i reach full boost at 3500rpm and i'm using the old blitz BOV. if i step on the gas gradually up to 4k without boosting(near 0 psi on boost gauge), should the BOV blow-off when i shift gears? if no, what could be the cause? i've noticed this before but only thought of asking it now.

thanks for any info.

 

What kind of boost gauge are you running? mechanical?

And where is the boost gauge source tapped? intake manifold or at the turbo?

 

if your not in boost, it wont blow off, there is no charged air for it to relieve.


Rob

 

i'm using autometer boost gauge and it is tapped at the stock fuel pressure reg vacuum source.

does that mean that it shouldn't blow off even if i shift gear at above 4k rpm cruise without boosting? is there something wrong with my bov?

 

at 0 psi, at rpms where your turbo is spooling, your BOV should be going off. it's either set too hard or you just cant hear it.

 

how is a bOV going to opperate with no pressure to relieve?


Rob

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by _Endless_ &raquo;</TD></TR><TR><TD CLASS="quote">i reach full boost at 3500rpm and i'm using the old blitz BOV. if i step on the gas gradually up to 4k without boosting(<FONT COLOR="red">near 0 psi on boost gauge</FONT>), should the BOV blow-off when i shift gears? if no, what could be the cause? i've noticed this before but only thought of asking it now.

thanks for any info.</TD></TR></TABLE>
no...dosent sound like anything is wrong.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Smokinsax &raquo;</TD></TR><TR><TD CLASS="quote">
no...dosent sound like anything is wrong.</TD></TR></TABLE>

Thank you someone with some sense

if your not building boost, then there will be no boost to be relieved....

Rob

 

my car does the same thing. i here my turbo spooling around 3k-3.5k and the boost guage goes out of vacum and when it gets to 0psi i shift and i hear it blow off. doesnt blow off as loud as when im in boost but i can hear it alittle bit.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by civicflnum1 &raquo;</TD></TR><TR><TD CLASS="quote">my car does the same thing. i here my turbo spooling around 3k-3.5k and the boost guage goes out of vacum and when it gets to 0psi i shift and i hear it blow off. doesnt blow off as loud as when im in boost but i can hear it alittle bit.</TD></TR></TABLE>
then you gauge is off. If you here anything it is positive pressure being released, think about it, in vaccum this will not happen. there is no way for anytihng to get blown out of the BOV when you are in vaccum and sucking air in still. Remember your ambient air pressure...


Rob

 

yeah but if ur not in vacum and ur not building boost ( at 0 on guage) there is still air going through the charge pipes. so when the bov opens some air comes out. that is why it is still going off but it is very quiet

 

Yep a reading of 0bar is NOT a vacuum state. If you have 0bar in the charge pipes then snap the throttle plate shut vacuum will be less than 0bar.
Pressure differential = BOV opening
Depending if the BOV is adjustable (and if not adjustable- how high it is set for) you may not open under such situations or you may open alittle (venting very little air out) and making a small amount of noise.

 

Actually if you read 0 psi on your boost gauge then you are building boost. Otherwise you'd be in vaccum. I can watch my VAFC and it'll say -100mmHG or whatever in vaccum and I can still hear my RFL go off. You don't have to be reading any boost to have the blow off valve go off.

 

Lots of misinformation here.

If he is at 0 on his gauge, he has no pressure, and nothing from the manifold is going out the BOV. The gauge only indicated pressure IN THE INTAKE MANIFOLD.

HOWEVER, if you in an rpm range where there is sufficient exhaust gas volume to spool the turbo (he is at 4k, which is plenty high), you WILL have boost before the throttle body. This boost can be as high as 5-8 psi with a fast spooling turbo, trust me, I have watched it happen.

That is what vents.

 

&gt;&gt;Lots of misinformation here.&lt;&lt;

man, you said it.

edit: i meant, I agree!

&gt;&gt;If he is at 0 on his gauge, he has no pressure, and nothing from the manifold is going out the BOV. The gauge only indicated pressure IN THE INTAKE MANIFOLD.&lt;&lt;

I think this is the point of confusion in some of these posts. Bottom line is, the only time pressure in your charge pipes is anywhere near the same as intake manifold pressure is WOT. If you crack the throttle at mid revs enough to register 0 psi in the manifold, I guarantee the pressure in the charge pipes will be substantially higher. So, there certainly is some pressure for the BOV to relieve, especially when the throttle closes and that little compressor wheel is still spinning at 50,000 rpm's. Where is all that extra pressure (due to momentum of the compressor wheel) going to go?

But we need to think about what bov's are all about anyway. 2 things: 1 ) Bling, and 2) compressor surge. What the boost guage reads on the intake manifold is completely irrelevant to the (practical) function BOV's are meant to perform, and that is to prevent compressor surge.

little rant: Good BOV's aren't about gear changes anyway! That BOV comparison test in SCC was completely useless.

 

so the mother of all bottom line is, what i'm experiencing (and some people) is normal then?

 

yes very normal...mine makes little squeaks in between shifts when its close to the 0 on my guage, very normal....