Bov Question

[Cam84]

Hi guys

Just a quick one.

Just wondering, when should my BOV valve open? it is a standard R33 GTS-t S2 running 10psi, at what PSI/RPM should it open?

at this stage it won't open below about 6000rpm just getting flutter, but give it some and hit 7000rpm and it's fine. is this correct? or should it be opening at a lover PSI/RPM

Cheers guys

Cam

[Trozzle]

Obligatory comment about how you're probably unneccessarily flogging the standing engine, but I don't know shit lol

While I have no actual knowledge on how a BOV works, my understanding is that as you release the throttle, the throttle valve thingywhatsit in the throttle body (lolterminology) closes, causing a restriction to airflow, in turn causing backpreasure, which IN TURNNNNNN causes the BOV to open. If yours isn't opening correctly unless there is a rather high airflow when you're at high rpm, it could be that the spring is set too hard or is faulty in some way. Like I said I don't know the workings of it, so this is speculation (like most of my input)

Hope this helps

[Deano45]

Taken straight from a website as I couldn't be bothered typing an explanation:

A BOV releases turbo pressure when the throttle plate is closed. The turbo is still spinning and still creating pressure. The forced air will hit the throttle plate and return where it came from. When a BOV reads vacuum from the manifold, it either opens a valve, or softens the valve. Which lets the pressure escape from it's opening.

To fix this, you need to adjust your BOV. Most BOVs have a screw or nut to adjust the tension. You can turn the screw/nut to the right and increase the tension. Do this several

times with a test drive in between. If your BOV stops letting out the pressure, you have

adjusted it too tight. You will then need to start adjusting soft again. You must keep

playing with this adjustment until you get it just right. A good adjustment will allow the

BOV to release pressure after slight boost, and not stall afterwards. It is not necessary for

the BOV to release pressure when you rev the car.

You say you are running 10PSI, is your BOV adjustable? and at what RPM does your car hit the 10 PSI? it's a matter of adjusting the BOV so it justs holds you required pressure, but will open when the throttle is closed and the BOV senses vacuum.

[Trozzle]

yay I was right

[Cam84]

Running standard BOV, dousn;t matter what RPM even if you slowly build boost it won't open. if you put your foot flat hit 7000RPM then back off it will open. can you adjust a standard BOV?Hmmm i'll have a look

Cheers

Cam

P.S

Trozzle, i didn't buy this car to put around, why would anyone do that?would be a huge waste of my money. Nor did i buy it to thrash it, but if i feel the urge to hit 7000RPM in 1st and 2nd going onto the highway, why not? thats what there made for, and if a standard engine can hold 18psi with no hassles at all (as long as it's well looked after) i'm sure 10psi won't hurt.

[tridentt150v]

are you getting your BOV and wastegate mixed up?

You don't want your BOV openning too soon or too early [and theoretically if there is equal pressure on both sides it shouldn't happen [unless it is faulty], because if it opens early, it is bleeding off boost you are using.

[89CAL]

with stock intercooler? it might not be great

As for your stock BOV. It should open pretty much at any boost level and any rpm. I replaced mine with an aftermarket plumback BOV just cause i was sick of the sound of the stock one because it opened up all the time.

Your bov works through differential pressure, You have a vac/boost feed that comes from your manifold that plugs into the top of the BOV. Then you have the boost that exists in your pipe. So when you close your throttle body, you get manifold vacum to pull your bov up combined with pressure from the piping that pushes it up.

So... check your vacumm line to the top of the BOV to see if its blocked or something, make sure its coming from the manifold as well.... maybe pull the bov off and make sure that the valve is still operating by giving the valve a push it should move resonably freely. Check those two things first, if everything seems ok then maybe your bov is stuffed.

Thats all I can think of right now

[Cam84]

it's the BOV not Waste Gate.

Hmm, i'll check it tomorrow. i did check that the valve could open, which was abit hard to push in. But as this is my first Skyline i wouldn't know what is normal.

Everything is in standard form with the BOV, i had it put back buy the Toy Shop after it didn't have one for awhile.

May just buy new one see what happens.

thanks for all the knowlage guys, my guess is the spring is set to tight because it does open when there is a high amount of boost, will see.

Cheers blokes

Cam

[Adriano]

If its a stock BOV then it sounds like it is stuffed, or there is something blocking the vacuum hose

[89CAL]

yeh maybe try pulling the vac line that goes to the top of the bov off and blow through it, if u can then u may have a faulty bov. Should be easy to find one on here in the for sale section or put in a wanted to buy for one.

Think they only go for about $30-$50 usually so no big loss anyway. Or you could go aftermarket, but if u do I recommend going with a plumback arangement like stock, atmo bov's are more problems then they are worth

[PROXIMITY]

agreed with others.

Stock bovs are forever opening at any rev really when backing off as the spring is very soft.

Something is wrong with yours if its only opening up that high, i would replace it because too much flutter will help Mr Ceramic wheel fall of earlier than it should lol.

[toddr33]

Better than creating a new thread I'll just ask here. My 33 is stock running 9psi, stock bov plumbed back. I can never hear the sound when I throttle off... at high rpm or low. Is this normal?

[Trozzle]

Trying to make sense of the above replies, would that mean that MY stock bov is f**ked if it releases at any RPM when I back off, and when it does, it feels like I completely took my foot off the throttle and placed it back on just enough to not come back onto boost? It's possibly the most annoying thing in the world to be in 4th, give it some throttle (don't even have to come into POSITIVE manifold pressure, can remain below 0mmHg on the stock guage), back off a little and then have the car feel like I hit the brakes...running 11psi currently

[Branelly]

@ toddr33, Just in case you didnt know you wont really hear your blow off valve unless you have a pod filter, or similar. The stock panel filter completley muffles the sound.

@ Trozzle, The stock blow off valve should release the pressure at generally any rpm. If its only opening at 6000rpm or above it definitley sounds like theres some sort of problem with the way its been set up. Either way get it sorted soon, not releasing the pressure can damage your turbo.

[toddr33]

@ toddr33, Just in case you didnt know you wont really hear your blow off valve unless you have a pod filter, or similar. The stock panel filter completley muffles the sound.

Thanks heaps dude, I thought that was the case... sometimes really late at night (like 2am); I can hear the bov go off... but even then it's reallllly feint.

[Trozzle]

Thanks Brandon, mine DOES currently release pressure at any RPM, the only thing that concerned me was how it feels when it does release if you're under acceleration.