vogun16

iTrader: (7)

2 things, at an idle it will be open just a little bit, but as soon as it comes off idle it will close, second when i shift it will give out a long burst of air instead of a short burst, i already have it tightened all the way, is the blow off valve to small? do i need a stronger spring? its a 38mm turboxs

TurboZ28408

iTrader: (18)

its a piston type and not a diaphram type. its always going to open at idle

vogun16

iTrader: (7)

is a diaphram type a better blow off valve? and is the long blow offs normal?

bboyferal

iTrader: (9)

No, a BOV should not be open at idle...

Why would anyone want the engine idle to draw in unfiltered air to the motor, piston or not?

It should be adjusted to be just closed shut at idle inches of vacuum and then open or at least move at the blip of the throttle. Some can be manually adjusted. Some have springs you change.

TiAL

it's not sucking in, it would be blowing out

open at idle doesn't matter as long as the MAF or MAP is after the bov...if it's before then you run into issues with stable idle and running rich when you let off the gas...that is when you need to have the bov closed at idle

bboyferal

iTrader: (9)

Hmmm... So, while the engine is idling, you're saying air is blowing out the BOV opening if it's opening?

Um, when an intake manifold is in vacuum (at idle) because air is not compressed and the engine is feeding itself, how can air EXIT any opening on the intake side of the turbo?

I agree the issues are more important if the MAF is connected to the air filter element, but I always believed air should never have access to the engine unless being drawn from the air filter element, which if the BOV is open at idle, the vacuum from the motor can pull air from elsewhere in addition to from the air filter. Am I missing something?

ta02zx10r

iTrader: (19)

I'm thinking the same thing. The engine doesn't make air. It sucks it in. The only way it would be blowing air is if you had a supercharger that is spun to the moon and is making boost at idle or a turbo on there that is extremely tiny for the application right?

koolrayz

iTrader: (26)

You guys kill me. TIAL takes his time to help you out with QUALITY information and you want to argue with him????????????
His screen name is TIAL does that ring any bells??????

ls1290

iTrader: (20)

Correct, the BOV is closed at idle.

WS6HUMMER

iTrader: (19)

lol!

Dean95z28

iTrader: (7)

Well I have a JGS BOV and I was wondering the same. At idle ny BOV stays open. as soon as you blip the throttle it closes. I called JGS about this they said that that is how there unit works. I was concerned also about dirty air being sucked in but I guess since the throttle body is closed the motor is only sucking a little bit of air thru the IAC valve.

SiL3NtXWS6

iTrader: (17)

on blower applications, the BOV will be open at idle. The way he described it is the exact same way my TiAL50mm behaves

RealQuick

iTrader: (14)

I don't care what his name is (or anyones name), when you are wrong you are wrong. My JGS BOV is open at idle and you can feel air suck in at idle with your finger near the BOV.

TiAL

think so?
i didn't want to go make my own vid, so here is one proving my point.

http://www.youtube.com/watch?v=B_RWZASfE3M

veee8

iTrader: (40)

After the throttle body is where vacuum is registered.

vogun16

iTrader: (7)

but is that considered a boost leak??

elias_799

iTrader: (8)

yea, when he started reeving up the bov should of closed. i have no idea how that guy hooked it up.

mike13

iTrader: (27)

Yes they can be open, that's one of the reasons people run recirculating bov's or filters on the valve. Also you have to remember the vacuum is before the throttle blade, it's possible to have no vacuum or slight pressure in the intake tract. My turbo set ups that had vent to atmosphere always had air exiting the bov at idle.

bboyferal

iTrader: (9)

lol, not my cup of tea...

nice vid of idle and load...

BUT...

I wonder what would happen in a manual car with such a set up coasting down a couple of thousand rpm. Hmmm...

Besides, during that time my turbo is spinning at idle, I'd rather that air make it to my TB, not outside... That's just me.



And just what I've always wanted, lol, for my air from the turbos' intake charge to come out a bit from my BOV... lol, no thanks.

bboyferal

iTrader: (9)

Yup... The turbo's (obviously a small one) efficiency range being so much on the low rpm side that it's spinning pretty well only with the idle's exhaust gases PLUS feeding a small displacement motor that won't pull much vacuum anyway compared to a V8. In such a case, yes, I imagine you can find such a condition of the air being pushed instead of pulled at idle.

Not gonna happen on the turbos we run or on V8's.

This is LS1tech, IMO there may be a better, technical answer that encompasses more, but ultimately the answer should suit our motors and their conditions. Especially if some LS1 owner is just trying to set up his damn BOV, not learn the various different BOV set-ups... lol

My answer was the practical one.