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Discussion Starter · #141 ·
Here's some pics of two 3" ID vibrant ultra quiet resonators installed on one of our shop k-swapped ek's. A pretty tight fit but clears the tunnel nonetheless...

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Interesting concept, putting them back there like that. The consistent bit of advice I've gotten from every muffler manufacturer I've chatted with is that the biggest body I can fit as far upstream in the exhaust the quieter it will be. Based on that, my intent is to fit one of those Kooks or Borla mufflers right after the exit of the downpipe. If those ultra quiet resonators fit back there, an extra 1/2" on each side seems like it aughta reasonably fit further up in the area below the shifter where the tunnel is wider.

It's freaking snowing here again, so I'm delayed, but I need to measure more to confirm or disconfirm the theory.

--Matt
 

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Might have to try the set up you have , for the 3” mid pipe did you buy the piping from a certain company or ????
The midpipe I found used , it was an eBay/Amazon special “godsnow” brand. They no longer are available online it would seem. My plan otherwise was going to be using the kteller 3” stainless bend kit I just got lucky with a friend coming across the for sale ad for my midpipe.
 

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Discussion Starter · #143 · (Edited)
Ok, snuck my car home during the break in the weather and had an opportunity to get some measurements. At the very tippy top of the tunnel, the narrowest spot is about 7" on the dot.

This is what I see just forward of the mounts in the tunnel:
Automotive tire Liquid Fluid Yellow Finger


It does flare out a bit below that but doesn't really get substantially wider below that, unless you go way lower, which I don't really think I can because of ground clearance. On the upside, there's very little lateral movement in the pipes up at this point. With ploy mounts on the engine nearby being the main limit to the amount of movement, it's pretty tight here. That said, the exhaust is approximately 1/4" closer to one side than the other as things go further back. Given that the rear muffler is going away, and I'm going from a center inlet offset outlet muffler to a center/center in the back, some adjustment will be needed in the back either way.

Things do widen up as you go further forward. I don't know that I'd wanna try to cram in the 7.5" or 7.8" wide options, but that does leave quite a few options on the table:

Vibrant Ultra Quiet:
((4.75" / 2) * (6.5" / 2) * π * 9.75") - ((3" / 2)² * π * 9.75") = 167.4257813in³

Summit 630437:
((4.5" / 2) * (6.75" / 2) * π * 10") - ((3" / 2)² * π * 10") = 167.79375in³

1320 Ultra Quiet:
((4.375" / 2) * (7" / 2) * π * 10") - ((3" / 2)² * π * 10") = 169.75625in³

Quick Time Performance 12300:
((4.5" / 2) * (7" / 2) * π * 13.5") - ((3" / 2)² * π * 13.5") = 238.44375in³

I've got 21" between the hanger points and the step up from 2.5" to 3", so length isn't really a limiting factor. Based on that, it seems like the QTP 12300 might be a winner. With the body at 13.5" long, the inlet/outlet collars can be cut down to make the install a bit more flexible by pushing the muffler forward a bit. I don't love whatever's going on with the perforated divider down the center of that muffler - their "dual flow" feature. It's by far the biggest case that seems like it'd reasonably fit though and the core is otherwise 3" perforated pipe. Possible turbulence from the divider set aside, it doesn't seem like a major restriction. It's the same thing Dynatech does with their split flow mufflers, and I don't really see anyone complaining about it there.

--Matt
 

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Discussion Starter · #144 ·
Well, ordered the QTP muffler. As far as I can tell, it's a clone of a Dynatech Split Flow made with better materials. Seems like it aughta fit, and has substantially more internal mass than anything else that seems like it'd fit.

The manufacturer quotes the weight at 8lbs, too, so it's only trivially heavier than the 5lb of Dynomax race bullet that's under there right now. The Dynomax can theoretically cut 4dB of sound, whereas this is intended to cut 10dB, so that's a pretty massive difference.

I also got another Mishimoto v-band setup for the front end of the mid-pipe, since the 3 bolt setup and needing a new gasket makes dropping the exhaust suck way too much. 😂

--Matt
 

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I am absolutely pleased with Vibrant exhaust products. For the most part they are compact, quality made, and they are packed well which helps them last. They have a "class" sound with little drone and are cold start "neighbor friendly" for the most part.

For home owners, I want to design a sound catch cylinder that can be left in a driveway. Basically a thick tube (sch 40-80) that's height is centerline to the muffler exit positioned so the sound is directed into it.
 

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Discussion Starter · #147 · (Edited)
I am absolutely pleased with Vibrant exhaust products. For the most part they are compact, quality made, and they are packed well which helps them last. They have a "class" sound with little drone and are cold start "neighbor friendly" for the most part.

For home owners, I want to design a sound catch cylinder that can be left in a driveway. Basically a thick tube (sch 40-80) that's height is centerline to the muffler exit positioned so the sound is directed into it.
I agree. They're definitely a pack leader in many respective product categories, certainly exhaust parts among them. Their build quality and fit and finish are top notch, and their sound is refined. I've never done a full system with their mufflers, since I'm old and tend to want to keep a lower profile in the looks and volume department. 😅. I have put Ultra Quiet resonators on a couple cars, though, and they certainly punch above their weight class. Their sizes and configurations are somewhat limited, though.

I'd always been a fan of Dynomax stuff, historically, but their products haven't evolved over time and their fit and finish can't compete with Vibrant. They're also on the rowdier side, which younger me liked but now me doesn't love as much.

Magnaflow...looks nice, but I've put their stuff on 3 or 4 cars over the years and always ended up changing it because the sound was bad, too loud, or they had bad drone problems.

Borla, I like. They tend to have a mellower tone, which I appreciate. Prices are a little high, though not prohibitively so, but every part I've had of theirs has been considerably heavier than the competition...which I don't love.

Flowmaster...is Flowmaster. I know, I get it. Not straight through, FlowFX excluded, and signature sounds you won't necessarily love. Their "wonky" designs that look good on paper until you try to use any sort of math with the "we don't believe in flow benches because exhaust is delivered in pulses" and minimal data otherwise. Nevertheless, they don't tend to kill perf on dynos any more than any other non-straight-through mufflers, and their louder designs even tend to keep pace with max perf straight through stuff. Their quieter designs tend to do their quieting job well, though, and their build quality is great.

I've still been toying with the idea of a streetpower instead of the Flowmaster out back. I've got till Friday when I go to the exhaust shop to shake it up, and still might. I really wanna overshoot on lowering the sound level, if at all possible, though. If it ends up "too quiet", which I don't have a ton of faith in, I can always consider it afterwards.

My main holdup with any Vibrant mufflers back there right now is that I need to get the pipe over the rear lower control arm inboard a couple inches. I've got a 5x9 oval center inlet muffler on now, which just clears the mount for my bar, but the pipe taps the links with them as short as I can go and is closer than I'd like to my rear brake lines. I'd have to go with a 6 inch round street power, which likely would not muffle as much as I'm wanting.

Oh my, and there I went making a wall of text. 😂 I like Vibrant. I really do. I've got a bit of a fitment pickle, though, and they don't seem to have anything that'll help me and still be as quiet as I want.

--Matt
 

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Thanks for doing this, quieter is definitely relative to my interests (I leave the house a 5am, lol). Have you thought about using one of the phone apps to track frequency and noise level to see a db reduction?
 

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Discussion Starter · #149 · (Edited)
Thanks for doing this, quieter is definitely relative to my interests (I leave the house a 5am, lol). Have you thought about using one of the phone apps to track frequency and noise level to see a db reduction?
There's a measurement back here:#81

Here it is just for consistency:
Colorfulness Rectangle Slope Font Screenshot


That covers 50mph flat road cruising in 6th, since that's the worst case scenario for me at the moment.

The scale here represents the maximum Spectroid can record using the microphone as 0dB, so that peak is 28dB from "as loud as it gets".

Here's a pull from 3000rm to my 8600rpm redline in 2nd.
Colorfulness Slope Rectangle Font Line


1dB louder at its peak in the low freqs but, as you can see, the upper frequencies are also elevated while passing through there.


For scale, here's a sample from my '19 Fiesta ST (stock intake and exhaust), which isn't a terribly quiet car, holding 50mph on a flat road:
Colorfulness Water Rectangle Slope Font


Unfortunately, this is done with a different device than the first two, since I upgraded my phone since then, so they probably can't be directly compared. 😞 Interesting that the FiST is about 10x less loud at the spot where the Civic is it's loudest, but is apparently even louder down near the lower limit of what I can hear.

If I can get out tomorrow evening before this swap is done, I'll try to get some fresh recordings. These were all taken at steering wheel level in the center of the front seating area with the windows up.

--Matt
 

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Discussion Starter · #150 · (Edited)
Ok, got some samples this evening. Everything was taken with a Pixel 6.

Here's a video of the idle at 6' behind the car:

Here's a specragraph of the same:
Colorfulness Light Rectangle Font Slope


Here's one of steady state cruising on a flat surface road at 50mph in 6th:
Colorfulness Rectangle Slope Font Line


Here's [email protected] starting in 3rd, then coasting back to 40:
Colorfulness Light Rectangle Slope Font


Here's cruising at 30mph in 4th on a flat surface road:
Colorfulness Rectangle Font Slope Line


--Matt
 

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Thanks for the update.
I have Spectroid on my phone for a while now and while I like it I found the db aspect was confusing. I have a decibel meter and then today I downloaded a decibel meter app which confirmed my cheapie meter was a little low (3db). It's loud in here, averaging 80db, with VTEC peaking 93db.
I started to work on a drone of about 100hz at 80 mph, (@ 3200 rpm) but realized I should buy and install the QTP, and then circle back to the drone issue incase the frequency shifts. Hopefully this will help us both.
 

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Discussion Starter · #152 · (Edited)
🤞really hope the QTP fits. Will find out tomorrow! Appointment is at 11:00 EST. I'll just roll with the Vibrant if the shop thinks its too tight. It's honestly just shy of 1/2" wider, though, so I'm trying to stay positive about it. 😁

Spectroid seems like a reasonable enough tool for the job. The lack of absolute measurements is an upside and a downside. Since a phone mic won't be a calibrated instrument, and its frequency response won't necessarily be linear or predictable, but it seems like a pretty reasonable at-hand option for side-by-side comparison...provided all other variables are held constant. A basic dB meter, even a well calibrated one, while providing a nice absolute figure which can be compared across devices and locations doesn't offer the level of resolution it does.

Obviously, a calibrated spectrum analyzer would be best...but I'm not about to go down that road for personal use.

--Matt
 

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Discussion Starter · #158 ·
Here's how the rear section wound up (before the hangars went on). He was able to sort out the pipe around the gas tank and suspension. The edge of the tank is rolled slightly, but the additional cleanup with the over the axle bend paired with that spaced it out enough that they never touch...which is a big improvement.
Tire Wheel Vehicle Motor vehicle Automotive tire
 

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Discussion Starter · #159 · (Edited)
My video clip of idle is screwed up, and it started raining, so I'll have to grab a new one another time. I did get some measurements though!

These are all Before (Stainless Works + Bullet) then After (DBX + AR3).

Here's idle:
Colorfulness Light Rectangle Font Slope
Colorfulness Light Rectangle Font Line


Here's 30mph:
Colorfulness Rectangle Font Slope Line
Colorfulness Rectangle Slope Font Parallel


Here's 50mph:
Colorfulness Rectangle Slope Font Line
Colorfulness Rectangle Slope Font Parallel



Subjectively: The drone, at its worst, is not less loud. Drone does appear at fewer points, though, so I am able to at least find gear/speed combos that find tolerable spots where I previously couldn't. 40mph and 50mph were absolutely intolerable, but 5th and 6th are tolerable. The Stainless Works muffler had horrible chainsaw-at-redline rasp from about 3k up that is also totally gone.

Objectively: It's far quieter. The range of frequencies where it is loud has been substantially reduced. I couldn't really hear the intake much before, and it's a really loud intake, but I can hear it quite well now. The higher frequencies, as you can see above, are definitely managed far far better - and this can be heard

The mind does wonder what the SW would have been like with the AR3, but what's done is done. I know that the prior setup mellowed after 100 miles or so, which I generally experience with most exhausts, so I'm assuming this will too. Need to wait for the weather to improve and put on some more miles.

The QTP muffler fits great where they put it. There's an easy 3/4" at the closest spot, and there's really not much movement up in that spot. It definitely seems like a contender for EG/EK setups that need to cram some more muffling under the chassis.

I need to get some more miles on it, but I may still consider adding a hot dog shaped resonator or this Vibrant that I already have in the middle. The 26" MBRP would definitely fit, and there's a good chance either one of them would help attenuate that frequency. I'd also like to give the damper another try when I have time.

So...after yet another wall of text...that's where I'm at. ;)

--Matt
 

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Discussion Starter · #160 · (Edited)
My 24 hour update is that the drone is still very much an issue and something more needs to be done. With the current revised pipe routing, I do believe a Street Power would fit. There's also plenty of room where one of those 24" or 26" glasspack shaped options could fit in the underbody.

Given the extremely narrow range of the problem frequency, a Helmholtz or quarter wave resonator would probably be fantastic. Sourcing and fitting one on this chassis is not so straightforward though. I don't have room for a canister by the muffler, let alone meters of pipe.

I tried, again, to get an idle clip and the mic just clips no matter what behind the car at this distance.

So, while it's otherwise quite tame at most frequencies, it seems like the DBX has a serious flaw in this configuration.

As a heavily performance-oriented engineer who makes small compromises for big improvements all day long, in my line of work, it's an awfully deflating outcome. 😂 A big spike in a tiny range of a graph where everything else is otherwise much lower is normally a rousing success. 30x reduction in sound level at 10kHz looks great on paper, but not so great when my ears are left with that.

--Matt

Edit: I was curious, and happened to have it here, so I stuck the 18" Dynomax Race Bullet I had sitting in my shed into the tip of the DBX and it made a tight seal. The sound level was reduced as a whole, but not by much.
 
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