Bosch BOV question: why is mine not holding boost?
#17
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Originally Posted by toddk911
Oh, while doing some BOV reseasrch, I found an anser to the spring rate question.
"Stiffer will hold more boost, but will be less responsive, so it won't blow off so easily when you let off after part-throttle driving. Softer will be more responsive (better for driveability), but may leak air at idle or under boost. You basically want it as soft as possible while still holding the boost you want to run."
"Stiffer will hold more boost, but will be less responsive, so it won't blow off so easily when you let off after part-throttle driving. Softer will be more responsive (better for driveability), but may leak air at idle or under boost. You basically want it as soft as possible while still holding the boost you want to run."
Okay thanks, but where did this come from? Got a link? I'd like to get some additional info. Thanks. E
#18
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Did you try it with the lines to the BOV capped off?
If it holds boost just fine in that situation, check what the line feeding the nipple on the top is doing. If I read this right, you already tried your BOV in a friend's car, and it works?
If it holds boost just fine in that situation, check what the line feeding the nipple on the top is doing. If I read this right, you already tried your BOV in a friend's car, and it works?
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Ehall:
I sent an email to a company selling a lot of BOV and asked them what is the difference in spring rates and that was his email reply.
I sent an email to a company selling a lot of BOV and asked them what is the difference in spring rates and that was his email reply.
#20
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I'll try the valve backwards & with the nipple capped, see what happens. I'm wondering if my valve is too close to the turbo: as it's about 5" off the compressor housing, but if anything were to theoretically be askew, it would be that It couldn't recirculate enough & possibly hold more boost...I'll have to dick with it a bit I guess
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Originally Posted by MarkRobinson
I'm wondering if my valve is too close to the turbo: as it's about 5" off the compressor housing, ...
Laust
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Keep in mind that I am pressurizing the side of the BOV, which would hold it closed, regardless of increased pressure due to turbo proximity. My vacuum line to the BOV is taken from the throttle body (long vacuum line)
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To the best of my knowledge the BOV opens due to a pressure difference between its side port and control port, which is why it will stay closed at a 30 psi boost pressure (at WOT), but will open if you close the throttle (change gear) at for example 15 psi.
I assume your control signal is taken after the throttle plate and that it senses static and not the combined static and dynamic pressure.
Laust
I assume your control signal is taken after the throttle plate and that it senses static and not the combined static and dynamic pressure.
Laust
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It is as if you didn’t catch my first point (or politely avoided a comment because you don’t agree ), namely that out of the turbo comes a swirling air flow much like a tornado, which will have a cross-sectional non-uniform pressure distribution. The mean pressure, which is the pressure that the BOV’s side port should see, is more than the pressure at the center of the tube and less than the pressure at the inside wall of the tube, which according to your picture is what the BOV’s side port is seeing.
That theory could be substantiated or disproved by doing two simultaneous real-time pressure measurements.
If you do get adequate boost pressure with the long blue line clamped, then the above would be my best guess.
Laust
That theory could be substantiated or disproved by doing two simultaneous real-time pressure measurements.
If you do get adequate boost pressure with the long blue line clamped, then the above would be my best guess.
Laust
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Doh, for the mock-up, I have the BOV in backwards. Geez, it's been a very long week. Yes, with that picture, I'm boosting against the spring, which is opposite of what i"m doing now.
I may move the BOV to the intake (post intercooler) ala 951 this weekend & try it like that, that's how I did it before, though not as "clean" a design.
I may move the BOV to the intake (post intercooler) ala 951 this weekend & try it like that, that's how I did it before, though not as "clean" a design.
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Originally Posted by toddk911
Ehall:
I sent an email to a company selling a lot of BOV and asked them what is the difference in spring rates and that was his email reply.
I sent an email to a company selling a lot of BOV and asked them what is the difference in spring rates and that was his email reply.
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[QUOTE=MarkRobinson]Doh, for the mock-up, I have the BOV in backwards. Geez, it's been a very long week. Yes, with that picture, I'm boosting against the spring, which is opposite of what i"m doing now.QUOTE]
Do I win a prize? Is it backwards? I have seen BOV's (non recirc) built into the intercooler. I don't know what or how your EMS works but thats an option.
Do I win a prize? Is it backwards? I have seen BOV's (non recirc) built into the intercooler. I don't know what or how your EMS works but thats an option.
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I thought the inverted BOV was part of the experiment mentioned in post # 20.
It should be possible to catch the mean pressure just out of the turbo, but that will require some baffling and/or angling of the outlet to the BOV. Some careful measurements and luck are also needed.
True, that set-up certainly looks clean and elegant.
It should be possible to catch the mean pressure just out of the turbo, but that will require some baffling and/or angling of the outlet to the BOV. Some careful measurements and luck are also needed.
True, that set-up certainly looks clean and elegant.