Disconnected The Bov - Very Weird Result

[The Mafia]

Hig guys, I've got a bit of a problem \ issue

I have a Standard Motor RB25DET with a Genuine Garrett GT30 (.7 comp cover, .63 ex housing)Sucking through a 4 inch stainless pipe, Q45 AFM and Pod filter.

I decided to disconnect the Factory BOV and chocked the hose up. (definately wasn't leaking). Here's where the trouble started......

Usually I'm running 18psi of boost through a $22 Bleed valve.

The Turbo would only spool to 13 psi and the car was very underpowered (most likely because of the missing boost) and didn't make anywhere near the amount of induction noise it usually does. When I backed off, instead of hearing fluttering, I sounded like I had one of those poffter style stuttering BOV's.

THEN it started idle hunting really bad.

Pluged the stocko BOV back in, and everything normal again (boost back to 18psi, and lots of induction noise, and spastic amounts of power once again)

What the hell could cause it to react like this?

[limpus]

Just blocking the vacuum hose that runs to the bov alone won't work...the bov is meant to bleed/recirculate air on load too...i'd reckon thats whats causing the problem...if you want to block of the stocky bov...probably best to fit a plate between the bov and the crossover pipe flanges...

[paulr33]

reversion of the air bouncing back past the q45

when its chopping its probably goin past the compressor and forcing pressure out past the afm. moral of the story, keep the bov

its there for a reason

ps; hows things ?

[paulr33]

do a datalog trace of AFM volts and REVS and let it run

then fang around, repliace the problem and paste the data dump here

i would to see the afm bouncing quiet a bit

[Fastrotor]

When you say "plugged' im assuming you mean just removing the boost hose to it ?? If so, it needs the boost fed to the top to offset the boost inside the pipe pushing on the valve. these two counteract each other, and then your left with just spring pressure effectively holding it closed.

ie boost in pipe pushing on one side..... boost pressure + spring pressure resisting opening on other

Without it , obviously all the boost in the pipe has to do is overcome the spring pressure and it starts bleeding pressure off. And there goes your power.

For interest sake, i have had car on dyno boosting it to 18psi while another guy held hand over bov and no leak at all for me... (R33 S1)

Gary

[gtst25]

Boost leak

[AlexCim]

Fastrotor is right, one side balances the other, with the hose coming after the TB and the pipe being before the TB, when the pressure is larger in the pipe than the plenum it just "blows off"

what you are experiancing is a MASSIVE boost leak as the BOV is just opening, always.

[The Mafia]

ahhh I See.

Well, I haven't had any problems with the standard one at 18psi.

I might just leave it on.

[Guilt-Toy]

is it a adjustable BOV ? you can also tighten them up.

[cln]

my mate and i blocked our bov's to get a fully sick flutter (we were bored) and copped the same as you. My turbo didnt boost past 10psi and it was as lazy as a cop on his day off. Moral of the story; dont block/get rid of your bov unless you plan on flatshifting like you stole it

[Adriano]

Cops are NOT lazy on their day off, only on their day on.

my mate and i blocked our bov's to get a fully sick flutter (we were bored) and copped the same as you. My turbo didnt boost past 10psi and it was as lazy as a cop on his day off. Moral of the story; dont block/get rid of your bov unless you plan on flatshifting like you stole it