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Old 02-14-2012, 04:14 PM   #1
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Cool 100% of the power. 0% of the sound. Winning

Alright bros, so lets pretend for a second that a fellow was planning on building yet another turbo miata. Lets say he wanted as much of the 3" exhaust flow as possible, but with absolutely as little noise as possible.

As most know, manual cutouts are a pain in the bootie.
As most also know, electric ones usually fail quickly.
IMO they fail becuase the stupid motors don't have any sort of limiters or "shutoff" when opening/closing, so the longer you hold the button, the more it tries to overpower itself and its opening limitations, and with time basically kills self.
There's also the spring loaded flapper valve that Jason put into his exhaust which is relevant to my interests, but I also heard from folks that these tend to fail/rattle/etc over time.

So I was thinking about something like this:
Either this, something like this, or making my own version of this.
Activated in boost only, smooth transition into free flow, not too many failure prone parts, and easy to set up.

Tell me why this is a:
GREAT idea
TERRIBLE idea
I realize the 90* isn't optimal, but that can easily be remedied with faefloras sawzall skills
Discuss.
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Old 02-14-2012, 04:21 PM   #2
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Great idea. I had an electric one on my Talon, and although it didn't outright fail, I'd have preferrred a vac operated one after repairing the wiring for the twentieth time. One thing I'd recommend is putting a valve on the vac line that you can operate from the cabin so that you can keep it quiet all the time, instead of having it blow open every time you hit the wg pressure.

What is the lowest pressure this will open?
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Old 02-14-2012, 04:23 PM   #3
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Having the wastegate flap on the straight part would make the idea better in my mind. You could have a dual exhaust where the T acts as a 90 when not in boost. it would route over to the exhaust and out the normal bumper opening, but when in boost, it would open that valve and go straight out the driver side. I think that way would make for the best use of the flow design of it.

I do like the idea.
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Old 02-14-2012, 04:32 PM   #4
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Quote:
Originally Posted by matthewdesigns View Post
One thing I'd recommend is putting a valve on the vac line that you can operate from the cabin so that you can keep it quiet all the time, instead of having it blow open every time you hit the wg pressure.

What is the lowest pressure this will open?
You can easily fit a 10 dollar mbc on it and do exactly that, which is cool.
And this particular one comes with 11psi can i believe, but those universal cans are all over bay starting from 5psi and all the way to 20 or something.

But again, an mbc could pretty much dial in whatever you wanted (with only downside being that it wouldn't be as smooth with an mbc, and more of a on/off switch)
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Originally Posted by rharris19 View Post
Having the wastegate flap on the straight part would make the idea better in my mind.
I do like the idea.
I was thinking more along the lines of a y-pipe, like the "traditional" cutouts these days. And have it on the end of a 3" dp with stock exhaust still in place, this way vacuum = stock, boost = OMFGWTFBBQSOUS
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Old 02-14-2012, 04:40 PM   #5
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Exhaust cutouts, flaps, etc. are all a huge waste of money. I use the same big-*** Magnaflow that y8s and Braineack use, there is no discernible power difference between that and my 3" straight-pipe, and it is extremely quiet (84dB) even at WOT.

Compare these two videos. The Laguna exhaust is so quiet that the camera ends up picking up a bunch of wind noise and other bullshit, so listen for the comparison between the BOV and the exhaust note.

Standard 3" straightpipe (~97dB):


22x5x11 Magnaflow (84dB):


If you think the 22x5x11 Magnaflow is too loud, I would suggest a Buick and an AARP card.

Last edited by Savington; 02-14-2012 at 04:51 PM.
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Old 02-14-2012, 04:40 PM   #6
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Quote:
Originally Posted by 18psi
And this particular one comes with 11psi can i believe, but those universal cans are all over bay starting from 5psi and all the way to 20 or something.
I'd go for as low as possible and switch it with the valve. I had mine in a 3" dp on the Talon, connected to the stock catback. Full spool and peak airflow was 1000rpm earlier with it open, so you'd want to get it open as soon as possible.
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Old 02-14-2012, 04:43 PM   #7
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I'd think a 5x11x22" muffler would flow better than that cutout.


But you are suggesting you want a flapper, not a dump right?
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Old 02-14-2012, 05:16 PM   #8
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Quote:
Originally Posted by Savington View Post
Exhaust cutouts, flaps, etc. are all a huge waste of money. I use the same big-*** Magnaflow that y8s and Braineack use, there is no discernible power difference between that and my 3" straight-pipe, and it is extremely quiet (84dB) even at WOT.

If you think the 22x5x11 Magnaflow is too loud, I would suggest a Buick and an AARP card.
I hear ya loud and clear.

And I had EXACTLY what you're talking about for over a year on my 1st turbo setup. Literally ordered the same one y8s and Brain have (though in 2.5" which technically should be even quieter than theirs). At first it was flawless. After about a year it definitely got louder. Cruising @ 4k on the freeway for an hour you definitely get sick of it.

If you're going to say its a waste of money, can you be more specific? This would replace an exhaust system that would cost approx 350, and costs approx 200 (or less), and "in theory" would give me exactly what I'm looking for: silent (or as close to it as possible) when out of boost.

PS: ordering AARP as I type this

Quote:
Originally Posted by Braineack View Post
I'd think a 5x11x22" muffler would flow better than that cutout.


But you are suggesting you want a flapper, not a dump right?
No, I'd use this as a dump.

3" downpipe-> y-pipe -> 1 end leading to stock catback and 1 to this cutout thingie venting to atmo.

Is there a flaw in this theory?
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Old 02-14-2012, 05:17 PM   #9
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I like my cars quiet. If I could have 300whp and be silent like a Prius I'd choose that option (and don't tell me to buy a Tesla lol)
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Old 02-14-2012, 05:20 PM   #10
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I have the same bigass 3" Magnaflow, and puttering around town at low RPM the sound was dronier than my former custom 2.5" exhaust with slightly less bigass Magnaflow.

The spring loaded flapper valve I installed quieted it down during around town driving. I'm very pleased with it now.

I looked into cutouts, whether pneumatic or electric, and they were expensive. I decided a spring loaded one follows the KISS principle.
If it fails/rattles later, I will look into improving it rather than doing something complicated.
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Old 02-14-2012, 05:26 PM   #11
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/\ Exactly.
But I don't see the vacuum activated one being very complicated. Its exactly what you have except with a wga can instead of the spring. That's it.

(I know you use yours as a restrictor and not a dump, but for the sake of discussion lets explore both ideas)
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Old 02-14-2012, 05:48 PM   #12
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Quote:
Originally Posted by JasonC SBB View Post
The spring loaded flapper valve I installed quieted it down during around town driving. I'm very pleased with it now.
Do you have any photos of your flapper set up? I would like to try something like this . Thx
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Old 02-14-2012, 05:55 PM   #13
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If you want a quick way to turn the cutout on/off, don't mess around with an MBC and all that crap. Get a pneumatic switch from someone like Clippard Minimatic (I've used a lot of their stuff for projects at work). A 3-way toggle switch will allow you to have it on (boost pressure controls cutout) or off (cutout always closed) with the flick of a switch, and they're pretty cheap and panel mountable. Way easy, probably about the same cost.
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Old 02-14-2012, 08:21 PM   #14
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I like the yellow-foam ear plugs. Cuts way down on wind/semi-truck noise too.
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Old 02-14-2012, 08:37 PM   #15
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Quote:
Originally Posted by hornetball View Post
I like the yellow-foam ear plugs. Cuts way down on wind/semi-truck noise too.
And then when you're done driving, you can swap them for your hearing aids so you can hear the bingo numbers being called out.
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Old 02-14-2012, 08:58 PM   #16
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Quote:
Originally Posted by sturovo View Post
Do you have any photos of your flapper set up? I would like to try something like this . Thx
Even google finds it
https://www.google.com/search?client...spring+flapper
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Old 02-14-2012, 09:51 PM   #17
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Quote:
Originally Posted by 18psi View Post
/\ Exactly.
But I don't see the vacuum activated one being very complicated. Its exactly what you have except with a wga can instead of the spring. That's it.
If you've ever heard a Gallardo start up and wondered why it has a huge bark on startup but then it's not too loud right thereafter, this is why... they have just exactly what you're describing. One just upstream of each muffler. I had to wire them closed on a customers car because he was shipping it to Taiwan and it wouldn't pass their sound regs with it open at startup.
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Old 02-14-2012, 09:53 PM   #18
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Here's a DIY jobbie from SR20forum.com
http://bit.ly/ACxYet

Quote:
Originally Posted by GTI-R LEMONDROP View Post
Seeing how my experimental dual vette muffler install was partially successful (quiet now), I still needed to find a way to reduce the backpressure.

ATP had a neato exhaust cut out that worked off boost pressure to open it up and close it at no boost. Of course I wasn't willing to pay around $300 for this - and they are out of stock with no in-stock date known, I made my own.
You need two things to make this work - first you will need some kind of precision made butterfly device in a housing. A throttle body off a 4.6 Ford Crown Vic was big enough (2 3/4) opening and cheap - $9.99.
Second you need a turbo wastegate actuator. Brand new Dodge SRT take-off for $40 will work just fine.

So, concept is simple - it will open up based on the wastegate you choose to use (SRT is 4 psi) and of course is closed with the same tension when driving normally. Add in a bit of creative fab/cut/weld and you my friend have a effective cutout which requires no electrical wiring, no cables and no reaching under the car to open and close. Yes, you will have to route boosted air there, but 1/4 soft copper line is cheap, easy to bend and very durable.
Does it work? Damn skippy it works - and works freaking awesome! I hesitated to post this, as it has only been on the car for a couple days and I cannot prove its long term reliability.

Just thought I would give those looking for a very stealth exhaust for normal driving and a wide-open in-your-face screaming no back pressure LOW DOUGH option.
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Old 02-14-2012, 09:55 PM   #19
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Why would a dump be quiet?
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Old 02-14-2012, 10:05 PM   #20
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It's not when in boost.
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