ITT: quiet BOVs/bypass valves
#41
"
You dont really care that its open
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.
#43
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)
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)
#44
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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.
#52
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.
#53
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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?
Anyone think I'm missing something important/any issues having it that far from the TB?
#54
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?
Anyone think I'm missing something important/any issues having it that far from the TB?
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/.
#55
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.
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.
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.
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.
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.
Last edited by Asx; 04-22-2011 at 10:15 PM.
#57
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.
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 12:24 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.
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.
#59
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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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?
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?