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Old 04-22-2011, 01:34 AM   #41
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Originally Posted by Asx View Post
You're the one that got all huffy, twice, when asked to clarify what you're saying, so I did it for you.
oh you clarified what i said eh? Really?
"
You dont really care that its open as the pipe goes to the turbo so either way there is a filter keeping it a clean loop because the majority of people on here use a speed density type EMS, instead of a MAF type"

wtf is that dude? Hes asking about the bovs and you cross out my explanation and toss something completely useless. "because the majority of people on here use a speed density type EMS, instead of a MAF type"

So let me get this right, "because the majority of the people here are running 15-20 psi i should turn up the boost too because they do it? or wait because the majority of the new people here are have blown motors i should too? "the majority of people on here can run whatever they wish to run, what matters to him is what HE runs.

"Recirculating ones MOST BOVsare very simple"
whats the point of that "correction" right there when i'm clearly talking about Recirculating bovs?

"Its just 1 piston that opens when in vacuum pressure*'vacuum side valve area' is greater than combined 'spring rate'*preload and boost*'pressure side valve area' force. Which causes you to choose between response and the ability to stay closed at idle. "

wtf is vacuum pressure vacuum side valve area?... Vacuum is the lack of pressure yet you're saying vacuum pressure... Thats like saying the fire is hot on the ice hot side.
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Old 04-22-2011, 01:52 AM   #42
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ʞɹoʍ ʎǝɥʇ op ʍoɥ s,ʌoq buıʞɔnɟ
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Old 04-22-2011, 05:26 AM   #43
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Speed density matters because there is no harm in having a controlled leak in the intake tract, aside from a little unfiltered air. I've yet to see any harm done from unfiltered air only at idle.

There is no difference between a recirculating and VTA valve, as covered. I say most because I'm sure someone, somewhere has made some complicated electronically controlled blow off valve that only vents just before compressor surge. I'm also pretty sure that the blow off valves used as part of an anti-lag system are controlled a little differently.

Absolute pressure. Engine vacuum is about 30KPa. pressure*area is a force, if that force, which is pushing the valve closed, is less than the force pushing from the other side of the valve, it opens. I just realized I made a mistake before, the signal (vacuum)side force has the same direction as the spring force so it should read:

(signal side pressure)*(signal side valve area)+(springrate)*(spring preload + valve displacement)= (charge pipe side pressure)*(charge pipe side valve area)
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Old 04-22-2011, 06:19 AM   #44
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The problem with recirculating valves is that most of them are only 1 piston therefore they are open when in vacuum and allow unfiltered air to enter into the engine.
From where? All of the recirc valves I've seen recirculate into the intake pre-turbo.

If you recirc, all the air is filtered all the time. if you VTA, you've gotta use a filter or just live with unfiltered air at ide.
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Old 04-22-2011, 11:03 AM   #45
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Originally Posted by Savington View Post
From where? All of the recirc valves I've seen recirculate into the intake pre-turbo.

If you recirc, all the air is filtered all the time. if you VTA, you've gotta use a filter or just live with unfiltered air at ide.
I'm pretty sure he is referring to using a recirc valve in a VTA application.
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Old 04-22-2011, 11:05 AM   #46
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Originally Posted by Jeff_Ciesielski View Post
I'm pretty sure he is referring to using a recirc valve in a VTA application.

all valves can be recirculated, one way or another.
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Old 04-22-2011, 12:03 PM   #47
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all valves can be recirculated, one way or another.
Obviously. I misread the second half of Sav's post.
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Old 04-22-2011, 12:25 PM   #48
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So is anyone here actually running a recirc BOV in recirc configuration?
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Old 04-22-2011, 12:28 PM   #49
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I had run my valve that way a long time ago.

but I mean, it's not made as a recirulating valve, it just happens that it has an outlet that accepts a 1" hose so it can be recirculated.
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Old 04-22-2011, 03:16 PM   #50
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Originally Posted by Savington View Post
If you recirc, all the air is filtered all the time. if you VTA, you've gotta use a filter or just live with unfiltered air at ide.
Right he wants to run Recirc valve and VTA.. as i said no biggy just run a filter on there to be safe.
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Old 04-22-2011, 03:19 PM   #51
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Quote:
Originally Posted by MartinezA92 View Post
So is anyone here actually running a recirc BOV in recirc configuration?
Yes.
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Old 04-22-2011, 03:26 PM   #52
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Quote:
Originally Posted by Asx View Post
Speed density matters because there is no harm in having a controlled leak in the intake tract, aside from a little unfiltered air. I've yet to see any harm done from unfiltered air only at idle.
Try calling it a map sensor next time... Technically its not just at idle, its any time where the piston is retracted but the turbo is not spooled yet.. Such when stepping on the throttle. Either way why take the risk while the fix is a 5 bucks autozone filter?

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Originally Posted by Asx View Post
There is no difference between a recirculating and VTA valve, as covered.
In something as simple as a 1 piston bov, adding a 2nd piston makes it a different animal. I didnt bring up the computer controlled ones here as there is ... no point.
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Old 04-22-2011, 04:20 PM   #53
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Quote:
Originally Posted by hornetball View Post
Yes.
Checked out your build thread...hmm I'm not down with the Begi crossover pipe so I'm going to do something like you, except I may just put the BOV right next to the intercooler and run some rubber hose along the pipes to pre-turbo. If thats too much of a pain in the ***, I'm going to just use it as a VTA.

Anyone think I'm missing something important/any issues having it that far from the TB?
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Old 04-22-2011, 04:57 PM   #54
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Quote:
Originally Posted by MartinezA92 View Post
Checked out your build thread...hmm I'm not down with the Begi crossover pipe so I'm going to do something like you, except I may just put the BOV right next to the intercooler and run some rubber hose along the pipes to pre-turbo. If thats too much of a pain in the ***, I'm going to just use it as a VTA.

Anyone think I'm missing something important/any issues having it that far from the TB?
Purpose of BOV is to relieve pressure on the compressor. Doesn't really have much to do with the TB, although that's a common location for some reason.

Don't think it matters much. At least that was the consensus last time I asked. See https://www.miataturbo.net/diy-turbo-discussion-14/bov-location-intake-manifold-34268/.
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Old 04-22-2011, 08:09 PM   #55
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Quote:
Originally Posted by triple88a View Post
Try calling it a map sensor next time... Technically its not just at idle, its any time where the piston is retracted but the turbo is not spooled yet.. Such when stepping on the throttle. Either way why take the risk while the fix is a 5 bucks autozone filter?


In something as simple as a 1 piston bov, adding a 2nd piston makes it a different animal. I didnt bring up the computer controlled ones here as there is ... no point.
whether or not the the valve is open when not in boost wholly depends on manifold pressure and spring rate. for a sane spring rate the valve should be completely closed once any throttle is applied. often they're setup such that the valve is closed at idle but usually the pressure difference at a low boost lift isn't enough to open the valve. It's a linear relationship, governed by the equation I gave earlier, not an on/off switch.

Again, the second piston is an integrated check valve and some clever naming. It's semantics, I know, but I think it's an important point since you keep insisting that recirculating and atmospheric valves are fundamentally different. the only thing that designates a valve as VTA is the lack of a fitting suitable for hooking up a recirculation hose. The check valve is a neat little trick that a couple makers implement, whether integrated like the Forge, or an add-on like synapse. It's main purpose is to let people that use mass flow EMSs (MAF based) vent to atmosphere with a soft spring in the BOV for good response, without a vacuum leak that screws up their idle mixture. Not to mention that sweet VTA sound while saving a couple ounces of recirculating hose. To reiterate, the check valve is a nifty add-on, but it doesn't operate fundamentally different to any other common pneumatically controlled BOV.
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Originally Posted by hornetball View Post
Purpose of BOV is to relieve pressure on the compressor. Doesn't really have much to do with the TB, although that's a common location for some reason.

Don't think it matters much. At least that was the consensus last time I asked. See https://www.miataturbo.net/showthread.php?t=34268.
It's a carryover from the old argument that air in the pipe after the blow off valve reverses direction to flow out the bov if it's near the turbo and you'll get slower boost response after blowing off. The flow goes turbulent at the butterfly and reverses to some degree, so it's a wash. A lot of people agreed with the argument and plumbed their bovs near the tb. monkey see monkey do. If they were so concerned with response they'd recirculate, which helps to some degree, but not appreciably.

Last edited by Asx; 04-22-2011 at 11:15 PM.
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Old 04-23-2011, 07:21 AM   #56
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I love when the guys who know what they are on about come on and repeat what I said to start with but was told was wrong.

Cheers guys lol.

Dann
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Old 04-23-2011, 01:06 PM   #57
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They react different. Finally found the website with the cutaways.
http://www.evilution.co.uk/249

All the stock (such as bosch) recirculating ones are like the first one (either rubber diahram or a piston)

The 2nd one is the one with the 2nd piston and thats made to prevent crap from going back into your intake even when the main valve is open. Thats how most regular VTA are.

Last edited by triple88a; 04-23-2011 at 01:24 PM.
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Old 04-23-2011, 01:49 PM   #58
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It seems like it wouldn't matter, "pressure is equal in all directions" etc etc.
I don't see how it affects boost response either since it is getting rid of all excess pressure whether its at the TB or an inch after the IC. You are still filling the same size chamber with pressure.

Maybe someone smarter than me can chime in.
Sorry if I dont make sense I am slightly hung over.
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Old 04-23-2011, 02:22 PM   #59
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When you close the throttle there is a nasty spike right when you close the throttle. That is when you need the bov the most. If response time is too slow... the turbo slows and then the valve opens which kills the whole point. If you have a compressor with very low flow at high pressure, a valve opening at either end wouldnt matter however on a turbo the cfm is a lot higher which throws a wrench into the all pressure being equal idea.
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Old 04-23-2011, 03:01 PM   #60
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But if the BOV is still way past the compressor, it is still eliminating that spike before it would have an effect on the compressor wouldn't it? I also dont see how high cfm would change the "pressure is equal in all directions" idea.
Maybe im just not understanding the theory behind this, but I just can't see the location of the BOV having an effect on compressor speed. As soon as that plate closes, is pressure not instantly spiking throughout the whole intake?
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