blowing off in vac.
 

well recently i have lost boost from 8 psi to 5 psi and am yet to determine why.... but anyways today i noticed that my car blows off in vaccume... like around 10-15 vac. is this normal???

-thanks

Re: blowing off in vac.
 

i think your gague might be messed up, to have thw blow off sound you need pressure

Re: blowing off in vac.
 

...yea i unno i really dont think it is my gauge tho...

Re: blowing off in vac.
 

my DSM kind of whistles in low vac, if i give it gas up to about -5 then let off it has a faint blow off

Re: blowing off in vac.
 

same here. not loud, but still blows like at -5 vac.

Re: blowing off in vac.
 

My DSM makes a bike bell sound at low vav, though right now it's disconnected because the line had a hole, so I've got the good old compressor surge going on.

Re: blowing off in vac.
 

My DSM BOV is partially open at idle, but Im attaining boost under full throttle.

Re: blowing off in vac.
 

the bov works off vacuum, it only makes sense that it would be open at idle when the vac pressure is highest in the intake mani. I get a whoosh too when i shift even if I am not making positive pressure.

I have a theory as to why, the turbo is still working, just not fast enough to make boost at low throttle positions, and when you close the throttle plate, it pressurizes the charge pipes just a lil and the vac in the intake mani makes the bov open releasing this little bit of pressure. Maybe I am all wrong but it would make sense to me. does anybody else smell what i'm stepping in?

Re: blowing off in vac.
 

bingo :y

Re: blowing off in vac.
 

Well first off the bov opens when it see's vac.
your boost guage is probably hooked up to the intake manifold, therefore when the throttle plate closes there is vac and thats whats your guage is reading at the same time as your bov see's it and opens to release the boost from the charge pipes so that it does not try to push the turbine backwards.