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Discussion Starter · #1 ·
I drive a 2018 Focus st with about 42k miles on it. I haven’t done many upgrades aside from minor appearance stuff as well as a sound sympose delete and an injen cold air intake. A couple days ago I purchased a COBB Acessport and plugged it in and mapped the OTS stage 1 tune. Car is running fine and feels as it should from the factory.

Yesterday I noticed while driving, it almost sounds like the stock BPV is “burping” almost like it can’t hold any pressure so it’s releasing even while I’m cruising. I’ll be driving at highway speeds and will just hear PSH PSH PSH PSSSSSSSHHH PSH until I let of the gas and then hear the complete release from the valves. I also noticed as if the bpv is releasing a lot more then usual. I chalked it up to having something to do with the tune but I’m new to turbo charged cars and don’t wanna spend a bunch of money at a shop if it’s an easy fix.

please let me know what y’all think ?
 

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I drive a 2018 Focus st with about 42k miles on it. I haven’t done many upgrades aside from minor appearance stuff as well as a sound sympose delete and an injen cold air intake. A couple days ago I purchased a COBB Acessport and plugged it in and mapped the OTS stage 1 tune. Car is running fine and feels as it should from the factory.

Yesterday I noticed while driving, it almost sounds like the stock BPV is “burping” almost like it can’t hold any pressure so it’s releasing even while I’m cruising. I’ll be driving at highway speeds and will just hear PSH PSH PSH PSSSSSSSHHH PSH until I let of the gas and then hear the complete release from the valves. I also noticed as if the bpv is releasing a lot more then usual. I chalked it up to having something to do with the tune but I’m new to turbo charged cars and don’t wanna spend a bunch of money at a shop if it’s an easy fix.

please let me know what y’all think ?
Get rid of the stock bypass valve their junk fail and cause boost leaks. Get yourself an action figure market blow off valve or an uprated mountune bypass valve if you want to be more stealthy. Then hook it up to the symposer delete for a true vacuum reference
 

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We had another member recently post with this problem. He said when he went with custom tunes (from whom, i dont remember) the issue went away. Basically its a quirk with the off the shelf cobb tunes.
 

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Discussion Starter · #5 ·
So update: I was driving home and I noticed it starts to flutter right before I’m about to hit boost and if I hold it, that’s when it starts to release. When it does this I managed to look at the boost pressure gauge and it starts to decrease by like .10-.20 increments. Is that a boost leak? And if so what is the best way to diagnose and fix it?
my car is throwing no codes and runs fine while under full boost, but I don’t like how it releases like that.
 

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Any recommendations on a good BOV?


is this ultimately what I have to do?

It helps. Doesn't nearly blow off is easy once it's hooked up to a true vacuum. you'll actually need a few pounds of pressure to make it blow off instead of every time you let off the throttle whether there's boost or not.
 

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Thanks man! I’ll give it a shot and see if it fixes the issue.

if you hook it to the symposer delete follow Nick Baldwin's thread on here that shows how to do it. And if you go with the turbosmart 50/50 because it's adjustable just to make sure you screw the cap on far enough so that you're just covering all the o-rings for the cap. That is the lowest setting that's where I run mine.
 

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Discussion Starter · #10 ·
if you hook it to the symposer delete follow Nick Baldwin's thread on here that shows how to do it. And if you go with the turbosmart 50/50 because it's adjustable just to make sure you screw the cap on far enough so that you're just covering all the o-rings for the cap. That is the lowest setting that's where I run mine.
if you hook it to the symposer delete follow Nick Baldwin's thread on here that shows how to do it. And if you go with the turbosmart 50/50 because it's adjustable just to make sure you screw the cap on far enough so that you're just covering all the o-rings for the cap. That is the lowest setting that's where I run mine.
im trying to find his thread but it’s not popping up. You got a link ?
 

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It helps. Doesn't nearly blow off is easy once it's hooked up to a true vacuum. you'll actually need a few pounds of pressure to make it blow off instead of every time you let off the throttle whether there's boost or not.
Maybe a dumb question, but since I have the Mountune BPV on my car, would it benefit me at all to run this from a true vacuum source instead of the solenoid? I've got the symposer delete on my car, but it doesn't have the port in it, so I'd need to drill/tap/install a 1/8" NPT nipple into it. Should I go ahead and try to add that to the list of things to do this weekend (along with the ESP intercooler install)?
 

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Maybe a dumb question, but since I have the Mountune BPV on my car, would it benefit me at all to run this from a true vacuum source instead of the solenoid? I've got the symposer delete on my car, but it doesn't have the port in it, so I'd need to drill/tap/install a 1/8" NPT nipple into it. Should I go ahead and try to add that to the list of things to do this weekend (along with the ESP intercooler install)?
There is a functional reason that the bypass is commanded to do this. If i were to guess, probably something to do with either MPG or spool. If you think about it, using the bypass to bleed off boost at cruising rpm decreases drive pressure which is reduced backpressure for the cylinders. It also allows the turbo to spin faster (without knowing what the wastegate is doing at this point in time) without having resistance on the compressor which would also translate to quicker response when you put your foot in it.
 

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im trying to find his thread but it’s not popping up. You got a link ?
 

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Discussion Starter · #14 ·
Thanks man
 

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We had another member recently post with this problem. He said when he went with custom tunes (from whom, i dont remember) the issue went away. Basically its a quirk with the off the shelf cobb tunes.
for what it worth my car will do this on any tune that I have if you hit the right rpm/boost. Ots, stock, or mountune. Usually at like negative two psi or something like that and hold it
 
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I ran the stage 3 OTS tune for a while and now I'm running a custom tune from JST I've never experienced this. But I wasn't hooked up to the factory solenoid for very long. I got tired of it blowing off every time you pulled your foot off the throttle.
 

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Maybe a dumb question, but since I have the Mountune BPV on my car, would it benefit me at all to run this from a true vacuum source instead of the solenoid? I've got the symposer delete on my car, but it doesn't have the port in it, so I'd need to drill/tap/install a 1/8" NPT nipple into it. Should I go ahead and try to add that to the list of things to do this weekend (along with the ESP intercooler install)?

I actually believe mountune recommends that you leave it hooked to the factory solenoid.
 

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Discussion Starter · #18 ·
I ran the stage 3 OTS tune for a while and now I'm running a custom tune from JST I've never experienced this. But I wasn't hooked up to the factory solenoid for very long. I got tired of it blowing off every time you pulled your foot off the throttle.
So you did
I ran the stage 3 OTS tune for a while and now I'm running a custom tune from JST I've never experienced this. But I wasn't hooked up to the factory solenoid for very long. I got tired of it blowing off every time you pulled your foot off the throttle.
so you did the turbo smart BOV and then did The true vacuum (nick Baldwin’s)?
 
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