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V8 Miata Exhaust Air In/Air Out...This area focuses on allowing your V8 Miata to exhale in the most efficient and acoustically pleasing manner possible.

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Old 12-13-2014, 05:53 PM   #1
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Default Muffler replacement options

Looking for a thoughts / advice / experiences with a couple different muffler choices I'm currently considering.

My current set up is true dual exhaust with Monster Miata headers / 3" exhaust / Magnaflow cats / 2 x Flowmaster Super40 mufflers. I *love* the Super40s but the resonance at low engine speed is intense and completely unbearable with the top up (rare, but it does happen). I'm also getting a lot of - ahem - comments on how loud they are (esp from the missus....).

So my thought at the moment is swapping out the Super40s for two Flowmaster ProSeries, which should turn down the volume a bit and cure the resonance. They ain't cheap though so I'm curious if anyone has experience with these in a V8 Miata. Also welcome advice on other options (Borla ProXS? Magnaflow?) though I've looked around at these and there don't seem to be many 3" options that would likely fit on the Miata.
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Old 12-13-2014, 09:34 PM   #2
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sounds like you need a couple of resonators in line.
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Old 12-14-2014, 08:12 AM   #3
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I have the Magnaflows & like them. I suggest that you start with an x-pipe in your current set-up.
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Old 12-14-2014, 04:47 PM   #4
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Flowmasters are horrible for resonating. Have them on my 91 stang, cannot stand them. Going with Magnaflows down the road.
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Old 12-14-2014, 10:18 PM   #5
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I'd keep the system you have and just fix it with a resonator in it. Much cheaper than changing out the mufflers. I've had really good luck with car chemistry inserts.

http://www.summitracing.com/parts/cci-3di25r/overview/

I've used both 2 and 3 discs and I'd go with 3 for what you are doing. Just shove one in each header and that should do the trick.

If you want to go a cheaper route screw inserts work just about as well but probably cost a bit of power. This is what I'm running in mine right now.

http://www.summitracing.com/parts/pte-h3844/overview/

I'm just using 2 screws and it works great to kill the drone on the hwy.
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Old 12-16-2014, 09:30 PM   #6
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I ran 2 1/2" pipe back to a Magnaflow dual in/out muffler. Used one of each end as in and the others as outs. It had very little drone but I added resonated tips to take the rasp out of the tailpipes. Search "Nadine drive by" on youtube to hear it.
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Old 12-21-2014, 11:51 AM   #7
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Many thanks for the tips and advice! I was intrigued by Meiernutz's setup - which IMHO sounds fantastic in the drive-by video - but I decided the resonator option would allow me to avoid re-plumbing the whole exhaust. With Tbone's x-pipe and Charchri4’s insert suggestion, I set off on a bit of an internet wander to figure out which would likely work best for me. I learned a couple things along the way I'd thought worth sharing.

First, an x-pipe won’t cost any power. One indication was an old Car Craft article ( Exhaust System Installation H-Pipe, X-Pipe,- Car Craft Magazine ) that shows an x-pipe set up delivering the same HP as open headers, in contrast to an h-pipe set up that cost 10hp in this set up. The usual caveats about “your results may vary” etc apply here but I’m highlighting this article because (i) it shows dyno results for three set ups on the same car, (ii) it was Magnaflow doing the installs and (iii) the set up with the x-pipe is pretty neat and may be of interest (2-½-inch tubing from the headers to the X-pipe, 3-inch out of the X-pipe, flaring to 26 inches of 3½-inch tubing that necks back down to 3-inch entering a pair of Magnaflows; there’s a pic with the article).

Of course, this article doesn’t show the dyno sheets so, before I get taken down a peg by h-pipe proponents, let me acknowledge that I do realize that the curve from this arrangement should show a gain in torque at lower revs. I'm guessing that few will think that V8 Miatas need a bump in low-end torque (then again, who am I to argue with more…) but some may prefer the more traditional “muscle car” sound from an h-pipe.

Speaking of sound, the second thing I learned is that an x-pipe should also dial the volume down. Apparently, an x-pipe promotes better scavenging and a more “laminar” flow of exhaust gases (i.e. more parallel to the walls of the tubing), which is much quieter. According to Magnaflow (in the article above), an x-pipe set up can be up to 8 decibels quieter than an h-pipe. This neat video visualizes the different flows in x- and h-pipes (
) but I note there’s no attribution on who made it so caveat emptor.

Third thing I learned is that my 3-inch exhaust is probably overkill for my engine size & power, at least according to this handy little reference table ( How To Calculate Muffler Size and Exhaust Pipe Diameter - Exhaust Videos | Exhaust Videos ), which indicates that 2 1/2-inch would be plenty. I confess, I didn’t dive into the math (I’m a metric kid, and inches and feet get me all muddled…) but I do note that a lot of V8 Miata seem to have exhausts smaller that 3-inches that folks are pretty happy with (the best stamp of approval).

So, bottom line for me is looking like, come springtime, a Magnaflow 3” Tru-X ( MagnaFlow Performance Exhaust ) will be among the first things installed on my NA. I’m going to try to get a hold of a decibel meter and do some dyno pulls before and after the change, and will post the data if I can.

Hope the above is somewhat useful / interesting and, again, thanks much for the tips and advice.
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Old 12-21-2014, 12:10 PM   #8
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A long while back, Hot Rod did a side by side dyno of exhausts to see what flowed best. To the surprise of many, the best system was a 2 1/2 into one 3" pipe, then muffler with 3" ins/outs. I would imagine for all the same reasons you stated above. Science be damned, car guys love the look and sound of duals!

Last edited by Meierznutz; 12-21-2014 at 12:15 PM.
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Old 12-26-2014, 12:10 AM   #9
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^^ Roger that Chris and the good news Darren is you have probably the best sounding small block ever built. Thanks for the great write up that is really good stuff!
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Old 01-01-2015, 05:30 PM   #10
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I run stock 2006 mustang GT muffler and i like it. Only muffler with high flow cat converter. Ad a small h-pipe.
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Old 11-10-2015, 01:01 PM   #11
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Default UPDATE - new mufflers

This past June I took the plunge and swapped out the Super 40s for twin Flowmaster Hushpower dBX mufflers (part # 12514310). Local heros at Wicked Garage did the install. I was worried I was going to kill the awesome soundtrack but turns out the new laminar-flow miracle mufflers sound, I think, just as awesome. They are somewhat quieter when right foot is restrained, have a fantastic bark when deeper into the throttle and the only thing that was killed was the oppressive low-speed drone / resonance of the Super 40s.

Hear them here, let me know what you think:

(ps - I know, I know, the pulley chirp! It's been fixed!)
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Old 11-10-2015, 01:05 PM   #12
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Sorry can't tell from the video you'll need to come to Atlanta in April and show us!
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Old 11-10-2015, 03:29 PM   #13
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Quote:
Originally Posted by charchri4 View Post
Sorry can't tell from the video you'll need to come to Atlanta in April and show us!
Love to! But the trip would be a lot more feasible if our dollar could recover substantially from its present sorry rate of exchange...
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Old 11-11-2015, 02:03 PM   #14
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LOL I hear you just had to ask! Sounds good like all Fords do but I think Gabes is still my fav. The car looks great and I'd like to see more of that hood.
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