Thread: Is my BOV adjusted properly? (Video inside)

I installed the Greddy Type RS knock off and was having crazy compressor surge. I changed my vacuum source thinking the BOV wasn't getting enough vacuum but that was not the issue. Finally I took the BOV off and used a vacuum pump to see if and when it was opening.

This was at about 25 in. vaccum. You can see the plunger BARELY opening. No wonder there was compressor surge.
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After teflon on the bolts failed to make a difference I took the BOV apart and removed the smaller spring. There was little change. I then put the smaller spring back in and removed the big spring. There was definitely a change but the valve was still not opening properly. There was too much tension on the spring.

I cut a little less than half of the length of the spring off and stretched it out. Once I put it back together the plunger was finally opening. From what I read on this forum it should start to open around 15 in vacuum. Anyway I think I adjusted it to where it should open when the throttle shuts but please confirm.

YouTube - MOV03042.MPG

Is that the one that has an adjustment screw on top?

I have the "chinese" imitation of the Greddy type RS and it has an adjustment screw on top, if it does you have to unscrew it and it will lower the pressure, the tighter it is the more pressure it aplies until it wont open at all...

Yes it's the one with the adjustment screw on top. I should have clarified but the first picture was with the screw backed out as far as it would go without coming loose. . In the video it's still on full soft so I can adjust it stiffer if necessary, just need opinions on how stiff it needs to be since I've never done this before.

Id say its more like try and see thing... At least that what I did to mine, just keep turning loose the screw till there was no compressor surge, and I never had a problem with loosing boost...

FuLLah you are way ahead of most Chinese knock-off BOVs with your modded version. I think you are well on your way to getting some good function out of it. It is weird that it is "sticking" but those are the ropes.

I think you should be well within the ballpark now with how it is opening. If you want like beto said just install it and tighten the screw down until you get some compressor surge and then back it off until it stops. I think it will stop though. If not, obviously you'll have to weaken the spring some more, but I think where you are now is a great starting point.

In regards to the sticking the shaft on the plunger did feel a little rough. If it opens with the way I modded it I will take the valve apart again and polish the plunger so it will move more freely.

You could just use different springs.... I had one set that was 2 stiff springs and another that was 2 soft springs, put one soft and one stiff together and its perfect.

OK so I was finally able to put it back on the car this morning. At idle the plunger is staying open (as I expected it to be) and as soon as I pull the throttle it snaps shut. There is no more compressor surge!

The downside is that this BOV makes a really soft sound (makes sort of a "cute" girly whistle) HAHAHA but atleast no more surge. Does the spring change the sound at all or just the opening point? Any way to make it more of a deeper sound?

Also I recall reading people saying they have issues running vented BOV and they would have stalling issues when coming to a stop. I have ZERO issues, in fact my idle is even more stable than before.

You can run a slightly stiffer BOV when venting to atmosphere because the stiffer BOV won't allow unmetered air in under idle.

When you pull a vacuum you want to see it hold about 20-25in because you want the BOV to open with vacuum on the top and boost pushing it open from the other side. If the BOV spring is too weak it will cause the BOV to open under high boost.

But too stiff will cause a little compressor surge. Some light surge is tolerated with most turbos. But any heavy surging should be fixed.

If the spring is too weak and causing the BOV to open under boost wouldn't I notice that on the boost gauge? (reading 5-6 psi instead of 7-8?)