust systems for the S197 2011-14 and current S550 2015-20 Mustang to the general public. However, they may be willing to custom fabricate a one-off system for your particular application? Anyway, here's the link if your interested in contacting them directly https://shop-solo-performance.com/en/31-ford-mustang Meanwhile, hope you find the info provided as useful.

Enfield · Dec 15, 2020

Thanks, 06. Given the lack of cats and the LTH I've got, the [relatively] quietest set of axle-backs is the one I'm looking for. I suspect stock would be OK, but they are pretty expensive. My local muffler shop quoted $230 apiece plus installation. Is there any reliable way you can rank the A/B's you mentioned according to loudness?
There's a muffler manufacturer called Walker nearby, and they offer a set of stock-looking mufflers: PN 53739 and 53740. Anyone have any experience with those?
tia, Enfield - just a fng

Juice · Dec 15, 2020

Stock mufflers for $60 in the for sale section.

Forty61 · Dec 15, 2020

Enfield said:
Thanks, 06. Given the lack of cats and the LTH I've got, the [relatively] quietest set of axle-backs is the one I'm looking for. I suspect stock would be OK, but they are pretty expensive. My local muffler shop quoted $230 apiece plus installation. Is there any reliable way you can rank the A/B's you mentioned according to loudness?
There's a muffler manufacturer called Walker nearby, and they offer a set of stock-looking mufflers: PN 53739 and 53740. Anyone have any experience with those?
tia, Enfield - just a fng

If you want stock mufflers just troll Craigslist, I found a quality used set of factory axle backs with the nice tips on them for $50 locally. Hell, if you trade what’s on your car now you may end up with stock stuff and a little cash on top!

tjm73 · Dec 15, 2020

I have a set of stock mufflers I took of a car at about 20,000 miles. Sitting in a box in my barn. Car is long gone. Forgot I had them till about a year ago.

Enfield · Dec 15, 2020

Good catch on the classifieds. Will a 2011 Coyote muffler work on a 2007 3v?
As a 70+ type with a C survivor wife, I've stayed away from CL and FB transactions strictly for health reasons.
Enfield

tjm73 · Dec 15, 2020

Enfield said:
Good catch on the classifieds. Will a 2011 Coyote muffler work on a 2007 3v?
As a 70+ type with a C survivor wife, I've stayed away from CL and FB transactions strictly for health reasons.
Enfield

Probably not without some modifications.

AHaze · Dec 15, 2020

Enfield said:
Good catch on the classifieds. Will a 2011 Coyote muffler work on a 2007 3v?
As a 70+ type with a C survivor wife, I've stayed away from CL and FB transactions strictly for health reasons.
Enfield

IIRC, the Coyote cars (maybe the '10 GT as well?) use a ball type connection from the over axle pipes to the mufflers while my early 3V uses a slip fit.

Juice · Dec 15, 2020

Sorry about that, I missed the ball type connection. No, won't work as is. My bad.

06 T-RED S/C GT · Dec 15, 2020

Enfield said:
Thanks, 06. Given the lack of cats and the LTH I've got, the [relatively] quietest set of axle-backs is the one I'm looking for. I suspect stock would be OK, but they are pretty expensive. My local muffler shop quoted $230 apiece plus installation. Is there any reliable way you can rank the A/B's you mentioned according to loudness?
There's a muffler manufacturer called Walker nearby, and they offer a set of stock-looking mufflers: PN 53739 and 53740. Anyone have any experience with those?
tia, Enfield - just a fng

According to Borla, the touring axle back mufflers provide more of a mellow, but deeper exhaust tone and also just slightly louder than stock when paired with the stock catted exhaust. With an off/road setup or LT header setup, their obviously going to be louder, but not obnoxiously loud. There was also a member on this site who had the Borla Touring mufflers paired with LT headers and high-flow catted H-pipe on his modified 2008 Mustang/Bullitt and said they provided the right kind of sound he was looking for with zero drone.

Enfield said:
Good catch on the classifieds. Will a 2011 Coyote muffler work on a 2007 3v?
As a 70+ type with a C survivor wife, I've stayed away from CL and FB transactions strictly for health reasons.
Enfield

As the other posters have mentioned, more than likely not without some serious modifications.

oldVOR · Dec 15, 2020

Enfield - Where are you located?
I see Shenandoah Valley in your profile.
I believe I have a set of '05-10 GT OEM mufflers kicking around that came off a 2009 GT/CS.

06 T-RED S/C GT · Dec 15, 2020

If the OEM set is from a "10" GT? the tips are going to stick out further on an "05-"09 GT's rear valance due to the design changes made to the rear valance from '09-10' Anyhow, just saying.

Enfield · Dec 15, 2020

TLM, what year? Depending on what's below, we may be able to deal.
oldVOR, are yours the slip-on type? If so, please furnish price and shipping to 24450. I see you're in NoVA; I'm near Lexington.
Thanks to all,
Enfield

06 T-RED S/C GT · Dec 15, 2020

Enfield said:
TLM, what year? Depending on what's below, we may be able to deal.
oldVOR, are yours the slip-on type? If so, please furnish price and shipping to 24450. I see you're in NoVA; I'm near Lexington.
Thanks to all,
Enfield

Doesn't matter if their slip-on or not! If his OEM axel back mufflers are from a 2010 GT? the tips are going to stick out by at least 1 inch further on a 2005-09 GT due to design changes made to the rear valance between 2009-2010. If your willing to deal with that? then they will otherwise fit onto your OTA pipes, being as they are slip-on types.

oldVOR · Dec 15, 2020

06 T-RED S/C GT said:
Doesn't matter if their slip-on or not! If his OEM axel back mufflers are from a 2010 GT? the tips are going to stick out by at least 1 inch further on a 2005-09 GT due to design changes made to the rear valance between 2009-2010. If your willing to deal with that? then they will otherwise fit onto your OTA pipes, being as they are slip-on types.

Read my post, came off 2009 GT/CS

Enfield · Dec 15, 2020

PM sent to oldVOR.

tjm73 · Dec 15, 2020

Mine came off a 2005.

06 T-RED S/C GT · Dec 15, 2020

oldVOR said:
Enfield-
I believe I have a set of '05-10 GT OEM mufflers kicking around that came off a 2009 GT/CS.

06 T-RED S/C GT said:
If the OEM set is from a "10" GT? the tips are going to stick out further on an "05-"09 GT's rear valance due to the design changes made to the rear valance from '09-10' Anyhow, just saying.

oldVOR said:
Read my post, came off 2009 GT/CS

Your posted stated '05-10' GT mufflers.. My response was intended to clarify only "IF" they were from a '10' GT that the tips would stick out further due to the change in design to the rear valance from '09-'10.. I didn't say specifically that they were. Just wanted to make certain that your set are for 2005-09 models, knowing the 2010's are different. However, being as they came off a 2009 GT/CS, it's more than obvious that your intention was actually meant towards having a set of OEM '2005-'09 mufflers. That being said, I now stand corrected for the misinterpretation on my part.

Enfield · Jan 17, 2021

Got the stock mufflers from oldVOR. They were delivered in a very clean white 08 GT/CS with sweet-sounding Borlas. Now installed, and they sound pretty good with the BBK LTH and catless X. Thanks to all.

oldVOR · Jan 17, 2021

You're very welcome. Glad someone could put them to use and they worked for your needs.

No exhaust threads any more.

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