Rb25det Bov Leaking....car Still Boosts And Runs Well

[604JD]

So I got my Nistune done a couple days ago, spent about 3 hours on the dyno.

My mods

-blitz intake

-blitz front mount

-blitz front pipe

-blitz cat back

-blitz SBC

-no cat (test pipe)

-splitfire coils

-stock turbo

When we did some load pulls on the actual road the car blew off a vacuum line on the manifold. We fixed this leak and all seemed good.

At idle the car reads -19 vacuum, and on decel off the pedal i get -23 vacuum ....the car is tuned for a max of 13.5lbs of boost, but I turn it down to around 12lbs boost.

I ran into an issue the other day that anytime around 4000rpm in 3rd, 4th, or 5th the car would completely loose power. I can creep into 12psi by using partial throttle but full throttle and the car cuts.

So today I take it back and they boost leak test the car, do some smoke to help find the problem but not much luck. Then we take a look at the stock bov, we T into the vacuum line running from the manifold to the bov, and un hook the recirc side of the bov that goes into the intake tube. Apply some air and the BOV starts leaking like crazy, and there is maybe 2-3psi running through it.

Its evident the BOV needs replacing, but what gets me is why the car runs well still and how it can even make any boost with the BOV not being able to hold any pressure and leaking like that.....would it be because the turbo is compensating and spinning even faster to achieve its target boost level?

[GTSBoy]

Standard BOVs do let some go around.

Search.

[Missileman]

Lube the inner shaft of the bov with a tiny bit of moly grease, take the unit completely off, remember the orientation of the gasket. apply the grease to the shaft, then with your thumb push down on the bottom of the valve whilst sucking on the tube that connects to the manifold, and work the valve back and forth a few times. When I installed my hiflowed turbo I also discovered my 25 year old bov was leaking, but as it looked to be in mint condition I tried this as a last resort, glad I did! Pressure test it again and it now holds 20psi with ease.

[604JD]

I'm going to go with an upgraded turbosmart plumb back bov, want to keep the stock recirculating design.

But that's a good idea with what to do to the stock bov, kind of brings it back to life.

And yes I know the stock bov does let some pressure past, but no pressure would build up at all, it flowed right through....

[Hadouken]

What

Standard BOVs do let some go around.

Search.

What he said.

Just remove and plug it. Dose for days, zututu

[AngryRB]

so flutter is basically the same as surging which stuff's the bearings/cartridge??? Do the aftermarket ones flutter on low boost still or silent at all boost levels??

[scotty nm35]

Depends on the spring used Mark, Turbosmart Kompact recirc valves have a few to choose from, they act differently depending on the car.

[Trex]

put a screw into the small hole, and bash the nov top in a little until you have a tiny little bit of flutter in low rpm.

[scotty nm35]

Yeh, I used to grub screw the stock ones, but they are getting too old now, and the Turbosmart product works better without farting.

[Trex]

Yeh, I used to grub screw the stock ones, but they are getting too old now, and the Turbosmart product works better without farting.

farting? haha

mine will flutter a little a low rpm, and is almost silent above 3500rpm

[hypergear]

Ive tested stock bov blocked and open and it made no difference in boost level on the dyno. Check its vacuum plumbing, must be sourced behind throttle body.

[hardsteppa]

Ive tested stock bov blocked and open and it made no difference in boost level on the dyno

I found the difference to be in the on-off throttle responsiveness, rather than outright power, with blocked obviously giving the best response and making the throttle more 'twitchy'.

[scotty nm35]

Ive tested stock bov blocked and open and it made no difference in boost level on the dyno. Check its vacuum plumbing, must be sourced behind throttle body.

Some cars it will definitely make a difference. I notice a few psi usually on the Stagea. It's a 4mm hole, it can't leak that much air back to the compressor, but the more boost, the more escapes, and the faster the turbo shaft needs to spin to counteract it. Why would you ever want it there? For drivability only.