My 3" custom exhaust with spring loaded flapper valve - Page 5 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-22-2015, 01:26 PM   #81
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add splitter box, attach to regular throttle cable

...oh wait...
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Old 09-22-2015, 02:44 PM   #82
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What's the advantage of a complicated setup vs a simple spring?
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Old 09-22-2015, 03:08 PM   #83
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Quote:
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What's the advantage of a complicated setup vs a simple spring?
Never use one part when three will do! Use a vacuum motor!

--Ian
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Old 09-22-2015, 03:39 PM   #84
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What's the advantage of a complicated setup vs a simple spring?
Biggest thing that sold me on the one I got was the completely bolt-in install. No cutting/welding/etc.

Also it shouldn't cost even a single hp in backpressrue, since it doesn't use exhaust pressure to open.

I would also have "settleed" for a vacuum operated setup, except the quality ones are absurdly overpriced, and most of them are cutouts, which is not what I'm looking for.

I'll post results after it comes in.
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Old 09-23-2015, 11:27 AM   #85
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Also it shouldn't cost even a single hp in backpressrue, since it doesn't use exhaust pressure to open.
Have you seen my actual measurements? IIRC it was 0.3 psi. And that's with the stiffer of 2 springs.
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Old 09-23-2015, 08:23 PM   #86
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Ya know, back when I was a boy the muscle cars had vacuum operated valves on the mufflers to open them up when the throttle was opened.

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Old 09-23-2015, 08:38 PM   #87
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They still do on "boring" cars...
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Old 09-23-2015, 09:34 PM   #88
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That doesn't work quite as well on boosted cars
And actually a whole lot of these "boring" cars use electric motors, and they fail quite often

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Have you seen my actual measurements? IIRC it was 0.3 psi. And that's with the stiffer of 2 springs.
Yup. And again, this is much easier cause I don't have to hack up my $1300 exhaust to put it on.
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Old 09-23-2015, 09:37 PM   #89
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my dad's bimmers all had wastegates on their exhausts.
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Old 09-23-2015, 10:31 PM   #90
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Quote:
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That doesn't work quite as well on boosted cars
That's what vacuum reservoirs and check valves are for, same as on an NA car.

--Ian
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Old 09-24-2015, 08:51 AM   #91
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this is from a 330i:







oh but it don;t work on boosted cars he says....



takes a look at the 335i exhaust:






#boringcarsmatter
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Old 09-24-2015, 12:21 PM   #92
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Lol @ "vacuum reservoirs" on a Subaru/miata custom exhaust system
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Old 09-24-2015, 12:35 PM   #93
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ever seen a VICS IM?
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Old 09-24-2015, 01:19 PM   #94
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What is the fascination with vacuum and overcomplicating the everliving crap out of things?

oh that's right you're a mercedes driver now
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Old 09-24-2015, 01:28 PM   #95
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My B6 S4 had vacuum-operated exhaust flappers. They were ECU-controlled with solenoids, and the reservoir for them was buried in the trunk somewhere. It eventually started leaking so I disconnected them and that left the flappers open all the time, which was still substantially quieter than the Miata.

I'm pretty sure the C7 S6 has the same system, but I haven't needed to go looking for it.

Vacuum actuators are actually a decent solution for this kind of occasional thing, because they're simple, powerful, cheap, and have minimal moving parts.

--Ian
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Old 09-24-2015, 01:33 PM   #96
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More simple and less moving parts than the valve I ordered?

lol

You all know I've liked that whole idea for a long time now, in fact I've made a few threads about it along the way.

Scottiac made sure to derail each of them

(but seriously, I like vacuum activated flappers. just not gonna happen this time)
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Old 09-24-2015, 01:38 PM   #97
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Quote:
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More simple and less moving parts than the valve I ordered?
If you're a German OEM, needing to meet German idle noise laws, but still want your car to make good power and sound fast at WOT (and fake out the emissions test!), a passive spring-actuated flapper isn't gonna cut it.

--Ian
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Old 09-24-2015, 01:40 PM   #98
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Why not?
I didn't get the spring flapper, but the manual valve, but now I'm curious why you think that. The mitsu evo and many others do this very successfully
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Old 09-24-2015, 01:48 PM   #99
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Quote:
Originally Posted by 18psi View Post

What is the fascination with vacuum and overcomplicating the everliving crap out of things?

oh that's right you're a mercedes driver now

im driving a 2015 c300 right now, wanna talk about over complicating? it took me a few minutes to get it out of park.
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Old 09-24-2015, 01:54 PM   #100
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exactly my point
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