Best Way To Have You Adjusable Bov Set

[GtstCoupe]

Hey Peeps,

I have done a bit of reading and i have a few mixed opions on adjusting a

aftermarket bov ,now i know how to but where is the "sweet spot",

now i have read that some people run it so that it wont open and until

positive boost is reached, others before. now the first i think is the right idea

and you woundt get really and compressor surge ,just seeing what we all think.

Regards Lee

[BHDave]

It depends on your setup really.

If the bov vents to atmosphere then it absolutely has to stay seated until you acheive positive pressure or you will run into stalling problems.

If the bov is plumbed back then you can get away with it being open at idle as there is vacuum in the plenum sucking it open, provided that boost pressure isn't also forcing it open at partial and full throttle and so wasting the turbos effort.

I still like mine to be completely closed until it sees boost though, even though it's plumbed back.

[Beer Baron]

you dont want either of your two options. if it open when positive boost is achieved then you will just be venting boost everytime your turbo spools up. if it's open whilst under vacuum then it will be leaking all the time whilst you are off the throttle/part throttle. it should only vent when there is a pressure differential between the intercooler piping and the plenum (post throttle). the area post throttle is under vacuum and the area pre throttle will be under a temporary pressure spike, this is when the bov opens and vents the excess boost. as soon as this differential is reduced it will (should) snap shut.

[mokompri]

..provided that boost pressure isn't also forcing it open at partial and full throttle and so wasting the turbos effort.

this *shouldnt* actually happen because both sides of the diaphragm will be seeing the same boost pressure. although a pressure loss through the IC may give a difference between the boost on the vacuum feed and the boost on the IC pipe that the BOV is on, if its mounted before the IC.

even though my BOV is also plumbed back, i still get a drop in revs below idle sometimes when i get off the throttle sharply

i dont think there is any sweet spot so to speak either, but then it just goes back to the age old argument of how a bov really affects your cars performance, if you think the 'unloaded' compressor surge on closed throttle causes damage or slows your car down, then adjust the bov so it opens asap without causing stalling issues. if your a believer of the other side of the fence, which i am, you can set it at a higher point so that it only opens when you hit high boost.

Edited July 5, 2006 by mokompri

[BHDave]

I knew someone would have something to say. Thats waht happens when you have to rush a response

I should clarify. I was mainly refering to throttle closed situations, not throttle open situations.

When throttle is closed on gear change, you only want it venting when there is positive pressure in front of the bov, not everytime the throttle is closed.

What you want is the spring to be stiff enough that it is only opening when you are making positive pressure as you change gear, if you know what i mean, or it will be open as you slow to idle and cause stalling problems.

Partial throttle situations where you are making boost will cause a pressure differential if you have a slight lift off, which i also don't like

Edited July 5, 2006 by BHDave

[GtstCoupe]

Ok i see alright i will see how i go with that,but is a very interesting

topic thought.

thanks for all your help guys

many thanks lee