BOV making too much noise (Watch bryantaylor turn into a douche bag before your eyes) - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-16-2007, 03:28 AM   #1
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Default BOV making too much noise (Watch bryantaylor turn into a douche bag before your eyes)

Hey Guys,
I have a problem. My TC setup runs a Turbo XS BOV that plumbs back into intake. I'm running a FM Link ECU and a MAP sensor. What happens when I lift off is that the vented air goes out through my open pod filter, making a whole load of noise.

I've actually once dis-connected my plumb back and vented directly to air, and the sounds are comparably loud to each other. I'm now considering taking the plumb back piping and attaching some sound deadening material at the tip and just venting directly to air.
Does this make any sense at all? I've already tightened the spring in the BOV, but i think the sound is just too loud.
Would a factory BCV work softer with a MAP setup?
Is there any benefit to run a Plumb back over atm vented bov on a MAP ECU?
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Old 11-16-2007, 10:14 AM   #2
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try loosening the spring.

What model BOV is it? Some are designed to be loud.

there's no benefit to recirculating on a MAP ECU.
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Old 11-16-2007, 12:36 PM   #3
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Sounds like a TurboXS RFL.

The RFL stands for "Really ******* Loud."

Change BOV's if it is that model.
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Old 11-16-2007, 02:10 PM   #4
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Indeed. If you want to spend a few dollars, pick up one of the Chinese knockoffs of a Greddy Type S or Type RS BOV from any of the eBay vendors that sell them. Get one with a recirculating fitting on its outlet- most of them only have a noisemaker horn fitting on the outlet.

Open up the BOV and remove the small (inner) spring. The BOV will now leak at idle, but seal up as soon as you step on the pedal.

You can either recirc it or place a K&N filter on the outlet. Either way, it'll give you a fairly subdued sound.
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Old 11-16-2007, 08:30 PM   #5
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Quote:
Originally Posted by SloS13 View Post

there's no benefit to recirculating on a MAP ECU.
it's generally more quiet.
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Old 11-16-2007, 08:33 PM   #6
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my BOV makes a sounds everytime i shift, does that mean its going bad?
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Old 11-16-2007, 10:03 PM   #7
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Originally Posted by bryantaylor View Post
my BOV makes a sounds everytime i shift, does that mean its going bad?
No, that means it's working properly. When it's adjusted juuuuust right, you should get a little *pssht* on almost every shift, even if you're not in boost.
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Old 11-16-2007, 10:04 PM   #8
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HAHAHAHAHAHAHAHAHA, someone believed me!
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Old 11-16-2007, 10:33 PM   #9
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Quote:
Originally Posted by bryantaylor View Post
my BOV makes a sounds everytime i shift, does that mean its going bad?
Quote:
Originally Posted by bryantaylor View Post
HAHAHAHAHAHAHAHAHA, someone believed me!
That was a stupid set of posts. Laughing because you asked somebody a question and "tricked" them into giving you an intelligent answer is pretty ****** dumb.
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Old 11-16-2007, 11:05 PM   #10
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Originally Posted by jasonrobo02 View Post
That was a stupid set of posts. Laughing because you asked somebody a question and "tricked" them into giving you an intelligent answer is pretty ****** dumb.
that is an even dumber post. this is an internet forum, not UN meeting. shut the **** up
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Old 11-16-2007, 11:10 PM   #11
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that is an even dumber post. this is an internet forum, not UN meeting. shut the **** up
I forgot I was on the internet.
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Old 11-16-2007, 11:19 PM   #12
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yep.

The Internet: All the hooting dickholes you ever cared to talk to and some you didn't.



EDIT: bryan, I did catch the humor in that, btw.
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Old 11-16-2007, 11:24 PM   #13
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Guys,
Thanks for the help and answers.
Joe Perez, thanks for your patience and your faily detailed replies. Can I ask what the point of removing the small inner spring is?

What would be the difference with placing a factory By pass valve instead?
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Old 11-16-2007, 11:28 PM   #14
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Quote:
Originally Posted by supersaiyan93 View Post

EDIT: bryan, I did catch the humor in that, btw.
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Old 11-17-2007, 02:16 AM   #15
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Quote:
Originally Posted by qes78 View Post
Joe Perez, thanks for your patience and your faily detailed replies. Can I ask what the point of removing the small inner spring is?
Considering that the primary functions of the BOV are to keep the turbo spooled up during shifts and reduce as much as possible the pressure spikes that cause the "gobbling" sound, it makes sense for the valve to be sprung as softly as possible without leaking under boost.

As delivered, the Type S / RS BOV's are sprung very stiff. All else being equal, the stiffer the spring, the less responsive the BOV will be to small differentials in manifold pressure. A stiff spring may be helpful if you plan to run 30 PSI, but for those of us living in reality it makes sense to soften it up somewhat. This allows the valve to open sooner, relieving pressure quicker and more effectively.

Quote:
What would be the difference with placing a factory By pass valve instead?
Factory, as in one of the Bosch valves that are OEM on Porsches and Volvos? Nothing, really, except that the Greddy knockoffs can often be had for less money, have larger valves, and are constructed of metal rather than plastic. They're both diaphragm-type valves that operate in essentially the same way.
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Old 11-17-2007, 02:19 AM   #16
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Originally Posted by bryantaylor View Post
HAHAHAHAHAHAHAHAHA, someone believed me!
Why shouldn't I have? Mine does, and if yours does not then it is not set up optimally.

I usually tend to give people the benefit of the doubt- ie: assume that they are telling the truth, rather than automatically assume that they are flame-baiters. Since you've proven otherwise, next time I'll know to ignore you.
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Old 11-17-2007, 02:50 AM   #17
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Originally Posted by Joe Perez View Post
Considering that the primary functions of the BOV are to keep the turbo spooled up during shifts and reduce as much as possible the pressure spikes that cause the "gobbling" sound, it makes sense for the valve to be sprung as softly as possible without leaking under boost.

As delivered, the Type S / RS BOV's are sprung very stiff. All else being equal, the stiffer the spring, the less responsive the BOV will be to small differentials in manifold pressure. A stiff spring may be helpful if you plan to run 30 PSI, but for those of us living in reality it makes sense to soften it up somewhat. This allows the valve to open sooner, relieving pressure quicker and more effectively.
Does that mean that there is benefit in plumbing back to intake? here's my logic. Air under pressure under boost goes back ito intake before the turbo. some of it gushes out of the intake, making the sound that's irritating me, and some of it keeps the turbo spinning in the right direction, reducing lag. Am I being logical here?
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Old 11-17-2007, 09:14 AM   #18
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Quote:
Originally Posted by qes78 View Post
Does that mean that there is benefit in plumbing back to intake? here's my logic. Air under pressure under boost goes back ito intake before the turbo. some of it gushes out of the intake, making the sound that's irritating me, and some of it keeps the turbo spinning in the right direction, reducing lag. Am I being logical here?
Whether it's a recirculated or a VTA setup, the air that's gushing out of the BOV making the sound that annoys you is the same air that's keeping the turbo spinning. As you said- the idea is to allow the turbo to keep pumping air to somewhere- whether it's getting vented to the outside or merely coming back around into the intake and getting pumped again is not so much important.

The primary advantages of VTA are slightly less plumbing clutter in the engine compartment, and the somewhat theoretical (and very minute) fact that it maintains the velocity of the air through the whole system, including the filter-to-compressor section.

Recirculated systems on the other hand are generally more suitable for vehicles that run an airflow sensing device (AFM or MAF) since a VTA in this situation would have to be valved more stiffly (so as not to leak at idle) than a recirculated system, and thus it would be less responsive.

All else being equal, VTA systems tend to be slightly louder than recirculated systems. In actual practice, much of this tends to do with the design of the valve itself. Some units are specifically designed to be loud, since the kids think this is cool. The HKS SSQV and TurboXS are example. Just look at some of the ad copy: "With new and improved styling, the BOV-H-RFL remains true to it's roots - it's still really f'n loud!"

Many units have removable devices that, when installed, enlouden then. The Type RS is a good example. Have a look:



You see those holes drilled in the outlet horn? Those cause the valve to be loud. When air is rushing out, they cause a sort of whistling effect. If you remove that horn and install a recirculating fitting, this unit becomes significantly quieter.


There is some confusion in terminology surrounding BOVs. You will see the terms "Blowoff Valve" and "Bypass Valve" used interchangeably. Both units are constructed similarly, and both perform the same function. The difference is generally that a Bypass Valve is specifically designed for recirculated use (though it can be left VTA) whereas a Blowoff Valve, from a language-geek standpoint, must be a VTA unit.
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Old 11-17-2007, 10:06 AM   #19
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Good posts Joe, I might even suggest these be added to the FAQ.

Another thing to note about recirc: some believe recirculating charge air back into the intake to be a bad idea since the air would be hotter than the air the intake would otherwise use. Dodge/Mopar cites this theory in their marketing of the SRT-4 VTA adapter for the stock surge valve.
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Old 11-17-2007, 12:13 PM   #20
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Quote:
Originally Posted by bryantaylor
I am the biggest douche in the universe.
Tsk tsk... If only you'd adjust your BOV properly, perhaps that wouldn't be the case.
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