Upgraded diverter valve question

SlowE93

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Jul 2, 2017
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E93
So last night I was doing a pull and towards the top of 3rd, I hear what sounds like a garden hose spraying water ,but 10x louder. Let off the gas, all is well, drive it home. Open the hood, found vacuum line that runs to the top of my turbo smart valves (VTA), came off from the "T". Plugged back in and did 2 runs. Boost held 25+psi with no problems. Question is, what exactly does that vacuum line do ? How does it hold boost with it attached, but not when its off ? I would assume there is a diaphragm inside, but how would that help the car hold boost ? I thought maybe a coupler gave but when I saw the hose, I decided to attach and try that before tearing everything apart. All went back to normal but I want to know why it works the way it does.
 

Torgus

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Nov 6, 2016
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You can always secure your vac line with a small plastic zip tie after the flange. I always do this, cheap insurance costs nothing and no time worth mentioning. Unless of course you have a good multi barb fitting etc. But for the single ridge style, zip tie. Older lines are also more likely to have issues.
 

SlowE93

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Yes, but do you know the answer to my question ? I even looked online and could not find exactly why that would cause the air to rush out . It has me confused, LOL !
 

1and1

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Although it is also a vac line, it's more accurately a boost reference source. When under boost that line feeds boost to the top of your BOV allowing it to stay closed by equalizing the pressure over and under the valve.

When that line popped off there was no longer a boost source over the valve to equalize the pressure and hold it closed. You were hearing both the valve releasing pressure as well as that reference line releasing boost and no doubt whooshing like an air compressor line releasing pressure...

Following this most basic understanding comes how important the inside diameter of that reference line is for quick response, and the importance of the spring strength that helps hold the piston closed. You can google those :) There is plenty on BOV functionality out there to keep you occupied for a few minutes...
 
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SlowE93

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Although it is also a vac line, it's more accurately a boost reference source. When under boost that line feeds boost to the top of your BOV allowing it to stay closed by equalizing the pressure over and under the valve.

When that line popped off there was no longer a boost source over the valve to equalize the pressure and hold it closed. You were hearing both the valve releasing pressure as well as that reference line releasing boost and no doubt whooshing like an air compressor line releasing pressure...

Following this most basic understanding comes how important the inside diameter of that reference line is for quick response, and the importance of the spring strength that helps hold the piston closed. You can google those :) There is plenty on BOV functionality out there to keep you occupied for a few minutes...
Holy Shit ! Thats what I was looking for ! Thanks, I didnt put enough thought into and got confused, but your explanation set everything straight in my mind !
 
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