DIY Turbo Discussion greddy on a 1.8? homebrew kit?
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Very quiet turbo exhaust - LFN sensitivity

 
Old 07-12-2017, 08:40 AM
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Originally Posted by shuiend View Post
​​​​​​​$1400 and I can have a manifold, turbo, and full exhaust delivered to your door next Thursday morning. I will be driving up through Indiana on my way to Michigan City.
Poscat for smooth salesmanship.
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Old 07-12-2017, 08:43 AM
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I took out the package tray and put pink, houseing fiberglass in the two chambers either side of the gas tank. Absorbed almost all of the remaining noise from the 3", Magnaflow muffled exhaust, as well as transmission and diff noise.
I actually did this with old rags...probably doesn't work as well as insulation, but it did help a lot with the high frequencies. Low frequencies still seemed to cut right through though...maybe the fiberglass would help more with that?

$1400 and I can have a manifold, turbo, and full exhaust delivered to your door next Thursday morning. I will be driving up through Indiana on my way to Michigan City.
Dude....why do you have to temp me with such tantalizing propositions on short notice? It would include a cat and resonator too? How much more for the intercooler kit and oil lines? I think that would complete my setup all in one shot. I could potentially pay in cash too if that merits a discount :-)

Meditate on this, I will.


P.S. I appreciate the apparently coordinated 1984 references amongst the moderators.
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Old 07-12-2017, 08:48 AM
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Originally Posted by Engi-ninja View Post
Dude....why do you have to temp me with such tantalizing propositions on short notice? It would include a cat and resonator too? How much more for the intercooler kit and oil lines? I think that would complete my setup all in one shot. I could potentially pay in cash too if that merits a discount :-)

Meditate on this, I will.


P.S. I appreciate the apparently coordinated 1984 references amongst the moderators.
I have to tempt you because currently I am running my Red, White, and BOOOOOST sale. I honestly don't think I can have a cat installed by then. Mostly because I don't have any on hand and don't think I can get one to me before next Wednesday and still have time to weld it into the exhaust. I do think I have a resonator or two. I would have to check tonight on those. No clue what brand, but are still 3". I also sort of lied about what all I could deliver then. I would only be bringing up the exhaust and maybe oil line setup. I know I can't have an IC setup done by then and I won't have the turbo. Send me an email to [email protected] if you want more info or are serious.
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Old 07-12-2017, 09:22 AM
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Email sent. Seriousness depends upon how much money can be saved.
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Old 07-12-2017, 09:43 AM
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Originally Posted by Engi-ninja View Post

Dude....why do you have to temp me with such tantalizing propositions on short notice?
He did the same thing to me ...lol. Just PM'd him about pricing and 4 days later I was meeting him and picking-up my kit ...
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Old 07-12-2017, 09:52 AM
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Originally Posted by Supermoto65 View Post
He did the same thing to me ...lol. Just PM'd him about pricing and 4 days later I was meeting him and picking-up my kit ...
I try to deliver quickly when I can. I still have to get your oil lines and clamp out. I have not had a box that is reasonably sized to ship them in.

​​​​​​​This weekend I am driving to Knoxville to deliver a NA setup to a guy who placed an order last weekend.
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Old 07-13-2017, 04:07 PM
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So I found EO2K's exhaust party post...however, it only shows a single resonator. Did he add a cat later? Would it be better to have one resonator and a cat, or 2 resonators....if they would fit...?

Sunday was rather productive

I drove up to Gesso's place and arrived much later than expected (about noon.) Pat didn't get there much before I did so I don't feel quite so bad for making people wait. We got started pretty much immediately by ripping out the stock exhaust.


Steady state highway cruise at 80~ish really has a tendency to heatsoak things. Great big fan really helped pull the heat out of the cast iron behemoth manifold so I could actually, you know, unbolt it.

Not shown, removal of stock exhaust, manifold and installation of turbo, manifold and downpipe.


Clever muffler mounting trick is clever. This gave us the support needed to figure out where to put the hangers. Not sure where Gesso saw that but holding up the giant magnaflow would have been a challenge without it.


Gesso using his magical machine to add said hangers to said muffler.


Much marking, cutting, thinking, cutting again, and tack welding thus commenced!


That's no joke... I think we were at this for something like 8 hours? Its insane. We made a lot of quick progress then got bogged down in fitting all the crazy little bendy sections.


My god, its full of stars!


Little lower angle for you. I was not sure that big *** 5" OD resonator was going to fit, but Gesso said we could do it, so we did it! You can see the flex joint in the ARTech downpipe just ahead of the resonator body.


A small variation on the classic "broomstick test." Exocet can be seen in the background mean-mugging. I think it wants to be next.


The fitment really is quite amazingly good, seeing as how none of us had ever done this before. I was sure to turn on the flash so I could make Jeffbuc's eye twitch


On the far left you can see the 180° we had to cheat about 3/4" out of the middle to get things to tuck properly. In the end it really should not matter.


Here she is on the ground. That far exhaust hanger will get triangulated before everything is said and done.


So much win! 3" from turbo to bumper. ALLTHEFLOWS! It should be epicly silent as well.

As promised, here is the shopping list:

1 x 4" x 5.25" Stainless Double Wall Angle 3" Inlet Tip ~ DT-30101
1 x 3.00" Mild Steel, 4.00" Radius, 16 Gauge, 180 Deg. Mandrel Bend ~ MS-16-300-400-180
2 x 3.00" Mild Steel, 4.00" Radius, 16 Gauge, 90 Degree Mandrel Bend ~ MS-16-300-400-090
2 x 3.00" Mild Steel, 4.00" Radius, 16 Gauge, 45 Degree Mandrel Bend ~ MS-16-300-400-045
2 x 3.00" Mild Steel, 4.00" Radius, 16 Gauge, 18 Degree Mandrel Bend ~ MS-16-300-400-018
2 x 3.00" Mild V-Band Assembly ~ VBAND-300-ASM-MS
4 x 3.00" OD, 16 Gauge, Mild Steel Straight Tube ~ MS-300-065

1 x Magnaflow PN 12579 5x11x22 C/C 3" I/O w/2.5" dual cores

1 x Vibrant PN 17950 Large Diameter Bottle Style Resonator, 3" I/O, 5" OD body

Notes:
  • I think we only used about 1' of the 4' of pipe that I purchased due to the resonators length
  • We could have probably used at least one more 18 degree section
  • I stole a chassis mounted hangar off another exhaust that was in Gesso's garage to add a 4th hangar location for the muffler
  • A couple of cuts will need to be made somewhere along the system to add v-bands to make things a bit easier to remove.

Right now its tacked up and sitting on the floor in Gesso's garage. The plan is to backpurge the whole mess and he can finish tiging up the seams at his leisure. I'm hoping to be there so I can try to maybe screw up some of his hard work

Yeah, that's right, its mild. Come at me bro! It was significantly cheaper than stainless and for my needs, it will do just fine. I also found that there was a significant lack of angular diversity when I was hunting for stainless bends. I don't drive in the salt/snow so meh.

V-Bands will make it a lot more modular as well. If the front section with the resonator becomes too troublesome, we can remove it and replace it with a smaller one, or maybe even a high flow cat. This should also be modular enough that if I do something silly like changes horses midstream YET AGAIN the system can change with my frivolous desires.

Keep in mind this is all "practice" for when we spring into action on Gesso's car. I have a sneaking suspicion that exhaust will be very similar to this one. I think we will probably be building something for the Exo and Pat's car as well, depending on how things go.

Once again, I cannot thank Gesso and Pat Cleary enough for the mad romp through exhaust land. Time and effort are very much appreciated
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Old 07-13-2017, 04:24 PM
  #28  
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Originally Posted by 18psi View Post
I say this to everyone, because it's true:
you want the quietest-est exhaust: go copy EO2K's. It uses the MT approved Maggie and then adds a resonator and cat. It doesn't get much quieter, and that even includes a stock muffler, which rattles like crazy on a turbo car (I actually tried it)
My car is even quieter, because I have a similar setup, but added a flapper valve. It really quiets it even more when cruising.

https://www.miataturbo.net/diy-turbo...r-valve-62488/
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Old 07-13-2017, 04:52 PM
  #29  
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Maybe I mis-remembered and he's catless. In which case, adding a cat would reduce sound even more.

And yes Jason, I ran a flapper on my Subaru after our discussion about it. Agreed, it helped even more. (though I went the cable operated flapper route and not sprung)
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Old 07-13-2017, 04:58 PM
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My car is even quieter, because I have a similar setup, but added a flapper valve. It really quiets it even more when cruising.

https://www.miataturbo.net/diy-turbo...r-valve-62488/
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I tried on of these when I had the race pipe and cobalt; it seemed to help more with the high frequencies, but it didn't really do much for the low frequencies.

Maybe I mis-remembered and he's catless. In which case, adding a cat would reduce sound even more.

And yes Jason, I ran a flapper on my Subaru after our discussion about it. Agreed, it helped even more. (though I went the cable operated flapper route and not sprung)
Would adding a cat be better than adding a second resonator?
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Old 07-13-2017, 05:07 PM
  #31  
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a resonator tones down resonance. that's all it does. if you want to get rid of rasp, a resonator is your friend
to muffle sound you need lots of packing/sound absorbing material, or something in the direct flow of sound. a resonator doesn't do either of these.
many people think it quiets down the volume of exhaust, but that's not really the case. a muffler muffles the exhaust, and a cat also mufflers the exhaust.

if you copy E02K's exhaust setup and still think your Miata is too loud, then I would start looking for a different car
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Old 07-13-2017, 05:15 PM
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Something like this then?

Ultra Flo? Welded Round - Centered / Centered Muffler - P/N: 17223 - DynoMax® Performance Exhaust

I think that particular one might be too large in diameter, but maybe there are smaller ones.

**edit**

Like this one! One of these and one of the vibrant resonators...that ought to be sneaky silent.

Amazon Amazon
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Old 07-13-2017, 08:58 PM
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Nevermind...on further inspection, that magnaflow inline muffler is just a resonator. Confusing.
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Old 07-14-2017, 12:50 AM
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Originally Posted by Engi-ninja View Post
I tried on of these when I had the race pipe and cobalt; it seemed to help more with the high frequencies, but it didn't really do much for the low frequencies.
No, my flapper greatly reduced the fundamental tone from idle on up. It's very noticeable from idle on up cruising up to 4000 RPM. Try idling your car, then put a rag loosely in your tailpipe, so the rag flaps in and out the pipe. There is a big reduction in the fundamental tone (bass!). That's what my flapper does.

Resonators greatly reduce the high frequency harmonics.

Would adding a cat be better than adding a second resonator?
No.
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Old 07-14-2017, 12:57 AM
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In terms of power.
But in terms of sound reduction, yes.
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Old 07-14-2017, 01:10 AM
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Hi flow cats offer very little flow resistance, ergo will not reduce sound much.
Resonators and straight-through mufflers on the other hand damp the pressure pulsations without offering much flow resistance. Ergo quietness.
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Old 07-14-2017, 01:12 AM
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I did a sound test on about 3 different subarus, catted downpipe vs catless, it was a very noticeable difference in sound, each and every time.

I'll try to dig up actual numbers if I still have them. This was a hi-flow metalic cat too
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Old 07-14-2017, 09:24 AM
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So, let's think about the physics for a moment. See if this makes sense:

Sound is essentially just a form of energy, and reduction in noise = reduction in energy. A muffler reduces energy by slowing down the flow using baffles. Each time the flow hits a baffle, energy is absorbed by the baffle in the form of heat and vibration. The heat is contained, which would be why the muffler gets louder as it heats up, because less heat energy is absorbed. The vibrations are absorbed and dissipated by the fiberglass or whatever the packing is. In addition, each time the flow changes direction, some energy is lost as momentum is transferred from the flow to the muffler, which would have to be absorbed by the exhaust hangars.

Does this seem reasonable so far? So a traditional muffler removes energy by 3 methods: loss of heat, vibration, and momentum.

As far as I can tell, resonators and straight through mufflers are pretty much identical in construction, so I'll treat them as the same (also, this ignores Hemholtz resonators, which are completely different). Resonators have a straight through construction with holes in the walls and some kind of sound absorbing material. As I understand it, these holes allow the gas to expand as it passes through, which will allow it to cool a bit, which = loss of energy. Furthermore, there are sound waves bouncing all over, and the higher frequency sound waves (shorter wavelength) will hit the walls inside the resonator more perpendicularly to the wall, allowing some of these frequencies to be trapped in the holes and absorbed by the packing material. Longer wavelength sound waves will hit the walls more tangentially, which would result in less energy being absorbed from these frequencies. This would explain why resonators seem to affect higher frequencies more than lower frequencies. However, the expansion of gasses would also result in lower velocity, which should also remove a little energy at least from the lower frequencies too.

So far so good? This seems to make sense to me at the moment. So, resonators remove energy through 2 means: loss of heat, and absorption of some vibrations.

A catalytic converter, on the other hand, forces the flow through a lot of tiny holes. This acts as a flow straightener, reducing the turbulence of the flow, which lowers the total kinetic energy. It also reduces the velocity, which further reduces total kinetic energy. The energy removed from the flow must be mostly converted into heat, which is necessary for the function of the catalytic converter. Some of this heat would be absorbed through the chemical reactions occurring between the material of the cat and the exhaust gasses. The rest of the heat would be dissipated into the air.

So, the cat just removes a lot of energy from the flow and dissipates it through heat and chemical reactions, which would effectively reduce volume at every frequency. However, the cost of this is significantly increased back pressure.

When I started writing this, I thought I would agree more with Jason in the end. However, assuming this reasoning is good, I would have to agree with 18PSI that the cat would lower volume across the board more effectively than a resonator, albeit at the cost of higher pressure differential across the cat.
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Old 07-14-2017, 10:57 AM
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". A muffler reduces energy by slowing down the flow using baffles"

The sound comes from the pressure pulsations, not the average velocity nor average flow. IOW you reduce the peaks and fill in the dips.

You can do that with a flow resistance (e.g. cat, baffled muffler) or with some kind of expansion chamber (straight through muffler) wherein as the small portion of gas that gets forced into said chamber during a pressure peak, and get sucked back in during the subsequent pressure dip.

Cats DO reduce noise, but high flow cats reduce noise a lot less than restrictive ones.
A good resonator of the same size will reduce noise more without any meaningful backpressure.
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Old 07-14-2017, 11:11 AM
  #40  
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I guess we'll agree to disagree on that specific part, Jason. I completely agree with everything else.

Engi, I disagree with most of your theory about sound reduction, lol. It's not about flow or energy or heat, it's about dampening or cancelling the sound waves specifically, just like Jason said. There are plenty of well engineered exhausts that are extremely quiet by cancelling out the sound waves. Those cars (usually OEM, since most companies don't have the budget for that much engineering) usually sound like giant vacuum cleaners. There's just the rushing of exhaust, but almost no other "sound".

There's really no need to re-invent the wheel here. The MT.net approved Maggie is a giant straight through muffler with just about the maximum amount of packing you can get. Can't get much better than it, and esp for the money. It is very effective. You can add a huge resonator as well, I like the vibrant oval because it's about as much packing as you can get in a resonator. It will be really quiet on a turbo Miata.
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