Bov Operation?

[A//// Guy]

So Im driving my car in blow thru mode (91 gsx) and I just redid it to that setup. At idle is there supposed to be slight airflow coming out of the BOV outlet? or only under boost. I have a new vacuum leak since I redid a couple things this past couple weeks. It used to read 18-19 at idel but now its like 17-18.

I havent put pull boost down yet but when it was hitting like 2-3 psi and let off the throttle the BOV didnt woosh as normal is just kinda made some fluttering noise. Is this because its cold or what?

I did have it beadblasted at work so I could paint it, and I sealed it all up , nothing got inside.

[john]

What kind of bov? If it were my car, I wouldn't care about a vaccum difference of 1hg. That could just have something to do with the temp. I bet your car still idles perfectly fine. Maybe your bov is leaking.

[A//// Guy]

Yea I figured out the vacuum. When I switched to 550s I also switched the Translatro for 550s which made everything super lean. I have idle cranked up to +20% on the AFC. Once I richened it up the idle jumped +300-400 rpm and then I lowered it and the vacuum was normal (18-19)

But my (stock) BOV is making some weird noises. It flutters and makes a groaning noise when you let off the gas after boost.

[1ViciousGSX]

There should not be any airflow coming out of the BOV at idle, only when it opens to relieve boost pressure.

[A//// Guy]

Great now I have a shitty BOV. Anybody recomend a cool sounding one? I like the stock but it squeaks and makes weird noises even when normal.

I dont want to spend more money. ;(

[CVD]

It is perfectly normal for it to suck in air at idle. The BOV is before your MAF right?

I know this seems obvious, but did you hook up the vacuum line? The stock bov flutters sometimes, but it's not very common. Usually that flutter is asociated with BOV-less turbo cars.

Mike at QPR has a device that he can hook up to the vacuum fitting on your BOV to test it and see if it will open. That would be another good thing to try.

[A//// Guy]

I hooked everything up right and the BOV doesnt suck air into the valve it blows it out as it would when it lets out boost.

When I was cleaning it I could push the valve inward if I pushed really hard.

Yea the BOV is before the MAF. I dont think this is how it performed before I painted it and blasted it so maybe some stuff is stuck in there.

[CVD]

That is very strange. It would take some funky voodoo shit to get a bov to blow out air at idle.

Being able to push the spring isnt the same as hooking up a vacuum line to see if the bov still works properly.

[Shane@DBPerformance]

Well, 19" of vaccum is a little high for DSM at normal 750rpm idle. They usually seem to be closer to 16-17". The vacuum is so high that it is probably sucking the BOV open. BOVs open at high vacuum(like after a shift), if your is very high at idle, it can start to open the valve.

[Matt D.]

Regardless, if the BOV is opening under vacuum conditions it is only sucking in air, not blowing it out.

[1ViciousGSX]

Originally posted by Matt D.@Jan 27 2004, 12:40 PM
Regardless, if the BOV is opening under vacuum conditions it is only sucking in air, not blowing it out.

It's blowing out because even at idle the turbo is spooling.

[CVD]

It may be spinning a little, but you wont see positive pressure in the IC pipes. With the kind of vacuum present in the system I wouldnt even think it would be possible to have air come out of the bov.

[A//// Guy]

Yea Im stumped I dont know what is going on it seems backward. The vacuum and air blowing out doesnt make sense.

When I reved the engine and held my hand over the BOV outlet it was pushing air out at idle and then during rev it wasnt and then when i let off it pushed out more air than at idle.

[1ViciousGSX]

Originally posted by CVD@Jan 27 2004, 12:57 PM
It may be spinning a little, but you wont see positive pressure in the IC pipes. With the kind of vacuum present in the system I wouldnt even think it would be possible to have air come out of the bov.

There is no vacuum at the UICP. All vacuum is behind the throttle body in the intake manifold. I wouldn't expect to see high pressure air either at idle, but if some air is coming out, then there is pressure behind it, even if it's very little.

[CVD]

There is vacuum in my IC pipes at idle. Enough so that I wouldnt think that my car is unique in this. I really dont think that the exhaust flow at idle is enough to put any pressure into the IC pipes.

[A//// Guy]

So anybody have any suggestions on what is wrong or is this something completely new to alot of people...

Ill talk to Mike tonight.

Can having a bad BOV hurt the engine by not letting out the air?

[Shane@DBPerformance]

Vacuum opens BOVs. If your vacuum is high at idle it can start opening the BOV. There isn't vacuum in the I/C piping, since vacuum is caused by the throttle body. But there is a hose that runs from the intake manifold(where you have vacuum) to the BOV(opens from vacuum). So unplug that annoying line and problem solved. :stick:

[Shane@DBPerformance]

Originally posted by EclipseTurbo@Jan 27 2004, 03:52 PM
Can having a bad BOV hurt the engine by not letting out the air?

No, but it can hurt the turbo.

[A//// Guy]

What does the line from the intake to the top of the BOV do? Does it just aid operation or is ther another purpose. But, so there shouldnt be air blowing out the BOV? What would cause the weird noise its liek a groaning or berp. Not a woosh at all and the turbo sounds weird too now.

[Shane@DBPerformance]

Damn dude, just try a different BOV, I was joking about the hose going to the BOV, it controls the BOV. With the stock intake, piping, and BOV setup it doesn't matter if it's open at idle because it's sucking in metered air.