Garage Storage Organization and Garage Cabinets

PaintPeelinPbod · **Leaking BOV's?**

Ok Im perplexed by this idea...how is a BOV supposed to hold a certain amount of boost, when its letting air out. I have a talon bov.

My Talon bov is clearly blowing air out of it as the throttle is depressed. I put a string in front of it, at idle it was blowing it away from the bov, and as i went up in the rpms, it blew it away harder, then when it "blew off" it would suck a little bit of air back in, then at idle it would start blowing it out again.

I've done some searches, but they all the answer in this category are "its normal leave it alone".

How are you supposed to hold a certain boost level when your bov is leaking a certain amount out? Please explain.

mwinkle353 · 07-03-2005, 09:59 AM

most all BOV's will be open during vacuum conditions of the motor. They close (or supposed to) when the motor is in boost conditions. This holds true for *most* plumb back type valves. That's why they recommend a filter on the end of the BOV's outlet.

Some aftermarket units will stay closed during vacuum conditons, as long as it's properly tuned (adjusted) so that it will blow open under heavy differential pressure.

Since you're using a typical plumb back type of BOV, I'd bet that's normal operation. As long as it closes during boost conditions, I wouldn't be worried.

I'm guessing you did you're tests when the car was not moving. So you're not properly loading the turbo enough to build boost. If I'm wrong in assuming this, please clarify.

Wink

93 Lebaron 3.0L 5 speed
Project "Headless Horseman"
http://www.cardomain.com/ride/252407

89 Shadow ES 2.5L TI 3 speed
"Casper"

PaintPeelinPbod · 07-03-2005, 01:46 PM

You sir are correct.

Why does it "blow off" then if its not under boost?

How would correctly test a bov to make sure your not leaking boost?

xrattiracer · 07-03-2005, 02:23 PM

the valve will be open any time there is intake vacuum present, like at closed or mostly closed throttle positions. instead of just bringing the rpms up slowly with small throttle openings, snap the throttle open and closed. it should only let air out after you let off of it. if its an auto, have a friend put it in gear and feed it some throttle with the brakes on.

Una · 07-03-2005, 02:45 PM

Quote:

Originally Posted by PaintPeelinPbod

How would correctly test a bov to make sure your not leaking boost?

Put the car on a dyno. Then you can feel around in the engine bay while the car is under full load/full boost.

ezspool · 07-03-2005, 03:51 PM

take the bov apart and stretch the spring to twice the size and glue the bov back together, and wa la 20 psi and no leaks, and no compressor surge either

aerosmith145 · 07-03-2005, 04:42 PM

Dirt and other debris can keep a bov from seating all the way under boost - check that out also.

PaintPeelinPbod · 07-03-2005, 06:20 PM

This is how my setup is, tell me if sounds right. I have the Grainger hooked up to the wastegate, the grainger gets its vaccum from the nipple on the turbo, next to the wastegate, and between the grainger and the wastegate is a T elbow.One side of the T is plugged, one side goes to the BOV, and the other to the waste gate. Did I explain that well enough? Is this correct?

Una · 07-03-2005, 06:59 PM

Your BOV is supposed to get it's signal from the small nipple on the throttle body. Straight from there to the BOV, make sure you've removed that thing the factory had in line for the original BOV.

PaintPeelinPbod · 07-03-2005, 07:02 PM

where is this nipple on the TB?

PaintPeelinPbod · 07-03-2005, 07:16 PM

Im sorry, the BOV does get vaccum from the plug on the back of the intake manifold, but i do see where it could go on the TB if i wanted to.

Lebaronguy2001 · 07-03-2005, 10:41 PM

any vac source will work.....the only place that will not work it the throttle body nipple that doesnt see boost, and i dont know for sure which one of the two that is....one only shows vac, and that wont seat your bov during boost...

PaintPeelinPbod · 07-06-2005, 06:54 PM

BOV is fine, had a friend brake torque while i felt the air in front of the bov, no leaking.
I think my boost issues may be related to the Gvalve, Im still trying to learn what is high and low on it.

GLHNSLHT2 · 07-06-2005, 07:24 PM

use an intake source for your grainger too. The turbo outlet can see ported vacuum under boost at times and the boost level may be unstable. Gus Mahon did some testing way back and found the intake was a more stable source.

A talon BOV will be open anytime it sees over 15.5" of HG or less if there is boost pressure pushing up on the bottom of the diaphram through the little hole in it's base. It should be open and blowing out at idle The reason it sucks in when you blip the throttle is cause the intake is sucking more air now. It'll close as the vacuum decreases but the turbo is also starting to spin faster now too so when you let off the air the turbo is pushing now goes out the BOV as it opens up when the intake sees more than 15.5" HG.
Wanna spool your turbo at the line in your 5spd car? Don't just hold the throttle at a certain rpm. Blip the throttle as hard and quick as you can around the rpm you want to launch at. This really gets the turbo spinning so when you launch and the BOV closes you have boost in the lines. Try it like your doing outside the car, just open the throttle a bit to maybe 2500rpms and hold it there and put your hand over the end of the BOV. Now have someone blip the throttle repeatedly right keeping it right around 2500rpms. You'll really hear and feel the turbo spool up a lot more. And with a 5spd it made my launches much much more consistent. Just holding the throttle at a certain rpm would make the car either bog or roast the tires. This works only with a 5spd and if you don't have a 2 step rev limiter or some trickery where you can build boost at the line by creating load on the the motor.