Blow Off Valve (BOV)

[Lextreme II]

I have a question you guys. How do u know if your BOV is working properly? How can you test it and find out the status of it.

 

[cowboy bebop]

You can take it apart and inspect your diaphram for leaks, tears, ect. You can also check the spring to make sure it's operating 100%. We diagnosed a bad BOV this weekend at the Tampa meet. What's your BOV doing to make you suspect it's not workng properly?

Eric

 

[Lextreme II]

I suspect its not opening. When i rev the engine, i hear BOV sound at my turbo compressor instead of BOV. Vacuum line is intact. I manually pushing the diaphram and it moves....

 

[cowboy bebop]

It's possible that the spring is a stiff spring, or the adjustment screw is wound down tight. As long as you have movement in the diaphram, an intact vacuum line, the BOV should operate a fine under boost. If it's any consolation, I can't get my BOV to open when the car revs with no load, either

Eric

P.S. I'd like to sign you up for a set of these aluminum 1/2uz-fe pulleys. Can we do that?

 

[Lextreme II]

I wonder if the spring rating like:
SPRING PRESSURE: 9 PSI (-14 to -17 in/HG) SPRING PRESSURE IS USED FOR VACUUM PRESSURE, NOT BOOST PRESSURE!

SPRING PRESSURE: 11 PSI (-18 to -21 in/HG) SPRING PRESSURE IS USED FOR VACUUM PRESSURE, NOT BOOST PRESSURE!

Would the spring rating affect the opening of the BOV? Is it possible my BOV spring is too hard so it wont open.

 

[cowboy bebop]

It sure would. I run two Greddy Type R Heavy Springs to keep the BOV's snapped shut under pressure, and they don't make a peep at idle. Unless there's positive manifold pressure on a heavy spring equipped BOV, it'll have a tough time opening under boost.

Also, you can rev the motor from under the hood and put your hand over the BOV discharge to see if it's leaking.

Eric

 

[Lextreme II]

There is a spring rating on BOV. I noticed some are 7 psi and some rate 11 psi. What does the rating affect BOV and pressure.

 

[stevechumo]

Manually do this first before taking out the BOV. Remove the black plastic that covers the throttle body cable. If your BOV outlet isn't flowing back in, which isn't the case for many aftermarket BOVs anyway, then just rev the engine up and release it. You should feel alot of air coming out of the outlet when you release it along with the lovely whoos sound. Do it at low RPM and at high RPM and see how it respond to the throttle body/boost. That's also true for the BOV to open too soon when adjusted too soft, and slowly to open when adjusted too stiff. Clockwise = stiffer, counter-clockwise = softer. In my opinion, use the low psi spring first and see how it react to your boost. If not, then the higher spring is in place. However, always adjust the screw from soft to stiff before changing out the spring.