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Part throttle Boost ?

1K views 18 replies 6 participants last post by  Kyred 
#1 ·
I just turned my boost up this week to 17 PSI for the first time since fall. (17 psi in snow sucks!) Since last year I switched out my E-bay BOV for a real HKS SSQV. I am now having a problem when I part throttle boost. As I Roll on the throttle and approch roughly 12 PSI the BOV opens and closes real fast and makes the car buck. Full throttle I have no issues. The only difference with this BOV is that I installed the check valve that came with the BOV in line from the manifold to the BOV. I checked and it is installed the correct way. Could the check valve be the issue, or do you think it could be the tune? Thanks
 
#2 ·
check valve on a BOV ?? wtf? boost/vacuum is what opens closes it..whyd you have one of them? sorry never heard of it, then again i dont run those rip off $400 BOV's.
 
#5 ·
Really? I thought I read somewhere that it wasn't supposed to see boost on the vac line side. Maybe that was the wastegate I'm thinking of. I assumed it was a check valve, because it had an arrow pointing which way to install it. Could be a filter I guess. I'll pull it off and see if that helps. I'll try it tomorrow. Thanks for the quick replies!
 
#4 · (Edited)
lol just as i thought. yeah dude, run a hose from manifold directly to BOV.. filter? wheres that go?



sounds like you havwe check valve blocking the boost in vacuum line from getting to bov which helps hold down the valve/spring so you dont leak boost. and the pressure inside boost pipes is blowing the valve UP letting the air out so engine falls on its face. and you say it works WOT... The boost pressure inside vacuum line is prolly to much for the check valve so some boost is making it to the BOV to help keep it closed, but i bet its not 100% SEALED and you are loosing effiency of the turbo, cause it to spool faster than it needs to, to make that PSI. in other words, your losing out both ways. run a vacuum line to the bov and be done. no check valve
 
#7 ·
sounds like you havwe check valve blocking the boost in vacuum line from getting to bov which helps hold down the valve/spring so you dont leak boost. and the pressure inside boost pipes is blowing the valve UP letting the air out so engine falls on its face. and you say it works WOT... The boost pressure inside vacuum line is prolly to much for the check valve so some boost is making it to the BOV to help keep it closed, but i bet its not 100% SEALED and you are loosing effiency of the turbo, cause it to spool faster than it needs to, to make that PSI. in other words, your losing out both ways. run a vacuum line to the bov and be done. no check valve
 
#10 ·
OK so quick update. I blew through the piece I thought was a check valve and found out it is a filter, but I pulled it off anyway and re-ran a new vac line. It still does it, but I thought I should re-explain the symptoms. It might be normal or just my driving style. When rolling onto the throttle it's fine. Builds boost and accelerates great. Now, if I stop rolling onto the throttle and keep the throttle at lets say 3/4, the revs build up and it accelerates until about 5500 to 6000 rpm where it levels off and that's when the BOV starts pulsing. Is it possible that this BOV is just really sensitive and when the pressure equalizes it blows off. I just don't remember it doing this before. I would think that if I'm at part throttle it would just build as much boost as it could with the load given and the BOV would stay closed until full release of the throttle. B.T.W. the BOV has it's own vac source.
 
#13 ·
still tho, just cause the bov opens doesnt seem like you should be feeling it fALL On its face so fast like that. i was testing mine today to see what U meant. push throttle like 1/4 way down let it take it up as many rpms at 1/4 will take it...but no fallign on its face, just keeps pulling normal...i dunno..this is weird. you say your idle is fine...humm..my old d15b7 would do exactly what you are saying, but it wasnt turbo..just a certain partial throttle would make the engine drop on its face at a certain rpm/vacuum..i dunno... im thinking.
 
#14 ·
No it doesn't really fall on it's face. I don't think I described it that well. It bucks because the Bov is opening and closing real fast. So the pressure isn't remaining constant. It's kind of like someone who's learning how to drive a stick and releases the clutch to fast and the car bucks back and forth, just at a higher speed and faster. I wish I had a camera to show it. It Goes chirp, chirp, chirp, chirp, real fast. LOL! If I give a little more throttle, the BOV shuts and the car takes off again.
 
#17 ·
its normal... car goes into vacume, and bov opens... thats how they work. i dont understand what problem your having...

just say you half throttle, cruising at 55mph... cruising at a steady speed, your in vacume and the bov is open... it closes when positive pressure is holding valve down.
 
#19 · (Edited)
No, it's still in boost when this happens. Like 12 lbs. Here's I think the best way to say it. I Roll on throttle to 3/4 throttle, Accelerates into boost and revs to about 6000 rpm and starts to level out and boost starts to drop just a little because the load is getting lower, then the BOV opens and closes really fast at a rate of about 3 times per second.

Sorry if this thread is giving people headaches. I fail
 
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