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Discussion Starter · #1 ·
i was just wondering how long different bov/ piping sizes made the blow off sound longer or shorter.

i got mostly 1 7/8 piping,when i chop the throttle at 5 psi it blows off for about 2 maybe 3 seconds or so.
 

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You can actually kinda apply bernoulli's principle to this one...



I couldn't find the equation I'm looking for, but basically, the static pressure, the kenetic energy, the potential energy, and the total head loss of a laminar, constant flow rate, incompressible fluid is equal to a constant.

P1 = boost pressure (about)
V1 = mass flow rate (can't really calculate this)
Z1 = Z2 = negligible

P2 = 1 atmosphere
V2 = 0 m/s

Hm. But then it comes down to how your BOV works. Does it run off the vacuum canister, or is it electronic, or what?

Ideally, you want a very large diameter of pipe where the BOV is. You'll bring your mass flow rate down, so your static pressure goes up, and you'll vent more quickly. It's actually counter intuitive. Most people would think that you want a small pipe to "build up" pressure to vent... but it's the other way around.
 

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its going to say open till eather you get back on the gas or till the amout of Vac. it takes to open it is there.

I dont think you need math to work that out.
 

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2-3 seconds? that is along time. i would say mine at most is a secodn and that is when i feather it out to swoosh more then pssstttt.

NEUMAN
 

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Chances are that it's a spring-opposed diaphragm. Where are you taking vac from? Chances are you could rig up a couple check valves and create a vac buffer to increase or decrease the duration of venting.
 

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Discussion Starter · #6 ·
all it is is a cyl with a piston and a spring. you have to keep it greased to make it not seaze. mines fully adjustable so i can make it long or short depending on how tight it is.if i wanted to, i could make it so there is still pressure in the intake at all points. it would only blow off if its over like 5psi.. which would be good for autoX
 

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Discussion Starter · #7 ·
i looked into it a little more. if i boost 8psi and back the throttle off to 20'' itll blow off for about 4-5 seconds. if i booost 8psi and dump the throttle itll blow off for about 3-4 seconds. it really depends on rpm. if i back it off at 5500 itll blow off for up to 6 seconds..


an example of how it sounds: keyboard cleaner bottle.but a little more high pitched.
 
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