Need crushing BOV info- PLEASE NO DODGEGARAGE LINKS

[Caithness]

Sorry about the caps, I feel they're necessary from the last 2 years of crushed bov threads I looked through where there was no info on crushed bovs, just links to the dodgegarage mod.

I need a link to a faq or just general info on crushing a bov. What I need to know is how you test the vacuum holding capability of the valve. Do you just hook a vacuum pump up to the intake manifold reference port? I'd also like to know more about what vacuum level you can safely crush it to, 23" being the number I found in one thread out of 50 I looked through. Finally, with the valve crushed this far, does it stay closed at idle, which only draws around 20"?

Don't worry, I'm not actually crushing one, I'm taking an overcrushed valve apart and modding it sort of like wret did, but not quite the same.

 

[wret]

http://www.geocities.com/MotorCity/Garage/8384/crushBOV.html

 

[Highwayrun]

http://www.geocities.com/MotorCity/Garage/8384/crushBOV.html

That link says that 1 inHg = 1 psi, but that's not true.

1 inHg = 0.5 psi

The analysis also didn't account for boost pressure forcing down the valve when the throttle plate is open and boost is being made.

Given that 1 inHg = 0.5 psi, then, as per the link, the stock 2G BOV should only hold 7 psi. Of course, we know it holds more, since boost pressure helps the spring to keep the BOV closed.

There's more to the story as well. The larger the area of the valve head (inside the top of the BOV) compared to the area of the valve seat (where the BOV meets the UIC pipe) the more boost can be handled for the same spring force.

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Yes, if you crush the BOV to open at more vacuum than your car makes, the BOV will remain closed at idle. It'll also probably stay closed in light driving.

 

[Highwayrun]

I prefer this link.

http://www.jumptronix.com/2g_go_faster/Stages/details/BlowOffValve.htm
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To check the BOV, remove it from the UIC pipe, then attach a vacuum pump to the nipple and apply vacuum. Looking into either the dump port or base port, note the vacuum reading when the valve begins to open.

It might be a good idea to crush 1 inHg at a time and see how the car works.

You may as well measure your engine vacuum while you've got the vacuum pump. I trust the vacuum pump over a mechanical boost/vac gauge any day.

 

[Caithness]

Ok, that tells me what I needed to know. The valve is crushed already. I'm going to take it apart, uncrush it, then weld a nut to the top of the valve and run an adjustment bolt with a washer welded to it inside the unit and a locknut outside the unit. Essentially make it an adjustable BOV so I can easily play around with different vacuum levels and see how it responds.

 

[PieEyedPiper]

When I crushed my 1g bov, last week, I completely ruined it.

I didn't have a vacuum pump of any kind so i just went ahead and crushed it. I squashed the thing maybe 2mm? I installed it and pressure tested to find I could now hold 18psi.

I figured wow this works great, maybe another 1mm would net me a solid 20psi! Ao I did so and then decided I wanted to lube the thing up with some oil before I reinstalled it.

I forced the valve open with my fingers and jammed a screw driver in there to hold the valve open while I squirted oil on the piston etc. I carefully removed the screw driver and reinstalled the bov.

I could now build and amazing! 0psi!!!

I figured I just over-crushed it ( though in retro-spect it was the perfect amount). But then it dawned on me.. the screwdriver is made of harder metal and had no doutb scathed the portion of the valve housing that meets with the piston. That could be the only reason it leaked so bad that it would hold zero pressure.

awesome story eh?

Huzzah to the stock 2g bov!!
(ebay type s will be my next victom)